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