plate tectonics

What happens to oceanic crust at a divergent plate boundary?

New oceanic crust is created.

What happens to oceanic crust at a convergent plate boundary?

It is subducted and destroyed.

At deep-sea trenches, what is subducted and where does it go?

Oceanic crust subducts into the mantle.

At mid-ocean ridges, where does magma rise from, and what does it form?

Magma rises from the mantle and forms new oceanic crust.

What process continues to move Africa and South America apart?

Seafloor spreading.

What type of plate boundary runs through California, and what is its name?

Transform; the San Andreas Fault.

What two types of plate boundaries are commonly associated with volcanoes?

Divergent and convergent.

What type of plate boundary produces large, high mountain ranges without volcanoes?

Continental-continental convergent.

What kind of forces operate at divergent plate boundaries?

Tensional forces.

What happens to plates at a mid-ocean ridge spreading center?

They move apart as new crust forms.

What is the main mechanism that drives plate movement?

Mantle convection.

What heat sources drive mantle convection?

Radioactive decay and residual heat from Earth's formation.

How does slab pull help move tectonic plates?

The dense sinking slab pulls the rest of the plate along.

What percentage of earthquakes occur near plate boundaries?

About 95%.

What is the difference between a hot spot and a plate boundary volcano?

Hot spots form from mantle plumes, unrelated to plate boundaries.

What is an example of oceanic hot spot volcanism in the United States?

Hawaii.

What is an example of continental hot spot volcanism in the United States?

Yellowstone.

What evidence did Glossopteris fossils provide for continental drift?

The same plant fossils appear on separated continents.

What fossil evidence helped link the Gondwana continents?

Glossopteris and Mesosaurus fossils.

Why was fossil evidence connecting Gondwana continents considered compelling?

These species could not have crossed the ocean.

What evidence suggests the northern continents were once joined near the equator?

Coal deposits and tropical fossils.

What does paleomagnetism study?

Ancient magnetic fields recorded in rocks.

Why is paleomagnetism possible in cooling lava?

Magnetic minerals align with Earth's field as they cool.

What is the Curie point?

The temperature below which minerals lock in their magnetism.

What do magnetic stripes in oceanic basalt look like around ocean ridges?

Symmetric, alternating bands.

What does the symmetrical pattern of magnetic stripes around ocean ridges indicate?

Seafloor spreading.

What did differing paleomagnetic records from each continent show?

Continents have moved relative to one another.

What are magnetic reversals?

Flips in the polarity of Earth's magnetic field.

How have plate tectonic processes influenced earthquakes, volcanoes, mountains, ore deposits, climate, oceans, and life?

They are the primary driver shaping all of these Earth systems.