tectonics 1.2 Flashcards
what is a mid oceanic ridge
a underwater volcano mountain chain linearly located on the ocean floor at divergent plate boundaries
what are oceanic trenches
deep depressions in found in the ocean floor where one oceanic plate is subducting beneath another plate
what is the process of seafloor spreading
-where two plates move away from each at divergent plate boundaries, seafloor spreading occurs( only in divergent plate boundaries )
-magma from deep within earth rises through the mid oceanic ridge formed
-thus, new oceanic crust is formed
why does evidence of seafloor spreading support the plate tectonic theory
-rocks nearer to the crest of the mid oceanic ridges are younger than the rocks further away from the ridge.
-it shows how new oceanic crust is formed at divergent boundaries and it moves side to side on both sides of the mid oceanic ridge as seafloor spreading continues
-as older crust is being destroyed at oceanic ridge, little sediment accumulation occurs.
-proof that new crust is continuously formed at divergent boundaries at mid oceanic ridges as plates move.
example of sea floor spreading between oo divergent plate boundaries
oceanic north american and eurasian plate move apart and forms the mid atlantic ridge.
In the centre of the ridge there is a deep rift valley with steep sides .
Magma rises through weak areas in the crust to earth’s surface. Thus, forming underwater volcanoes.
Volcanic islands form after many eruptions occur and they break the surface of the ocean. Example of such is surtsey island in Iceland. ( frequent earthquakes here due to movement )
