Geology Test: Ch. 2

Typical rate for seafloor spreading

15 cm a year, 2 cm a year out on atlantic ocean

Evidence to Pangaea:

Continental Jigsaw puzzle, Fossils, Rock types and geologic features, Ancient climates- India, found evidence of glaciation and coal fields

Divergent plate boundaries

New crust is generated as two plates move apart, Oceanic ridges and seafloor spreading, Rift valley, Seafloor spreading, Rates of spreading, Continental rifting

New evidence after WW2

Oceanic ridge system winds through all the major oceans, No oceanic crust older than 180 million years old, Sediment accumulation in the deep oceans was relatively minor

Convergent plate boundaries

Older portions of oceanic plates are returned to the mantle, Subduction zones, Deep-ocean trenches, Oceanic-continental boundaries

Ocean drilling evidence

Oldest sediments are furthest from the spreading center, Sediments thickest at the furthest points from the spreading center

What supercontinent existed 200 million years ago?

Pangaea

Continental boundaries

Plate tectonics can bring two continents together Less dense, buoyant continental lithosphere does not subduct, Collision, mountains

Transform plate boundaries

Plates slide past one another , Fracture zones

What book did Alfred Wegner write?

The Origin of Continents and Oceans 1915

Oceanic boundaries

Two oceanic slabs converge and one will decent beneath the other, Volcanic island arc

Ridge-push

a gravity driven force that results from the elevated position of the ridge.

Convergent plate boundary (Destructive margin)

along south america plate, as coming together one plate is usually going to melt

Transform (conservative margins) (transform fault)

along west coast, California (most famous)

Why are volcanoes associated with plate boundaries?

bc we have convergent plate boundaries who have that crust that is descending into the earth

Convective flow

convection in the mantle enhances plate motion when the velocity of the asthenosphere exceeds that of the overlying plate.

Divergent plate boundary (Constructive margin)

in the middle of Atlantic ocean ridge, building new rock as those plates diverge

Slab pull

results from the sinking of a cold, dense slab of oceanic lithosphere and is the major driving force of plate motion.

Plate boundaries

where the plates meet