Minerals and Rocks
We live on a planet that has a crust miles thick with the rock. Rock is the basic unit that makes our planet earth. It supports everything from the ground we walk on to our oceans, deserts, and mountains. When we talk about rocks, we are also talking about minerals. All rocks are made from more than one mineral. Geologists define a mineral as a naturally occurred solid that has a distinct chemical composition and consistent in internal structure. Minerals can be elements or compounds gold, silver and diamonds are three examples. The earth is constantly changing and so are the rock and minerals it contains. They get redistributed and recycled over and over again in a process called the rock cycle. Over millions of years, rocks are continuously made, changed and destroyed. At the surface, people break down the earth’s rocks and put them to good use. Throughout the history, we have learned to depend on them. Today they help to cover our roads, support our buildings etc. Forces of nature also take the toll on the rocks of the earth’s surface. Wind, water, and gravity are always at work. The results can be very dramatic but for all this destruction, new rocks are constantly forming.
Some particles of rock get deposited and harden into sedimentary rock. Others get buried, compacted, heated and re-crystallized beneath the surface of the earth. Temperatures are so hot at great depths of earth that minerals and rocks often melt and become liquid. Over time the liquid cools creating new rocks that eventually get pushed to the surface again. Sometimes this process happens quickly during events like volcanic eruptions and earthquakes but most of the times it takes millions of years. As a result of this ongoing cycle, earth holds a tremendous variety of rocks that differ in the minerals they contain. They vary in color, texture, and permeability and so on. Geologists study these rocks in search of invaluable clues about the history of the earth. Like rings in a tree, they hold information about past environments and the events that formed them.