Home >> Science & Nature >> Rocks & Minerals

The History of Rock Formation

There are three types of rock: sedimentary, metamorphic, and igneous, all of which formed in different ways. Sedimentary rocks are formed by mineral deposition under water; igneous rocks form from the eruption of magma from volcanoes; and metamorphic rock forms under heating and pressure.

Sedimentary Rock Formation
- Sandstone and limestone form layers of sedimentary rock.
  
  When diatoms, crustaceans and other forms of sea life die, they fall to the sea floor like a gentle rain of debris. Over the eons, the particles pack together due to the weight of the overlaying layers to form limestone, a sedimentary rock. Visually, this rock formation appears as layers of sedimentation. The top-most layers are the youngest and those toward the bottom are the most densely packed and oldest rock layers.
Igneous Rock Formation
- Devil's Tower is the remains of the internal magma chamber of a volcano.
  
  Volcanic, or igneous, rocks are composed of crystals formed from magma as it cools and solidifies after a volcanic eruption. Molten rock flows from a volcano with temperatures ranging from 1100 degrees to 2400 degrees Fahrenheit. Magma that cools slowly forms larger crystals, while fast cooling magma forms smaller crystals and has a glassy appearance.
Metamorphic Rock Formation
- Metamorphic rock folds and bends under heat and pressure.
  
  Rocks formed under metamorphic conditions may either be igneous or sedimentary rock that has morphed or changed into another type of rock due to heat or pressure. Under tons of pressure, sedimentary limestone heats up and compresses further to form marble.

Rocks & Minerals