Mid-ocean ridges (MORs), which are the sites of new oceanic crust formation, are linear mountain chains that run along divergent plate boundaries. Why does an MOR sit up higher than the surrounding oceanic crust? A. Hot materials are less dense and shrink, thus the new crust will sit higher than the surrounding crust. B. As the hot magma exits the MOR, it shoots up higher than the surrounding crust. C. Hot materials are less dense and expand, thus the new crust will sit higher than the surrounding crust. D. Hot, geothermal waters cause the new crust to expand and sit higher than the surrounding crust.

The correct answer is - As the hot magma exists the MOR, it shoots up higher than the surrounding crust.

The mid-ocean ridges are linear mountain chains on the ocean floor. They appear on places where there are divergent boundaries, meaning where two or more plates are moving away from one another.

As the plates move away, they leave thinner crust and gaps behind them, so the high pressure from the mantle manages to push upward the magma with ease. As the magma pushes upward it manages to move up the ocean floor as well. The magma cools of very quickly, thus creating new crust in no time. This new crust sits higher than the older one because the magma manages to push upward the ocean floor itself. Since the magma is continuously coming up and creates more and more new crust, it also gets out much higher because it makes a mountain of very hard igneous rocks around the source, thus constantly coming above the layers formed before.