Rock Cycle
Tyler was walking through a forest when he saw some rocks laying near the trail. He found a rock that looked to contain a small fossil (preserved remains of a living thing), and Tyler was really excited to show his dad. How could a rock contain a fossil. As Tyler's dad explained, rocks go through what is known as the rock cycle, a process in which rocks are constantly changing form as they rise and fall within the layers of the Earth. As the rocks move, they heat up deep underground, cool off as they move toward the surface, and pick up matter like fossils along the way.
Stages of The Rock Cycle
The movement of the rock cycle happens very, very slowly--over thousands of years--so we can't really see the changes as they happen. But we can look at a piece of rock and gain insight into what it's been through and what stage of the rock cycle it's in. There are three main stages of the rock cycle: igneous, sedimentary, and metamorphic. Let's discuss these below.
The rock cycle
Igneous
Igneous rock is rock that starts off in the core of the Earth and is transformed by magma, the hot fluid in Earth's crust that forms lava. The magma melts the rock material, which then makes its way up toward the Earth's crust, cooling and crystallizing as it gets closer to the surface. This cooled and crystallized rock is igneous. These rocks are classified by where they cool off. Rock that cools at Earth's surface is usually pushed up quickly by a volcano or other force, and it's called extrusive. Rock that cools more slowly below the surface is called intrusive.
Igneous rock can be intrusive or extrusive.
You have probably seen sedimentary rock in your own home. It comes in forms like granite and basalt, which are often used to make countertops. Statues are sometimes made out of a very shiny, dark igneous rock called obsidian, and pumice is a rough igneous rock used to clean things and even scrape dead skin off your feet.
Sedimentary
Sedimentary rock is rock that is made up of sediment. Sediment is broken down bits of Earth caused by weathering from wind, water, and other sources that break up rock. As those bits of rock break off, they gather and press together, eventually creating a hardened chunk of sediment layers.