Question

plate tectonics: divergent boundaries
iceland provides a notable example, as it sits on a divergent boundary where the eurasian and north american plates are separating, causing distinct geological features such as rift valley. this makes it a prime location for studying plate tectonics.
what happens to the earths crust as new crust is formed at divergent boundaries?
the total crust volume remains constant.
the total crust volume decreases.
the total crust volume varies randomly.

Explanation:

To answer this, we recall the concept of plate tectonics and the Earth's crust dynamics. At divergent boundaries, new crust is formed (e.g., at mid - ocean ridges or in Iceland's case). However, at convergent boundaries, old crust is either subducted (pushed down into the mantle) or destroyed. The Earth's crust volume is maintained in a sort of balance because the creation of new crust at divergent boundaries is offset by the destruction of crust at convergent boundaries. So the total crust volume remains constant. The option "The total crust volume decreases" is incorrect because new crust is being added, and there's a balancing process. The option "The total crust volume varies randomly" is also incorrect as the processes of crust creation and destruction are systematic and not random, leading to a relatively constant total volume.

Answer:

A. The total crust volume remains constant.