Recall
Notes:
51: TLW understand what creates erosion.
53: TLW will understand new vocabulary associated with soil: weathering,
mechanical, chemical, soil, topography, erosion, mass movement, acid rain,
creep, slump, deflation, abrasion, runoff, bedrock, clay, glacier, humus, horizon,
loam, loess, parent material, permeability, pore spaces, porosity, silt, subsoil, and
topsoil
51: Erosion: The process by which water, ice, wind or gravity moves
fragments of rock and soil.
- Movement of sediment
- Carves earth’s surfaces: creating canyons, gorges, and beaches
4 different agents of erosion:
1. wind erosion: wind blows and picks up sediment and abrades
away rock.
- The intensity of wind erosion is determined by:
Sum
Speed
Slope
Surface
Abrasion: the sediment or sand blows into roc and causes pits or
scratches in the rocks. (Not a Mass Movement)
Deflation: Wind erosion can cause the erosion of land and lower
the lands surface.
Determining the wind direction and direction of migrating sand:
- Draw picture of sand dune and compass rose.
Loess: accumulation of silt or fine sediment
- Created by deposits of sediment and dust from glaciers
- Extremely fertile: topsoil
2. Water Erosion: runoff, rivers and streams
- creates most of the changes in the earth’s landscape
- Runoff pick of piece of rock and runs downhill cutting tiny
groove. (rills)
Sheet Flow: When water moves downhill in thin sheets (Similar to
washing a car)
Rills: small channels cut in sediment
Gullies: larger channels (.5 meters across)
-lead to streams
How much water erosion takes place depends on
SUM
Slope
Speed
Surface
3. Ice Causes Erosion: Glaciers wear down the landscape by moving
and picking up sediment and even boulders.
Glaciers: snow accumulates faster than it melts; gravity pulls the
massive ice down to a lower elevation.
-Continental Glaciers: cover a whole continent (huge)
Antarctica, Arctic, and Greenland
-Valley Glaciers: Located in high mountains and are smaller
glaciers running down between mountains
- Glaciers form U-shaped Valleys
The amount of erosion that takes place is determined by the
SUM
Slope
Speed
Surface
What is left behind glaciers when glaciers melt?
-till: sediment deposition from melted glaciers: can range from
clay to boulders
-moraine: landforms made from deposition of till
Terminal Moraine: The farthest that the glacier goes; melts
quickly and deposits a great amount sediment: Forms ridges.
Ground Moraine: The glacier dropped sediment off, but
started to recede and results in a small deposit.
-When melting occurs from the glacier, streams form and carry
and deposit sediment.
Outwash: sand and gravel deposits laid down by these melted
glacier streams.
3. Gravity causes erosion: Creep, slump, landslide, mudslide, and
avalanche
-creep: Because of freezing and thawing, slow moving mass
movement down a slope; page 324 and 325
-slump: a mass of rock or sediment moves down hill leaving a
curved scar; page 324
-rock slides: layers of rock break off and move to the bottom of a
slope; page 324
-Mud flow: A mass of wet sediment that flows downhill; page 324
The amount of erosion depends on:
SUM
Slope
Speed
Surface
52: TLW understand the effects of erosion.
52: Sediment is removed
-forms canyons, valleys and mountain cirques
-cirque: A bowl-shaped rock valley on the side of a mountain; often
with a glacier or permanent snowfield in it
Sediment deposition
-forms deltas, sandbars, and sand dunes
Preventing Erosion:
Plants cause weathering
Plants can prevent erosion:
Other preventions:
-plant roots
- tree wind barriers beside fields
- Terrace gardening
- horizontal plowing
- tracking instead of smooth
- build walls
Deposition: Process which sediments are laid down in new locations:
Erosion and Deposition build new landforms.
- Deltas, canyons, meanders, and flood plains
Delta: where a river and ocean meet is the mouth of the river;
sediment builds up and builds-up land
Canyon: large valley created by river and streams
Meander: Wandering stream in S shapes. Areas of erosion and
deposition
Flood plains: form along the banks of streams and rivers; low area
subject to flooding.