Continental Drift
Scientists have observed that the continents move apart or come together at speeds of a few centimeters per ____.
What is Year?
Seafloor spreading occurs because ____.
molten material beneath Earth's crust rises to the surface
The crust and upper mantle make up Earth's ____.
Lithosphere
Plates slide past one another at ____.
transform boundaries
A lack of explanation for continental drift prevented many scientists from accepting that a single supercontinent called ____ once existed.
Pangaea
Matching ____ on different continents are evidence for continental drift.
What is rock structures
The magnetic pattern of ocean-floor rocks on one side of an ocean ridge is ____.
a mirror image of that of the other side
Plates of the lithosphere float on the ____.
asthenosphere
The boundary between two plates moving together is called a ____.
convergent boundary
The East African Rift is an example of a ____.
continental rift
Continental drift was not widely accepted when it was first proposed because ____.
Wegener couldn’t explain why or how the continents moved
A ____ is a sensitive device used to detect magnetic fields on the seafloor.
magnetometer
____ currents inside Earth might drive plate motion.
Convection
A ____ can also form when two oceanic plates collide
line of volcanoes
At an oceanic-oceanic convergent plate boundary, ____.
old crust is recycled by subduction
Wegener believed that the continents were assembled as part of a supercontinent about ____ years ago.
250 million
The youngest rocks on the ocean floor are located ___
at mid-ocean ridges
Places where plates move apart are ______________________________.
Divergent plate boundaries
Active volcanoes are most likely to form at ____.
convergent oceanic–continental boundaries
A change in Earth’s magnetic field is called a(n) _________________________.
Magnetic reversal
The presence of the same ____ on several continents supports the hypothesis of continental drift.
Rocks and Fossils
These features form as new crust rises to the surface during seafloor spreading
What are mid-ocean ridges?
The result of plate movement can be seen at ____
plate boundaries
Crust is neither destroyed nor formed along which of the following boundaries?
Transform
This is the term for one plate being forced underneath another plate.
Subduction