Running water:
• The major force of erosion
acting on Earth today.
• If it weren’t for the mountainbuilding activity of plate
tectonics, Earth would be
completely flat.
• Running water takes the form
of rivers, groundwater, and
glaciers.
• 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.
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.
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
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.
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.
Oxbow Lake
• 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.
Delta
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).