Original materials of soil formed through long ages from the earth's crust. Earth's crust consists of three kinds of rocks formed in different ways.
Igneous Rocks:Formed when molten material of the earth cooled and solidified.
Example: Granite (very hard).
Sedimentary Rocks: Formed by the accumulation of materials carried by rivers to the sea.
Materials slowly pressed and cemented together.
Found in various places, even on high mountains.
Examples: Shale, limestone, and coal-bearing rocks.
Metamorphic Rocks: Formed by changes due to Earth's internal heat.
Example: Lavas ejected by volcanoes affecting the material.