Soil Processes Wk 1 Flashcards
Which 4 spheres is the pedosphere related to?
atmosphere, hydrosphere, lithosphere, biosphere
how do you get parent material?
It can be newly deposited or fresh rock that has reached the surface.
what is the effect of physicsal weathering?
the surface area to volume ratio increases.
why do weathering processes take place?
minerals in the earth are formed under different conditions including:
high pressure, high temperature, no water, no oxygen, high pH
List 6 physical weathering processes
pressure release
decrease in temperature
daily temperature changes
frost wedging
root expansion
salt weathering
what is pressure release? also called exfoliation
rocks rise and decrease in pressure causes expansion and thus cracks to form.
decrease in temperature physical weathering?
volume change so cracks form.
what is salt weathering?
salt crystals grow and these retain water so freeze-thaw occurs.
Which processes result in the formation of soil structure?
erosion, transportation as sediment, plant cycles and earthworms.
equation for pore space %
water% + air%
what are the components of soil?
mineral matter, organic matter, water, air
Where is the list of many equations you need to learn?
BACK OF YOUR BOOK!
particle density of mineral matter
2.65 g cm -3
particle density organic matter
0.9-1.3 g cm -3
particle density water
1 g cm -3
what is dry bulk density?
the weight of soil without water per volume of hte total soil.
why do we use dry bulk density?
if we have g of C per kg of soil, we can convert to g of C per cubic meter of soil.
how do we measure dry bulk density?
take a fixed volume of soil and place it in an oven for 24 hours.
what is the mass fraction water?
the amount of water divided by the mass of the DRY soil
what is equivalent depth of soil water
if you have 250mm of water in 1 m3, you pretend you stack all the soil on top of all the water. The equivalent depth of soil water is then 0.25m.
how do we classify soil texture?
by particle size distribution. you have the fine earth fraction <2mm and above this is gravels and stones.
what is the fine earth fraction split into?
clay, silt, sand ( in increasing order of size.)
properties of clay
sticky, formable, soft, shiny surface, high plasticity.
properties of silt
non-sticky, rough, and floury surface after squeezing
properties of sand.
cannot be deformed, feels grainy.
what is leem?
a combination of clay and silt. It is not the same as loam.
