Understanding erosion and deposition is vital in order to understand how Earth’s landforms form. Through erosion, bits of rock and dirt are worn away while deposition builds landforms by depositing sediment in specific places.
Geologists use characteristics like sorting to ascertain what original depositional environment a rock was formed in, such as fast-flowing mountain streams or still lakes, providing them with an accurate representation of past landscapes.
Weathering
Weathering, or physical and chemical erosion, refers to the gradual degradation of rocks and minerals at Earth’s surface through direct exposure to elements such as water, salts, other chemicals and extreme temperatures. It occurs through interactions with elements like saltwater, plants and extreme temperatures as well as biological factors like bacteria. Weathering differs from erosion in that its effect involves transport of disintegrated material away from its place of degradation whereas there are three forms of weathering: physical, chemical and biological.
Longer an exposed rock is exposed to the elements, the greater its susceptibility is to weathering. Sand, mud and other particles of rock that come loose from it will eventually be deposited by wind, gravity or ice and eventually form sedimentary rock formations.
Erosion
Erosion is a natural process that alters Earth’s landscape. This occurs when water or wind wear away bits of rock and soil to move them to new places; fast erosion occurs during landslides while slow erosion takes the form of stream beds forming.
Sand dunes on beaches form when winds continuously toss sand particles against rocks, gradually altering their shapes over time. Ocean waves, flowing water and glacial erosion all cause erosion as well as other forms of natural degradation such as storm surges or melting glaciers.
Sediment refers to loose particles of rock and soil moved by erosion that accumulate on the bottom of a stream or river bed, creating a delta. Sediments may also build up on slopes like those found in Louisiana swamps.
Lithification
Geologists investigate sedimentary rock formations to understand their depositional environments and reconstruct past conditions at specific times and locations. This allows them to gain an in-depth knowledge of geological formations.
Lithification is the gradual transformation of loose sediments to solid sedimentary rocks through compaction and cementation processes.
Compression reduces space between sediment particles, forcing out excess water and air (desiccation), while cementation fills in any remaining pore spaces with minerals like quartz or calcite to create a solid rock from this sedimentary mass.
These steps produce sedimentary rock known as sandstone, distinguished by the lithification process from other two major types: igneous and metamorphic rocks.
Compaction
Geologists investigate sediment and rock composition to gain an understanding of their formation in terms of wind, water, ice and other fluid transport systems such as rivers. Transport medium energy consumption and distance traveled leave clues behind in final sediment deposits: for instance sulfides indicate deposition in an environment with reduced conditions, while red iron oxides (which indicate oxidizing conditions) indicate non-marine deposition.
Compaction refers to the mechanical pounding of soil or weathered rock to create dense masses with sufficient strength or impermeability for supporting structures, and can be used in construction to build durable roadways, airport runways, dams, foundation pads and clay liners for secure landfills. Successful compaction requires proper moisture conditioning, material placement and adequate pounding using the appropriate equipment.
Cementation
Cementation is a crucial element of the process of turning loose sediment into solid rock, known as lithification, and vital for understanding Earth’s geological history.
Mineral cements such as calcite and quartz form in the pores between sediment grains to bind them together – an essential step in the lithification process that ultimately forms rocks like sandstone and conglomerates.
Cementation rates in sedimentary formations depend on several variables, and the types of cements precipitating can alter reservoir properties such as porosity and permeability – all key components for understanding hydrocarbon behavior in sedimentary environments.