Time Period | Events Supporting Continental Drift |
1500's |
|
1800's |
|
1912 |
|
Mid-1900's |
|
Evidence | Details |
Sea-Floor Spreading |
· melted rock; o rises through the cracks o cools o forms new oceanic crust · spreading centers o old crust is pulled away to make room for new material o the sea floor slowly spreads apart |
Age of the Sea Floor |
o rock samples show; o youngest rock is closest to the ridge o oldest rock is farthest away o oldest ocean floor is 160 to 180 million years old o continental crust is up to 4 billion years old o the ocean floor is always forming & moving o sea floor moves = tectonic plates & continents move |
Ocean Trenches |
o old crust is being destroyed at the same rate that new crust is forming o dense oceanic crust is sinking into the huge trenches in the sea floor & then into the asthenosphere |