What is a rock?
The solid mineral material forming part of the surface of the earth and other similar planets, exposed on the surface or underlying the soil or oceans.
- Formed by cooling and crystallization of molten rock.
- Formed in and around a volcano.
- The main types of igneous rocks is intrusive and extrusive. Intrusive is when the magma cools inside the volcano, causing the crystal size to be large. Extrusive is when the lava cools outside the volcano, causing the crystal size to be small.
- Formed by the compacting and cementing of other rocks.
- Formed on the earth's surface.
- The main types of sedimentary rocks are clastic, bioclastic, and crystalline. Clastic is made up of different sized particles cemented together. Bioclastic are rocks formed by the accumulation of plant and animal remains. Crystalline are deposited with chemicals in seawater precipitate and fall to the ocean bottom evaporates.
- Formed when other rocks are exposed to heat and pressure, without melting.
- Deep in the earth's core.
- The types of metamorphic rocks are regional metamorphism and contact metamorphism. Regional metamorphism are large masses of rock changed by deep burial within the earth (Pressure). Contact metamorphism are the chemical and physical change in a rock caused by nearby infusion or extrusion of molten rock.
Rock Type Examples
- Formed outside the volcano. Cooling was slow.
- Fine texture with small crystals.
- Has a lighter color, lower density, and a felsic composition.
- 20% potassium feldspar, 40% quartz, 20% plagioclase feldspar, 10% biotite, and 10% amphibole.
- Inorganic land-derived.
- Clastic texture with a grain size of pebbles, cobbles, and/or boulders embedded in sand, silt, and/or clay.
- Mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks and minerals.
- Rounded fragments.
The Rock Cycle
The model showing how rocks and sediments change over time.