Exam 7: Plate Tectonics: a Scientific Theory Unfolds

Mount St. Helens and the other Cascade volcanoes are ________.

If you could time travel back to the 1920s and meet Alfred Wegener, who was the original proponent of the continental drift hypothesis, what could you tell him about our modern idea of plate tectonics? What would you tell him regarding the structure of the Earth's interior, what evidence exists for plate tectonics, what is the relationship between volcanoes and earthquakes to plate tectonics (specifics), and what are some (if any) of the problems we still have in explaining certain features of plate tectonics?

The oldest rocks on the seafloor are much younger than the oldest rocks on the continents.

Seafloor spreading rates can be estimated if the geologic ages of the magnetic field reversals are independently known.

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

________ most effectively outline the edges of the lithospheric plates.

Deep-oceanic trenches are most abundant around the rim of the ________ ocean basin.

A very long-lived magma source located deep in the mantle is called a ________.

Matching. Match the plate boundary with the appropriate phrase. -plates are moving apart from one another

In general, rocks of the continental crust are less dense than rocks of the oceanic crust.

The volcanoes and deep valleys of east Africa are related to a ________.

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.

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

Matching. Match the plate boundary with the appropriate phrase. -where lithosphere is sinking into the mantle

In the early part of the twentieth century, ________ argued forcefully for continental drift.