1.1 earth has several layers. denser material sinks less dense material rises to the top
TRANSCRIPT
•Crust: Thick layer of cool rock, surrounding earth. There are 2 types: oceanic and continental•Mantle: Earth’s thickest layer, 1700 miles thick, hot rock, less dense than core•Outer Core: Layer of liquid metal that surrounds inner core• Inner Core: Ball of solid, hot metal
Lithosphere: most rigid of the layers, contains the outermost part of the mantle, and the crust
Asthenosphere: layer of hotter, softer rock in the upper mantle
Continental DriftHypothesis proposed by Alfred Wegener in 1912
Earth’s continents were once joined in a single landmass and gradually moved apart.
Fossils: mesosaurus found in South America & Western Africa – not found anywhere else!
Climate: evidence of change: Warm weather plants in Greenland, glacial evidence in South Africa
Geology: rocks from Brazil match those of Western Africa, Limestone of Appalachian mountains matches Scotland’s highlands
Pangaea: Greek meaning “all lands”
Giant continent that reached from pole to pole and covered area where Africa lies today
Mid Ocean Ridges: huge underwater mountain ranges◦Sea Floor Spreading – ridges form along
cracks in the crust, molten rock rises through the cracks making new crust
◦Age of sea floor – sea floor is youngest at the ridges, older farther away
◦Ocean trenches – deep canyons where the sea floor is sinking into asthenosphere.
Convection: energy transfer by the movement of material
Convection current: sinking and rising motion that transfers heat in a material
Theory of plate tectonics: Earth’s lithosphere is made of huge plates that move over the surface of the earth.
Divergent boundaries: occurs where plates move apart – most are found in the ocean
Convergent boundaries: occurs where plates push together
Transform boundaries: occurs where plates scrape past each other
AKA spreading centers Rift valley: deep valley formed as tectonic
plates move apart, as a long a mid-ocean ridge
Mid-ocean ridges are the longest chains of mountains on Earth
Mid-Atlantic ridge world’s longest mountain range
Subduction: when one plate sinks beneath another
Oceanic crust: crust under ocean floor - more dense
Continental crust: crust forming the continents – less dense
Two plates carrying continental crust push together
Same density, neither one skinsRocks crumple and fold to form mountains
Examples: European Alps, Himalaya
One plate of oceanic crust subducts (sinks) beneath another plate of oceanic crust
Older plate is colder and denser, and sinks below younger plate
Creates two features:◦ Deep ocean trenches – deep canyons in ocean
floor example: mariana trench◦ Island arcs – chains of volcanic islands that form
on the top plate parallel to trench. Example: Japanese islands
Ocean crust sinks under continental crust
Oceanic crust is colder and denser than continental crust
Features created:◦Deep ocean trenches – can cause underwater earthquakes
◦Coastal Mountains – Examples: Cascade Mountains
Transform boundary: plates scrape past each other in opposite direction
Crust is neither created nor destroyed Example: San Andreas Fault, San Francisco
California