Earth science 75 points
1. along which features does seafloor spreading occur?
a. ocean basins
b. mid-ocean ridges***
c. fault lines
d. ocean trenches
2. which statement identifies a major reason for the subduction that to form volcanoes?
a. the difference in density of oceanic and continental plates
b. the upwelling of magma between diverging plates
c. the unusually high temperature at hotspots
d. the release of hot ash and steam in a pyroclastic flow***
3. ocean trenches form over millions or billions of years. which statement accurately describes how ocean trenches form?
a. a plate of oceanic crust is subducted under a plate of continental crust***
b. two plates of oceanic crust pull away from each other
c. a plate of continental crust collides with another plate of continental crust
d. two plates of continental crust slide past each other
4. fill in the blank
in trying to prove continental drift, alfred wegener used evidence from long ago to show that in the distant past, similar animal species lived in places that are blank today. for example, fossils of the blank were found in india, africa, and antarctica.
5. why is no land created or destroyed at transform boundaries?
a. because the plates are more dense at these boundaries
b. because the plates crumble into each other at these boundaries***
c. because magma rushes into gaps at these boundaries
d. because the plates only slip past each other at these boundaries
6. fill in the blank
iron particles in basalt on the ocean floor tell scientists blank. in two adjacent magnetic stripes, the iron particles show blank alignments.
7. geologists observed signs of widespread ancient glaciers from the same time period in areas across south america, africa, antarctica, india, and australia. what theory did this observation support?
a. earth was much farther than the sun than it is today.
b. those continents were once together as one supercontinent.
c. most of earth was once covered in a vast ice sheet.**
d. glaciers were once more common than they are today.
8. which features do most stratovolcanoes and cinder cone volcanoes have in common?
a. steep sides and violent eruptions
b. broad base with quiet eruptions
c. violent eruptions and thin, flowing lava
d. wide dome shape and thick lava**
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