Our World of Rocks & Minerals
There many different kinds of rocks, but they all have some things in common. First l, rocks are made naturally. Second they are solid. Rocks are groups of smaller particles and minerals that are stuck together by external forces such as heat and or pressure. Minerals are naturally occurring substances. They form crystals and are made of specific atoms, usually in an organized fashion.
Rocks are divided into the three basic types: Igneous, Sedimentary, and Metamorphic. These groups reflect the different conditions under which rocks are made. The further down the road you get with investigating rocks you will begin to see some overlapping. You will learn what makes each group of rocks different, and the things they all have in common.
Igneous Rocks are formed from magma. Magma forms deep beneath the earth’s crust where it is very hot. When under pressure Magma will get pushed towards the earth’s surface and squeezes through the cracks and holes in the solid rocks in the earth’s crust.
Sedimentary Rocks are formed at the earth’s surface, and are caused by the weathering conditions: rain, ice, snow, wind, chemicals, plants, animals, people, very hot or cold temperatures. These conditions cause rocks to break into large and small pieces. The broken rocks are then deposited as strata called sediment. Over time this sediment can be buried under thousands of feet of sediment and this much pressure can squeeze the sediment together and form new sedimentary rocks.
Metamorphic Rocks are usually formed deep underground, high pressure or heat or both can force rocks such as sandstone or granite to change. They might melt a little bit, cool down and solidify, they are now called metamorphic which means something has changed.
Some examples are: shale becomes slate, granite becomes gneiss, coal becomes diamonds.