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Sedimentary

Sedimentary rock forms when water or wind deposits sediment. Those layers build up and are smashed together by their own weight. Minerals in the rock dissolve into water. Finally, those minerals harden to cement the rock together. Two examples of sedimentary rocks are limestone and sandstone.

Igneous

Igneous rock can form very quickly. Igneous rock forms when magma cools below Earth's surface, or when lava cools on Earth's surface. Two examples of igneous rocks are basalt and granite.

Metamorphic

Metamorphic rock forms very slowly. Over time, forces push rock toward Earth's interior. heat and pressure will change minerals into other minerals, such as gniess.

Mechanical Weathering

Mechanical weathering is the type of weathering in which rock is physically broken into smaller pieces.

The parts of mechanical weathering include abrasion, plant growth, animal actions, ice wedging, and release of pressure.

In abrasion, sand and other rock particles carried by wind, water, and gravity grind rock down. In plant growth, roots of plants and trees grow in cracks pf rock and spread them apart. In animal actions, animals dig and break rocks in the soil. In ice wedging, water seeps into cracks and freezes. the ice expands and when it thaws, the crack in the rock is bigger. In release of pressure, rocks that reach Earth's surface can develop cracks and flakes due to reduced pressure.

Chemical Weathering

Chemical weathering is the process that breaks down rock through chemical changes.

The parts of chemical weathering are water, oxygen, carbon dioxide, living organisms, and acid rain.

In water, a rock can dissolve in water and completely mix with the water over time. In oxygen, iron combines with oxygen and water in a process called oxidation. Oxidation creates rust, making the rock weak. In carbon dioxide, carbon dioxide dissolves in the rain to become carbolic acid, a weak acid. In living organisms, plants and other organisms let out weak acids that slowly dissolve rock. In acid rain, pollutants mix with water and air to create acid rain, which weather quickly.

Rivers

Rivers are parts of running water and are very good at eroding. This is how they form:

Rills are tiny grooves in the soil where water runs after sheet erosion. These come to gether to form gullies. Gullies are large grooves or channels in the soil that flow after rainstorms. Gullies come together to form streams. Streams never stop flowing. Big streams are also known as rivers.

Erosion by Rivers

Rivers create valleys, flood plains, meanders, oxbow lakes, and waterfalls through erosion. Here is some information about these.

Valleys: Valleys form when the river erodes its bed deeper.

Flood plains: A flood plain is a flat, wide area of land along which a river flows. A river covers flood plains when it floods and overflows its banks.

Meanders: A meander is a loop-like bend in the course of a river. Meanders form when rivers erode the outside of acurve and deposit sediment on the inside. meanders become more curved over time.

Oxbow lakes: An oxbow lake is a meander that has been cut off from the river. Oxbow lakes form when the river floods and finds a more direct route and sediment clogs the meander.

Waterfalls: Waterfalls form when there is hard rock that doesn't erode very fast and there is softer rock downstream that erodes easily.

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Factors of Erosion

Factors that affect how much a river can erode and the speed of a river are the slope, the volume of flow, and the streambed shape.

Slope: A slope is the amount the river drops toward sea level over a given distance.

Volume of flow: The volume of flow is the amount of water a river carries past a certain point. This increased flow means increased speed and erosion.

Streambed shape: A straight line means a river moves faster in the center A curved line means water moves faster on the outside of the curve, and sediment is deposited on the inside.