While there are many types of landforms caused by weathering and erosion, this second-grade level unit will focus on seven particular landforms caused by the flow of water and deposition of sediments. (images to be added)
Braided Channels:
Braided channels form as the result of a river or stream carrying a heavy load of sediment. The channels through which the water flows divide and rejoin, forming a stream pattern that resembles the strands of a braid as opposed to the look of a meandering stream straight channel. Temporary islands are formed and eroded as the heavy load of sediment is deposited and carried away. Braided channels form when the soil is highly erodible with an abundant supply of sediment, there is a steep channel gradient, and there is a frequent variation of the rate of water flow.
4
Canyon:
Canyons form when flowing water carves a steep channel through the surrounding land. Over a long period, the continuous flow of water erodes the underlying bedrock and the sides of the channel. The headwater is at a higher elevation than the estuary and the encompassing earth consists of hard and soft rock.
Cliff:
A cliff is a steep, vertical rock exposure usually found along coastal waters or mountainous areas. Cliffs can be formed by tectonic activity or by the erosion caused by continuous lapping of water against rock as the sediment is eroded away.
Delta:
A delta is formed when the river or stream empties out into a lake or ocean. As the kinetic energy of the water decreases, sediment is deposited in layers. Heavier sediment is dropped first, followed by finer sediment. When a river deposits more sediment than the lake or ocean can carry away, a delta is formed.
Meander:
A meander is a bend in the stream or river. Meandering streams and rivers often take on a snake like appearance as the stream curves inward and outward over the course of the stream distance. A meander, or bend, occurs when the moving water erodes the outer banks and widens its valley, and the inner part of the river has less energy and deposits silt. The outer bank is deeper than the inner bank and the water flows faster. As silt builds up and is deposited on the opposite side, the course of the stream is diverted and the meandering pattern is formed.
Oxbow Lake:
An oxbow lake is the result of a loop in a meandering stream becoming cut off from the rest of the stream. As deposited sediment fill in the cutoff in the loop, the u shaped point of the curve is left and an oxbow lake is formed.
Valley:
A valley is a depression in the land often caused by the erosion of land by either rivers and streams or glaciers. There are three main types of valleys: V-shaped, U-shaped, and flat formed. Young, fast moving rivers or streams usually create v-shaped valleys. Over time, soil and rock is eroded and cuts into the land. A U-shaped valley has steep sides that curve at the bottom, characteristic of the letter “u”. Slow moving glaciers usually create them. Sometimes, glacial ice travels down a previously carved V-shaped valley and flattens the bottom as the glacier is pulled downstream. A flat-floored valley is formed by a mature stream that is no longer fast moving. The valley floor widens as the slope of a stream’s channel becomes smooth and it erodes the bank of its channel rather than the valley walls. The stream continues to meander and erode the valley's soil, widening it further. The material that is eroded and carried in the stream is deposited and builds up the floodplain and the valley. During this process, the shape of the valley changes from a V or U shaped into one with a broad flat valley floor.