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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