Chapter 17: Plate Tectonics Flashcards
Continental Drift
the proposition that Earth’s continents had once been joined as a single land mass
Pangea
a super continent that split apart 200 million years ago
evidence to support continental drift
- mountain chains line up
- fossils
- puzzle piece
Why did many reject the theory of continental drift
because he could not explain how the continents could move and what would power them to do so
magnetometer
a device that can detect small changes in magnetic fields
what major discoveries did they find on the ocean floor
vast underwater mountain chains and ridges
what is paleomagnetism
the study of the magnetic record
seafloor spreading
new ocean crust is forms at ocean ridges and gets destroyed at deep-sea trenches
how is seafloor spreading the missing link to continental drift
it showed that the continents were not pushing through the sea but they were along for the ride while the earths surface was moving
plate tectonics
earth’s crust and rigid upper mantle are broken into enormous slabs called plates. Tectonic plates move around the earth in different directions and speeds
Name 5 major tectonic plates
- pacific
- eurasian
- North American
- African
- Indian-Austrailian
Divergent boundary
- places were plates move apart
- form ridges on the ocean floor
- on land form deep narrow depressions called rift valleys (east Africa)
- earthquakes
convergent boundary
- places where two tectonic plates are moving toward each other
- oceanic vs. oceanic, oceanic vs. continental, continental vs. continental
subduction
one of two plates descending beneath the other, it happens because one plate is denser and cooler than the other plate and so when it collides with the other plate it goes beneath it
why do convection currents drive plate tectonics
convection currents push and pull the continents
