GEOS1100 Lecture 7: GEOS1100 WEEK 7
29 May 2018
School
Department
Course
Professor
WEEK 7
LECTURE 1
Erosional Processes
Mass wasting
• Soil creep
• Landslip
• Earthflows
• Landslide
Water
• Dissolution
• Fluvial processes
Ice
• Glaciation
Wind
Mass wasting - soil creep
• Material moving downhill under the force of gravity
• Gradual downhill movement occurring all the time
• Goes on everywhere all the time and progressively
Landslip
Material slow downhill movement
• occurs when soil is wet
• Human induced/accelerated
• Typically, when rain occurs
• What can water do? Trees aren't there to use water, rainfall
• Friction between individual particles of soil changes when it rains (reduced)
• Soil is more wet as trees haven't transpired
Dissolution
• Where soluble rocks dominate (limestone, chalk, dolomite)
• Dissolution by the ocean (Cliffs)
• Dissolution by rainfall - production of sinkholes, caves development of Karst landscape
• Precipitation effects may also be important (Silcrete/ferricrete landforms)
In more moist environments….
• formation of sinkholes
• Jack of surface drainage lines
• Sub-surface caverns
• Towers as remnants
Chemical Deposition Landscapes
• Movement of iron (or silica) in groundwater
• Evaporation causes precipitation
• Cementation
• Erosion resistance
• Landscape inversion
Fluvial landscapes
Steep slopes
• Rapid erosion
• High stream capacity
• Rapid erosion
Gentle slope
• Deposition of material
• Low stream capacity
• Little erosion/deposition
Fine sediment
• Carried to the sea
Graded stream
• Recent uplift
• Waterfalls, rapids
• Steep stream gradients
• Rapid erosion
Stream development
• Gradient evening out
• Lakes/marshes drained
• Catchment development
Graded stream profile
Landscape evolution
• Recent tectonic landscape
-steep stream grades
-rapid erosion
• Mature streams
-gentle stream grades
-slow erosion
• Peneplain
-very low stream grades
-near zero erosion
Peneplain- very low stream grades, near 0 erosion
Based level change -
Glacier systems
• Becomes glacier when it starts to move
Glacial period
Glaciation in Europe + America
• Renewal of landscape
• Also other ice ages
No glaciation in south
• Ocean limited expansion
• No renewal
Glacial loess
-wind blown
Freshly ground rock
Document Summary
Mass wasting: soil creep, landslip, earthflows, landslide. Mass wasting - soil creep: material moving downhill under the force of gravity, gradual downhill movement occurring all the time, goes on everywhere all the time and progressively. Trees aren"t there to use water, rainfall: friction between individual particles of soil changes when it rains (reduced, soil is more wet as trees haven"t transpired. Dissolution: where soluble rocks dominate (limestone, chalk, dolomite, dissolution by the ocean (cliffs, dissolution by rainfall - production of sinkholes, caves development of karst landscape, precipitation effects may also be important (silcrete/ferricrete landforms) Jack of surface drainage lines: sub-surface caverns, towers as remnants. Chemical deposition landscapes: movement of iron (or silica) in groundwater, evaporation causes precipitation, cementation, erosion resistance, landscape inversion. Steep slopes: rapid erosion, high stream capacity, rapid erosion. Gentle slope: deposition of material, low stream capacity, little erosion/deposition. Graded stream: recent uplift, waterfalls, rapids, steep stream gradients, rapid erosion.
