Molten magma will start to crystallise when it cools, forming rock. The rock formed is called an igneous rock. If it crystallised at depth it is called a plutonic or intrusive rock. If it erupted onto the surface of the earth or into the oceans it is called a volcanic rock. Granites formed deep within the earth, cooling slowly, which allowed large crystals of minerals to grow. Basalts are volcanic rocks, and have smaller crystals because the cooled faster.

These rocks after uplift to the surface of the earth will be subject to weathering by wind, water and freezing. As they break down mechanically or chemically they will form sediment. This then may be transported and redeposited. If hardened it will form a second type of rocks called sedimentary rocks, made up of grains of sediment. They tend to be made rounded grains of sediment or bits of shell cemented together. Sandstones and limestones are sedimentary rocks.

If the rocks are later subducted back into the earth, or heated by an igneous intrusion, or deformed by the pressures of mountain building they will be changed into Metamorphic rocks. These are rocks that have been altered by heat and pressure within the earth, and the minerals have been re-aligned or recrystallised. Slates (clays altered by pressure) and marbles (limestones that have been recrystallised due to heat) are examples of metamorphic rocks.

If heating continues the rock will melt and form magma; and the cycle begins again.

Of course Sedimentary rocks and metamorphic rocks will be subject to weathering if exposed, and will form sediments. Also igneous rocks could be metamorphosed.