ROCKS FOR JOCKS AND SOIL FOR GUYRLS
Jan 05, 2016
ROCKS FOR JOCKS AND SOIL FOR GUYRLS
ROCK CYCLE
IGNEOUS ROCK
• Formed when – magma cools
underground• EX: granite
– Or above ground• EX: lava rock/pumice
SEDIMENTARY ROCK
• Repeated settling of eroded soil.
• Compressed layer by layer until it turns into rock.
• Ex: shale, limestone
METAMORPHIC ROCK
• Sedimentary or igneous rock that has morphed into another type of rock
• Due to intense pressure or heat
• EX: schist, gneiss
SOIL
What is soil?
• The loose covering of broken rock particles and decaying organic matter (humus) covering bedrock.
Why is soil important?
• Grow food• Wood for building• Plants provide oxygen• Filter pollutants
How is soil created?
• Rock is chemically and physically weathered.
• Bacteria, fungi, lichens, & insects live in weathered rock.
• These organisms die and add nutrients to weathered rock.
• As soil builds, larger organisms can move in and colonize.
• Takes 100’s of years to create a few cm of soil.
What is a soil profile?• Vertical sequence of soil layers
(horizons).• O Horizon- vegetation/ leaf litter on
top of soil• A Horizon- dark-colored thin layer;
rich in organic matter; humus• B Horizon- thick layer of subsoil;
may be red or brown; clay based soil• C Horizon- contains weathered
parent rock; larger particles of rock; no organic matter
• R Horizon- unaltered parent bedrock
O horizon
R horizon
TYPES OF SOIL
• Polar soil– Form at high
elevations & high altitudes
– No distinct horizons- soil too thin
– Under top few inches of soil, ground is permanently frozen- PERMAFROST.
• Temperate soils– Vary depending on
rainfall & type of vegetation
– Tropical Grasslands- very thick, rich, humus
– Forests- thinner, less fertile clay soil
– Prairies- less rain, so soil not as thick, but still fertile.
• Desert soils– Very thin A horizon
– Very little organic matter
– High in minerals
– Soil is usually light colored and coarse textured.
• Tropical soils– Intensely weathered
due to high precipitation and temp.
– Very little humus & very few nutrients
– High concentrations of iron- when oxidizes causes characteristic red color.
SOIL TEXTURES
• Size of particles determines– Water holding capacity
– How compacted soil is
– Ability to support plant
• Sand- larger particles
• Silt- smaller particles
• Clay- smallest particles
• Loam- equal mix of sand, silt, and clay
SOIL FERTILITY
• Measure of how well soil can support plant life.
• Factors that affect fertility of soil:– Level of minerals &
nutrients
– Level of bacteria
– Amount of precipitation
– Topography
– Acidity of soil
• Farmers may adjust level of fertility by– Adding commercial
fertilizers
– Crop rotation- alternating corn crop with legume (peas, beans, clover) to add nutrients back to soil
– Limestone- reduces acidity of soil
– Organic fertilizers- compost, mulch, peat moss
SOIL CONSERVATION
• Soil is easily eroded.• Methods to prevent
erosion include:
Contour Farming- plowing along slope instead of up and down it. Furrows btwn rows of crops collect water.
•Terracing- series of platforms are built into slopes. Effective with steep slopes, slows water flow.
•Shelter Belts- rows of trees planted along outer edges of s creating a windbreak to prevent wind erosion.
Strip-Cropping- Farmers plow so that plowed strips are separated by planted strips. Roots of planted strips hold soil in place.
• Reduce Grazing Permits
• Put up fencing– Animals cannot
compact and destroy plants