A rock is a naturally occurring solid composed of one or more minerals. Considering that rocks comprise much of the Earth’s environment and the lithosphere (outermost shell of the planet), in a geological sense this is a critical area of study. However, in a less scientific context, rocks have been utilized by civilization throughout time and continue to be used today. For example, some uses (past and present) for rocks include tools, construction materials and in power plants to make electricity (coal).
In terms of classification, rocks can be split into three different categories:
1. Igneous Rocks: Igneous rocks, which can be further subdivided into plutonic and volcanic rocks, are rocks formed from the cooling and solidification of magma and lava. Plutonic rocks are formed within the Earth’s crust when magma cools and crystalizes. Conversely, volcanic rocks are formed when lava reaches the Earth’s surface.
Granite: Plutonic Rock
Pumice: Volcanic Rock
2. Sedimentary Rocks: Sedimentary rocks are formed over extremely long periods of time by the sedimentation of particles which get blown or washed away to the bottom of water bodies. Sedimentary rock can be formed near the Earth’s surface as well when loose particles get pressed down into layers eventually forming rocks.
3. Metamorphic Rocks: Metamorphic rocks are formed when the forces of pressure and temperature transform the original form of a rock. Any type of rock, igneous, sedimentary or an already metamorphic rock, can have their physical and chemical properties transformed.
Title Image Credit: FreeAussieStock. (2014). Rocks and Rodondo. Retrieved from http://freeaussiestock.com/free/Victoria/Wilsons%20Promontory/slides/south_point_rodondo_island_rocks.htm