1.1 Earth has several Layers

Denser material sinksLess dense material rises to the top

•Crust: Thick layer of cool rock, surrounding earth. There are 2 types: oceanic and continental•Mantle: Earth’s thickest layer, 1700 miles thick, hot rock, less dense than core•Outer Core: Layer of liquid metal that surrounds inner core• Inner Core: Ball of solid, hot metal

Lithosphere: most rigid of the layers, contains the outermost part of the mantle, and the crust

Asthenosphere: layer of hotter, softer rock in the upper mantle

Tectonic plates fit together like a jigsaw puzzle

Contain both continental crust and oceanic crust

1.2 Continents Change over Time

Continental DriftHypothesis proposed by Alfred Wegener in 1912

Earth’s continents were once joined in a single landmass and gradually moved apart.

Fossils: mesosaurus found in South America & Western Africa – not found anywhere else!

Climate: evidence of change: Warm weather plants in Greenland, glacial evidence in South Africa

Geology: rocks from Brazil match those of Western Africa, Limestone of Appalachian mountains matches Scotland’s highlands

Pangaea: Greek meaning “all lands”

Giant continent that reached from pole to pole and covered area where Africa lies today

In the mid 1900’s scientists proved that tectonic plates move.

Built upon Wegener’s ideas.

Mid Ocean Ridges: huge underwater mountain ranges◦Sea Floor Spreading – ridges form along

cracks in the crust, molten rock rises through the cracks making new crust

◦Age of sea floor – sea floor is youngest at the ridges, older farther away

◦Ocean trenches – deep canyons where the sea floor is sinking into asthenosphere.

Convection: energy transfer by the movement of material

Convection current: sinking and rising motion that transfers heat in a material

Convection

Theory of plate tectonics: Earth’s lithosphere is made of huge plates that move over the surface of the earth.

1.3: Plates move apart

Divergent boundaries: occurs where plates move apart – most are found in the ocean

Convergent boundaries: occurs where plates push together

Transform boundaries: occurs where plates scrape past each other

AKA spreading centers Rift valley: deep valley formed as tectonic

plates move apart, as a long a mid-ocean ridge

Mid-ocean ridges are the longest chains of mountains on Earth

Mid-Atlantic ridge world’s longest mountain range

Earth’s magnetic poles switch places, called magnetic reversals

How stuff works

Like the sea floor, continents can split apart at a divergent boundary

Great Rift Valley

View plate boundaries

Hot spot: heated rock rising in thin columns from the Earth’s mantle.

Hawaiian islands

1.4: Plates converge of scrape past each other

Subduction: when one plate sinks beneath another

Oceanic crust: crust under ocean floor - more dense

Continental crust: crust forming the continents – less dense

Two plates carrying continental crust push together

Same density, neither one skinsRocks crumple and fold to form mountains

Examples: European Alps, Himalaya

One plate of oceanic crust subducts (sinks) beneath another plate of oceanic crust

Older plate is colder and denser, and sinks below younger plate

Creates two features:◦ Deep ocean trenches – deep canyons in ocean

floor example: mariana trench◦ Island arcs – chains of volcanic islands that form

on the top plate parallel to trench. Example: Japanese islands

Ocean crust sinks under continental crust

Oceanic crust is colder and denser than continental crust

Features created:◦Deep ocean trenches – can cause underwater earthquakes

◦Coastal Mountains – Examples: Cascade Mountains

Transform boundary: plates scrape past each other in opposite direction

Crust is neither created nor destroyed Example: San Andreas Fault, San Francisco

California

The plates lithosphere has been in motion for millions of years

By studying rock layers geologists can uncover the history of any region.

Plate tectonics gives scientists a way to study and predict geologic events such as earthquakes and volcanic activity