Geology geology is the study of the earth, the processes that formed it and how it will continue to change in the future. Earth is approximately billion years old. Rocks are always in a process of changing. Heat, pressure, weathering and erosion cause the changes and are referred to as the rock cycle. There are three types of rock; igneous (volcanic), metamorphic (changed) and sedimentary (layered). Igneous rocks are formed from lava that has cooled. Metamorphic rocks are changed by heat and pressure. Many are stacked with.
