Internal Forces Shaping the Earth Updated 8/21/12

Earth’s Structure: 1) Core: solid metallic center of the earth. 2) Mantle: 1800 miles thick 3) Crust: thin layer of rock at the surface

PANGAEA

Pangaea: 200 million years ago there was 1 super continent. Continental Drift: Theory that supercontinent separated and drifted apart.

Evidence of Pangaea Fossils-distribution of ancient plants and animals Paleoclimatology-sedimentary rocks indicate climate and latitude of original placement Rock magnetism-rocks, especially volcanic rocks, preserve a record of the orientation of the earth’s magnetic field Sea floor spreading-formation of the Mid-Atlantic Ridge

Fossil Support

Plate Movement Tectonic Plates are enormous pieces of the earth’s lithosphere that are slowly moving Plates move along 3 boundaries: Divergent: plates move apart, spreading horizontally Convergent: Plates collide, causing one plate to go underneath or both edges crumble Transform: Plates slide past one another

Plate Absolute Velocity (cm/yr)* Antarctic ~2.05 African ~2.15 Arabian ~4.65 Caribbean ~2.45 Cocos ~8.55 Eurasian ~0.95 Indian ~6.00 Nazca ~7.55 North American ~1.15 Pacific ~8.10 Philippine ~6.35 South American ~1.45

EXAMPLES Divergent: between Saudi Arabia and Egypt: plate movement is causing the Red Sea to become wider than ever before. Convergent: Himalayas are caused by the Indian plate crashing into the Asian plate. Transform: San Andres Fault, California.

Divergent Plate Boundary

Convergent Plate Boundary

Transform Plate Boundary

Plate Boundaries

EARTHQUAKES Earthquakes: as plates grind or slip past each other at a fault, the earth shakes or trembles. Seismograph: Measures size of waves created by earthquake. Epicenter: -Location on the earth where earthquake begins.

Richter Scale: C. E. Ritchie developed a scale to measure amount of energy. Tsunami: Earthquake below the ocean and can cause a giant wave.

Volcano: An opening in the earth’s crust where Magma and gases escape Volcano: An opening in the earth’s crust where Magma and gases escape. Most are found near the tectonic plate boundaries. Magma that reaches the earth’s surface is called lava.

Ring of Fire: A zone around the rim of the Pacific Ocean where most active volcanoes are found.