Topic 6 – Running Water

How does running water weather rock? Lifting – fast-moving water pushes into cracks, lifting off rock pieces Abrasion – Sand, pebbles and rocks carried by the water scrape against other rock 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: River channel gets narrower Rapids Waterfalls Outside corners of streams/rivers Steep mountain slopes ** Note: Fast water tends to move in a straight line

Occurs at the bottom (underwater base) of the stream/river Called downward erosion Water cuts the earth downwards Causes a V-shaped valley

Occurs at the head of the stream/river (where it begins up the mountain) Called headward erosion Happens because water pools at the head of a stream Causes the stream to cut itself higher up the mountain

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

Can undermine waterfalls Undermining = when rock at the base of a waterfall is eroded, causing the rock above to become unstable and fall Causes a waterfall to recede (move backwards)

Deposition happens when running water moves SLOW: 3. Deposition from running water Deposition happens when running water moves SLOW: River channel gets wider River enters lake/pond/ocean Inside corners of streams/rivers River valleys Floods ** Note: Slow water tends to meander/curve

Occurs where the river ends (at the ocean) Deposits called a delta Occurs when running water rounds a bend Deposition occurs on the inside edge of the bend The inside of the bend is where the water is running slower

Deposits are sorted Heavy materials are deposited first (first gravel, then sand, then silt, then clay)

4. Running Water in Mountains vs. Valleys Water is a stream (it gets bigger the further down it flows) Water travels over steep slopes Water flows fast and straight

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

Erosion and deposition in a meandering river:   End result: The meander gets wider!