C2- landform Ms. Leung
Focus • We have been looking at how things change the Earth. • From inside the earth (the shifting of the plates) and from the outside with weathering and erosion. • Today we are going to focus on how the rivers change the land.
River • Rivers begin high in the mountains or hills as small tributaries. • Tributaries- is a stream or a river that flows into a main stem or a river. Tributaries do not flow directly into an ocean or a sea. • Tributaries are fed by run-off. • Run-off- Precipitation that flows across the land’s surface or falls into rivers and streams. • The area where the water is drained is called a watershed. • Watershed- Area from which water is drained; region that contributes water to a river or river system.
Water flows down steep hills faster • The speed at which the water flows down hill is directly linked to how much sediment the river can carry. • Sediment- Pieces of material carried and deposited by water and wind. • Larger faster flowing streams can carry larger loads of sediment. • Sediment ranges in size from large boulders to sand and silt and dissolved materials.
As the water flows down the slope into flatter land… water slow down!!! • When the water slow down, the sediment begins to DROP. • When the river slow down and the sediment will thick the rivers bend. • Meanders- Bends or S-shaped curves in a river - Here the river erodes material on the outer side deposits material on the inner side.
Flood plains • As the land continues to flatten flood plains may form along the banks of the river. Some of the world’s most important agriculture is found in the flood plains. • Flood Plain- Land that is likely to be underwater during a flood. A river may over flow its banks following a heavy rain. When it does it releases sediments. Over time sediments build up creating fertile farmland.
All River eventually end as they empty into a lake or ocean • This is called the MOUTH • Mouth (of a river)- is the place where the river flows into the ocean. • At the mouth of the river, the water slow down so much that it drops MOST of its sediment there. The sediment forms a DELTA. • Delta- Fan shaped region formed by deposits of sediments found at the mouth of a river. • Deltas are also a VERY fertile source of soil.