Controls => what determines how much or how
fertile a soil is?
1. substrate : residual vs. transported soils
->controls
texture and amount of nutrients
2. duration: controls soil maturity-> amount and
quality
3. Climate: most important factor=> soil type
4. Topography: slope
angle => gravity
aspect
= amount of sunlight.......
5.
Vegetation - plant types
Soil profile:
* soil horizons.......
1. O-horizon => organics (litter and humus)
2. A1& A2-horizons => zone of leaching:
O+A
= topsoil
3. B-horizon => zone ofaccumulation: subsoil
4. C-horizon => broken up parent material (bedrock)
Soil types: climate affects character of soil horizons
=> soil type
1. Temperate = pedalfer: moderate leaching of Fe&Al from A: good accumulation of humus..É
2. Arid
=pedocal: little leaching
in A: evaporation=> precipitation of calcite= caliche: poor input of
organics
3. Tropical = laterite: thorough leaching in A: left with
insoluble Fe&Al - oxides: little or no humus=> decay in the tropics is
very efficient....É
=> paradox
of tropical soils
=>
Detailed Soil types
- UNESCO = 110
different soil types
- United States
= 10 major types ÒSoil Orders of the
Seventh
ApproximationÓ - 12,000 total types
- Based on where
soil forms
and types of
horizons
Importance of
soil:
=> A
non-renewable natural resource
=> soil
erosion: a natural process enhanced by humans
=> soil erosion has environmental and economic implications...
Mass
Wasting:
a surface
process controlled by gravity....
Controls:
1) topography
2) type and
orientation of rocks
3) nature of
unconsolidated material: effects angle of repose;
4) amount of
water and vegitation;
5) tectonism
Types of Mass
Wasting
1.
Flow; 2. Slide; and 3. Fall
1. Flow = unconsolidated regolith; fluid movement
a)
creep -> slow soil
movement
b) debris
flow-> fluid; coarse
grained
c) mudflow-> fluid; fine grained
2. Slide = regolith or bedrock move as large blocks
a) slump -> blocks of regolith slide along
curved surface
(a
fault)
b) rockslide -> blocks of bedrock slide down a
slope.......É
3. Fall: -> requires steep slopes
Mass Wasting => often
triggered by human activities
=> oversteepened slopes