A Delta
It is called a delta.
A structure built up by stream deposits at the foot of a mountain is called an alluvial fan. Alluvial fans form when rivers or streams carrying sediment from the mountains suddenly lose velocity and deposit the sediment in a fan-shaped pattern.
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Alluvial means deposited by running water. An alluvial fan is a fan shaped mass of alluvium deposited as the flow of a river decreases in velocity.
A cone shaped mountain that is built from layers of lava is called a volcano.However, that description does not quite fit any of the three accepted descriptions of the world's volcanoes.A dome shaped mountain built from layers of lavais called a 'shield volcano'.A cone shaped mountain built from layers of cinders (tephra) is called a 'cinder cone' or a 'cinder cone volcano'.A cone shaped mountain built from alternating layers of lava and cinders is called a 'composite volcano'.
Levees. They are built up by the deposition of sediment during flood events, which causes the river channel to become elevated above the surrounding floodplain.
A delta is built up by sediment transported by a river and deposited at its mouth where the river meets a body of standing water, such as a lake or ocean. Over time, these deposits accumulate and form a triangular or fan-shaped landform.
A hogan (Najavo)
A volcano can be a cone-shaped mountain that is built from layers of lava.
The flat low-lying land built up from soil carried downstream by a river and deposited at its mouth is called a delta. Deltas form at the confluence of a river and a larger body of water, such as an ocean or lake, where sediment settles due to a decrease in water velocity. This accumulation of sediment creates fertile land that can support diverse ecosystems and agriculture. Deltas are often characterized by their triangular or fan-shaped appearance when viewed from above.
Landforms built up by the deposition of sediment at the ocean include deltas, barrier islands, and beaches. Deltas form where rivers deposit sediment as they enter the ocean, creating fertile areas. Barrier islands are elongated landforms that develop parallel to the coast, often formed by the accumulation of sand. Beaches are created through the continuous deposition of sand and other sediments along coastlines, providing dynamic environments shaped by wave action.
A large amount of water that has built up under the ground is called an aquifer. Aquifers are underground layers of rock or sediment that hold and transmit water. They are an important source of freshwater for many regions around the world.