Which phrases describe an extrusive rock? Check all that apply.

fine texture

cooled slowly

small crystal size

found deep underground

different, easily observed minerals

The correct answers are:

- fine texture;

- small crystal size;

The extrusive rocks are type of rocks that form on the surface of the Earth, be in water or on land. They form from the magma that cools of very quickly on the surface. Because of the quick cooling, this type of rocks have very small crystals, or none at all, as they do not have the time and the conditions to form. Usually they are also finely-grained rocks, which is a often a good indicator that it is an extrusive rock when observed.

This types of rocks can mostly be found close to volcanoes, both active and non-active, as well as the mid-ocean ridges.