Question

Why do Earth’s crust remain the same size despite sea floor spreading?

A. Older rocks eventually disintegrate on the ocean floor.

B. As new rocks are formed along mid-ocean ridges, older rocks are pushed down deep into the Earth into ocean trenches.

C. Hot magma dissolves all the old rock near the eruption site.

D. None of these choices are correct.

Answer 1

B. As new rocks are formed along mid-ocean ridges, older rocks are pushed down deep into the Earth into ocean trenches.

Why is the Earth not getting larger if the sea floor is slowly spreading?

Mainly due to the Atlantic experiencing seabed expansion. The sea bottom is subducting, or moving underground, in the Pacific. This is how the Earth's tectonic plates and geological activities function. The top side of the mantle travels to the bottom at one end and to the top at the other, similar to a conveyor belt. This explains why there are volcanoes, why continents drift, and why our planet's surface is continually changing over the span of millions of years.

Therefore, the planet is not getting bigger because its surface is constantly recycling itself.

Answer 2

Answer: B
New rocks were formed along mid ocean ridges older rocks were pushed down deep into the Earth into ocean trenches.