Rocks are formed in three primary ways, and each method produces rocks with different characteristics. Rocks are either classified as sedimentary, igneous or metamorphic, depending on the manner in which they were formed. Most rocks encountered in everyday life are sedimentary, although some igneous rocks, such as granite, are also common.
Sedimentary rocks are formed over thousands or millions of years as fine particles are compressed to form stones. As the layers accumulate, they impart incredible pressure on the bottom layers. Sandstone, limestone, shale and gypsum are all examples of sedimentary rocks. Sedimentary rocks often form in deltas and rivers because the constant flow of the river drags sediments from the river bed and deposits them in a confined area.
Igneous rocks are formed when molten rocks cool. Magma and lava spewing from volcanoes are the two most common source for igneous rocks. Granite, pumice, obsidian and scoria are all examples of igneous rocks.
Metamorphic rocks begin as either sedimentary or igneous rocks. Sometimes such rocks end up being moved into the deep parts of the Earth’s crust, where temperatures are high and pressures are extreme. These unusual conditions serve to heat and change the rocks. Marble, slate and gneiss are examples of metamorphic rocks.Learn More
Archipelagos form when underwater volcanoes continually produce molten magma that cools and builds up to eventually form a group of islands. Although archipelagos can form by erosion or by the movement or evaporation of water, volcanic activity is the most common cause of archipelago formation.Full Answer >
Conglomerate rocks are formed by the sedimentary rock process, which is: erosion, transport, deposition and cementation. Two characteristic properties of conglomerate rock are that the sedimentary particles, or clasts, are greater than 2 millimeters in size, and the clasts are rounded in appearance. Sedimentary rocks with angular clasts are distinguished from conglomerates and are called breccias.Full Answer >
Rocks come from magma, which is the molten material found within the earth. When magma cools, either above or below the earth's surface, it crystallizes and forms the igneous rocks that can later be changed into metamorphic or sedimentary rocks. Magma, which can be considered molten rock, is referred to as lava when it reaches the earth's surface.Full Answer >
Rocks have a broad range of uses that makes them significantly important to human life. For instance, rocks are used in construction, for manufacturing substances and making medicine and for the production of gas. Rocks are also extremely vital to scientists as they provide clues about the Earth’s history.Full Answer >