Transcript for NASASciFiles - The Case of the Shaky Quake

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HEY, THERE, I'M JOHNNY ALONSO.

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YOU MAY RECOGNIZE ME FROM MY
ROLE AS JIMMY ON DAWSON'S CREEK.

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NOW, ON TODAY'S EPISODE OF NASA SCI
FILES, THERE'S GONNA BE A WHOLE LOT

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OF SHAKING GOING ON WHEN THE TREE
HOUSE DETECTIVES USE SCIENCE, MATH,

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AND TECHNOLOGY TO REVEAL
THE SECRETS OF EARTHQUAKES.

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SO STAY TUNED AND HOLD ON FOR THIS
EXCITING EPISODE OF NASA SCI FILES,

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THE CASE OF THE SHAKY QUAKE.

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COME ON, NOW, AND LEARN ABOUT
MATH, SCIENCE, AND TECHNOLOGY.

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NASA SCI FILES.

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DISCOVERING THE WORLD WE'RE
IN, DOING COOL EXPERIMENTS.

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NASA SCI FILES.

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NASA SCI FILES.

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ON THIS SEGMENT OF THE
CASE OF THE SHAKY QUAKE,

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YOU'LL BE ASKED THE FOLLOWING
QUESTIONS: WHAT IS A SEISMOLOGIST?

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DESCRIBE THE LAYERS OF THE EARTH?

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WHAT ARE TWO TYPES OF
CLUES THAT HELP US LEARN

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ABOUT THE EARTH'S HISTORY?

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AND WHEN YOU SEE THIS ICON, YOU
WILL KNOW THAT THE ANSWER IS NEAR.

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I THINK THIS BONE GOES RIGHT HERE.

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I THINK IT'S PART OF THE TAIL.

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WRONG.

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IT'S ACTUALLY PART OF THE HEAD.

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I GUESS SO.

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BUT THIS IS THE CLOSEST THAT WE'RE
GOING TO GET TO A DINOSAUR DIG.

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JACOB IS GOING TO HAVE SO MUCH
FUN LOOKING FOR DINO BONES.

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EXCUSE ME?

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THEY'RE CALLED FOSSILS.

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DID YOU FEEL THAT?

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HUH?

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I DID.

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WHAT COULD IT BE?

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I FELT THAT ONE.

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NOW THAT YOU'RE WITH US,
WHAT DO YOU THINK IT IS?

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IT'S AN EARTHQUAKE.

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DON'T JUMP TO CONCLUSIONS.

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GO TO THE NASA SCI
FILES WEBSITE AND SEE

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IF THEY HAVE ANY INFORMATION
ON EARTHQUAKES.

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VISIT THE RESEARCH RACK ON
THE NASA SCI FILES WEBSITE

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FOR RESOURCES ON EARTHQUAKES.

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I FOUND TWO PLACES IN VIRGINIA

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WHERE SEISMOLOGISTS
RECORD EARTHQUAKES.

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A SIZE WHAT?

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A SEISMOLOGIST IS SOMEONE WHO
STUDIES AND MEASURES EARTHQUAKES.

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LOOK; I FOUND A SEISMOGRAM
LOCATED NEAR US

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AT TIDEWATER COMMUNITY COLLEGE.

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LET'S CALL SEISMOLOGIST
MICHAEL LYLE.

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MICHAEL LYLE, TIDEWATER
COMMUNITY COLLEGE.

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SEISMOLOGY LAB.

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HELLO, MR. LYLE.

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TONY DE ANGELO, TREE
HOUSE DETECTIVE.

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I WOULD LIKE TO INQUIRE
IF YOUR INSTRUMENT PICKED

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UP A TREMOR A FEW MINUTES AGO.

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YES, OUR SEISMOGRAPH
DID DETECT SOMETHING.

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WAS IT AN EARTHQUAKE?

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MAYBE, BUT IT'S NOT CLEAR
FROM OUR READING HERE.

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OKAY, WE'LL CHECK BACK WITH YOU.

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MR. LYLE SAYS THERE'S A VERY
GOOD POSSIBILITY THERE'S BEEN

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AN EARTHQUAKE.

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MAYBE I EXAGGERATED A LITTLE BIT.

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WE ALL KNOW IT'S GOING TO
TAKE A LOT MORE RESEARCH

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TO SOLVE THIS PROBLEM.

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LOOK, HERE'S AN UPDATE FROM KSNN.

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I'M TED TUNE WITH THIS KID SCIENCE
NEWS NETWORK SPECIAL REPORT.

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STRANGE VIBRATIONS IN THE AREA
HAVE LOCAL RESIDENTS CONCERNED.

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WE'VE SENT OUR REPORTER, THE
USUALLY UNSHAKABLE I.M. LISSNING,

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OUTSIDE TO LOOK AROUND.

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I.M.?

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WELL, TED, I'M OUTSIDE.

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I DON'T SEE ANYTHING.

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WELL, I.M., DON'T GET SHAKEN UP.

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WHY DON'T YOU LOOK AROUND A LITTLE?

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MOSTLY BECAUSE IT'S
STARTING TO RAIN, TED.

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I'M COMING BACK IN.

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I.M.?

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I.M.?

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AND SHE CALLS HERSELF AN
INVESTIGATIVE JOURNALIST.

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ANYWAY THAT WAS I.M.
LISSNING WITH A LIVE -- OW!

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I'M GLAD WE'RE NOT THE ONLY
ONES WHO FELT THE VIBRATION.

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I THINK THERE'S SUFFICIENT
EVIDENCE TO SHOW THAT WE NEED

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TO LAUNCH AN OFFICIAL
INVESTIGATION.

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IN SIMPLE WORDS: LET'S
GO TO THE PROBLEM BOARD.

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WE KNOW WE FELT THE SHAKE.

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TCC RECORDED SOMETHING.

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AND KSNN REPORTED A
MYSTERIOUS VIBRATION.

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SINCE WE'RE PRETTY SURE IT'S
AN EARTHQUAKE, I THINK --

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WAIT A MINUTE; WE NEED TO DO A
LOT MORE RESEARCH BEFORE WE COME

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TO THAT CONCLUSION.

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OKAY, SO WE NEED TO DO MORE
RESEARCH ON EARTHQUAKES.

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THEY'LL SEE I'M CORRECT.

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WE NEED TO KNOW WHAT
ELSE CAUSES VIBRATIONS.

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I'M SORRY; WHAT DID YOU SAY?

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I WAS CALCULATING THE COST
OF REMODELING THE TREE HOUSE

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TO MAKE IT EARTHQUAKE-PROOF.

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TONY, WE DON'T EVEN KNOW
IF IT WAS AN EARTHQUAKE.

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AND WE SURE DON'T HAVE ENOUGH
INFORMATION TO KNOW HOW

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TO MAKE A TREE HOUSE
EARTHQUAKE-PROOF.

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I ESTIMATE THAT IT WOULD COST ABOUT
$20,000, AND IF WE TOOK OUT A LOAN

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WITH AN INTEREST RATE
OF 6.5% FOR 30 YEARS,

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THEN OUR PAYMENT WOULD BE...

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$128 A MONTH FOR PRINCIPAL
AND INTEREST.

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OKAY, OKAY.

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LET'S GET BACK TO THE PROBLEM.

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DR. D'S FROM CALIFORNIA.

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I'M SURE HE'S BEEN
IN A FEW EARTHQUAKES.

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HI, DR. D. HI, GUYS.

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WHAT'S UP?

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WE FELT OUR TREE HOUSE SHAKE
THIS MORNING AND WANTED

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TO KNOW WHAT HAPPENED.

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YEAH, I FELT SOMETHING TOO.

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WE THINK THAT IT MIGHT
HAVE BEEN AN EARTHQUAKE.

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BUT WE CAN'T PROVE IT YET.

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HAVE YOU EVER BEEN
IN AN EARTHQUAKE?

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YES, I HAVE, BUT IT DIDN'T FEEL THE
SAME AS WHAT I FELT THIS MORNING.

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SEE?

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I TOLD YOU IT WASN'T AN EARTHQUAKE.

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WAIT A MINUTE; ALL
EARTHQUAKES DON'T FEEL THE SAME.

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TO BEGIN UNDERSTANDING EARTHQUAKES,
YOU HAVE TO KNOW SOMETHING

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ABOUT THE STRUCTURE OF THE EARTH.

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THAT MAKES SENSE.

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WHAT CAN YOU TELL US?

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COME ON; LET ME SHOW YOU.

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OKAY.

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LET ME CUT THIS PEACH IN HALF.

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OKAY.

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BE CAREFUL.

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I WILL.

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THANKS.

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THIS WILL BE OUR EARTH.

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ONLY IT'S A LOT SMALLER.

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IT'S CALLED A SCALE MODEL.

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THE PIT IS LIKE THE
CORE OF THE EARTH.

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THE EARTH'S CORE IS ABOUT
HALF OF ITS DIAMETER.

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WHAT'S IT MADE OF?

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WE'VE NEVER BEEN THERE, BUT WE
THINK IT'S MADE OF IRON AND NICKEL.

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THE INNER PART OF
THE CORE IS SOLID.

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AND THE OUTER PART IS LIQUID.

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IT IS SO DENSE, IF WE
HAD A GALLON JUG FULL

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OF THE EARTH'S CORE MATERIAL,
IT WOULD WEIGH OVER 100 POUNDS.

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WAIT, DR. D. YOU LOST ME.

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HOW DO WE KNOW HOW BIG THE
CORE IS AND WHAT IT'S MADE

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OF IF WE'VE NEVER BEEN THERE?

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WELL, IT'S JUST A GUESS.

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YOU'RE KIDDING.

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ACTUALLY, IT'S A PRETTY GOOD GUESS
BASED UPON A LOT OF EVIDENCE.

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ONE OF THE BIGGEST CLUES WE HAVE
TO THE STRUCTURE OF THE EARTH COMES

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FROM OUR STUDY OF EARTHQUAKES.

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SO WE'RE USING EARTHQUAKES TO
HELP US UNDERSTAND EARTHQUAKES?

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THAT'S RIGHT; THE PART OF THE PEACH

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THAT YOU EAT IS CALLED
THE EARTH'S MANTLE.

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IT'S NOT AS DENSE AS THE
CORE, BUT IT'S MORE DENSE

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THAN WHAT'S ON THE OUTSIDE.

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WHAT'S THE OUTSIDE CALLED?

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IT'S CALLED THE CRUST.

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JUST LIKE THE CRUST OF A BREAD.

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VERY GOOD.

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LIKE THE SKIN OF A PEACH, THE
EARTH'S CRUST IS VERY THIN.

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THE CRUST UNDER THE OCEANS
IS TYPICALLY BETWEEN FIVE

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AND TEN KILOMETERS THICK.

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IT'S MADE OF A DARK
DENSE ROCK CALLED BASALT.

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CONTINENTAL CRUST IS BETWEEN
30 AND 70 KILOMETERS THICK.

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IT'S MADE OF A LIGHTER, LESS
DENSE ROCK LIKE THIS GRANITE.

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IS THERE A REASON WHY THE
EARTH IS LAYERED LIKE THIS?

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IT'S BECAUSE OF DENSITY.

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WATCH THIS EXPERIMENT OVER HERE.

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I'M GOING TO PUT THIS GREEN
TINTED WATER AND THIS SALAD OIL

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INTO THIS GRADUATED CYLINDER
AND THEN SHAKE THEM UP.

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LET'S SEE WHAT HAPPENS.

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THE SALAD OIL IS ON
TOP AND THEN THE WATER.

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LET'S PUT IN SOME MOTOR OIL.

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IT TURNS OUT, THE LEAST DENSE,

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WHICH IS MOTOR OIL,
FLOATS ON THE TOP.

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AND THE MOST DENSE,
WATER, SINKS TO THE BOTTOM.

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IT'S JUST LIKE THE EARLY HISTORY OF
THE EARTH, WHEN IT WAS ALL LIQUID.

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EARTH?

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LIQUID?

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STRANGE, BUT WHAT DOES THIS
HAVE TO DO WITH EARTHQUAKES?

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WHEN THE EARTH COOLED, THE
CRUST'S UPPER MANTLE BECAME RIGID

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AND BRITTLE.

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IT BROKE INTO ABOUT 12
SEGMENTS, WHICH WE CALL PLATES,

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KIND OF LIKE THIS
CRACKED BOILED EGG.

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THESE PLATES FLOAT ON THE MORE
DENSE BUT FLEXIBLE MANTLE BELOW,

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KIND OF LIKE THIS EGG WHITE.

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THESE PLATES ARE IN
CONTINUAL MOVEMENT.

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WOW, THIS IS TOO WEIRD.

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WHY DON'T WE FEEL THEM MOVING?

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THEY MOVE ABOUT AS FAST
AS YOUR FINGERNAILS GROW,

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WHICH IS ONLY A FEW
CENTIMETERS PER YEAR.

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BUT WE HAVE FOSSIL
EVIDENCE OF THIS MOVEMENT,

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WHICH WE CALL PLATE TECTONICS.

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ARE FOSSILS ALSO CLUES TO
UNDERSTANDING EARTHQUAKES?

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WELL, UH, YES.

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BUT, DR. D., AREN'T THERE OTHER
THINGS THAT COULD CAUSE VIBRATIONS?

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WELL, YES, THAT'S A GOOD QUESTION.

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ANYTHING THAT MAKES A VERY LOUD
SOUND CAN MAKE THINGS SHAKE

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A LITTLE.

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I WATCHED FIREWORKS ON THE 4TH.

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AND SOME WERE SO BIG,
I DID FEEL A VIBRATION.

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OH, NO, I'M LATE FOR
AN APPOINTMENT.

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WHY DON'T YOU STAY FOR A WHILE AND
DISCUSS THIS AMONGST YOURSELVES?

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OKAY.

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BYE, DR. D. LET'S GO OVER
THERE AND DISCUSS THIS.

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WHAT ABOUT A SONIC BOOM?

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WE LEARNED FROM THE
CASE OF THE BARKING DOG

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THAT A SONIC BOOM IS CREATED
WHEN A PLANE TRAVELS FASTER

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THAN THE SPEED OF SOUND.

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THAT'S IT; IT'S OUR HYPOTHESIS.

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IF THERE ARE AIRPLANES FLYING
FASTER THAN THE SPEED OF SOUND,

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THEN IT'LL CAUSE THE
GROUND TO VIBRATE.

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I DON'T THINK A SONIC
BOOM IS OUR HYPOTHESIS.

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I FORGOT MY DAD SAYS THAT THE
MILITARY NEVER FLIES FASTER

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THAN THE SPEED OF SOUND
OVER LAND ANYMORE.

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OH.

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I THOUGHT WE HAD IT.

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I'M GLAD RJ AND JACOB ARE GOING TO
CALIFORNIA FOR THE SCIENCE FAIR.

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MAYBE THEY CAN RESEARCH
EARTHQUAKES FOR US.

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WAIT A MINUTE.

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JACOB IS IN UTAH LOOKING
FOR FOSSILS.

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DR. D SAID THERE'S FOSSIL
EVIDENCE OF PLATE TECTONICS.

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I WONDER IF THAT'S THE SAME THING

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AS THE CONTINENTAL DRIFT
THEORY MY TEACHER TALKED ABOUT.

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MAYBE, BUT I DON'T UNDERSTAND
WHAT FOSSILS HAVE TO DO

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WITH PLATE TECTONICS
OR EARTHQUAKES.

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LET'S EMAIL JACOB AND SEE IF
HE CAN FIND THE ANSWERS FOR US.

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OKAY, I'LL DO IT.

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WE NEED TO DO SOME
RESEARCH ON OUR OWN.

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LET'S GO BACK TO THE
TREE HOUSE AND FIND

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OUT IF ANYONE ELSE HAS
FELT THE VIBRATIONS.

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[MUSIC]

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WOW, THIS IS AMAZING.

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THIS IS SO COOL.

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I CAN'T BELIEVE I'M
TOUCHING A DINOSAUR BONE.

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IS THIS REAL?

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YES, IT IS.

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HI, I'M DAVID WHITMAN.

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I'M A PARK RANGER HERE, AND THESE
BONES ARE 150 MILLION YEARS OLD.

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WOW.

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WANT TO SEE SOMETHING REALLY NEAT?

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YES.

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FOLLOW ME.

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AMAZING.

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I'VE NEVER SEEN ANYTHING LIKE THIS.

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DID YOU JUST PUT THESE
BONES IN THE WALL?

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NO, WE DIDN'T.

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EXCAVATION STARTED HERE
IN 1909 AND ENDED IN 1990.

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WE'RE DOING EXCAVATIONS ELSEWHERE,
BUT DURING THAT PERIOD OF TIME,

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WE UNCOVERED OVER
1,000 DINOSAUR BONES.

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HOW DID THEY ALL GET HERE?

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A LOT OF THEM DIED OF NATURAL
CAUSES, AND SOME OF THEM DIED

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WHEN THE RIVER DRIED UP AND
THEY DIDN'T HAVE ENOUGH WATER.

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I ALMOST FORGOT.

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MY FRIENDS WANTED TO FIND

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OUT IF FOSSILS ARE CLUES TOWARDS
PLATE TECTONICS AND EARTHQUAKES.

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I CAN HELP WITH THAT.

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I HAVE LOTS OF QUESTIONS.

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WHAT WAS THE ENVIRONMENT LIKE?

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WELL, THIS WAS THE BOTTOM OF A
RIVER, AND THE AREA WAS FLAT, ARID.

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THERE WERE A LOT OF PLANTS GROWING
ALONG THE RIVERS, AND OF COURSE,

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THAT'S WHERE THE DINOSAURS
CONGREGATED.

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ANOTHER QUESTION: HOW
WARM WAS THE CLIMATE?

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IT WAS HOT YEAR-ROUND, AND
THE REASON FOR THAT WAS

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THAT THIS AREA WAS A LOT CLOSER TO
THE EQUATOR 150 MILLION YEARS AGO.

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SO OVER THE LAST 150 MILLION
YEARS, BECAUSE OF PLATE TECTONICS,

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OR CONTINENTAL DRIFT, THIS AREA
HAS MOVED NORTHWARD 400 MILES.

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IT'S HARD TO BELIEVE THAT LAND
CAN ACTUALLY MOVE THAT FAR.

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I READ IN A BOOK ONCE THAT NO
ONE BELIEVED ALFRED WEGENER

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IN THE EARLY 1900S WHEN
HE PROPOSED THE IDEA KNOWN

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AS CONTINENTAL DRIFT.

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WHAT IS CONTINENTAL DRIFT?

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IT WAS A THEORY THAT STATED

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THAT THE CONTINENTS WERE ONCE ONE
LARGE LANDMASS CALLED PANGAEA.

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CLUES INDICATE THAT IN THE
LAST 200 MILLION YEARS,

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THE CONTINENTS HAVE MOVED
OR DRIFTED HORIZONTALLY

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TO THEIR CURRENT LOCATIONS.

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THE REVISED THEORY,
CALLED PLATE TECTONICS,

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EXPLAINS WHY CONTINENTS DRIFT.

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CONTINENTS ARE PART OF
LARGE PLATES THAT MOVE

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ACROSS THE EARTH'S SURFACE
AND BANG INTO ONE ANOTHER,

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CAUSING EARTHQUAKES AND
PUSHING UP MOUNTAIN RANGES.

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YOU MEAN FOSSIL CLUES?

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YES, FOSSILS CAN BE CLUES
TO CONTINENTAL DRIFT.

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FOR EXAMPLE, FOSSILS OF THE
REPTILE MESOSAURUS HAVE BEEN FOUND

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IN SOUTH AMERICA AND AFRICA.

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THESE REPTILES LIVED IN
FRESH WATER AND ON LAND,

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SO HOW COULD THEY BE FOUND

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ON DIFFERENT CONTINENTS
UNLESS THE CONTINENTS HAD

[00:12:45.269]
AT ONE TIME BEEN TOGETHER?

[00:12:47.149]
WELL, ANOTHER CLUE
CAN BE FOUND IN ROCKS.

[00:12:49.389]
STRANGE; HOW DO YOU KNOW THAT
A ROCK FOUND HERE IS THE SAME

[00:12:52.229]
AS ANOTHER ROCK FOUND
IN THE COLORADO PLATEAU?

[00:12:54.609]
WELL, WHY DON'T YOU COME WITH ME?

[00:12:55.609]
WE'LL TAKE A WALK AND FIND OUT.

[00:12:57.289]
GREAT.

[00:12:57.979]
WELL, JACOB, THIS
IS THE GREEN RIVER.

[00:13:02.789]
WOW; I KNOW I'VE NEVER SEEN
ANYTHING LIKE THIS BEFORE.

[00:13:06.229]
AS YOU CAN SEE, THERE'S LOTS OF
DIFFERENT KINDS OF ROCKS HERE.

[00:13:09.209]
ROCKS CAN BE CLUES
TO CONTINENTAL DRIFT.

[00:13:11.169]
BUT THAT'S NOT THE CASE HERE.

[00:13:12.179]
THEY ALL LOOK THE SAME TO ME.

[00:13:13.749]
HOW CAN YOU TELL THE DIFFERENCE
BETWEEN ROCK STRUCTURES?

[00:13:16.369]
WELL, IT'S LIKE A DETECTIVE STORY.

[00:13:17.989]
IF YOU LOOK OVER AT THIS
SANDSTONE OVER HERE,

[00:13:20.049]
IT LOOKS LIKE SIX OTHER TYPES
OF SANDSTONE THAT WE HAVE

[00:13:24.179]
IN THE MONUMENT, SO HOW
DO WE TELL THE DIFFERENCE?

[00:13:26.669]
WE HAVE TO LOOK AT THE ROCKS
THAT ARE ASSOCIATED WITH IT.

[00:13:29.619]
IF WE LOOK AT THE ROCK THAT'S
JUST BELOW THAT SANDSTONE,

[00:13:32.719]
WE CAN TELL IT'S THE
CHINLE FORMATION.

[00:13:34.669]
CHINLE LOOKS THE SAME ALL
ACROSS THE COLORADO PLATEAU.

[00:13:37.849]
SO NOW WE KNOW THE ROCK
ABOVE IT, THE SANDSTONE,

[00:13:40.069]
IS THE GLEN CANYON SANDSTONE.

[00:13:41.919]
DO YOU HAVE EARTHQUAKES HERE?

[00:13:43.649]
HERE EARTHQUAKES ARE CAUSED
BY MOUNTAIN-BUILDING FORCES.

[00:13:47.459]
SO 65 MILLION YEARS AGO, AS THESE
FLAT ROCKS WERE BEING PUSHED

[00:13:52.159]
UP INTO AN ARCH, EARTHQUAKES
OCCURRED.

[00:13:55.489]
IF YOU'VE EVER SEEN A CAKE IN AN
OVEN, IT'LL RISE AND RISE AND RISE,

[00:13:59.679]
BUT AT SOME POINT, WHAT HAPPENS
TO THE CAKE IF IT RISES TOO MUCH?

[00:14:03.209]
IT HAS TO SINK BACK
DOWN EVENTUALLY.

[00:14:04.819]
IT'LL COLLAPSE.

[00:14:05.809]
WELL, THE SAME THING
HAPPENS WITH ROCKS.

[00:14:08.209]
THEY'LL BE BENT, BUT THEY
CAN ONLY BEND SO FAR.

[00:14:10.799]
AND AT SOME POINT,
THEY'LL EVENTUALLY BREAK.

[00:14:13.639]
WHEN THE ROCKS BREAK, IS THAT
WHAT CAUSES AN EARTHQUAKE?

[00:14:16.099]
THAT'S CORRECT.

[00:14:16.629]
THAT BREAK IS THE FAULT LINE.

[00:14:18.499]
WHEN THE ROCKS MOVE ALONG THE FAULT
LINE, IT CREATES AN EARTHQUAKE.

[00:14:22.219]
WELL, HAVE I ANSWERED
ALL YOUR QUESTIONS?

[00:14:23.809]
YEAH, I CAN'T WAIT TO GO EMAIL
THE TREE HOUSE DETECTIVES.

[00:14:25.929]
WELL, DO YOU HAVE SOME TIME
TO GO LOOK FOR SOME FOSSILS?

[00:14:28.769]
SURE.

[00:14:29.469]
ALL RIGHT; LET'S GO.

[00:14:34.189]
SO WHAT'S UP?

[00:14:35.339]
WILL FOSSILS HELP THE TREE HOUSE
DETECTIVES SOLVE THE MYSTERY?

[00:14:37.969]
DO YOU THINK THE TREE HOUSE
DETECTIVES EXPERIENCED

[00:14:40.549]
AN EARTHQUAKE?

[00:14:41.109]
WHAT ELSE COULD HAVE
CAUSED THE VIBRATION?

[00:14:42.999]
STAY TUNED FOR THE
NEXT EXCITING CHAPTER

[00:14:49.179]
OF THE CASE OF THE SHAKY QUAKE.

[00:14:52.069]
TRY TO ANSWER THESE QUESTIONS
FOR THE NEXT EPISODE OF THE CASE

[00:14:56.629]
OF THE SHAKY QUAKE: WHAT
ARE THREE TYPES OF FAULTS?

[00:15:02.089]
WHAT ARE THREE TYPES
OF PLATE BOUNDARIES?

[00:15:06.319]
HOW DOES A SEISMOGRAPH MEASURE
THE SHAKING OF THE EARTH?

[00:15:12.889]
THAT WAS MY LAST CALL.

[00:15:16.789]
A LOT OF PEOPLE ON MY LIST
SAID THEY FELT A VIBRATION.

[00:15:19.949]
WE'VE RECEIVED A LOT OF EMAILS.

[00:15:21.659]
SOME PEOPLE SAY IT
FELT LIKE AN EXPLOSION.

[00:15:23.969]
LET'S EMAIL KSNN AND ASK
IF THERE WERE ANY REPORTS

[00:15:27.189]
OF AN EXPLOSION IN THE AREA.

[00:15:31.829]
MAYBE THIS IS OUR NEW HYPOTHESIS.

[00:15:33.879]
IF THERE WAS AN EXPLOSION, THEN IT
WOULD CAUSE THE GROUND TO VIBRATE.

[00:15:36.629]
I WAS TALKING TO ONE PERSON

[00:15:38.109]
WHO SAID IT FELT LIKE A
HEAVY TRUCK DRIVING BY.

[00:15:40.439]
THERE WAS ALSO AN EMAIL
DESCRIBING IT AS A SONIC BOOM,

[00:15:43.269]
BUT WE KNOW IT'S NOT A SONIC BOOM.

[00:15:45.249]
HERE COMES AN UPDATE FROM KSNN.

[00:15:47.719]
I WONDER IF THEY RECEIVED
OUR EMAIL.

[00:15:49.609]
THIS JUST IN.

[00:15:51.439]
AH, THE TREE HOUSE DETECTIVES
HAVE RAISED THIS QUESTION:

[00:15:54.579]
WERE THERE ANY EXPLOSIONS
THAT COULD ACCOUNT

[00:15:56.209]
FOR THE VIBRATIONS DETECTED
YESTERDAY AROUND NOON?

[00:15:59.519]
FOR THE ANSWER, WE GO TO
I.M. LISSNING, ON THE SCENE.

[00:16:02.729]
TED, WE'RE HERE AT THE SITE
OF THE NEW MEGABULK MART.

[00:16:06.439]
YESTERDAY, AT EXACTLY 12:00 NOON,

[00:16:08.549]
THE ORIGINAL THIS LITTLE PIGGY
BARBECUE RESTAURANT WAS DEMOLISHED

[00:16:12.319]
TO MAKE WAY FOR CONSTRUCTION.

[00:16:13.879]
WE HAVE THIS EXCLUSIVE VIDEOTAPE
SENT TO US BY MR. FLANGE LUGNUT.

[00:16:18.199]
THERE YOU HAVE IT, FOLKS.

[00:16:24.329]
THE TREMORS FELT YESTERDAY WERE
SIMPLY GIGANTIC EXPLOSIONS.

[00:16:28.269]
NOTHING TO WORRY ABOUT.

[00:16:29.849]
BACK TO YOU, TED.

[00:16:32.299]
I.M. IS OBVIOUSLY NOT A SCIENTIST.

[00:16:34.709]
DOESN'T SHE KNOW YOU JUST
CAN'T JUMP TO CONCLUSIONS?

[00:16:36.829]
YOU MUST DO RESEARCH.

[00:16:38.579]
COOL; THAT CONFIRMS MY HYPOTHESIS.

[00:16:41.349]
LOOK AT OUR CLOCK.

[00:16:42.329]
IT STOPPED AT NOON, SO THEY
MUST BE THE SAME EXPLOSIONS.

[00:16:45.739]
THAT'S WHAT I CALL USING
MY OBSERVATION SKILLS.

[00:16:48.399]
OBSERVATION IS AN IMPORTANT
PART OF THE SCIENTIFIC PROCESS.

[00:16:51.599]
YOU'RE LIKE I.M.,
JUMPING TO CONCLUSIONS.

[00:16:54.029]
I STILL THINK IT COULD
BE AN EARTHQUAKE,

[00:16:55.229]
AND I DON'T WANT TO
TAKE ANY CHANCES.

[00:16:57.139]
MAYBE TONY IS RIGHT.

[00:16:58.659]
JACOB SAID IN HIS EMAIL FROM
THE DINOSAUR NATIONAL MONUMENT

[00:17:02.049]
THAT THE MOVEMENT OF THE
EARTH'S CRUST AND UPPER MANTLE,

[00:17:04.479]
CALLED PLATE TECTONICS,
CAUSES EARTHQUAKES.

[00:17:06.879]
I'M READING MORE ABOUT PLATE
TECTONICS IN MY EARTH SCIENCE BOOK.

[00:17:10.139]
IT SAYS THAT CRUSTAL MOVEMENT
OCCURS ALONG FAULT LINES.

[00:17:13.249]
MAYBE WE SHOULD LEARN
MORE ABOUT FAULTS.

[00:17:15.329]
LET'S DO AN INTERNET SEARCH.

[00:17:17.129]
I'LL GO TO A SEARCH ENGINE AND
TYPE IN THE WORDS "EARTHQUAKE,"

[00:17:20.349]
"FAULTS," AND "VIRGINIA."

[00:17:23.069]
[00:17:25.839]
FINDING ANYTHING?

[00:17:27.269]
THE SEARCH SHOWS SEVERAL WEBSITES

[00:17:28.779]
FOR THE UNITED STATES
GEOLOGICAL SURVEY,

[00:17:31.029]
OR U.S.G.S. LET'S GO
TO THEIR HOMEPAGE.

[00:17:33.969]
I HEARD THEY MONITOR
EARTHQUAKES ALL

[00:17:35.239]
OVER THE U.S. IT SOUNDS LIKE
THEY'D BE ABLE TO HELP US.

[00:17:38.809]
I CLICKED ON CALIFORNIA ON THE MAP,

[00:17:40.359]
AND THEY HAVE AN OFFICE
IN SAN FRANCISCO.

[00:17:42.979]
LET'S EMAIL JACOB AND
RJ AND ASK THEM TO TALK

[00:17:48.889]
TO THE U.S.G.S. READY, RJ?

[00:17:50.739]
MM-HMM.

[00:17:51.779]
HEY, GUYS, I'M HERE AT
THE SAN ANDREAS FAULT,

[00:17:56.019]
NEAR WHERE THE EPICENTER

[00:17:56.919]
OF THE 1906 SAN FRANCISCO
EARTHQUAKE OCCURRED.

[00:17:59.979]
HI, GUYS.

[00:18:00.779]
YOU MUST BE THE TREE
HOUSE DETECTIVES.

[00:18:02.049]
HOW CAN I HELP YOU?

[00:18:02.919]
OUR FRIENDS IN VIRGINIA FELT
A VIBRATION THE OTHER DAY,

[00:18:05.209]
AND THEY WANTED TO FIND OUT
IF IT WAS AN EARTHQUAKE.

[00:18:07.639]
THEY SAID WE NEED TO
LEARN ABOUT FAULTS.

[00:18:10.049]
WELL, A FAULT IS A WEAK
ZONE IN THE EARTH'S CRUST

[00:18:12.159]
WHERE THE ROCK LAYERS HAVE
BROKEN AND SLIPPED APART.

[00:18:14.289]
WOULD YOU LIKE TO SEE
THE SAN ANDREAS FAULT?

[00:18:17.089]
RJ, BE SURE AND GET ME ON CAMERA.

[00:18:24.659]
[00:18:26.029]
OKAY.

[00:18:26.939]
SO WHERE'S THE FAULT LINE?

[00:18:28.649]
YOU CAN SEE IT HERE.

[00:18:30.339]
SEE THE LINE...

[00:18:32.139]
[00:18:33.159]
AS IT GOES UP THE WALL?

[00:18:34.499]
ARE THERE DIFFERENT
KINDS OF FAULTS?

[00:18:37.589]
YES, THERE'S THREE KINDS OF FAULTS.

[00:18:39.329]
ONE'S CALLED A NORMAL FAULT.

[00:18:40.529]
THAT'S WHEN THE FAULT
IS AT AN ANGLE.

[00:18:42.409]
THE TOP BLOCK IS CALLED
THE HANGING WALL.

[00:18:45.189]
THAT MOVES DOWN RELATIVE TO THE
LOWER BLOCK, CALLED THE FOOTWALL.

[00:18:48.559]
THIS HAPPENS WHERE
THERE'S EXTENSION

[00:18:50.159]
IN THE CRUST, AND IT PULLS APART.

[00:18:51.619]
IS THERE AN ABNORMAL FAULT?

[00:18:53.309]
WELL, THERE'S NOT
REALLY AN ABNORMAL FAULT,

[00:18:54.999]
BUT THERE IS A FAULT THAT'S
OPPOSITE OF A NORMAL FAULT,

[00:18:57.479]
AND THAT'S WHEN THE HANGING
WALL BLOCK MOVES UP RELATIVE

[00:19:00.219]
TO THE FOOTWALL BLOCK,
AND THIS HAPPENS

[00:19:02.159]
WHERE THERE'S CRUSTAL COMPRESSION.

[00:19:04.409]
THOSE FAULTS ARE CALLED
REVERSE FAULTS OR THRUST FAULTS.

[00:19:07.089]
WHAT'S THE LAST TYPE OF FAULT?

[00:19:08.189]
THE LAST KIND OF FAULT IS
CALLED A STRIKE-SLIP FAULT.

[00:19:10.739]
THAT'S LIKE WHERE WE ARE NOW
ON THE SAN ANDREAS FAULT.

[00:19:13.149]
WE LEARNED THAT THE EARTH'S
LITHOSPHERE IS BROKEN

[00:19:14.939]
UP INTO PLATES, AND THE
PLATES' MOVEMENT IS WHAT

[00:19:17.209]
CAUSES EARTHQUAKES.

[00:19:18.519]
BUT I DON'T GET IT.

[00:19:19.359]
ARE PLATES AND FAULTS
THE SAME THING?

[00:19:21.729]
WELL, MOVING PLATES GRIND
AND SCRAPE AGAINST EACH OTHER

[00:19:24.089]
AT THEIR EDGES, AND THOSE
EDGES WE CALL PLATE BOUNDARIES,

[00:19:27.689]
AND PLATE BOUNDARIES ARE
USUALLY MADE UP OF MANY FAULTS.

[00:19:30.099]
ARE THERE DIFFERENT KINDS
OF PLATE BOUNDARIES,

[00:19:31.809]
LIKE DIFFERENT KINDS OF FAULTS?

[00:19:34.049]
YES, THERE'S ALSO THREE OF THOSE.

[00:19:35.839]
DIVERGENT BOUNDARIES ARE WHERE
THE CRUST IS BEING PULLED APART.

[00:19:39.099]
THIS CAN FORM NEW CRUST
OR CAUSE RIFT VALLEYS

[00:19:41.749]
AND EVEN MAKE VOLCANOES.

[00:19:43.539]
THE PULLING APART CAN HAPPEN AT
ABOUT TWO CENTIMETERS A YEAR.

[00:19:46.209]
THAT'S NOT VERY MUCH.

[00:19:47.739]
IT MUST MOVE REALLY SLOWLY.

[00:19:49.499]
YEAH, THEY DO.

[00:19:50.409]
AND A CONVERGENT BOUNDARY IS
WHERE THE PLATES CRASH HEAD-ON.

[00:19:53.079]
I HOPE THOSE BOUNDARIES
MOVE SLOWLY TOO.

[00:19:55.889]
YEAH, THEY DO.

[00:19:56.579]
THEY ONLY MOVE A FEW CENTIMETERS
A YEAR, AND BECAUSE IT'S SLOW,

[00:19:59.469]
IT CAN TAKE MILLIONS OF
YEARS FOR THEM TO FORM.

[00:20:01.839]
WHEN THE PLATES COLLIDE, SOMETIMES
YOU CAN GET LARGE MOUNTAIN CHAINS,

[00:20:04.869]
LIKE THE HIMALAYAS.

[00:20:06.679]
WOW.

[00:20:07.239]
NOW I'M STARTING TO UNDERSTAND WHY
THE EARTH IS SHAPED THE WAY IT IS.

[00:20:10.339]
THE LAST BOUNDARY IS CALLED
A TRANSFORM BOUNDARY.

[00:20:12.829]
IT'S WHEN PLATES SLIDE
PAST EACH OTHER,

[00:20:14.599]
LIKE THE SAN ANDREAS FAULT HERE.

[00:20:16.349]
DOES THAT MEAN CALIFORNIA'S
NOT GONNA BREAK OFF

[00:20:18.449]
AND FALL INTO THE OCEAN?

[00:20:19.669]
NO, THAT'S A COMMON MISCONCEPTION.

[00:20:21.499]
ACTUALLY, LOS ANGELES MAY
SOMEDAY BE NEXT TO SAN FRANCISCO,

[00:20:24.499]
BUT THAT'LL PROBABLY
TAKE TEN MILLION YEARS.

[00:20:26.499]
THAT'S A LONG TIME.

[00:20:27.599]
I DON'T THINK WE HAVE ANY
BOUNDARIES IN VIRGINIA.

[00:20:30.509]
DO EARTHQUAKES OCCUR ANYWHERE ELSE?

[00:20:32.219]
YEAH, A FEW EARTHQUAKES OCCUR
IN THE MIDDLE OF PLATES,

[00:20:34.539]
CALLED INTERPLATE EARTHQUAKES.

[00:20:35.989]
AND IN 1886, THERE
WAS A LARGE EARTHQUAKE

[00:20:39.199]
IN CHARLESTON, SOUTH CAROLINA.

[00:20:40.759]
SOUTH CAROLINA IS NEAR VIRGINIA.

[00:20:42.709]
MAYBE THEY DID HAVE AN EARTHQUAKE.

[00:20:44.109]
DO YOU WANT TO TRY MAKING
YOUR OWN EARTHQUAKE?

[00:20:46.029]
WILL IT KNOCK HOUSES DOWN?

[00:20:47.449]
NO, IT WON'T BE A REAL EARTHQUAKE.

[00:20:48.939]
IT'LL JUST BE A SIMULATION
OF A VERY SMALL ONE.

[00:20:51.119]
LET'S GO.

[00:20:51.429]
I HAVE A SETUP HERE THAT WE'RE
GONNA PRETEND IS LIKE THE

[00:20:54.459]
EARTH'S PLATES MOVING.

[00:20:55.699]
SO YOU'RE GONNA TURN THE CRANK
AND APPLY STRESS TO THESE BLOCKS.

[00:20:59.149]
YOU'RE GONNA CAUSE A
FORCE TO BE PULLING THEM.

[00:21:01.819]
AND THIS IS GOING TO BE THE
EQUIVALENT OF ONE PLATE,

[00:21:04.149]
AND THIS IS GOING
TO BE THE EQUIVALENT

[00:21:05.249]
OF ANOTHER CRUSTAL PLATE.

[00:21:06.829]
AND WATCH AS YOU ADD MORE
AND MORE STRESS AND SEE

[00:21:10.029]
IF YOU CAN GET AN EARTHQUAKE.

[00:21:17.229]
RJ?

[00:21:17.389]
WOW.

[00:21:17.979]
WAS THAT AN EARTHQUAKE?

[00:21:18.979]
YEAH.

[00:21:19.039]
NOW THAT'S MY KIND OF EARTHQUAKE.

[00:21:22.099]
THIS HAS REALLY BEEN HELPFUL.

[00:21:24.149]
THANK YOU.

[00:21:24.829]
SURE.

[00:21:25.089]
EMAIL ME IF YOU HAVE
ANY MORE QUESTIONS.

[00:21:27.179]
OKAY.

[00:21:30.229]
DONE.

[00:21:31.069]
DO YOU KNOW WHAT KIND
OF DINOSAUR THIS IS?

[00:21:36.609]
YEAH, IT'S A TYRANNOSAURUS REX.

[00:21:39.179]
I'M BAD.

[00:21:40.709]
WHAT'S GOING ON?

[00:21:41.839]
I DON'T KNOW, BUT I DON'T LIKE IT.

[00:21:43.669]
NOW, THAT WAS AN EARTHQUAKE.

[00:21:44.989]
HOW DO YOU KNOW?

[00:21:46.169]
JUST FELT LIKE ONE.

[00:21:47.129]
MAYBE IT WAS ANOTHER
CONSTRUCTION BLAST.

[00:21:49.409]
I'LL CALL KSNN.

[00:21:50.409]
DO YOU THINK AN EARTHQUAKE
COULD AFFECT THE STOCK MARKET?

[00:21:54.299]
LISTEN, RIGHT NOW, WE
HAVE BIGGER PROBLEMS.

[00:21:58.659]
KSNN JUST CONFIRMED THAT THERE WERE
NO REPORTS OF A CONSTRUCTION BLAST.

[00:22:02.629]
I DON'T KNOW, BUT WE NEED
TO ORGANIZE OUR THOUGHTS.

[00:22:05.109]
LET'S GO TO THE PROBLEM BOARD.

[00:22:06.369]
WE KNOW THAT WE'VE
HAD A FEW TREMORS.

[00:22:08.629]
WE KNOW THAT KSNN SAID THE
FIRST OF THE TREMORS WAS

[00:22:11.489]
FROM A CONSTRUCTION BLAST,
AND THE SECOND WAS NOT.

[00:22:14.249]
WE KNOW THAT THE STRUCTURE OF
THE EARTH IS DIVIDED INTO LAYERS.

[00:22:17.859]
WE ALSO KNOW THE EARTH'S
CRUST IS DIVIDED INTO PLATES,

[00:22:20.659]
AND THESE PLATES CAN MOVE
AND CAUSE EARTHQUAKES.

[00:22:23.329]
OH, YEAH; REMEMBER THAT
EMAIL FROM JACOB AND RJ?

[00:22:25.929]
THEY TALKED TO MISS HEIDI STENNER,
WHO CONFIRMED THAT THERE ARE A LOT

[00:22:29.059]
OF FAULTS IN THE EARTH'S CRUST.

[00:22:30.659]
NOW WE NEED TO KNOW IF THERE
ARE ANY FAULTS IN THE AREA

[00:22:32.469]
THAT COULD CAUSE TREMORS.

[00:22:33.539]
I THINK WE NEED TO VISIT THE
SEISMOLOGIST AT TCC TO FIND

[00:22:36.719]
OUT IF THERE ARE ANY
FAULTS IN OUR AREA.

[00:22:38.769]
WE CAN ALSO SEE IF THEY RECORDED
ANOTHER TREMOR THIS TIME.

[00:22:41.219]
LET'S GET UP AND GO.

[00:22:43.089]
I THINK WE'RE CLOSER TO FIGURING

[00:22:44.529]
OUT IF THIS VIBRATION
WAS AN EARTHQUAKE.

[00:22:46.749]
THIS MUST BE A SEISMOGRAPH.

[00:22:50.039]
I RECOGNIZE IT FROM TV.

[00:22:52.549]
I WONDER IF MR. LYLE IS HERE.

[00:22:55.259]
OH, HI, MR. LYLE.

[00:22:56.989]
HI, GIRLS.

[00:22:58.269]
WE'RE THE TREE HOUSE DETECTIVES.

[00:22:59.829]
WE CALLED YOU ABOUT
AN EARLIER TREMOR.

[00:23:01.449]
NOW WE NEED TO KNOW IF
YOU'VE RECORDED ANYTHING

[00:23:03.299]
ON YOUR SEISMOGRAPH TODAY.

[00:23:04.739]
AS A MATTER OF FACT, WE DID,
AND HERE IT IS RIGHT HERE.

[00:23:07.579]
WOW; WAS THAT AN EARTHQUAKE?

[00:23:09.799]
CAN YOU REALLY TELL
FROM THAT READING?

[00:23:11.519]
WE'RE NOT SURE AT THIS TIME.

[00:23:13.269]
WE'RE ANALYZING THE DATA, BECAUSE
NOT ALL DETECTED TREMORS ARE

[00:23:15.939]
RELATED TO EARTHQUAKES.

[00:23:17.089]
ANALYZING YOUR DATA
IS VERY IMPORTANT

[00:23:19.239]
IN THE SCIENTIFIC PROCESS.

[00:23:20.419]
IN THIS AREA, MOST OF THE TREMORS
WE DETECT ARE RELATIVELY SMALL,

[00:23:24.249]
TRAVEL A SHORT DISTANCE, AND
GENERALLY OCCUR BETWEEN 8:00 A.M.

[00:23:27.369]
AND 5:00 P.M. THIS SUGGESTS
THEY'RE CAUSED BY HUMAN CONDITIONS.

[00:23:31.049]
WE LEARNED THAT THERE
ARE EARTHQUAKES

[00:23:32.429]
BECAUSE THERE ARE BREAKS
IN THE EARTH'S CRUST

[00:23:34.049]
THAT ARE MOVING ALONG FAULT LINES.

[00:23:35.399]
ARE THERE FAULTS IN VIRGINIA?

[00:23:36.909]
YES, THERE ARE NUMEROUS
FAULTS IN VIRGINIA,

[00:23:38.739]
BUT NOT ALL OF THEM
ARE ACTIVE FAULTS.

[00:23:41.689]
WOW; DOES VIRGINIA HAVE
A LOT OF EARTHQUAKES?

[00:23:44.339]
NOT REALLY.

[00:23:45.109]
IN THE LAST 30 YEARS, THERE HAVE
BEEN MORE THAN 150 EARTHQUAKES

[00:23:48.709]
IN VIRGINIA, BUT THESE ARE
LOW-INTENSITY EVENTS SELDOM FELT

[00:23:52.159]
BY PEOPLE.

[00:23:52.559]
WHERE DO MOST VIRGINIA
EARTHQUAKES OCCUR?

[00:23:54.949]
MOST SEEM TO OCCUR IN THE CENTRAL
AND WESTERN PART OF THE STATE.

[00:23:58.149]
WE DON'T LIVE NEAR
THAT PART OF THE STATE.

[00:24:00.259]
HMM.

[00:24:00.319]
WHAT OTHER THINGS COULD CAUSE
A READING ON YOUR SEISMOGRAPH?

[00:24:04.129]
ANYTHING THAT SHAKES THE
GROUND CAN BE RECORDED.

[00:24:06.439]
HERE'S A SEISMOGRAM,
OR PAPER RECORDING,

[00:24:08.589]
OF THAT CONSTRUCTION
BLAST FROM THE OTHER DAY.

[00:24:10.759]
IT LOOKS SO SMALL, BUT IT
CREATED SUCH A BIG BOOM.

[00:24:14.039]
OUR SEISMOMETER MEASURING
INSTRUMENT IS VERY SENSITIVE.

[00:24:16.619]
THIS IS WHAT AUTOMOBILE
TRAFFIC AND EVEN STORM WAVES

[00:24:19.509]
FROM THE BEACH LOOK LIKE.

[00:24:21.789]
THAT'S PRETTY NEAT.

[00:24:22.669]
THE SEISMOMETER IS
BURIED 70 METERS BELOW US.

[00:24:25.299]
IT IS SO SENSITIVE THAT WE HAD
TO PUT IT IN A VERY QUIET PLACE.

[00:24:29.029]
THAT'S WAY DOWN THERE.

[00:24:30.989]
WOULD YOU LIKE TO SEE A SEISMOGRAM
OF A CONFIRMED EARTHQUAKE?

[00:24:34.169]
YES.

[00:24:34.709]
WHAT ARE THE LITTLE SQUARE MARKS?

[00:24:36.689]
HOW CAN YOU FIGURE ANYTHING OUT?

[00:24:39.019]
YOU GUYS HAVE LOTS OF QUESTIONS.

[00:24:42.219]
WELL, EVERY SQUARE
TICKS OFF A MINUTE.

[00:24:44.389]
OH, SO YOU CAN TELL WHEN
AN EARTHQUAKE HAPPENS

[00:24:46.839]
AND HOW LONG IT LASTS.

[00:24:48.459]
THAT'S CORRECT.

[00:24:49.379]
TO MOST PEOPLE, THESE LOOK LIKE
SQUIGGLY LINES, BUT WHEN I LOOK

[00:24:52.029]
AT THEM, I SEE "S AND "P" WAVES.

[00:24:54.059]
LIKE SOUND WAVES.

[00:24:55.509]
THEY'RE SOMEWHAT LIKE SOUND WAVES.

[00:24:57.339]
THESE ARE VIBRATIONS IN THE EARTH.

[00:24:59.829]
THAT DOESN'T LOOK AT ALL
LIKE THE TREMOR WE FELT.

[00:25:02.009]
DOES THAT MEAN IT
WASN'T AN EARTHQUAKE?

[00:25:04.139]
NOT NECESSARILY.

[00:25:05.039]
A LOCAL EARTHQUAKE COULD LOOK
VERY DIFFERENT FROM THIS.

[00:25:07.649]
WE NEED ONE OF THESE
IN OUR TREE HOUSE.

[00:25:09.439]
THEN WE COULD MEASURE
THE NEXT TREMOR.

[00:25:11.109]
I THINK DR. D IS DOWN THE
HALL, BUILDING A SEISMOGRAPH.

[00:25:13.619]
DR. D?

[00:25:14.109]
A SEISMOGRAPH?

[00:25:16.269]
WE'RE THERE.

[00:25:16.649]
HI, DR. D. HI, KIDS.

[00:25:22.009]
IS THIS THE SEISMOGRAPH
YOU'RE BUILDING?

[00:25:23.669]
THAT'S RIGHT.

[00:25:24.259]
I'M ALMOST FINISHED.

[00:25:26.069]
THIS SEISMOGRAPH IS NOT VERY
SENSITIVE, BUT IT DOES WORK.

[00:25:31.489]
IT MEASURES HORIZONTAL MOTION.

[00:25:33.119]
SO YOU ACTUALLY USE A
PEANUT CAN AND AN OLD BRICK?

[00:25:36.489]
YEAH, SURE.

[00:25:37.289]
LET ME START FROM THE BEGINNING.

[00:25:38.819]
A SEISMOGRAPH MEASURES
THE SHAKING OF THE EARTH.

[00:25:40.849]
TO MEASURE THE SHAKING, WE TAKE
ADVANTAGE OF NEWTON'S FIRST LAW.

[00:25:44.039]
I THINK I REMEMBER; ISN'T
IT ALSO CALLED INERTIA?

[00:25:47.639]
I'M IMPRESSED.

[00:25:48.469]
SO WHAT IS INERTIA?

[00:25:50.289]
IT MEANS THAT WHEN AN OBJECT
IS AT REST, IT STAYS AT REST.

[00:25:53.189]
AND WHEN AN OBJECT IS IN
MOTION, IT REMAINS IN MOTION.

[00:25:55.849]
THAT'S RIGHT.

[00:25:56.969]
THIS BRICK HAS A LOT OF INERTIA,
SO IT'S HARD TO GET MOVING.

[00:25:59.969]
WHEN THE EARTH SHAKES, THE BASE OF
THIS SEISMOGRAPH WILL ALSO SHAKE.

[00:26:04.449]
BUT THE BRICK, WHICH IS NOT
TIED TO THE BASE, WILL NOT.

[00:26:07.789]
THE PEN OVER THERE
RECORDS THE VIBRATION.

[00:26:10.049]
CAN WE TRY IT?

[00:26:11.199]
SURE.

[00:26:11.549]
LET'S MAKE AN EARTHQUAKE
BY SHAKING THE TABLE.

[00:26:13.389]
IT REALLY WORKS.

[00:26:15.419]
LOOK AT THE WAVES.

[00:26:17.779]
DID WE DO THAT?

[00:26:18.819]
YOU SURE DID.

[00:26:20.589]
HERE'S A DIFFERENT
KIND OF SEISMOGRAPH.

[00:26:22.839]
IT MEASURES VERTICAL MOTION.

[00:26:26.079]
IT LOOKS REALLY DIFFERENT.

[00:26:27.999]
BECAUSE IT HAS INERTIA, THIS
MAGNET HANGING ON THIS SPRING TENDS

[00:26:31.489]
TO STAND STILL WHEN THE
TABLE MOVES UP AND DOWN.

[00:26:34.699]
A MAGNET MOVING THROUGH A COIL
OF WIRE PRODUCES ELECTRICITY,

[00:26:37.349]
WHICH THIS METER RECORDS.

[00:26:38.919]
CAN WE TRY THIS ONE TOO?

[00:26:42.429]
SURE.

[00:26:42.989]
ALL RIGHT.

[00:26:43.839]
BUT HERE'S A SENSITIVE SEISMOMETER
I'VE HOOKED UP TO THIS COMPUTER.

[00:26:47.359]
THAT GRAPH LOOKS LIKE THE
SEISMOGRAM THAT MR. LYLE SHOWED US.

[00:26:56.359]
[00:26:57.019]
THE HARDER I HIT THE TABLE,

[00:27:01.029]
THE LARGER THE SIGNALS;
THIS IS REALLY COOL.

[00:27:03.219]
AND LOOK AT HOW IT
VIBRATES UP AND DOWN.

[00:27:06.039]
BECAUSE IT PRODUCES AN ELECTRIC
SIGNAL, IT IS EASY TO AMPLIFY.

[00:27:08.999]
EVEN A SMALL VIBRATION CAN
BE SHOWN ON THE COMPUTER.

[00:27:12.059]
NOW, I CAN'T LOAN YOU THIS DEVICE,

[00:27:14.599]
BUT WHY DON'T YOU TAKE MY WOODEN
SEISMOGRAPH BACK TO THE TREE HOUSE

[00:27:18.559]
AND SEE IF YOU CAN
RECORD ANOTHER TREMOR?

[00:27:20.779]
I HAVE A FRIEND AT NASA'S JET
PROPULSION LABORATORY IN PASADENA,

[00:27:24.049]
CALIFORNIA, WHO USES SATELLITES

[00:27:26.059]
TO MEASURE THE MOTION
OF THE EARTH'S CRUST.

[00:27:28.079]
YOU MIGHT WANT TO TALK
TO HER IN YOUR QUEST

[00:27:29.829]
TO BECOME EARTHQUAKE EXPERTS.

[00:27:36.159]
SO WHAT'S UP?

[00:27:36.829]
WILL THE SEISMOGRAPH HELP THE TREE
HOUSE DETECTIVES SOLVE THE MYSTERY?

[00:27:40.399]
WILL SATELLITES PROVIDE THE ANSWER?

[00:27:42.319]
STAY WITH US FOR THE
NEXT EXCITING CHAPTER

[00:27:47.019]
OF THE CASE OF THE SHAKY QUAKE.

[00:27:54.269]
CAN YOU ANSWER THESE QUESTIONS?

[00:27:56.549]
WHAT IS GPS, AND HOW IS IT USED?

[00:28:01.319]
WHAT ARE SMP WAVES,
AND HOW DO THEY DIFFER?

[00:28:04.329]
[00:28:05.669]
WHAT ARE TWO TYPES OF SCALES
USED TO MEASURE EARTHQUAKES?

[00:28:09.569]
[00:28:11.709]
I'M NOT SO BAD.

[00:28:12.309]
WHAT?

[00:28:12.439]
I'M LOOKING AT MY SOCCER JOURNAL,
AND SO FAR IN MY SOCCER CAREER,

[00:28:16.779]
I'VE SCORED 282 GOALS
AND ATTEMPTED 670.

[00:28:20.409]
THAT MEANS THAT MY SHOOTING
PERCENTAGE IS 42.1 PERCENT.

[00:28:24.779]
THAT MEANS I SCORE A
GOAL ABOUT HALF THE TIME.

[00:28:27.779]
SEE?

[00:28:28.009]
YOU DO USE MATH IN SPORTS.

[00:28:29.269]
OKAY, GETTING BACK TO BUSINESS,
THIS IS A HOMEMADE SEISMOGRAPH

[00:28:32.649]
ON LOAN FROM DR. D.
NOW WE'LL BE PREPARED

[00:28:34.889]
IN CASE THERE'S ANOTHER TREMOR.

[00:28:35.839]
I DON'T KNOW IF I WOULD
DEPEND ON THAT MACHINE.

[00:28:38.349]
IT LOOKS RATHER WEAK.

[00:28:39.329]
BUT MAYBE THIS INSTRUMENT ISN'T
THE ONLY WAY TO DETECT EARTHQUAKES.

[00:28:43.499]
REMEMBER DR. D TOLD US ABOUT J.P.L.

[00:28:45.209]
AND HOW THEY MONITOR CRUSTAL
MOVEMENT USING SATELLITES.

[00:28:48.449]
HE GAVE ME THE NAME OF HIS
FRIEND, ANDREA DONNELLAN.

[00:28:50.979]
LET'S DIAL HER UP.

[00:28:52.849]
HI, WE'RE THE TREE
HOUSE DETECTIVES.

[00:28:54.899]
DR. D SAID THAT YOU MIGHT
BE ABLE TO HELP US LEARN

[00:28:56.669]
ABOUT HOW CRUSTAL
MOVEMENT IS MONITORED.

[00:28:58.689]
I SURE CAN; I USE GPS TO
MEASURE CRUSTAL MOVEMENTS.

[00:29:02.119]
I'VE HEARD OF GPS, BUT I'M NOT
SURE WHAT IT IS OR HOW IT WORKS.

[00:29:05.809]
GPS STANDS FOR GLOBAL
POSITIONING SYSTEM.

[00:29:08.539]
IT'S A SATELLITE NAVIGATION SYSTEM
CONSISTING OF 24 SATELLITES.

[00:29:12.259]
PILOTS AND BOATERS USE
IT TO PLOT THEIR COURSE.

[00:29:14.849]
GEOLOGISTS USE IT TO
ACCURATELY MEASURE THE POSITION

[00:29:17.189]
OF MONITORING STATIONS.

[00:29:19.039]
HERE IN SOUTHERN CALIFORNIA, WE
HAVE A NETWORK OF 250 GPS STATIONS.

[00:29:23.429]
HOW DOES KNOWING THE POSITION
OF THESE STATIONS HELP YOU

[00:29:25.839]
TO UNDERSTAND EARTHQUAKES?

[00:29:27.599]
IT SHOWS US THE STRETCHING,
WARPING,

[00:29:29.169]
AND MOVEMENT OF THE CRUST
THAT'S NOT REALLY NOTICEABLE.

[00:29:31.789]
HOW ACCURATE IS IT?

[00:29:33.979]
WE CAN MEASURE POINTS ON THE EARTH
TO THREE MILLIMETERS HORIZONTALLY

[00:29:37.039]
AND SEVEN MILLIMETERS VERTICALLY.

[00:29:39.009]
THAT'S SMALL.

[00:29:39.489]
HOW DOES THAT DIFFER FROM
WHAT A SEISMOGRAPH DOES?

[00:29:42.499]
A SEISMOGRAPH MEASURES
EARTHQUAKES WHEN THEY HAPPEN.

[00:29:45.349]
WITH GPS, WE CAN ACTUALLY MEASURE
THE QUIET MOTIONS OF THE EARTH.

[00:29:48.349]
THAT MEANS WE CAN MEASURE
THE STRAIN BUILDUP AS WELL

[00:29:50.779]
AS THE EARTHQUAKES THEMSELVES.

[00:29:52.109]
IT IS PARTICULARLY USEFUL IN
IDENTIFYING ACTIVE BLIND FAULTS.

[00:29:55.639]
WHAT'S A BLIND FAULT?

[00:29:57.379]
A BLIND FAULT IS A BREAK IN
THE CRUST THAT DOESN'T BREAK

[00:29:59.599]
THROUGH THE SURFACE ANYWHERE.

[00:30:01.309]
NATURALLY, THESE FAULTS ARE
NOT EASY TO LOCATE OR STUDY

[00:30:03.799]
AND MIGHT GO UNNOTICED
WITHOUT GPS TECHNOLOGY.

[00:30:06.859]
THAT'S PRETTY IMPRESSIVE.

[00:30:08.399]
I'M GLAD WE HAVE THE
ABILITY TO SEE THESE FAULTS.

[00:30:11.159]
WOULD THIS TECHNOLOGY HELP
US TO PREDICT EARTHQUAKES?

[00:30:13.779]
WE ARE INTEGRATING DATA FROM
A LOT OF DIFFERENT SOURCES

[00:30:16.029]
INTO COMPUTER SIMULATIONS.

[00:30:17.759]
THESE SIMULATIONS SHOULD HELP US
UNDERSTAND THE EARTHQUAKE PROCESS.

[00:30:20.719]
WE HOPE TO EVENTUALLY BE ABLE
TO DO SHORT-TERM FORECASTING.

[00:30:23.819]
CAN YOU GIVE US AN EXAMPLE?

[00:30:25.629]
BY MONITORING ALL THE STATIONS,

[00:30:27.029]
WE CAN FIND OUT WHICH FAULTS
HAVE THE GREATEST SLIP RATE.

[00:30:29.669]
THE SLIP RATE, TYPICALLY
MEASURED IN MILLIMETERS PER YEAR,

[00:30:32.409]
IS HOW FAST THE TWO SIDES OF A
FAULT ARE MOVING PAST EACH OTHER.

[00:30:35.709]
THESE FAULTS THAT HAVE THE GREATEST
SLIP RATES MAY BE THE LOCATIONS

[00:30:38.389]
OF FUTURE EARTHQUAKES.

[00:30:39.699]
I WISH YOU WERE ABLE TO
MAKE A PREDICTION NOW.

[00:30:41.859]
CAN GPS HELP US TO KNOW

[00:30:43.559]
IF WE EXPERIENCED AN
EARTHQUAKE IN VIRGINIA?

[00:30:45.499]
WE CAN USE GPS TO MEASURE
DISPLACEMENTS FROM EARTHQUAKES,

[00:30:48.299]
BUT WE DON'T MEASURE THE
SHAKING PART FROM AN EARTHQUAKE.

[00:30:50.839]
THE SEISMOMETER IS USED TO MEASURE
THIS, AND IT WILL BE BETTER ABLE

[00:30:53.449]
TO ANSWER YOUR QUESTION.

[00:30:54.499]
THANK YOU VERY MUCH, DR. DONNELLAN.

[00:30:56.499]
YOU'RE WELCOME.

[00:30:57.089]
EMAIL ME IF YOU HAVE ANY QUESTIONS,
AND SAY HELLO TO DR. D FOR ME.

[00:31:01.039]
COOL; I CAN'T BELIEVE THAT THE
GPS CAN DETECT THREE MILLIMETERS

[00:31:04.299]
OF MOVEMENT FROM SPACE.

[00:31:06.239]
CHECK THIS OUT: COME CLOSER.

[00:31:08.609]
THREE MILLIMETERS
IS ONLY THIS MUCH.

[00:31:11.579]
HI, TONY.

[00:31:12.479]
WE'RE TALKING ABOUT GPS.

[00:31:13.319]
IN THE FUTURE, IT MIGHT HELP
US TO PREDICT EARTHQUAKES.

[00:31:16.969]
YEAH, THAT'S GREAT, BUT WHAT
ABOUT THE PROBLEM RIGHT NOW?

[00:31:20.159]
DR. DONNELLAN SAID THAT IF THERE
WAS AN EARTHQUAKE IN VIRGINIA,

[00:31:22.969]
SEISMOGRAPHS WOULD PICK IT UP.

[00:31:24.999]
BUT WE LOOKED AT A FEW SEISMOGRAMS,

[00:31:26.289]
AND WE STILL DON'T
HAVE A DEFINITE ANSWER.

[00:31:28.629]
LET'S DO SOME PROBLEM SOLVING.

[00:31:30.229]
I HAVE AN IDEA.

[00:31:31.139]
WHY DON'T WE CALL RJ AND JACOB?

[00:31:32.559]
TELL THEM "HI."

[00:31:33.309]
I'VE GOT TO GO.

[00:31:34.169]
I'VE GOT SOCCER PRACTICE TODAY.

[00:31:35.929]
HI, GUYS.

[00:31:38.139]
HOW'S CALIFORNIA?

[00:31:39.299]
IT'S GREAT.

[00:31:40.219]
LOOK AT THE GOLDEN
GATE BRIDGE BEHIND US.

[00:31:41.919]
AND WE'RE LEARNING A
LOT AT THE SCIENCE FAIR.

[00:31:45.259]
SO ARE YOU STILL TRYING TO
SOLVE THE TREMOR PROBLEM?

[00:31:47.789]
YES, BUT WE NEED YOUR HELP
WITH THE PROBLEM BOARD.

[00:31:50.269]
OKAY, LET'S GO TO IT.

[00:31:51.549]
WELL, WE KNOW THAT THE FIRST SET

[00:31:52.849]
OF TREMORS WAS NOT
RELATED TO THE SECOND.

[00:31:55.419]
WE KNOW THE PLATES' MOVEMENTS
CAN CAUSE EARTHQUAKES

[00:31:57.719]
AND THAT THERE ARE A LOT OF FAULTS.

[00:31:59.519]
WE KNOW THERE ARE
FAULTS IN VIRGINIA.

[00:32:01.159]
AND WE ALSO KNOW THAT OTHER
THINGS CAN CAUSE MOVEMENT

[00:32:03.469]
ON THE SEISMOGRAPH.

[00:32:04.549]
LIKE WHAT?

[00:32:05.219]
THE SEISMOLOGIST TOLD US THAT
QUARRY BLASTS, SONIC BOOMS,

[00:32:08.179]
AND THUNDERSTORMS CAN OFTEN
BE MISTAKEN FOR EARTHQUAKES.

[00:32:11.389]
THUNDERSTORMS?

[00:32:12.549]
DID WE HAVE STORMS THAT DAY?

[00:32:13.669]
IT WAS CLOUDY AND STORMY THAT DAY,

[00:32:15.299]
BUT I DON'T REMEMBER
SEEING ANY LIGHTNING.

[00:32:17.439]
BUT IT DID SOUND LIKE
A CLAP OF THUNDER.

[00:32:19.559]
AND THAT WOULD REGISTER
ON THE SEISMOGRAMS.

[00:32:22.329]
AND EARTHQUAKES DON'T MAKE
NOISE, SO IT MUST BE THUNDER.

[00:32:25.319]
MAYBE THIS IS OUR NEW HYPOTHESIS.

[00:32:27.599]
IF THERE WAS THUNDER, THEN IT
WOULD CAUSE VIBRATIONS ON EARTH.

[00:32:30.499]
DON'T THROW AWAY YOUR
EARTHQUAKE HYPOTHESIS TOO QUICKLY.

[00:32:33.329]
DURING MY VACATION, I'VE BEEN DOING
A LOT OF RESEARCH ON EARTHQUAKES.

[00:32:36.629]
AND LOOK, I JUST HAPPENED TO FIND
THIS ACCOUNT OF AN EARTHQUAKE

[00:32:39.299]
IN OKLAHOMA, AND HERE IT IS: "I
HEARD SOMETHING LIKE A LOUD CLAP

[00:32:43.069]
OF THUNDER OR SOMETHING EXPLODING."

[00:32:44.919]
GREAT JOB, GUYS.

[00:32:46.179]
OUR COMPETING EARTHQUAKE
HYPOTHESIS STILL SURVIVES.

[00:32:49.189]
I STILL THINK WE NEED TO
KNOW IF THERE WAS THUNDER

[00:32:50.869]
AND LIGHTNING THAT DAY.

[00:32:52.279]
WE NEVER CHECKED OUT WHAT
THE SEISMOLOGIST SAID

[00:32:54.249]
ABOUT "S" AND "P" WAVES.

[00:32:55.809]
I THINK WE SHOULD.

[00:32:56.609]
IT MIGHT BE A CLUE.

[00:32:58.469]
SEE YOU GUYS.

[00:32:59.139]
HAVE FUN WITH DR. D. HEY, DR. D.
HI, GUYS; GOOD TO SEE YOU HERE

[00:33:05.339]
IN SAN FRANCISCO, CALIFORNIA.

[00:33:06.759]
I UNDERSTAND FROM THE EMAIL
THAT YOU WANT TO KNOW MORE

[00:33:09.199]
ABOUT EARTHQUAKE WAVES.

[00:33:10.299]
YES.

[00:33:11.159]
I PUT TOGETHER SOME
DEMONSTRATIONS FOR YOU.

[00:33:13.259]
GREAT.

[00:33:13.829]
LET'S TALK ABOUT THREE
DIFFERENT KINDS OF WAVES.

[00:33:16.169]
THE FIRST TWO ARE
"S" AND "P" WAVES.

[00:33:18.669]
THEY'RE CALLED BODY
WAVES BECAUSE THEY TRAVEL

[00:33:20.299]
THROUGH THE BODY OF THE EARTH.

[00:33:21.439]
MR. LYLE SHOWED THE OTHER
TREE HOUSE DETECTIVES THOSE

[00:33:23.979]
ON THE SEISMOGRAM.

[00:33:25.669]
"P" STANDS FOR PRIMARY
OR COMPRESSIONAL WAVES,

[00:33:28.609]
AND "S" IS FOR SECONDARY
OR SHEER WAVES.

[00:33:31.249]
"P" WAVES MAKE THE
EARTH VIBRATE BACK

[00:33:32.789]
AND FORTH ALONG THE
DIRECTION OF MOTION.

[00:33:34.919]
LET ME SHOW YOU WITH
THIS SLINKY OVER HERE.

[00:33:37.769]
[00:33:42.079]
THOSE DON'T LOOK LIKE THE WAVES I'M
USED TO SEEING, LIKE OCEAN WAVES.

[00:33:45.289]
THE WAVE YOU'RE USED TO SEEING HAS
UP-AND-DOWN OR SIDE-TO-SIDE MOTION.

[00:33:48.569]
THIS IS LIKE THE SHEER
WAVE, OR "S" WAVE.

[00:33:50.649]
LOOKS LIKE THIS.

[00:33:52.469]
[00:33:54.519]
ANOTHER IMPORTANT DIFFERENCE
BETWEEN "S" AND "P" WAVES IS THAT

[00:33:57.489]
"P" WAVES TRAVEL FASTER THAN
"S" WAVES, ALMOST TWICE AS FAST.

[00:34:01.079]
I GUESS THAT MEANS THAT "P"
WAVES WILL ALWAYS ARRIVE FIRST.

[00:34:04.259]
THAT'S RIGHT, AND THE DIFFERENCE IN
TIME BETWEEN THE ARRIVAL OF THE "S"

[00:34:07.319]
AND "P" WAVES CAN HELP US FIND
THE EPICENTER OF THE EARTHQUAKE.

[00:34:10.329]
WHAT'S AN EPICENTER?

[00:34:11.269]
IT'S THE POINT ON THE EARTH
DIRECTLY ABOVE THE FOCUS,

[00:34:13.809]
OR THE POINT WHERE THE
EARTHQUAKE ORIGINATES.

[00:34:15.489]
HAVE YOU EVER HEARD ABOUT
COUNTING THE SECONDS

[00:34:17.569]
BETWEEN SEEING THE LIGHTNING
AND HEARING THE THUNDER?

[00:34:19.899]
I HAVE, BUT I'VE NEVER DONE IT.

[00:34:21.919]
WELL, IT WORKS BECAUSE LIGHT AND
SOUND TRAVEL AT DIFFERENT SPEEDS.

[00:34:25.369]
FOR EXAMPLE, WHEN YOU SEE THE
LIGHTNING, START COUNTING.

[00:34:30.019]
1001, 1002, 1003.

[00:34:35.209]
THE SOUND ARRIVED ABOUT THREE
SECONDS AFTER THE LIGHTNING.

[00:34:37.899]
THAT MEANS THE LIGHTNING IS
ABOUT ONE KILOMETER AWAY.

[00:34:40.839]
FOR EARTHQUAKES, FIRST YOU'LL FEEL
A "P" WAVE, AND THEN SECONDS LATER,

[00:34:44.299]
YOU'LL FEEL A MORE
POWERFUL "S" WAVE.

[00:34:46.519]
FOR LOCAL EARTHQUAKES, EVERY
SECOND THAT YOU COUNT MEANS YOU'RE

[00:34:49.389]
ABOUT EIGHT KILOMETERS FURTHER
AWAY FROM THE EPICENTER.

[00:34:52.319]
I DON'T THINK I'D BE COUNTING THE
SECONDS IF I WAS IN AN EARTHQUAKE.

[00:34:54.909]
I DON'T THINK I WOULD EITHER.

[00:34:56.159]
AND THE THIRD AND SLOWEST OF
THESE WAVES, THE SURFACE WAVE,

[00:34:59.399]
IS THE MOST DESTRUCTIVE
OF THEM ALL.

[00:35:01.589]
HERE IN CALIFORNIA, THEY
HAVE TO BUILD STRUCTURES

[00:35:03.689]
TO WITHSTAND THESE DANGEROUS WAVES.

[00:35:05.759]
HOW DO THEY KNOW HOW TO DO THAT?

[00:35:08.159]
ONE WAY IS FOR ENGINEERS TO
USE SHAKY TABLES LIKE THESE,

[00:35:10.919]
ONLY MUCH BIGGER, TO
TEST THEIR DESIGNS.

[00:35:13.159]
LET'S TRY IT OUT.

[00:35:14.159]
I'LL BET MY STRUCTURE CAN
WITHSTAND THE GREATEST EARTHQUAKE.

[00:35:16.879]
WE'LL SEE WHO'S THE BEST ENGINEER.

[00:35:18.629]
YES.

[00:35:19.819]
[00:35:40.549]
I GUESS WE HAVE A
LITTLE BIT MORE TO LEARN

[00:35:43.329]
ABOUT THE POWER OF EARTHQUAKES.

[00:35:44.969]
DR. D, DIDN'T YOU SAY WE COULD
EXPERIENCE AN EARTHQUAKE HERE

[00:35:47.789]
AT THE MUSEUM?

[00:35:48.739]
YOU NEED TO GO SEE
MY FRIEND, DR. TANG.

[00:35:50.729]
THAT MUST BE THE EARTHQUAKE
THEATER.

[00:35:59.109]
I HOPE IT'S NOT LIKE THE
HURRICANE ROOM THAT BIANCA

[00:36:01.579]
AND CATHERINE WENT TO.

[00:36:02.919]
YEAH.

[00:36:03.859]
TREE HOUSE DETECTIVES?

[00:36:04.849]
THAT'S US.

[00:36:05.619]
NICE TO MEET YOU, DR. TANG.

[00:36:07.039]
I HEAR YOU'RE INTERESTED IN
EXPERIENCING AN EARTHQUAKE.

[00:36:09.269]
WELL, I DON'T KNOW ABOUT THAT,
BUT WE DO NEED TO LEARN MORE

[00:36:12.299]
ABOUT HOW EXPERTS MEASURE
THE POWER OF EARTHQUAKES.

[00:36:14.729]
ONE SUCH SCALE IS
CALLED THE RICHTER SCALE.

[00:36:16.789]
IT TELLS US THE STRENGTH
OF AN EARTHQUAKE.

[00:36:18.949]
ARE THERE OTHER SCALES
THAT SCIENTISTS USE?

[00:36:20.949]
NOW SCIENTISTS PREFER A MORE
PRECISE SCALE CALLED THE

[00:36:23.789]
MOMENT MAGNITUDE SCALE.

[00:36:25.699]
IT'S A NUMBER THAT TELLS US

[00:36:27.029]
ABOUT THE ENERGY RELEASED
FROM AN EARTHQUAKE.

[00:36:29.529]
WHAT'S THE NUMBER
OF OUR EARTHQUAKE?

[00:36:30.879]
WELL, IF IT WAS A QUAKE
THAT PEOPLE COULD FEEL,

[00:36:33.359]
IT MUST BE AT LEAST A 2.

[00:36:34.739]
A MODERATE EARTHQUAKE IS ABOUT A 5.

[00:36:37.359]
WASN'T THERE A MAJOR EARTHQUAKE
HERE IN SAN FRANCISCO IN 1906?

[00:36:40.559]
WHAT WAS ITS NUMBER?

[00:36:41.629]
IT WAS A 7.7, BUT TO UNDERSTAND
WHAT THAT MEANS, YOU REALLY OUGHT

[00:36:45.599]
TO EXPERIENCE THE EARTHQUAKE.

[00:36:47.069]
I'M NOT SURE I WANT TO DO THAT.

[00:36:49.009]
DON'T WORRY.

[00:36:49.609]
IT'S QUITE SAFE.

[00:36:50.609]
WE'LL DO IT HERE IN
THE EARTHQUAKE THEATER

[00:36:52.689]
AT THE CALIFORNIA
ACADEMY OF SCIENCES.

[00:36:54.709]
DON'T FORGET TO BRING THE CAMERA.

[00:36:56.669]
I GOT IT.

[00:36:59.019]
[MUSIC]

[00:37:08.019]
[00:37:22.009]
AT 5:04 P.M., OCTOBER 17, 1989,

[00:37:26.189]
THE SAN FRANCISCO BAY AREA
EXPERIENCED A POWERFUL EARTHQUAKE.

[00:37:30.299]
COOL.

[00:37:30.899]
IT SEEMED SO REAL.

[00:37:31.899]
HOW DO SCIENTISTS KNOW SO MUCH?

[00:37:34.869]
WELL, WE LOOKED AT PEOPLE'S DIARIES
AND ALSO AT HOUSES AND CHURCHES

[00:37:38.859]
THAT WERE DAMAGED
DURING THE EARTHQUAKE

[00:37:40.469]
AND ALSO HOW THE EARTHQUAKE
RUPTURED THE GROUND

[00:37:42.549]
AROUND SAN FRANCISCO
DURING THE TIME PERIOD.

[00:37:44.859]
I GUESS OBSERVATIONS ARE IMPORTANT.

[00:37:47.049]
YOUR SCIENCE JOURNAL MIGHT
BE VALUABLE EVIDENCE ONE DAY.

[00:37:49.679]
YES.

[00:37:50.069]
WELL, TAKE A LOOK AT THIS
EARTHQUAKE QUESTIONNAIRE.

[00:37:52.959]
YOU'LL SEE THAT EVEN TODAY, EVEN
WITH SOPHISTICATED INSTRUMENTS,

[00:37:56.319]
SCIENTISTS STILL DEPEND
ON PEOPLE'S EXPERIENCES

[00:37:59.019]
TO UNDERSTAND EARTHQUAKES.

[00:38:00.749]
WOW, LOOK AT THIS.

[00:38:01.799]
THEY WANT TO KNOW IF IT WAS
DIFFICULT TO STAND OR WALK.

[00:38:04.149]
AND DID OBJECTS RATTLE
OR FALL OFF THE SHELF?

[00:38:07.679]
HERE'S A SIMPLE QUESTION:
"WHAT'S YOUR ZIP CODE?"

[00:38:11.079]
DOES IT MAKE A DIFFERENCE
WHERE YOU LIVE?

[00:38:12.889]
YES, THE EFFECTS OF AN
EARTHQUAKE VARY GREATLY DEPENDING

[00:38:15.779]
ON HOW FAR AWAY FROM
THE SOURCE YOU ARE.

[00:38:17.919]
YOU MEAN THE FARTHER AWAY YOU ARE,

[00:38:19.419]
THE LESS SHAKING YOU
FEEL FROM A QUAKE?

[00:38:21.289]
YES, BUT IT ALSO DEPENDS
ON WHAT THE GROUND IS LIKE.

[00:38:23.919]
WHAT DOES THE GROUND
HAVE TO DO WITH IT?

[00:38:25.459]
WELL, LET'S TAKE A
LOOK AT THIS GELATIN.

[00:38:28.299]
IF I PUSH ON IT EVEN A
LITTLE BIT, IT JIGGLES A LOT.

[00:38:31.419]
AND YET, IF I TAKE A ROCK, NO
MATTER HOW HARD I PUSH ON IT,

[00:38:35.829]
IT'S NOT GOING TO JIGGLE AT ALL.

[00:38:37.429]
I KNOW WHERE I WOULD WANT TO STAND
DURING AN EARTHQUAKE: SOLID ROCK.

[00:38:41.149]
THAT'S RIGHT.

[00:38:41.939]
HOUSES BUILT ON MUD AND SAND DON'T
DO SO WELL DURING AN EARTHQUAKE.

[00:38:46.079]
THANKS, DR. TANG.

[00:38:48.939]
YOU'RE WELCOME.

[00:38:50.089]
SO WHAT'S UP?

[00:38:51.759]
COULD A THUNDERSTORM
HAVE CAUSED THE TREMOR?

[00:38:53.909]
WILL "S" AND "P" WAVES
HELP SOLVE THE MYSTERY?

[00:38:56.899]
WHAT SHOULD THE TREE HOUSE
DETECTIVES INVESTIGATE NEXT?

[00:38:59.259]
DON'T MISS THE EXCITING CONCLUSION
OF THE CASE OF THE SHAKY QUAKE.

[00:39:03.709]
IN THE CONCLUSION OF THE
CASE OF THE SHAKY QUAKE,

[00:39:10.529]
SEE IF YOU CAN ANSWER
THESE QUESTIONS:

[00:39:12.289]
HOW MANY EARTHQUAKES
OCCUR EACH YEAR?

[00:39:16.389]
HOW MANY SEISMIC STATIONS
ARE NECESSARY

[00:39:19.049]
TO PINPOINT THE EPICENTER
OF AN EARTHQUAKE?

[00:39:20.879]
WHAT ARE THE DIFFERENCES BETWEEN
METEORS, METEORITES, AND METEROIDS?

[00:39:29.879]
[00:39:31.549]
WHY ARE YOU SO DOWN?

[00:39:32.269]
I CALLED THE WEATHER SERVICE,

[00:39:34.039]
AND THEY SAID THEY DIDN'T RECORD
ANY LIGHTNING STRIKES IN OUR AREA

[00:39:36.849]
ON THE DAY WE FELT THE LAST TREMOR.

[00:39:38.679]
MAYBE I SHOULDN'T MENTION THAT
I CALLED ANOTHER SEISMOLOGIST

[00:39:41.229]
AT VIRGINIA TECH, WHICH IS
ABOUT 300 KILOMETERS AWAY,

[00:39:44.399]
AND THEIR SEISMOGRAPH PICKED UP
SOMETHING AROUND THE SAME TIME

[00:39:46.959]
THAT WE FELT THE TREMOR.

[00:39:47.639]
SO THAT DOESN'T MEAN MY
THUNDER HYPOTHESIS IS WRONG.

[00:39:50.989]
IT MIGHT.

[00:39:51.859]
THINK ABOUT IT.

[00:39:52.469]
THE SEISMOLOGIST SAID
IT WAS CLEAR THAT DAY.

[00:39:54.789]
NO THUNDERSTORMS IN SIGHT.

[00:39:56.719]
WELL, MR. LYLE SAID HIS SEISMOGRAPH
ONLY DETECTS LOCAL THUNDER.

[00:40:00.109]
WELL, MAYBE YOU'RE RIGHT.

[00:40:01.059]
THE SEISMOLOGIST ALSO SAID

[00:40:02.439]
THAT EYEWITNESSES REPORTED
SEEING A FIREBALL IN THE SKY,

[00:40:04.799]
AND THEY HEARD A LOUD NOISE.

[00:40:06.249]
I DON'T REMEMBER SEEING
A FIREBALL THAT DAY.

[00:40:08.899]
HERE COMES DR. TEXTBOOK.

[00:40:11.079]
HELLO, DR. TEXTBOOK HERE WITH
SOME EARTH-SHATTERING FACTS.

[00:40:16.659]
[00:40:19.099]
YOU'LL NEVER GUESS HOW MANY
DETECTABLE EARTHQUAKES THERE ARE

[00:40:22.079]
IN THE WORLD EACH YEAR.

[00:40:23.289]
TRY 500,000.

[00:40:25.529]
THAT'S HALF A MILLION
EARTHQUAKES A YEAR!

[00:40:27.719]
CALIFORNIANS, LISTEN UP.

[00:40:29.839]
EVERY YEAR, THE SOUTHERN PART OF
CALIFORNIA HAS 10,000 EARTHQUAKES,

[00:40:33.759]
BUT MOST OF THEM ARE NOT FELT.

[00:40:38.279]
YEE-HA!

[00:40:39.169]
NOW, WHICH STATE IS THE
MOST EARTHQUAKE PRONE?

[00:40:41.859]
NOT CALIFORNIA.

[00:40:43.239]
TRY ALASKA.

[00:40:45.309]
IT HAS A MAGNITUDE 7
EARTHQUAKE EVERY YEAR.

[00:40:47.599]
AND HERE IS A TRICK QUESTION.

[00:40:51.219]
IS THERE SUCH A THING
AS EARTHQUAKE WEATHER?

[00:40:53.859]
NO.

[00:40:54.549]
EARTHQUAKES HAPPEN IN THE COLD,
IN THE RAIN, AND IN THE HEAT.

[00:41:01.769]
NOW LET'S SEE IF WE CAN FEEL ONE
OF THOSE 500,000 EARTHQUAKES.

[00:41:06.699]
[00:41:10.669]
NOT A VERY GOOD IDEA.

[00:41:13.889]
EARTHQUAKES ARE LIKE HURRICANES:

[00:41:15.969]
THEY'RE SO POWERFUL
AND CAN BE SO DEADLY.

[00:41:18.549]
LOOK, WE HAVE AN EMAIL
FROM JACOB AND RJ.

[00:41:20.549]
THEY SAY DR. D TOLD THEM ABOUT
HOW TO USE "P" AND "S" WAVES

[00:41:24.679]
TO FIND THE CENTER
OF AN EARTHQUAKE.

[00:41:26.159]
DR. D SAYS YOU MUST HAVE
THREE SEISMIC STATIONS

[00:41:28.539]
TO LOCATE THE EPICENTER.

[00:41:29.759]
WE HAVE TWO.

[00:41:30.789]
MAYBE THAT'S ENOUGH.

[00:41:31.699]
I DOUBT IT, BUT I HAVE AN IDEA.

[00:41:33.379]
LET'S WRITE THE SCI FILES KIDS
CLUB AND ASK THEM IF THEY KNOW HOW

[00:41:36.389]
TO USE "S" AND "P" WAVES
TO MAP AN EPICENTER.

[00:41:39.449]
HEY, WE HAVE A RESPONSE

[00:41:41.889]
FROM ROBERTS PARK ELEMENTARY
SCHOOL IN NORFOLK, VIRGINIA.

[00:41:44.999]
HI, WE'RE FROM MR. DARYL
RANSOM'S THIRD GRADE CLASS

[00:41:50.309]
AT ROBERTS PARK ELEMENTARY
SCHOOL IN NORFOLK, VIRGINIA.

[00:41:55.079]
HI, WE'RE THE TREE
HOUSE DETECTIVES,

[00:41:56.429]
AND WE SEE YOU'RE DOING
AN ACTIVITY TO FIND

[00:41:58.299]
OUT WHERE AN EARTHQUAKE OCCURRED.

[00:41:59.769]
COULD YOU TELL US
SOMETHING ABOUT IT?

[00:42:01.379]
SURE.

[00:42:02.119]
OUR MENTORS FROM THE SOCIETY
OF WOMEN ENGINEERS HELPED US

[00:42:06.079]
WITH THE ACTIVITY
CALLED TRIANGULATION.

[00:42:09.209]
IT MUST HAVE SOMETHING
TO DO WITH THREES.

[00:42:11.729]
YES, WE LEARNED THAT IN ORDER TO
FIND THE ORIGIN, OR EPICENTER,

[00:42:15.579]
OF AN EARTHQUAKE, WE NEEDED DATA

[00:42:17.899]
FROM THREE DIFFERENT
SEISMIC STATIONS.

[00:42:20.679]
DID YOU NEED ANY SPECIAL MATERIALS?

[00:42:23.119]
NO, JUST A WORLD MAP, A SEISMOGRAM,
A GRAPH, AND A DRAWING COMPASS.

[00:42:29.249]
WHAT DID YOU DO NEXT?

[00:42:31.739]
FIRST WE LOOKED AT THE SEISMIC
RECORDINGS AND DETERMINED WHEN THE

[00:42:35.409]
"S" AND "P" WAVES EACH ARRIVED
AT THE SEISMIC STATIONS.

[00:42:40.309]
HOW COULD YOU TELL
WHICH ONE WAS WHICH?

[00:42:42.549]
WE KNOW THE "P" WAVES TRAVEL
FASTER AND ARRIVE FIRST.

[00:42:47.489]
WE THEN FOUND THE DIFFERENCE
BETWEEN THE TWO TIMES IN SECONDS.

[00:42:51.679]
FOR EXAMPLE, AT THE
DENVER, COLORADO, STATION,

[00:42:54.909]
THE "P" WAVES ARRIVED AT
10 HOURS AND 16 MINUTES,

[00:42:58.649]
AND THE "S" WAVES ARRIVED AT 10
HOURS, 18 MINUTES, AND 30 SECONDS.

[00:43:03.129]
I KNOW; THE DIFFERENCE WAS
2 MINUTES AND 30 SECONDS.

[00:43:06.499]
THAT'S CORRECT.

[00:43:07.629]
WE THEN USED A GRAPH
TO MARK OFF 2 MINUTES

[00:43:10.179]
AND 30 SECONDS ALONG THE
EDGE OF THE PIECE OF PAPER.

[00:43:14.009]
WE SLID THE PAPER ALONG THE
GRAPH BETWEEN THE "S" WAVES

[00:43:17.209]
AND THE "P" WAVES TO FIND
THE DISTANCE IN KILOMETERS

[00:43:20.069]
THAT THE WAVES HAD TRAVELED.

[00:43:22.049]
HOW FAR DID THE WAVES TRAVEL?

[00:43:24.199]
ABOUT 1,600 KILOMETERS.

[00:43:26.819]
AFTER FINDING THE DISTANCE
THE WAVES TRAVELED,

[00:43:29.689]
WE LOCATED THE CITY ON THE MAP.

[00:43:32.749]
WE USED THE MAP SCALE
AND OUR DRAWING COMPASS

[00:43:35.459]
TO MEASURE THAT DISTANCE.

[00:43:37.989]
WE PLACED THE POINT OF OUR COMPASS
ON THE CITY AND DREW A CIRCLE.

[00:43:42.509]
WHY A CIRCLE?

[00:43:43.319]
WE KNOW THAT THE EARTHQUAKE
OCCURRED 1,600 KILOMETERS

[00:43:47.609]
FROM DENVER, BUT THAT COULD BE
1,600 KILOMETERS IN ANY DIRECTION.

[00:43:53.299]
SO WE USED 1,600 KILOMETERS
AS OUR RADIUS,

[00:43:57.269]
AND THE EARTHQUAKE OCCURRED
SOMEWHERE ALONG THE CIRCLE.

[00:44:01.479]
HOW DO YOU PINPOINT THE LOCATION?

[00:44:03.749]
WE REPEATED THE STEPS WITH
THE NEXT SEISMIC RECORDING

[00:44:06.709]
FOR TERRE HAUTE, INDIANA.

[00:44:09.149]
BUT THE TWO CIRCLES INTERSECT
AT TWO DIFFERENT POINTS.

[00:44:11.629]
HOW CAN YOU TELL WHICH
ONE IS THE EPICENTER?

[00:44:14.149]
THAT'S WHY YOU NEED A
THIRD SEISMIC STATION.

[00:44:17.229]
ONCE ALL THREE STATIONS
ARE PLOTTED ON THE MAP,

[00:44:20.419]
YOU FIND WHERE THE
THREE CIRCLES INTERSECT.

[00:44:22.909]
THE INTERSECTION IS THE APPROXIMATE
EPICENTER OF THE EARTHQUAKE.

[00:44:28.879]
WELL, THEY ANSWERED
ONE QUESTION FOR US.

[00:44:30.629]
WE REALLY DO NEED THREE
SEISMIC STATIONS, NOT TWO,

[00:44:32.679]
TO MAP OUT THE EPICENTER.

[00:44:34.089]
IS A EARTHQUAKE OUR
ONLY HYPOTHESIS?

[00:44:36.269]
IT IS FOR ME.

[00:44:38.199]
JUST JOKING.

[00:44:39.639]
I THINK WE NEED MORE
CONCLUSIVE EVIDENCE TO SHOW

[00:44:41.519]
THAT IT WAS AN EARTHQUAKE.

[00:44:42.989]
WILL THIS HELP?

[00:44:44.379]
RJ, YOU'RE BACK.

[00:44:46.119]
I HAVE THIS DVD OF JACOB
AND ME IN AN EARTHQUAKE.

[00:44:48.879]
YOU WERE IN AN EARTHQUAKE?

[00:44:50.969]
WELL...SORT OF.

[00:44:52.589]
BUT REALLY IT WAS
AN EARTHQUAKE ROOM.

[00:44:55.379]
THAT DOESN'T LOOK LIKE WHAT
WE SAW AT OUR TREE HOUSE.

[00:45:04.379]
[00:45:09.929]
THIS CASE ISN'T AS EASY
TO SOLVE AS THE OTHERS.

[00:45:13.129]
NO ONE WILL CONFIRM
THAT IT'S AN EARTHQUAKE,

[00:45:14.759]
NOT EVEN A SEISMOLOGIST.

[00:45:16.959]
LET'S CALL ANOTHER SEISMIC
STATION TO SEE IF THEY PICKED

[00:45:19.179]
UP A TREMOR ON THEIR INSTRUMENTS.

[00:45:20.799]
MAYBE THAT'LL HELP CONFIRM IT.

[00:45:22.339]
I DON'T KNOW WHY, BUT I
THINK IT'S SOMETHING ELSE.

[00:45:25.109]
HERE COMES KSNN.

[00:45:26.459]
MAYBE THEY HAVE SOME
MORE INFORMATION.

[00:45:28.819]
LADIES AND GENTLEMEN,
WE ARE CONTINUING

[00:45:30.579]
TO INVESTIGATE THE RECENT TREMORS.

[00:45:32.459]
IT SEEMS THAT THE QUAKES FELT

[00:45:33.549]
BY OUR VIEWERS MAY HAVE
HAD DIFFERENT SOURCES.

[00:45:35.689]
FOR MORE, WE GO LIVE
TO I.M. LISSNING.

[00:45:38.749]
TED, I'M HERE WITH ESTEEMED
SCIENTIST DR. LIZ ARDE.

[00:45:42.899]
DR. ARDE, WHAT CAN YOU TELL US
ABOUT THE EVENTS OF YESTERDAY?

[00:45:47.189]
WELL, I.M., WE HAVE
RECEIVED VIBRATION REPORTS

[00:45:49.769]
FROM CITIES ALL ALONG
THE EAST COAST.

[00:45:52.099]
MANY PEOPLE ALSO SAW A FIREBALL,

[00:45:54.069]
WHICH WE NOW BELIEVE WAS A METEOR
ENTERING EARTH'S ATMOSPHERE.

[00:45:57.329]
OUR TRACKING CAMERAS WERE ABLE

[00:45:58.719]
TO RECORD THIS IMAGE BEFORE
THE METEOR FLEW OUT OF SIGHT.

[00:46:02.799]
AMAZING.

[00:46:04.379]
THANK YOU, DOCTOR.

[00:46:05.259]
BACK TO YOU, TED.

[00:46:07.479]
WELL, FOLKS, THOSE VIBRATIONS
WERE MERELY GIANT EXPLOSIONS

[00:46:10.399]
AND HUGE METEORS FALLING
FROM SPACE.

[00:46:12.669]
NOTHING TO WORRY ABOUT.

[00:46:15.319]
NOTHING...AT ALL.

[00:46:16.489]
MOMMY.

[00:46:17.899]
WHAT'S A METEOR?

[00:46:20.079]
I CAN TELL YOU.

[00:46:21.969]
I HAVE MY "M" ENCYCLOPEDIA.

[00:46:23.939]
OF COURSE.

[00:46:25.709]
[00:46:27.179]
LET'S SEE...

[00:46:28.389]
"A METEOR IS A SMALL PIECE OF ROCK
"THAT ENTERS THE EARTH'S ATMOSPHERE

[00:46:32.409]
AND BURNS UP AS IT FALLS."

[00:46:34.609]
COULD THIS METEOR BE
OUR NEW HYPOTHESIS?

[00:46:36.819]
NO, I DON'T THINK SO.

[00:46:39.149]
WE HAD A TREMOR, BUT
NOT A FIREBALL.

[00:46:41.179]
MAYBE WE JUST DIDN'T SEE IT.

[00:46:46.319]
IT SAYS IN MY NOTES THAT
IT WAS A CLOUDY DAY HERE.

[00:46:50.119]
THAT'S RIGHT.

[00:46:50.809]
VIRGINIA TECH REPORTED
SEEING A FIREBALL,

[00:46:52.629]
BUT THEY ALSO SAID
IT WAS A CLEAR DAY.

[00:46:54.419]
I WONDER IF A METEOR COULD TRAVEL
FASTER THAN THE SPEED OF SOUND.

[00:46:58.749]
IF IT DID, THEN IT COULD CAUSE A
SONIC BOOM, JUST LIKE AN AIRPLANE.

[00:47:01.979]
AND WE LEARNED THAT SONIC
BOOMS CAN CAUSE TREMORS.

[00:47:05.019]
THAT MIGHT WORK.

[00:47:06.539]
LET'S WORD THE HYPOTHESIS
LIKE THIS: "IF A METEOR

[00:47:10.339]
OR A FIREBALL IS MOVING FASTER
THAN THE SPEED OF SOUND,

[00:47:13.389]
THEN MAYBE IT CAN FORM A SONIC
BOOM THAT CAUSES THE TREMOR."

[00:47:16.059]
I THINK WE REALLY NEED TO LOOK INTO
THE METEOR AS THE POSSIBLE CAUSE.

[00:47:20.069]
WE JUST TALKED TO J.P.L.
LET'S CALL THEM AGAIN.

[00:47:22.519]
OKAY.

[00:47:24.509]
HI, MR. BAALKE.

[00:47:26.459]
IT'S NEAT THAT YOU ACTUALLY HAVE
A METEORITE NAMED AFTER YOU.

[00:47:29.719]
YEAH, WE'RE A LITTLE CONFUSED
ON WHAT A METEOR ACTUALLY IS.

[00:47:33.469]
ISN'T IT THE SAME THING AS
A METEOROID AND A METEORITE?

[00:47:36.319]
I'M GLAD TO HELP YOU.

[00:47:37.489]
ACTUALLY, I HAD AN
ASTEROID NAMED AFTER ME.

[00:47:40.489]
IT'S EASY TO GET THEM CONFUSED.

[00:47:42.149]
METEOROIDS ARE SMALL PIECES
OF ROCK FROM AN ASTEROID

[00:47:45.819]
OR COMET DRIFTING IN OUTER SPACE.

[00:47:48.129]
WHEN A METEORITE ENTERS
INTO THE EARTH'S ATMOSPHERE

[00:47:50.589]
AND BURNS UP, IT'S CALLED A METEOR.

[00:47:53.129]
PEOPLE OFTEN SEE THESE METEORS
AND CALL THEM SHOOTING STARS.

[00:47:56.629]
PEOPLE NEAR US REPORTED
SEEING A FIREBALL.

[00:47:58.859]
IS A FIREBALL LIKE A SHOOTING STAR?

[00:48:01.299]
YES, A FIREBALL IS A NAME GIVEN
TO A PARTICULARLY BRIGHT METEOR.

[00:48:05.029]
THEY ARE SOMETIMES SO BRIGHT
THEY CAN BE SEEN IN THE DAYTIME.

[00:48:08.169]
WHAT'S A METEORITE?

[00:48:11.159]
MOST METEORITES BURN UP
COMPLETELY WHEN THEY ENTER

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INTO EARTH'S ATMOSPHERE.

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BUT IF IT'S LARGE ENOUGH AND
SURVIVES AND IMPACTS THE EARTH,

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IT'S CALLED A METEORITE, SUCH
AS THE ONE I'M HOLDING HERE.

[00:48:21.349]
SOME METEORITES CAN CAUSE
CRATERS, SUCH AS THE ONE

[00:48:23.709]
IN METEOR CRATER IN ARIZONA.

[00:48:25.079]
WE UNDERSTAND THAT A FIREBALL
WAS SIGHTED NEAR OUR TOWN

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AND THAT IT MAY HAVE
CAUSED A SONIC BOOM.

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IS THIS POSSIBLE?

[00:48:31.719]
YES, IF IT'S LARGE ENOUGH.

[00:48:33.029]
THE LARGER SIZE WILL
ALLOW IT TO LAST LONGER

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AND PENETRATE DEEPER
INTO THE ATMOSPHERE.

[00:48:38.579]
THE SONIC BOOM IS CAUSED BECAUSE
THE METEOR'S TRAVELING FASTER

[00:48:41.939]
THAN THE SPEED OF SOUND.

[00:48:43.099]
WOULD A SONIC BOOM FROM A
METEOR BE POWERFUL ENOUGH

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TO CAUSE A SEISMIC READING?

[00:48:47.019]
YES, A SEISMOMETER WILL DETECT A
SONIC BOOM FROM A LARGE METEOR.

[00:48:50.909]
HOWEVER, TO HEAR THE SONIC BOOM,
YOU HAVE TO BE RELATIVELY CLOSE,

[00:48:54.949]
TYPICALLY WITHIN 50 MILES OR SO,
AND THE FIREBALL IS VISIBLE AS FAR

[00:48:59.859]
AS AWAY -- 500 MILES AWAY.

[00:49:01.469]
I WOULD LOVE TO SEE ONE.

[00:49:02.669]
MOST FIREBALLS ARE NOT
OBSERVED BECAUSE 75 PERCENT

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OF THE EARTH IS OCEAN, AND
THERE AREN'T TOO MANY PEOPLE

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IN THE MIDDLE OF THE OCEAN.

[00:49:09.239]
IN JULY OF 2001, THERE WAS
A FIREBALL THAT WAS SEEN

[00:49:12.449]
FROM VIRGINIA TO ONTARIO, CANADA.

[00:49:14.619]
AND SONIC BOOMS WERE REPORTED
BY PEOPLE STRETCHED OVER AN AREA

[00:49:17.579]
OF MORE THAN 100 MILES.

[00:49:19.499]
THIS HAS BEEN A LOT
OF HELP, MR. BAALKE.

[00:49:21.899]
I THINK WE'VE FOUND THE
ANSWER TO OUR MYSTERY.

[00:49:23.699]
DR. PETER BROWN AT THE UNIVERSITY

[00:49:25.789]
OF WESTERN ONTARIO IS
AN EXPERT ON FIREBALLS.

[00:49:28.579]
YOU MIGHT WANT TO SEND HIM AN EMAIL
AND ASK HIM SOME MORE QUESTIONS.

[00:49:32.009]
THANKS SO MUCH.

[00:49:32.899]
I'LL SEND DR. BROWN AN EMAIL.

[00:49:35.649]
WOW, I DIDN'T KNOW THERE COULD
BE SONIC BOOMS FROM METEORS.

[00:49:38.549]
WE TALKED ABOUT SONIC
BOOMS BEING THE ANSWER.

[00:49:40.809]
BUT NOT SONIC BOOMS FROM A METEOR.

[00:49:42.679]
HEY, YOU GUYS, I JUST GOT