Earth layers, plates

Chapter 11

Inner core: solid

pressure from above layers.

temp 5500°C

Fe Ni

Outer core: liquid

Fe Ni

temp 5500°C

Mantle: largest layer

Si O Mg Fe

plastic like

acts as a solid but flows like a liquid when under pressure

ex. Silly putty or taffy

Crust: varies in thickness Thick – continental

crust - granite Thin – oceanic crust

– basalt

Crust is divided into sublayers

Lithosphere – crust and upper mantle - broken into 12 large plates that float on the mantle.Asthenosphere – plastic like layer below the lithosphereMohorovicic' discontinuity – boundary between crust and mantle.

Lithosphere

Continental Drift

Alfred Wegener –

1912 proposed theory of continental drift

continents have moved to their current locations

Theory of continental drift

One continent – Pangaea

200 m years ago

Panthalassa – one sea

Pangaea separated into

Laurasia

Gondwanaland

Separated by the Tethys Sea

Clues that support Continental Drift

Pieces of continents fit together like a jigsaw puzzleFossil clues – Mesosaurus(lived on land and in fresh water) - found in South American and

AfricaGlossopteris – found in Africa, Australia, India, South America and Antarctic - various climates - must have once been joined

Climate clues – fossils of warm plants found in the arcticGlacial deposits – grooved marks in bedrock found in SA, Africa, India, and Australia - must have been covered with glaciers at one time near south pole

Rock clues – If continents connected than rocks that make them up should be the same. - similar rock structures are found on different continents ex; Appalachian Mts similar to mountains in western Europe and Greenland

Wegener’s theory was laughed at even though he had evidence

After his death more evidence of how the continents were able to move were discovered to prove Wegener correct.

Mid-Atlantic Ridge

Longest mountain range on earth

Extends from Iceland along middle of Atlantic

Mid-Atlantic Ridge

Harry Hess

Discovered seafloor spreading

Evidence of Seafloor spreading

Rocks along rift areas were younger than those farther away. New lava rocks were being laid on either side of the rift

Magnetic reversals of the iron bearing basaltic rocks of the sea floor.

As the new rock was formed the iron particles in the rock aligned themselves with the magnetic poles of the earth at that time

Plate Tectonics

Earth’s crust and upper mantle are separated into plates.

Plates float on the mantle.

Make contact with each other.

Cause earthquakes and volcanoes, mountains

Composition of plates

Crust and upper mantle – lithosphere Less dense layer

floats on more dense layer

Asthenosphere – mantle More dense Plates flow on this

Plate Boundaries

Divergent Boundaries Move away from

each other mid-Atlantic Ridge Great Rift Valley in

eastern Africa

Great Rift Valley of Africa

Convergent PlatesPlates that come together.1. Ocean/continental

the ocean sinks below the continent.

remelts in mantleSubduction zone- where

ocean plate goes under continental plates

Volcanoes form here.Andes Mts.

2. Ocean/ocean One ocean plate

subducts under another and melts.

Forms deep sea trenches

Forms an island arc volcano

Japan

Oceanic-Oceanic Convergence

                                                                                                  

Island arcs – two ocean plates collide and one subducts to remelt lithosphere to cause volcanoes in the ocean floor.

Ex. Japan

Deep sea trench – forms where subducted plate melts into the mantle.

Ex. Mariana Trench

Pacific Ocean

3. Continental/

continental

- collision between plates cause the boundaries to crumble forming mountain ranges.

- earthquakes formed

- Himalayan Mts formed

Transform Fault Boundary Two plates slip past

one another Moving in opposite

directions Moving in same

direction at different rates

Earthquakes occur San Andreas Fault

Transform fault

Earthquakes formed

Causes of plate tectonics

Convection currents- Hot less dense

asthenosphere rises Cools – more dense

drops Reheats cycle

begins again

Effects of plate tectonics

Volcanoes

Earthquakes

Mountain building FAULT/BLOCK- Compression forces

fault causes weakness. Part of the land drops. Leaving behind higher ground.

Ex. Sierra Nevadas.

http://glencoe.mcgraw-hill.com/sites/dl/free/0078617006/164213/00038307.html

Folded mountains

Two plates collide with each other.

Ex. Appalachian Mts.

Anticline – upward fold in rocks

Syncline – downward fold in rocks.

Strike-slip Faults – plates moving past each other.

Snag onto each other storing up stress

Ex. San Andreas Fault

Strike slip fault

Rio Grand Rift

Rio Grand Rift

Found from Colorado, New Mexico and Texas

Hidden underground below sediment and basalt

Wrangell Mountains Alaska

Wrangell Mt. Alaska

Formed on floor of the Pacific ocean 9600 km from present location

Theory; they were scraped off ocean plate as it was subducted

Red Sea

Formed due to divergence along a triple junction of the Great Reft Valley in Africa and the Gulf of Aden.

Page 113 Critical thinking

Section: 3 page 289

1, 2, 3, 4,

Page 294

Vocab

Checking concepts

Thinking Critically 15,16, 17, 18, 20 23,24, 25