What are igneous rocks, where do they form, and how do they form?
Igneous rocks are the oldest forms of rocks. Igneous Rocks are rocks that come from deep inside the Earth. Deep within the Earth, the temperature is very hot. The minerals that are deep within the Earth are in liquid form, called magma. As the magma begins to rise to Earth's surface, it begins to cool and and solidify. This solidification process of magma turns the magma into igneous rocks.
There are Two Types of Igneous Rocks that Form
- Intrusive Igneous Rocks - Intrusive Igneous Rocks are formed when the magma cools slowly in the earth. The rocks formed from the slow cooling process form with large crystals. These large, individual crystals are visible to the human eye. The slow cooling process of the magma creates rocks that are coarse grained.
Click here to watch a video on Intrusive Igneous Rock formation.
2. Extrusive Igneous Rocks- Extrusive Igneous Rocks are formed when magma erupted from a volcano, known as lava, quickly cools and forms small crystals. Extrusive Igneous Rocks cool faster and solidify quicker than Intrusive Igneous Rocks because lava is exposed to air and water. The exposure to air and water causes the lava to cool quicker and solidify at a faster rate, causing the rocks to form fine grained. Unlike Intrusive Igneous Rocks, Extrusive Igneous Rocks form small crystals.
Characteristics of Igneous Rocks
- Igneous rocks are classified by texture, mineral composition, and color
- The texture of igneous rocks are classified by its grain size (coarse or fine). Grain size is determined by how quickly or slowing the magma cooled
- Normally, igneous rocks contain no fossils .
- Usually are not comprised of many layers
- Igneous rocks are composed of large or small crystals
Dear Geologists,
Grab your science journals and click here to view your assignment on igneous rocks!
-Geologist Joe
Grab your science journals and click here to view your assignment on igneous rocks!
-Geologist Joe