Chapter 4Lesson 1

Plate Tectonics

What Are Earth’s Layers

Earth’s Layers

• Core- central part– Inner Core – solid

metals– Outer Core – liquid

metals

• Mantle – thick layer of solid and molten rock that surrounds the core

• Lower – solid rock• Upper – 2 parts

• Lithosphere – solid- upper mantle & crust

• Asthenosphere – upper mantle – melted rock

• Crust– Thin layer of solid rock

that makes up the outermost layer.

– Where we live

• Atmosphere – – All gases that

surround the Earth

• Hydrosphere– All of Earth’s liquid and

solid water (lakes, oceans, rivers, glaciers)

– Covers 70% of the Earth

Landforms – a physical feature of the Earth’s surface

Earth ~200 million years ago

The Continental Drift Hypothesis

Geologist – person that studies rocks

Thought of by Alfred Wegener in 1915.

Continents "drifted" to their present positions.

Supercontinent Pangaea started to break up about 200 million years ago.

Continental Drift: Evidence

Geographic fit of South America and Africa

Fossils match across oceans

Rock types and structures match across oceans

Ancient glacial features

Tight fit ofthe

continents, especially

usingcontinental

shelves.

Continental

Drift:Evidence

Continental Drift: Evidence

Fossil critters and plants

Continental Drift:

Evidence

Correlation of

mountains with nearly

identical rocks and structures

ContinentalDrift:

Evidence

Glacial features

of the same age

restore to atight polar

distribution.

Presumably,Pangaea was ripped apart

by such continental

rifting & drifting.

What causes the continents

to move?Plate Tectonics

•Theory to explain how forces deep within Earth can cause seafloors to spread and continents to move.

Tectonic PlatesTectonic Plates

Continental Divergent BoundaryExample: Red Sea / E. African Rift

•Magma – hot melted rock

• Tension – push or a stretch on the plates

•Seafloor Spreading – caused by magma pushing on the plates

Mid Ocean RidgesMid Ocean Ridges

- underwater mountain ranges

Subduction – when one tectonic plate can sink under

another plate- crust gets recycled back into the mantle

Mountain Formation• Compression – a squeezing

or pushing together of the crust

This creates folded mountains.

Fault – deep cracks in the Earth’s crust where rocks move in the opposite direction

• Fault Block Mountain – Caused by tension

when one block of rock moves down

– Sierra Nevada Mountains