How Are Different Types of rocks Formed? 

Introduction

     Did you know that some rocks get formed because they are squeezed and squeezed by the pressure deep below the Earth? That's how a diamond is formed!

    Some rocks are formed by volcanoes. Other rocks can hold the remains of animals that lived thousands or even millions of years ago.

   Let's go on an adventure to discover all about how different rocks are formed.

Types of Rocks

     The three main types of rocks are sedimentary, igneous, and metamorphic. Each type of rock is formed in a different way.  The outer layer of the Earth is called the crust. Earth is made up of many rigid rocks all around the crust.

Hardness Scale

     Some rocks can be hard and some can be soft. Some rocks crumble easily and some are very flexible.

    The hardness of rocks is measured by a 10 point scale called the Mohs scale. Talc is very soft and its hardness is a 1 on the Mohs scale. Talc is also called soapstone. It can be carved to make decorations or crushed to make powder.

    Diamond is the hardest mineral and it is a 10 on the Mohs scale.

Igneous

     Igneous rocks are formed from a molten material called magma. Magma is melted or hot liquid rock which hardens when it cools down. When magma cools down it turns solid and forms igneous rocks.

     Igneous rocks are mostly crystals and very hard to break apart.

     The black sand in Hawaii is actually made from tiny igneous rocks made by volcanoes. 

Sedimentary

     Sedimentary rocks are formed when clay, mud, sand, and minerals have been brought together by the actions of weather, water, wind, and ice. Fossils are found in sedimentary rocks. 

     Most sedimentary rocks are "glued" together by clay or minerals like silica. That's why sedimentary rocks sometimes crumble apart and break very easily. That's also why sedimentary rocks form in layers. The layers might contain fossils of plants and animals from long ago hidden in the layers of rock. 

Metamorphic

     Metamorphic means to change into something new and different. Metamorphic rocks are rocks that have been changed into a different type of rock by heat, pressure, or chemical reactions.

Minerals, Gemstones, and Diamonds

     All of the Earth's crust is made of minerals. Some are very common. Minerals are formed by geological processes, such as earthquakes, volcanoes, and the movements of the ocean.

   Some minerals called gemstones are very rare and beautiful. The most famous gemstone is the diamond, which is the hardest mineral in the world. Diamonds are used for drilling and sawing and cutting.

    Some minerals we even eat! For example, we get salt from the mineral halite. 

Conclusion

    Next time you pick up a rock, think about all the ways it could have been formed. Maybe it came from a volcano. Maybe you can crumble it with your bare hands. Or maybe it holds the fossil of a footprint from an animal that lived a million years ago.