Exam 5: Plate Tectonics: A Scientific Revolution Unfolds

Mount Hood (pictured)is part of the Cascade Range. These active volcanoes are a chain that stretches along the west coast from northern California to southern British Columbia, Canada. The Cascades are ________.

During the first two decades of the twentieth century, ________ was a vigorous proponent of continental drift.

Most of the world's ________ line(s)up along plate tectonic boundaries.

Examine this map showing the age of the crust in Africa and South America, and the position of ancient mountain belts (areas where mountain ranges used to exist, but have since been eroded down to their roots). This information was not available to Alfred Wegener. Would he find it consistent with the idea of continental drift, or would it prove his idea wrong? Explain.

The volcanoes of Hawaii are localized above a deep mantle hot spot; they are not part of the East Pacific oceanic ridge.

A(n)________ is a long-lived, stationary, magma source deep in the mantle, well below the base of the lithosphere.

Cooler, older, oceanic lithosphere sinks into the mantle at ________.

Lithospheric plates can consist of which of the following components?

During various times in the geologic past, the polarity of Earth's magnetic field has been reversed.

The San Andreas fault in California is a good example of a(n)________ plate boundary.

Continent-continent convergence results in subduction.

Which one of the following most accurately describes the volcanoes of the Hawaiian Islands?

The area of crust directly above a rising mantle plume is a(n)________.

Alaska's Aleutian Islands formed as part of a(n)________ along a(n)________ boundary.

Mt. Kilimanjaro and Mt. Kenya are ________ that occur along the East African Rift.

Slabs of oceanic lithosphere sink at subduction zones because the subducted slab is denser than the underlying asthenosphere. In this process, called ________, Earth's gravity tugs at the slab, drawing the rest of the plate toward the subduction zone.

Mantle convection may occur in two layers within the mantle - the active upper mantle and the sluggish lower mantle - as proposed in the layer cake model.

Ten million years from now, the East African rift valley system will most closely resemble the modern ________.

The ________ today marks the location of the rift along which Africa separated from South America.

Match the items in the first column with the correct descriptions in the second column. A)rising of warm material due to lower density. B)boundary where two plates slide past one another. C)the condition of the magnetic field where the magnetic force flows out of Earth's south pole and back in at the north pole. D)the crust and the stiff upper mantle combined; this is broken into plates. E)boundary where two plates move away from one another. F)the "weak layer" within the mantle. Motion here is thought to help drive plate tectonics. G)the condition of the magnetic field where the magnetic force flows out of Earth's north pole and back in at the south pole. H)boundary where two plates move towards one another. -1)lithosphere 2)asthenosphere 3)convergent 4)divergent 5)transform 6)normal polarity 7)reversed polarity 8)convection