Plate Tectonics
What evidence supports plate tectonic theory?
Evidence includes the fit of continents, matching fossils across continents, similar rock formations, magnetic striping on the ocean floor, and the global pattern of earthquakes and volcanoes.
Do plates come together or move apart?
They can do both, depending on the type of boundary.
What is a continental rift?
A continental rift occurs when a continent begins to split apart due to tensional forces.
What drives plate movement?
Mantle convection drives plate motion. Heat from Earth’s interior causes mantle material to rise, cool, and sink in convection currents.
What kinds of volcanoes and earthquakes happen?
Volcanoes commonly occur at convergent and divergent boundaries. Earthquakes occur at all types of boundaries, including transform boundaries.
How does an ocean form?
An ocean forms when a continental rift widens, continues to spread, and eventually creates a new ocean basin through seafloor spreading.
What happens at mid-ocean ridges?
At mid-ocean ridges, plates move apart, magma rises to fill the gap, and new oceanic crust forms. Shallow earthquakes and volcanic activity occur there.
What is a triple junction?
A triple junction is a point where three plate boundaries meet.
What is a hot spot?
A hot spot is a stationary mantle plume that creates volcanoes within a tectonic plate rather than at a plate boundary. The most famous example is Hawaii.
What is subduction?
Subduction occurs when one plate sinks beneath another into the mantle. This creates deep ocean trenches, volcanic arcs, and earthquakes.
Where do volcanoes form?
Volcanoes form at subduction zones, mid-ocean ridges, and hot spots. Earthquakes occur along all plate boundaries. Thick, non-volcanic mountain ranges form where two continental plates collide.
What are the differences between continental lithosphere and oceanic lithosphere?
Continental lithosphere is thicker, less dense, and generally older. Oceanic lithosphere is thinner, denser, younger, and composed mainly of basalt. Oceanic lithosphere readily subducts at subduction zones, while continental lithosphere usually does not because it is less dense.
What are the three types of plate boundaries?
Divergent boundaries occur where plates move apart. Convergent boundaries occur where plates come together. Transform boundaries occur where plates slide past one another.
What is a Wadati-Benioff zone?
A Wadati-Benioff zone is a deep zone of earthquakes that marks the path of a subducting plate in a subduction zone.