W.E.D + Caves Test Review

​Formed by deposition

Many layers of deposited sediment can form a flat area called a floodplain.

​​Floodplains

​Formed by deposition

Streams often deposit their loads in a fan shaped pattern called a delta.

Deltas

Movement of water underground can also cause erosion. Groundwater is the water located within the rocks below Earth's surface. When underground water erosion happens caves can form.

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Groundwater

A shoreline is the place where land and a body of water meet. Ocean waves crashing against the shoreline have a great deal of energy.

What forces shape a shoreline?

Waves play a massive role in building up and breaking down shorelines. Strong waves erode materials. Soft waves deposit materials.

Waves

Ocean currents are like giant rivers of water moving through the ocean. They flow in different directions and can be found near the surface or deep underwater. These currents are caused by things like wind, the Earth's rotation, and differences in water temperature and saltiness.

Currents

Sea caves form when waves cut large holes into weak rock along base of sea cliffs

Sea Caves

​Sea arches form when wave action erodes sea caves until a hole cuts through.

Arches

​Sea stacks form when the top of sea arches collapse and leave behind isolated rock.

Stacks

Broken sediments moving from one place to another.

Erosion

Erosion​

Rocks breaking down into smaller sediments.

Weathering

Desgasto​

Deposition

Deposicion​

Sediments from erosion stopping and building up in an new location.

Chemical weathering and erosion work together in the process of cave formation. Rainwater absorbs carbon dioxide from the atmosphere. Groundwater absorbs carbon dioxide from decaying organic matter as it moves through the soil. The carbon dioxide creates a mild carbonic acid solution with the rainwater or groundwater. In an area with a lot of limestone, carbonic acid can form caves. Limestone cannot absorb water, because it is nonporous. As a result, the acidic water flows slowly through the cracks and fractures of the limestone caused by mechanical weathering.

The carbonic acid dissolves calcium carbonate minerals like calcite (the main mineral in limestone), turning them into a calcium bicarbonate solution that is washed away. As the limestone is dissolved away, larger and larger holes form, allowing the liquid to flow and drain. The flowing solutions carry away the dissolved minerals through erosion. Over time, as more and more rock dissolves and washes away, a cave forms.

Many factors can affect the rate at which chemical weathering breaks down rocks. These factors include rock type, exposure to agents of erosion, climate, weather, and atmospheric composition and air quality.

Some rocks are more likely to undergo chemical weathering than others. Rocks that are made of minerals formed through evaporation are particularly susceptible to dissolution. They are susceptible because it is easy for water to dissolve them again. These minerals, such as halite and gypsum, are called evaporite minerals. Rocks made of minerals that are rich in iron, manganese, and other metals are more susceptible to oxidation. This is because oxygen easily reacts with these metals. Rocks that are easily broken by mechanical weathering are also more susceptible to chemical weathering.

Chemical weathering can only occur on surfaces that are exposed to agents of chemical weathering. The degree to which rocks are weathered depends on how much of the rock is exposed to weathering agents and how active or strong the agents are. When rocks are broken into smaller pieces by mechanical weathering, more surface area is exposed. This surface area can then be affected by chemical weathering. Rocks exposed to stronger weathering agents, such as rapidly moving water, are more likely to be strongly weathered. Rocks at high elevations are unprotected from weathering agents like wind, while rocks in other highly exposed areas are unprotected from weathering agents like wind, running water, and plants.

Climate and atmospheric conditions can have a major impact on weathering rates. Rocks in dry, desert climates are more exposed to mechanical weathering by wind. Rocks in warm, wet climates are more exposed to both mechanical and chemical weathering by plants and water. Certain gases from natural or human-made sources can also speed up chemical weathering. Pollutants, like carbon dioxide, and volcanic gases, like sulfur dioxide, can mix in the atmosphere with rainwater to make solutions like carbonic acid and sulfuric acid. This increase in acidity makes it easier for the water to dissolve rocks. This is why acid rain is a problem in areas with a lot of pollution.