![]() ![]() (Tectonic plates are large sections of the earth’s crust that move separately from each other. This tends to happen where tectonic plates come together: the pressure of the plates squish the rock that is heated from hot magma below. While underground, these rocks are exposed to high heat and pressure, which changes them into metamorphic rock. Metamorphism. Over very long periods of geologic time, sedimentary or igneous rocks end up buried deep underground, usually because of the movement of plate tectonics. After years of compaction and cementation, the sediment turns into sedimentary rock.ĥ. (Try making a stack of catalogs and watch how the bottom one gets squished as you add more on top – this is the same idea as the compaction of layers of sediment.)ĭissolved minerals fill in the small gaps between particles and then solidify, acting as cement. Compaction & Cementation. As the layers of sediment stack up (above water or below), the weight and pressure compacts the bottom layers. Often the sediment builds up faster than it can be washed away, creating little islands and forcing the river to break up into many channels in a delta.Ĥ. Deposition. As rivers get deeper or flow into the ocean, their current slows down, and the rock particles (mixed with soil) sink and become a layer of sediment. Transportation. Eroded rock particles are carried away by wind or by rain, streams, rivers, and oceans.ģ. When the particles are carried somewhere else, it is called erosion.Ģ. When the particles are broken off a rock and stay in the same area, it is called weathering. The result of all this? Large rocks are worn down to small particles. Water seeps into the cracks in mountain rocks, then freezes, causing the rocks to break open. Rushing river water, crashing surf, and precipitation all rub off the rough edges of rocks, leaving smooth rocks or pebbles behind. ![]() Wind carrying sand wears particles off the rock like sandpaper. Weathering & Erosion. Igneous, sedimentary, and metamorphic rocks on the surface of the earth are constantly being broken down by wind and water. Schist, slate, and gneiss (pronounced like ‘nice’) are metamorphic rocks. They usually have a more hard, grainy texture than the other two types. Metamorphic rocks are a combination of rock types, compressed together by high pressure and high temperatures. ![]() Clastic sedimentary rocks are rocks that people generally think of rocks that have pieces of other, pre-existing rocks that form a new rock. Sedimentary rocks often have lots of fossils in them because plants and animals get buried in the layers of sediment and turn into stone. Common examples of these rocks are limestone, sandstone, and shale. Sedimentary rocks are formed by layers of sediment (dirt, rock particles, etc.) being mixed and compressed together for extended periods of time. Because of all those air pockets, pumice can actually float! Pumice is a very porous rock because when the lava cooled, pockets of air were trapped inside. Granite, obsidian, basalt, and pumice are all common examples of igneous rocks. Igneous rocks are formed when hot magma cools rapidly, either by hitting underground air pockets (intrusive igneous rocks) or by flowing from the mouth of a volcano as lava on top of the ground (extrusive igneous rocks). They come in all colors: pink, green, orange, white, red.Īnd yet, scientists classify them all in only three groups! Keep reading to learn about the three types of rocks and the rock cycle. Rocks line river beds and jut above the landscape as mountain peaks they are fun to collect and sometimes are very beautiful.Įach rock is different some are smooth and round, some are sharp and dangerous. Rocks change very slowly under normal activity, but sometimes catastrophic events like a volcanic eruption or a flood can speed up the process. The difference is that, unlike the water cycle, you can’t see the rock cycle steps happening on a day-to-day basis. But rocks are always changing!Įxisting rocks undergo change as outlined in the rock cycle (which is similar to the water cycle). Rocks have a reputation for being solid, hard, and indestructible. ![]()
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