Chapter 4 Lesson 1 Plate Tectonics
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Transcript of Chapter 4 Lesson 1 Plate Tectonics
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