How does it explain the differences between seafloor and continental crust?
a. every time a bit of rock is subducted and expelled, its chemistry changes, making it heavier.
b. the heavier rock becomes the continental plates, while the relatively unprocessed rocks are the seafloor plates.
c. every time a bit of rock is subducted and expelled, its chemistry changes, making it lighter.
d. every time a bit of rock is subducted and expelled, its chemistry changes, making it heavier.
e. every time a bit of rock is subducted and expelled, its chemistry changes, making it lighter.

Option (C)

Explanation:

The sea floor refers to the oceanic crust that are comprised of basaltic rocks. The basaltic rocks contains olivine, feldspar and some pyroxenes that are usually denser than the minerals that are found in the continental crust.

On the other hand, continental crust refers to the rocks that are found in the continental landmasses, often comprised of rocks that are granitic in nature. The minerals such as silicates, feldspars are less dense.

When continental plate are subducted under the oceanic crust, the rocks at greater depths undergoes partial melting as a result of which the rocks melts and forms magma. These magma becomes less dense due to the high temperature and rises up towards the the surface in the over-riding plate.

Thus, as the plate subducts, the rock chemistry changes , thereby making it less dense.

Hence, the correct answer is option (C).

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