Enviro Unit 4 Flashcards
what is soil?
a mix of geological and organic components
soil components
⇨ sand, silt, clay
⇨ humus - main organic part of soil
⇨ nutrients - ammonia, nitrate, phosphates, etc.
⇨ water and air
⇨ living organisms - bacteria, worms, fungi
why is soil important?
⇨ medium for plant growth
⇨ carbon storage
⇨ filters water
⇨ habitat for organisms
⇨ breaks down organic material and recycled nutrients.
weathering
How?
breaking down of rocks into smaller pieces
- physical (wind, rain)
- biological (roots of trees)
- chemical (acid rain, moss, lichen)
erosion
transport of weathered rock fragments by wind, rain carried to new location and deposited.
soil formation from below
weathering of parent material produces smaller fragments that make up geological part of soil (sand, silt clay, minerals)
soil formation from above
⇨ breakdown of organic matter
⇨ erosion deposits soil particles from other areas.
effects on soil formation
parent material
topography
climate
organisms
effects on soil formation parent material
soil pH, nutrient content
effects on soil formation topography
steep slope = too much erosion
more level ground = deposition
effects on soil formation climate
warmer = faster breakdown of organic matter
more precipitation = more weathering, erosion and deposition
effects on soil formation organisms
soil organisms like bacteria, fungi, worms break down organic matter and mix up the soil
soil horizons O layer
Organic layer is layer of organic matter on top of soil provided nutrients and limits H2O loss
soil horizons A layer
top soil is a layer of humus and minerals with the most biological activity
soil horizons b layer
sub soil is lighter layer below topsoil, mostly sand, silt and clay some nutrients
soil horizons c layer
substratum is least weathered soil, composed of rock fragments no organic material
Soil degradation
the loss of the ability to support plant growth
loss of topsoil
tilling (turning soil) & loss of vegetation disturb soil and make it more easily eroded
loss of topsoil dries out soil, removes nutrients and soil organisms that recycle nutrients
compaction
compression of soil by machines (tractors) grazing, lifestock (cows), and humus reduces ability to hold moisture
- dry soil erodes more easily
- dry soil supports less plant growth, less root structure, leading to more erosion
nutrient depletion
repeadingly growing the same crops on the same soil removes key nutrients (N, P, K, Na, Mg) over time
- reduces ability to grow future crops
soil particles
geological portion of soil biggest to smalles
sand>silt>clay
soil texture
the % of sand silt and clay in soil
always adds up to 100% EX 40-40-20 = 40 sand 40 silt 40 clay
less compact soil vs compact soil
sand is bigger it has bigger pores (less compact) this allows water and air to eneter soil easily
clay has smallest pores wo its harder for air and water to enter heavy clay soils
porosity
the pore space within a soil
permeability
how easily water drains through
- more porosity = high permeability
H2O holding capacity
how well water is held
more porosity = low water holding Capacity
inverse relationship between porosity/permeability and H2O holding capacity
what is ideal soil for most plants
loam
soil fertility
abilty of soil to support plant growth
soil fertility nutrients
N, P, K, Mg, Ca, Na (all positively charged)
to increases nutrients soil fertility
- organic matter, humus
- decomposer activity
- clay
clay particles are negatively charged and are atracted to positve nutrients - bases pH >7 means there is less hydrogen (positively charged) to displace nutrients
to decrease nutrients soil fertility
- acids pH< 7 hydrogen displaces nutrients
- excessive rain drains nutrients
- excessive farming
to increases water holding capacity soil fertility
- derated soil (biological activity)
- compost/humus/organic matter
- clay content
- root structure (allows there to be gaps and spaces between soil particles therefore storing more water)
Decrease water holding capacity soil fertility
- compact soil (cows, machines)
- top soil erosion (contains humus)
- sand
- root loss
core
dense mass of solid (inner) and liquid (outer) iron, nickel and radioactive elements that release lots of heat
mantle
solid/ semi solid layer of rock/ magma surrounding core, kept malleable from imense heat form core
asthenosphere
softer layer of mantle, high pressure/ temp lead to magma
lithosphere
thin, brittle layer of rocks that includes solid upper mantle and crust (tectonic plates)
crust
very outer layer of lithosphere, earth’s surface
divergent plate boundary
-plates move away from each other
- forms mid oceanic ridges, volcanoes, seafloor spreading, rift valleys and earthquakes
convergent plate boundary
- plates move towards each other
- leads to subduction