HIS.

>>> HI, I'M JOAN CARTAN-HANSEN,
AND WELCOME TO SCIENCE TREK THE

WEB SHOW, AND JOINING ME TODAY
TO ANSWER YOUR QUESTIONS ABOUT

THE EARTH, ARE VIRGINIA
GILLERMAN AND JEFFERY JOHNSON.

THANK YOU BOTH FOR BEING HERE.

I APPRECIATE YOU TAKING THE
TIME.

>> THANKS FOR INVITING US.

>> THANK YOU.

>> OK.

LET'S GO TO YOUR QUESTIONS.

>> SHILA WOULD LIKE TO KNOW WHY
IS THE EARTH ROUND?

>> WHEN THE EARTH FORMED, IT WAS
A HOT GLOB OF MATERIAL.

AND GRAVITY PULLED IT TOGETHER
IN THE FORM THAT WAS MOST

CONVENIENT.

THEY COULD NOT PULL IT TOGETHER
IN THE FORM OF A CUBE BECAUSE

THAT WOULD BE UNNATURAL FOR THE
GRAVITATIONAL FIELD.

IT PULLED IT TOGETHER IN THE
SHAPE OF A SPHERE, A SLIGHTLY

DISTORTED SPHERE, BUT FOR, FOR
MOST PURPOSES, A PERFECT SPHERE,

THAT IS THE EASIEST SHAPE FOR
GRAVITY TO PULL AN OBJECT INTO.

>> I AM PURDUE, AND MY QUESTION
IS -- HOW DO EARTHQUAKES WORK?

>> EARTHQUAKES ARE WHEN ROCKS
MOVE PAST EACH OTHER, AND THEY

WILL FRACTURE, RELEASE ENERGY BY
FRACTURING QUICKLY, AND JEFF

WILL TELL US MORE.

>> EARTHQUAKES HAPPEN WHEN ROCKS
BREAK.

ROCKS CAN BREAK ON VERY SMALL
SCALES.

IF YOU HAD, LET'S SAY, A ROCK
THAT WAS THE SIZE OF A

REFRIGERATOR, THAT ALL OF A
SUDDEN BROKE, YOU WOULD HAVE A

MAGNITUDE OF ONE EARTHQUAKE.

NOW, IMAGINE YOU HAVE ROCK THAT
EXTENDS FOR HUNDREDS OF MILES

THAT BREAKS, YOU WOULD ALSO HAVE
A VERY SIMILAR EARTHQUAKE, BUT

IT WOULD BE MUCH, MUCH LARGER.

IN BOTH CASES, SMALL AND LARGE,
THE EARTH'S ROCKS ARE BREAKING.

AND BREAKING FAST.

>> DEBRA WOULD LIKE TO KNOW, IS
THE EARTH THE ONLY PLANET WITH

WATER?

>> IT'S NOT THE ONLY PLANET WITH
WATER, IT'S THE ONLY ONE THAT,

THAT WE KNOW OF THAT, THAT HAS
A, HAS ABUNDANT WATER, FOR

EXAMPLE, ABOUT THREE QUARTERS OF
OUR SURFACE IS COVERED WITH

WATER.

WE HAVE SOME EVIDENCE THAT ON A
PLANET LIKE MARS, THERE WAS

WATER IN THE PAST, OR THERE
MIGHT BE WATER THAT'S BOUND UP

WITH THE ROCKS OR FROZEN CARBON
DIOXIDE.

BUT, I DON'T THINK WE KNOW OF
ANY OTHER PLANETS WITH ROTS OF

LIQUID WATER ON THE SURFACE
LIKE, LIKE THE EARTH HAS.

BUT, WE'RE STILL LOOKING.

THERE IS A LOT OF PLANETS, WE
JUST DON'T KNOW THAT MUCH ABOUT.

>> AND ONE EXCEPTION THAT I CAN
THINK OF, IS UROPA, WHICH IS A

MOON OF JUPITER, WHICH DOES HAVE
PLENTY OF WATER ICE, AND MAYBE

EVEN AN OCEAN BENEATH THAT WATER
ICE.

MOST OF MARS' WATER IS PROBABLY
TIED UP RIGHT NOW IN ICE.

NOT VERY USABLE FOR, FOR ANY
SORTS OF LIFE THAT MAY, THAT MAY

LIVE THERE.

>> HI, I AM MIA.

AND MY QUESTION IS, WHICH PART
OF THE EARTH IS THE MOST

IMPORTANT TO LIVE?

>> I WOULD SAY THE SURFACE OF
THE EARTH, THAT INCLUDES THE

ROCKS THAT WE STAND ON.

THE SOIL THAT'S PRODUCED FROM
THOSE ROCKS, AND THE OCEANS, AND

THE SPHERE THAT WE BREATHE.

WE, ESSENTIALLY, LIVE AT, AT THE
JUNCTION OF ALL OF THOSE VERY

COMPLEX GEOCHEMICAL AND GEO
LOGIC SYSTEMS.

IT MIGHT BE THE DIVERSITY THAT
HAS HELPED TO CREATE LIFE AND

CREATED THE DELICATE BALANCE
THAT WE USE IN OUR DAILY LIVES.

>> SAM ASKS, WHERE DOES THE AIR
COME FROM TO SUPPORT LIFE?

>> SAM, THE AIR COMES FROM THE
OXYGEN IN OUR AIR COMES FROM

PHOTO SYNTHETIC PROCESSES, AND
MOST OF THE OXYGEN THAT WE NEED

AS HUMANS TO SURVIVE ON COMES AS
A BY-PRODUCT, OR A POLLUTION

FROM PLANT MATTER.

SO, OXYGEN ORIGINALLY CAME FROM
WATER AND CARBON DIOXIDE, WHICH

WAS SPEWED OUT BY VOLCANOES OVER
MANY, MANY EONS, AND PLANTS,

TREES, BLUE-GREEN ALGAE AND
OTHER VEGETATION TURNED THOSE

RAW MATERIALS INTO THE OXYGEN
THAT WE NEED.

>> I AM SABRINA FROM HILLCRUST
ELEMENTARY.

HOW ARE DINOSAUR FOSSILS STILL
UNDERI DON'T YOU UNDERSTAND?

>> THEY ARE BECAUSE 24E6 NOT
BEEN EROIDED OR WASHED DOWN FROM

THE MOUNTAINTOPS OR WHEREVER
THEY ARE FOUND YET.

FOSSILS FORM UNDERGROUND, AND
BACK WHEN THE DINOSAURS WERE

STILL LIVING, AND THEY WOULD
DIE.

THEIR BONES WOULD FALL TO THE
BOTTOM OF THE OCEAN.

OR THE RIVER BOTTOM, WHEREVER
THEY WERE LIVING.

OVER TIME, THOSE BONES WOULD GET
COVERED WITH DIRT, MUD, SAND,

ETC., AND THOSE SEDIMENTS WOULD
LIQUIFY, OR TURN INTO ROCK.

AS THEY DO SO, ANY WATER THAT
MIGHT HAVE SAY DISSOLVED SILICA

IN IT, IE QUARTS, CAN PERCOLATE
THROUGH THOSE, AND INTERACT WITH

THOSE BONES, AND REPLACE THEM
WITH FOSSILIZING MATERIAL.

SO, THOSE FOSSILS ARE, ACTUALLY,
FORMED UNDERGROUND.

UNTIL THEY ARE EITHER FOUND BY A
PALEONTOLOGIST OR A SCIENCE KID

OUT FOR A NATURE HIKE, OR ERODED
OFF, THEN THEY WILL REMAIN

UNDERGROUND.

>> I AM RYLEE, AND HOW DOES, HOW
DO THE LAYERS OF THE SPHERE ALL

CONNECT?

>> HOW DO THE SPHERES OF THE
EARTH CONNECT?

THERE ARE A LOT OF SPHERE WORDS.

THERE IS THE ATMOSPHERE, WHICH
COMPRISES THE EARTH'S GASES,

THERE IS THE HYDROSPHERE, WHICH
IS THE EARTH'S OCEANS, THERE IS

THE CRYOSPHERE, WHICH IS THE ICE
CAPS.

AND THEN BENEATH WE HAVE THE
LITHOSPHERE, WHICH IS THE ROCKY

OR RIGID PORTION OF THE EARTH
THAT COMPRISES OUR TECTONIC

PLATES.

BEFORE THIS WE HAVE THE
ESTHENOSPHERE, WHICH IS THE

REGION ON TOP OF WHICH OUR
TECTONIC PLATES FLOAT.

>> AND UNDER THAT, YOU CONTINUE
WITH THE MANTLE AND THE CORE,

WHICH ARE OTHER SPHERICAL-SHAPED
ROCKY OR MOLTEN ROCK REGIONS

WITHIN THE EARTH.

THEY JUST DON'T HAVE THE WORDS
SPHERE IN THEM FOR SOME REASON.

>> ALYSON WOULD LIKE TO KNOW,
HOW DOES THE EARTH ROTATE?

>> NOW, THE EARTH ROTATES
BECAUSE IT'S ALWAYS ROTATED.

THIS IS NOT A VERY SATISFACTORY
ANSWER.

BUT, WHEN THE EARTH WAS FORMED
SOME 4.6 BILLION YEARS AGO, IT

HAD SOMETHING WE CALL ANGULAR
MOMENTUM ASSOCIATED WITH IT.

THAT MEANS A TENDENCY TO SPIN,
AND NOW, AS ALL OF THE PARTICLES

IN OUR SOLAR SYSTEM ARE CREATED
TO FORM PLANETS, IT ALL SORT OF

CAME CLOSER TO THE SUN AND BEGAN
TO SPIN FASTER.

THINK OF AN ICE SKATER WITH HIS
OR HER ARMS EXTENDED OUTWARD,

AND AS THOSE ARMS COME IN
CLOSER, THE ROTATION OR THE

ANGULAR MOMENTUM IS CONSERVED
BUT THE SPIN BECOMES FASTER.

AND WE ARE SEEING THE RESULT OF
THAT INITIAL ROTATION IN TODAY'S

EARTH ROTATION.

THE EARTH WILL CONTINUE TO
ROTATE FOR A LONG, LONG TIME,

UNLESS IT COLLIDES WITH SOME
OTHER BODIES.

>> LEXI WOULD LIKE TO KNOW, DO
ALL PLANETS HAVE MOONS?

>> NO, NOT ALL PLANETS HAVE
MOONS.

VENUS DOESN'T HAVE ANY.

AND EARTH HAS ONE AND, AND SOME
PLANETS, LIKE JUPITER AND SATURN

HAVE MANY MOONS.

SO, IT VARIES.

>> BETSY WOULD LIKE TO KNOW, WHY
IS THE EARTH NOT BEING STUCK

INTO THE SUN?

>> BETSY, THE EARTH IS ALWAYS
FALLING TOWARDS THE SUN.

BELIEVE IT OR NOT, THE SUN'S
PULL OF GRAVITY CAUSES THE EARTH

TO MOVE TOWARDS IT ALL THE TIME.

BUT, I WOULD NOT LOSE ANY SLEEP
OVER IT BECAUSE AT THE SAME

TIME, THE EARTH HAS SOMETHING
CALLED INERTIA.

IT IS MOVING IT IN A DIRECTION
THAT IS AWAY FROM THE SUN.

SO, EVEN THOUGH THE EARTH IS
CONTINUOUSLY FALLING TOWARDS THE

SUN, IT IS MOVING AROUND THE
SUN, AND ULTIMATELY, IT IS

ORBITING IN A CIRCLE AROUND THE
SUN.

>> I'M SORRY BUT WE HAVE RUN OUT
OF TIME.

MY THANKS TO JEFF AND VIRGINIA
FOR ANSWERING QUESTIONS TODAY.

>> THANKS VERY MUCH FOR HAVING
US.

>> THANK YOU, AND THANK YOU TO
THE STUDENTS WHO SUBMITTED GREAT

QUESTIONS.

THANKS, ALSO, TO THE FOLKS HERE
AT BOISE STATE UNIVERSITY'S

EARTH, SCIENCE, RESEARCH LAB FOR
HOSTING US.

IF YOU WANT TO LEARN MORE, CHECK
OUT THE EARTH AREA ON THE

SCIENCE TREK WEBSITE.

YOU WILL FIND LINKS, GAMES, AND
EARTH BROADCAST SHOWS, AND LOTS

MORE.

EVERY WEEK, CHECK OUT MY BLOG
FOR THE LATEST SCIENCE NEWS FOR

KIDS.

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