Question

Which of the following best describes parent rock?

crushed gravel added to depleted soil to provide nutrients

the primary stone sheet from which a boulder or stone originated

high-nutrient igneous rock like obsidian, extruded from the earth’s magma

the lowest layer of the soil horizon, containing little or no organic matter

Answer 1

Parent rock, also referred to as substratum, refers to the original rock from which something else was formed. It is mainly used in the context of soil formation where the parent rock (or parent material) normally has a large influence on the nature of the resulting soil.