Running water: The major force of erosion acting on Earth today.

1. Running water: The major force of erosion acting on Earth today. If it weren’t for the mountain-building activity of plate tectonics, Earth would be completely flat. Running water takes the form of rivers, groundwater, and glaciers.

2. Rivers are formed by the run off of higher elevations. Drainage Basin- the area of land from which a stream gets its water supply. As rivers flow over land they erode the landscape in 4 main ways: Abrasion- occurs when rock particles buff/scrape the bedrock. Attrition- occurs when particles in the water collide and break down into smaller pieces. Corrosion- is the dissolving of soluble materials (materials that are easily dissolved in water). Hydraulic Action- is the breaking down of rock by water pounding on it’s surface.

3. The erosion and transportation of material Streams transport material through traction- the rolling of larger sediments along the river bed. Saltation- is the bouncing of particles along the river bed. Suspension- is the carrying of smaller sediments in the water by turbulent flow. Solution- is the dissolving of materials in the water.

4. Classification of Rivers: Rivers evolve through a series of stages from youth to maturity to old age. Youthful Rivers: • dominated by vertical erosion. This allows rivers to cut down into the landscape forming V-shaped valleys. • Tend to be fairly straight • Have rapids and waterfalls • Have a turbulent flow

5. Mature Rivers: • Dominated by lateral erosion. This allows the river to widen the valley. • Meanders begin to form • The river is smoother and the flow more gentle.

6. Old Age Rivers: • Dominated by deposition and lateral erosion. • The meandering river has created a wide floodplain (good for farming) • Oxbow lakes, back swamps, and natural levees form • Deltas are found at the mouth of the rivers where they enter large bodies of water.

8. Oxbow Lake

9. Back swamps is the section of a floodplain where deposits of fine silts and clays settle after a flood. They are usually behind a stream’s natural levees.

11. Delta

12. Deltas: A landform that forms at the mouth of a river. This occurs where the fresh water of the river flows into the ocean, sea, lake, or reservoir. Deposition of sediment occurs as the river flow leaves the mouth of the river. Over long periods of time, this deposition builds the characteristic geographic patterns of a river delta. *Reminder* Deposition= the process by which sediments, sand, soils, and rocks are added (deposited) to a landform. (This process may transport the material via water, wind, or through mass wasting).