The Rock Cycle
The Rock Cycle is a group of changes. The 3 rock types, Igneous, Metamorphic and Sedimentary, can all change into eachother by different processes. These processes are known as cooling and crystallization, melting, heat and pressure, compaction and cementation and weathering and erosion.
Igneous
When magma cools, ignous rocks are formed. This also creates crystals. Magma is basically lava before it actually comes out of a volcano and it is a extremely hot liquidy substance that is made up of a lot of melted minerals. The process of cooling takes place underground and it occurs slowly. It can also occur above ground, where the magma cools quickly.
Metamorphic
Metamorphic rocks are created when other rocks are transformed to another rock inside of the Earth from heat and pressure. Metamorphic rocks take millions of years to form. Some examples of metamorphic rocks are marble, slate, schist, gneiss, and quartzite.
Sedimentary
Sedimentary rock makes up about three fourths of Earth's surface. they form at places like beaches, rivers, the ocean, and anywhere that sand, mud, and other types of sediment collect. Slowly, the layer of sediment on the bottom of lakes, and especially on the bottom of the ocean grows deeper and deeper. The weight of all the sediment becomes immense, pushing down on lower layers of sediment with tremendous force. In addition, a number of minerals, which act like cement, bond the sediment together, causing it to form sedimentary rock.