How Rocks Are Formed
The whole earth is made of rocks & minerals. Inside the earth, there is a liquid core of molten rock and on the outside, there is a hard crust. he crust is made up of rocks and minerals. Much of the crust is covered by water, sand, soil, and ice. If you dig deep enough, you will always hit rocks.The rocks you see around you – the mountains, canyons & riverbeds, are all made of minerals. A rock is made up of 2 or more minerals. but you don’t need rocks to make minerals. All rocks are made of minerals. Rocks are generally not uniform and are of any shapes and sizes.
Scientists generally classify rocks by how they were made or formed. And this is called "The Rock Cycle".
Rocks are divided into 3 Types. They are classified by how they were formed.
- Igneous Rocks - Igneous rocks are formed by volcanoes. When a volcano erupts, it spews out hot molten rock called magma or lava. Eventually the magma will cool down and harden, either when it reaches the Earth's surface or somewhere within the crust. This hardened magma or lava is called igneous rock. Examples of igneous rocks include basalt and granite.
- Sedimentary Rocks - Sedimentary rocks are formed by years and years of sediment compacting together and becoming hard. Generally, something like a stream or river will carry lots of small pieces of rocks and minerals to a larger body of water. These pieces will settle at the bottom and over a really long time (perhaps millions of years), they will form into solid rock. Some examples of sedimentary rocks are shale, limestone, and sandstone.
- Metamorphic Rocks - Metamorphic rocks are formed by great heat and pressure. They are generally found inside the Earth's crust where there is enough heat and pressure to form the rocks. Metamorphic rocks are often made from other types of rock. For example, shale, a sedimentary rock, can be changed, or metamorphosed, into a metamorphic rock such as slate or gneiss. Other examples of metamorphic rocks include marble, anthracite, soapstone, and schist.
How the Rock cycle works?
1. Melted rock or magma is sent to the earth's surface by a volcano. It cools and forms an igneous rock.
2. Next the weather, or a river, and other events will slowly break up this rock into small pieces of sediment.
3. As sediment builds up and hardens over years, a sedimentary rock is formed.
4. Slowly this sediment rock will get covered with other rocks and end up deep in the Earth's crust.
5. When the pressure and heat get high enough, the sedimentary rock will metamorphose into a metamorphic rock and the cycle will start over again.
There are actually some rocks that come from space called meteorites.
They may have different elements or mineral make up than a typical earth rock. Typically they are made up mostly of iron.
Cool Facts about Rocks
- The word "igneous" comes from the Latin word "ignis" which means "of fire."
- Ores are rocks that include minerals that have important elements such as metals like gold and silver.
- Sedimentary rocks form layers at the bottoms of oceans and lakes.
- Marble is a metamorphic rock formed when limestone is exposed to high heat and pressure within the Earth.
- Layers of sedimentary rocks are called strata.