THE EARTH’S CRUST Notes for Test

Rocks and Minerals: Minerals are pure substances and all minerals are crystals. (halite which is salt, talc, quartz, diamond, mica, jade…) Minerals are the building blocks of rocks. Rocks are combinations of different minerals (granite, limestone). pp

IDENTIFYING MINERALS There are many different minerals and many characteristics that help identify them: Colour: least reliable Lustre: how it reflects light Hardness: Mohs Scale Cleavage: how it breaks Transparency: how see-through it is p 199

LAYERS OF THE EARTH Inner Core: Hottest but a solid due to all the pressure. Outer Core: Second hottest, liquid metal, second biggest. Mantle: Biggest, partly solid, partly liquid. Crust: Thinnest layer, solid, coldest layer, only layer with life on it.

MINING In order to get valuable minerals we must mine (dig out) and process the ore (separate from rock to extract the mineral).  Ore is rock that contains valuable mineral.  A deposit is a place that has ore in it. The type of mining used depends on where the mineral is found. Review the activity Explore an Issue, Mining for Minerals pp

Sedimentary Rock: water carries weathered rock downstream where it settles and turns into layered rock from pressure.

WEATHERING AND EROSION Weathering is the breaking down of rock. Weathering can happen through: BIOLOGICAL: done by living things (plants, animals). MECHANICAL: done by physical force (water, wind, ice). CHEMICAL: due to a rocks reactions with another substance (acid rain, dissolving). Erosion is the movement of broken down rock and mineral to a new location

SOIL HORIZONS LITTER: the surface of the soil is usually covered with leaves, broken branches and fallen trees called litter. Litter keeps the soil damp. TOPSOIL: usually contains dark, decaying plant and animal matter called humus that provides nutrients for plants. SUBSOIL: contains larger pieces of rock and clay. Usually a lighter colour because it contains less humus. BEDROCK: a layer of solid, unbroken rock that is subject to biological weathering and over time can become part of the subsoil.

SOIL HUMUS: decaying plant or animal matter that provides nutrients for plants. SAND: biggest particles, biggest spaces SILT: medium particles, medium spaces CLAY: smallest particles, smallest spaces

SPACES IN SOIL Spaces in soil provide room for air and water. AIR: allows room for roots to grow and air for decomposers to live and break down plant and animal matter. WATER: gives life to plants and decomposers.

ENRICHING the SOIL Adding substances to soil to improve it’s quality (fertilizers). Many changes in lakes and other water systems have happened because of fertilizer runoff from fields. When farmers plant and harvest the same crops year after year (monoculture) the nutrients from the harvest don’t get a chance to decompose and return to the soil. Therefore the soil will lose nutrients over time. Often farmers use crop diversity within a single field and/or crop rotation (changing crop from year to year) to avoid this problem.