5.1 Types of rocks
Rocks come in all different sizes, some are one colour, and some have grains or minerals that are made of different colours, some rocks are easy to crumble and some aren’t.
What is a rock?
Definition of a rock: the rocks in the lithosphere are natural materials made of minerals. They are usually solid. There are three main categories of rocks, classified according to how they were formed. The three different types of rocks are igneous rock, sedimentary rock, and metamorphic rock.
Minerals in granite
Granite is a very common rock in Québec. The cooling of magma inside the earth is what forms granite. the minerals inside the magma form crystals as it cools down. there are three main types of minerals in this piece of granite including quartz, biotite, and feldspar.
In granite, feldspar is the pink mineral. the black crystals in the granite are made of biotite, it can be easily separated and is made up of small flakes. Quartz is the hardest mineral of the three, there are usually white and look like a large crystal.
What is igneous rock?
The word igneous comes from the latin igneus, meaning “of fire” or “burning”.
Definition: Igneous rock comes from cooled magma or lava. magma is beneath the surface and lava is above.
Formation of igneous rocks
they are the most common in the lithosphere. Under the earth’s surface magma can be trapped but some of it escapes during a volcanic eruption but either way they both end up solidifying. A type of igneous rock is pumice.
formation of igneous rocks (continued)
The igneous rocks that form on the surface, normally during a volcanic eruption are called extrusive rocks because they are formed on the outside. for example an igneous rock is obsidian, it has a glassy structure.
But the igneous rocks that are formed under the ground are called intrusive igneous rocks. This happens when the magma never reaches the earth’s surface, this is when intrusive igneous rocks form. an example of an intrusive igneous rock is gabbro it has many minerals of different colour.
What is a sedimentary rock?
they are the most abundant type of rock on the surface of the planet.
Definition: Sedimentary rock is created when sediments gradually accumulate. Sediments are made of particles of various sizes. They come from eroded rocks or living organisms (shells, skeleton, etc.).
Formation of sedimentary rocks
if you fill a jar with muddy water and let it sit after a few minutes, the larger particles of mud settle to the bottom of the jar. After a few hours or days, even the smaller particles will have sunk to the bottom. Sedimentation is the main process behind the formation of sedimentary rocks.
Formation of sedimentary rocks (continued)
some sedimentary rocks are formed by the accumulation of debris for example sandstone is a sedimentary rock made of sand that has become super compact.
However other sedimentary rocks form from precipitates. Precipitates is when a liquid turns into a solid. an example of a sedimentary rock that is formed by precipitation is limestone which is a sedimentary rock made mostly of calcium carbonate, which comes from mollusks shells.
What is a metamorphic rock?
The word metamorphic comes from the latin word metarmorphis which means transformation.
Definition: metamorphic rock is formed due to a transformation caused by heat or pressure in the lithosphere.
Formation of metamorphic rocks
volcanoes, earthquakes and movement of tectonic plates can shape them and heat them to a very high temperature. this is how metamorphic rocks are formed. Either if it is an igneous rock, a sedimentary rock or a metamorphic rock they can all be transformed.
Formation of metamorphic rocks (continued)
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An example of a metamorphic rock that is formed by contact with magma is marble which is created when limestone transforms due to heat.
An example of a metamorphic rock that is formed by the movement of tectonic plates is gneiss which is created when rocks like granite transform.
