Rock that forms when molten rock cools and hardens
Answers
As magma (molten rock) cools and crystallizes, Igneous rocks form, either at volcanoes on the Earth's surface or while the molten rock is still within the crust.
Why does the topsoil contain much more humus than the subsoil? Options: A) Because of erosion B) Due to the action of microorganisms C) Because of plant decomposition D) All of the above