Topic 6 – Running Water

1.How does running water weather rock?

a)Lifting – fast-moving water pushes into cracks, lifting off rock pieces

b)Abrasion – Sand, pebbles and rocks carried by the water scrape against other rock

c) Dissolving – Some minerals in rock are dissolved as the water runs over them

2. Erosion from running water Produces rounded rocks (“spheroidal” weathering)

Happens where running water moves FAST:o River channel gets narrowero RapidsoWaterfallso Outside corners of streams/riverso Steep mountain slopes

** Note: Fast water tends to move in a straight line

Occurs at the bottom (underwater base) of the stream/rivero Called downward erosionoWater cuts the earth downwardso Causes a V-shaped valley

Occurs at the head of the stream/river (where it begins up the mountain)o Called headward erosiono Happens because water pools at the head of a

streamo Causes the stream to cut itself higher up the

mountain

Occurs when running water rounds a bendo Erosion occurs on the outside edge of the bendo The outside of the bend is where the water is

running faster

Can undermine waterfallso Undermining = when rock at the base of a waterfall

is eroded, causing the rock above to become unstable and fall

o Causes a waterfall to recede (move backwards)

3. Deposition from running water Deposition happens when running water moves SLOW:

o River channel gets widero River enters lake/pond/oceano Inside corners of streams/riverso River valleyso Floods

** Note: Slow water tends to meander/curve

Occurs where the river ends (at the ocean)o Deposits called a delta

Occurs when running water rounds a bendo Deposition occurs on the inside edge of the bendo The inside of the bend is where the water is

running slower

Deposits are sortedo Heavy materials are deposited first (first gravel,

then sand, then silt, then clay)

4. Running Water in Mountains vs. Valleys In mountains:

oWater is a stream (it gets bigger the further down it flows)

oWater travels over steep slopesoWater flows fast and straight

In valleys:oWater is a river (has gotten big)oWater travels over flat landoWater meanders and travels more slowly

Erosion and deposition in a meandering river:

o End result: The meander gets wider!