RocksGroup3

Rocks:
So basically what are rocks? Rocks are minerals combined to form a solid. There are many shapes and sizes of rocks. They have also been around for over four billion years.

Types of Rocks: There are three main groups of rocks. The way the rock is formed deteremines which group it belongs to.

Igneous: Basically these rocks are formed by the heating and pressure followed by cooling and hardnening of a rock. The heating starts deep below the surface of the earth at very high tempuratures. Down below the minerals are in a liquid form called //magma//. Very important information ! //__Magma__ // __:__ The name of the heated minerals under the earths surface //__Lava __// : The name of the heated minerals above the earths surface Not all Igneous rocks are the same. It all depends on the way they cool and harden. Some can cool slowly under the surface of the earth. The rocks that cool slowly under the surface develope large crystals. These are called //intrusive// rocks because they are "in"side of the earth. One example of this is Granite.

Other Igneous rocks can cool quickly due to an eruption of a volcano. Lava cools quickly and develops small crystals. These are called extrusive rocks. You can easily remember //extrusive// rocks because of "exterior". Obsidian is an example of an extrusive rock. It is glassy and has no crystals because it cooled so quickly on the surface. Sedimentary rocks: <span style="color: #c20f82; font-family: 'Comic Sans MS',cursive;">Since the earth's surface is always being eroded, there is constant weathering and breaking down of rock peices by: -Wind -Water -Ice <span style="color: #eb19bf; font-family: 'Comic Sans MS',cursive;">When rocks turn into pebbles and sand they can end up getting picked up by wind, travel down rivers or streams or get frozen into an iceburg. These small peices of rock settle at the bottom of a lagoon or shallow point of water usually and begin to pile up forming flat layers. After awhile of these layers building up they become presed together and create a solid figure called a sedimentary rock.

Two ways sediments can harden into sedimentary rocks are by: <span style="color: #f49a10; font-family: 'Comic Sans MS',cursive;">//__Pressure:__// When the top layers are compressed together from the pressure of the layers above. // __Cementing:__ // Minerals that are disolved in water can create a clay almost texture and stick together with pebbles and other small objects.

<span style="color: #3da6eb; font-family: 'Comic Sans MS',cursive;">Sandstone is an example of a sedimentary rock. The sand got glued or cemented to the rock (clay texture) and then hardened. <span style="color: #eb19bf; font-family: 'Comic Sans MS',cursive;">Metamorphic Rocks: <span style="color: #ec69e4; font-family: 'Comic Sans MS',cursive;">A metamorphic rock is a rock that has gotten changed by -tempurature -pressure -chemical reactions They begin to form under the earths crust. The rocks start changing form anywhere from 100 degrees to 800 degrees celsius <span style="color: #2830f0; font-family: 'Comic Sans MS',cursive;">Where does the heat come from? It comes from magma. The pressure comes from layers of rock piled on top of eachother. The bottom gets squeezed the most. For example: Sandstone can become quartzite Shale can become slate Limestone becomes marble

Sandstone to Quartzite

Rock Cycle:

Over billions of years rocks can change for and into different rocks. This journey is called the rock cycle. The magma goes straight up through the volcano and comes down. When the magma hits the earths surface it is called lava. Once the lava cools it forms Igneous rocks. // After this step, some rocks may roll down the mountains formed by the volcanos and fall into the ocean. When they roll peices may break off to form sediments. Layers and layers of sediments are pressed together and cemented forming sedimentary rocks. ** __Some of the sedimentary rocks on the bottom stay very hot because of the pressure and change into metamorphic rock. The metamorphic rock then gets burried deeper, gets even hotter and eventually melts. Back to step one it turns into magma and eventually might get pushed out of another volcano.__
 * // The first stop is the mantle. Magma is inside here trying to push up to the crust.

The cycle is shown on this link: [] Notes on the different types of rocks: [] Most of our information came from: []