Question

1. as new crust is formed, what happens to older parts of the seafloor?

○ they are pushed apart and eventually dissolved by the salt water.
○ they are pushed apart and eventually destroyed in deep sea trenches.
○ they are pushed together to form ridges on the opposite side of earth.
○ they fall apart once they get too old.

Explanation:

To solve this, we recall the concept of seafloor spreading and subduction. New crust forms at mid - ocean ridges. As new crust is formed, older seafloor crust is pushed away from the ridges. Eventually, this older crust is subducted (destroyed) in deep - sea trenches where one tectonic plate slides under another.

• The first option is incorrect because salt water does not dissolve the seafloor crust.
• The third option is incorrect as ridges are formed by new crust creation, not older crust pushing together to form ridges on the opposite side.
• The fourth option is incorrect as seafloor crust doesn't just "fall apart" due to age; it is destroyed by subduction.
• The second option correctly describes the process: older seafloor parts are pushed apart and destroyed in deep - sea trenches.

Answer:

B. They are pushed apart and eventually destroyed in deep sea trenches. (Here we assume the second option is labeled as B, if the original options had labels like A, B, C, D. If not, the answer is "They are pushed apart and eventually destroyed in deep sea trenches.")