Chapter 4 Lesson 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 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 of the continents, especially using continental shelves. Continental Drift: Evidence

Continental Drift: Evidence Fossil critters and plants

Continental Drift: Evidence Correlation of mountains with nearly identical rocks and structures

Continental Drift: Evidence Glacial features of the same age restore to a tight 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 Plates

Continental Divergent Boundary Example: 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 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