INTERNAL FORCES SHAPING THE EARTH

CH. 4.1

http://upload.wikimedia.org/wikipedia/commons/e/ec/World_map_blank_without_borders.svg

Earth’s Layers:• Core –

• Inner: solid metallic center of Earth • Outer: liquid metallic center of Earth

• Mantle – • soft layer of molten rock (Magma) floating on the core

• Crust – • thin layer of rock at the surface

• Volcanoes – • Openings in Earth's crust thru which molten lava, ash, & gases are ejected

• Magma – • Molten rock beneath the surface

• Lava – • Molten rock on the surface

• 1912: Alfred Wegener: • Suggested Continental Drift Theory after looking at map of world• Found fossils of extinct animals on different continents

• 1950s & 1960s: ocean floor was studied • Underwater mtns. ring the edges of continents • 1968:

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• 1968: Theory of Plate Tectonics • Earth’s crust is divided into rigid plates that move slowly on the upper

mantle—set in motion by convectional heat from the core • Move in different directions• Over 12 plates

• Pangaea • When all of Earth’s continents were one (225 mill. yrs. Ago)

• Laurasia• Northern half of Pangaea

• Gondwanaland • Southern half of Pangaea

Plate Boundaries • Divergence:

• Spreading/pulling apart• Mid-Atlantic Ridge• Iceland / Surtsey• Video clip

• Convergence:• Continental plates crash into one another• Himalaya Mtns.

• Subduction:• Lesser oceanic plate is forced under dominant continental plate • Trenches (Mariana Trench)• Mountains (Japan, Andes Mtns., Cascade Mtns.) • Video clip

• Transform:• Plates move laterally passed one another • New Madrid, MO• San Andreas Fault

Type:

SOME Geologically-Active Places:• Ring of Fire:

• Geologically-active region around the perimeter of the Pacific Ocean• 75% (452) of world’s active & dormant volcanoes• 90% of world’s earthquakes

• Video clip

• Great Rift Valley:• Divergent plate boundary in E. Africa

• Mariana Trench:• Subduction plate boundary• Deepest part of the ocean

• Challenger Deep• >36,000 ft. deep• James Cameron (March 2012)

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• Earthquake Monitor Site