Chapter 2 Quiz Flashcards
(14 cards)
Before the 1960s, how did geologists view the ocean basins and continents of the Earth?
Scientists believed that all ocean basins and landmasses were permanently fixed in their positions.
Name the early-twentieth-century hypothesis that was at first rejected by geologists and the more comprehensive theory that later replaced it.
continental drift hypothesis; theory of plate tectonics.
What evidence first indicated to scientists that the continents were once connected?
the apparent jigsaw-like fit of continents together, as in the case of South America and Africa
Which of the following statements explains why the presence of Mesosaurus in both South America and Africa supports the continental drift hypothesis?
Mesosaurus was a freshwater aquatic reptile with fossil remains in both South America and Africa.
In the early twentieth century, what was the prevailing view among scientists of how land animals apparently migrated across vast expanses of open ocean?
Land animals that moved from continent to continent did so by rafting on materials across the ocean.
What did Wegener propose as the driving force behind continental drift?
the gravitational forces of the sun and the moon
After World War II, what was discovered about the ocean floor?
There is no oceanic crust older than 180 million years old.
Compared to the Earth’s asthenosphere, the Earth’s lithosphere is
cooler and more rigid.
What are plate boundaries at which lithospheric plates that a) move toward each other, b) move past each other, and c) move away from each other called?
a) convergent, b) transform, and c) divergent
At divergent plate boundaries,
two plates move away from each other.
What is the average rate of seafloor spreading occurring in the Atlantic Ocean and occurring in the Pacific Ocean?
The rate of seafloor spreading at the Mid-Atlantic Ridge is 2 centimeters per year, whereas the rate of seafloor spreading at the East Pacific Rise is 15 centimeters per year.
Which of the choices below is a feature of the oceanic ridge system?
a rift valley
Why does oceanic lithosphere subduct under continental lithosphere, whereas continental lithosphere does not subduct under oceanic lithosphere?
The oceanic lithosphere is thinner and denser than the continental lithosphere, which is thicker and less dense.
What characteristic of a slab of oceanic lithosphere leads to the formation of deep-ocean trenches instead of shallow trenches?
A subducting oceanic plate forming a deep-ocean trench is older and denser than a subducting plate forming a shallow trench.
