The heated component is magma or lava that is made up of partially or totally melting material from original rocks in the earth’s crust.
These rocks are continually subjected to extreme heat, intense pressure changes, and distortion in composition.
When molten rock becomes solid under the earth’s crust it forms intrusive magmatic rocks.
When molten rock transforms on the surface of the earth it creates extrusive magmatic rocks
Examples of magmatic rocks and their formations
- Pumice is a light, light-colored magmatic rock ejected from a volcano at high temperatures and pressures. The gases escape as the rock hardens, leaving bubbles and holes throughout the rock, resulting in its light weight. Crushed pumice is often added to soaps to cleanse and exfoliate.
- Andesite , named for the Andes Mountains, is an extrusive magmatic rock made from a variety of minerals. One of its main components, plagioclase, is a mineral found in rocks on the moon.
- Granite is the most common magmatic rock found on the earth’s surface. Widely used in construction, granite contains crystals that are visible to the naked eye due to the very slow crystallization below the surface. Granite comes in a range of vibrant colors.
- Basalt, a dark, fine-grained magmatic rock, is found abundantly below the earth’s surface, making it the most common source rock. Like andesite, basalt is found on the surface of the moon and on Earth.
- Obsidian is an example of extrusive magmatic rock, igneous rock that cools above the soil surface rather than below. Obsidian is smooth like glass and generally jet black, although it can be seen in a variety of colors. While quite brittle, obsidian breaks relatively easily and has very sharp edges. It was widely used by ancient cultures in knives and arrowheads, and is used today in surgical instruments as its edges are sharper and thinner than surgical steel.
- Pegmatite is a crystalline magmatic rock that forms below the earth’s surface. One of the things that makes it visually striking is its large crystals, similar to granite. It forms during the later phases of magma chamber crystallization and sometimes contains rare minerals.
- Tuff, a magmatic rock that forms from many materials expelled from a volcano that later solidify. This rock is largely made up of ash. Tuff is widely used as a building material.
- Dacite is a rock that is formed from large volcanic eruptions. It is high in silica and high in crystals, making it a rock prone to violent eruption. In fact, dacite domes from earlier eruptions exploded in the catastrophic eruption of Mount Saint Helens in Washington state in 1980.
- Rhyolite is another heavy example of magmatic rock silica, prone to explosion in eruptions. Its composition also contains large portions of quartz and feldspar. Rhyolite eruptions often create obsidian and pumice stone igneous rocks.
- Peridotite , a very coarse-grained magmatic rock, forms under the Earth. Its composition contains high levels of olivine, which is rich in magnesium and iron. Peridotite is of special interest to scientists because the rock provides important clues about the formation of the Earth’s mantle.