Chapter 2

Why was Alfred Wegner's Theory of continental drift not accepted?

He could not explain what caused the continents to move.

Which of the following is NOT true about a hot spot?

Hot spots are primarily located near plate boundaries

Oceanic crust is primarily composed of __________ while continental crust is composed of ____________.

basalt ; granite

Oceanic crust is formed at __________ boundaries and destroyed at ___________ boundaries.

divergent ; convergent

The oceanic crust ___________________ than the continental crust.

is thinner,is more dense,sits lower in the mantle

Approximately how fast do tectonic plates move?

1-15 cm/yr

Magnetic minerals within rock which have an inclination of 90 degrees (are perpendicular to the surface) indicate that the rock formed ____________ .

At the magnetic pole

What causes tectonics plates to move?

Convection in the Mantle

Tectonic plates are part of the ____________ and float on the _____________ .

Lithosphere ; Asthenosphere

Paleomagnetic stripes on the ocean floor run parallel to _____________ .

Mid Ocean Ridges

Why isn't there much ocean crust older than 180 million years old?

Old ocean crust becomes cold and dense and eventually subducts back into the mantle

Which of the following did Alfred Wegner NOT use as evidence for his theory of continental drift?

Paleomagnetic stripes on the ocean floor