Plate Tectonics Earth’s Layers Continental Drift Seafloor Spreading Plate Tectonics Theory.

Plate Tectonics

•Earth’s Layers•Continental Drift

•Seafloor Spreading•Plate Tectonics Theory

Earth’s History

How old is our Universe?

13.7 billion years old

How old is Earth?

4.6 billion years old

Earth was once made of molten lava and magma, eventually

cooling to igneous rock

Weathering, Erosion,

Compaction, Cementation,

Heat, and Pressure

eventually formed the rocks that

cover our Earth’s surface.

What we know about Earth’s history comes from studying its rocks and rock formation and even the rocks from outer

space

Meteorites• All meteorites formed

about the same time that Earth formed, so studying them helps us study Earth.

• Meteorites have not been affected by erosion, weathering or other forces the way Earth’s rocks have.

Studying Earth’s Rocks

Rock Layers

• Which book was placed here first?

• The bottom one!

• Sedimentary rocks often follow a similar pattern, oldest rocks are found on the bottom.

http://www.prehistoricplanet.com/news/index.php?id=48

• Digging through the layers of rocks, helps us understand more about the history of Earth.

Fossils

• Most fossils are found in Sedimentary rock layers

• Why?– Heat, pressure, and

melting would probably destroy fossils during the formation of Igneous and Metamorphic rocks

• The Grand Canyon (AZ) was carved by the Colorado river, exposing millions of years worth of rock layers.

Sometimes, the rock layers aren’t always horizontal…

And sometimes ocean fossils are found high in the mountains…

Why?

• Turns out, our Earth’s surface is constantly shifting and changing.

• Sometimes layers get pushed around.

• Only in the last 200 years, have we begun to understand the structure and formation of our Earth.

I wonder what’s inside

Earth?

Homework: Draw a picture of an apple/egg/avocado cut in half and explain why this is similar to the layers of Earth’s

interior.

Page 135

Skin = crust“fruit” = mantle

Seed coat = outer core

Seeds = inner core

white = mantle

shell = crust

Center yolk = inner core

Outer yolk = outer core

Seed shell =

outer core

Seed center =

inner core

skin = crust

“fruit” =

mantle

Earth’s Layers

Earth’s Layers

Inner Core750 mileradius

Outer Core1,430 miles

Mantle1,800 miles

Crust(10-25 miles)

Inside Our Earth

The inner core is made of solid nickel and iron.

The outer core ismade of hot liquid nickel and iron.

The crust is made of soil, water and rock.

The mantle is hot. Partmelted and part solidiron and magnesium.

Composition of the Earth’s Layers

• The Lithosphere is made of the crust and upper mantle

• The Lithosphere is broken into many sections or plates.

• Some plates are lighter than others.

•The lithosphere is made of two igneous rock types:•Continental crust - granite (light)•Oceanic crust - basalt (heavy)

•Because granite is lighter than basalt, the continents sit on top of the denser oceanic plates

•Mantle is the largest layer over 1800 miles thick•It is composed of mostly liquid rock that moves due to temperature differences•1800 degrees F at the top, 4000 degrees F near the bottom.

•Outer Core-Very hot liquid metals 4,000 degrees F to 9000 degrees F•Made of Nickel and Iron •This liquid core produces a magnetic field that helps protect earth from coronal mass ejections (CME’s) produced by the sun.

Protective Magnetic Field

•In the Inner Core, temperatures and pressures are so great, the liquid metals are forced back into a solid despite the high temperatures that would normally melt them.•45,000,000 pounds of pressure per square inch. •3,000,000 times more pressure than felt at sea level.

How do we know what’s inside?

• Geologists study earthquakes and volcanoes

Seismic waves caused by

earthquakes change direction as they

move through different materials

(such as solids and liquids)

http://www.classzone.com/books/earth_science/terc/content/investigations/es0402/es0402page03.cfm

Earthquake wave animation:http://neic.usgs.gov/neis/eq_depot/2002/eq_021103/ak_seismic_waves.html

I’m going to dig a hole to _____

Dig a hole to the other side of Earth

http://www.ubasics.com/dighole/http://www.livephysics.com/ptools/dig-hole-through-earth.php

I’m going to dig a hole to China!

• You will have to start in Chile, South America

Will you make it to the other side?

• If you could survive the temperatures (over 8,000 degrees F) and the pressure (3,000,000 times the force of gravity) and you could “climb” out the other side (down is towards the center of Earth), then YES!

• If you could just freefall all the way through Earth (8,000 miles) it would take you about 67 hours falling at 120 mph.

http://www.daviddarling.info/childrens_encyclopedia/Dig_a_Hole_to_China_Chapter5.html