martes, 28 de septiembre de 2010

Minerals of Earth's Crust

Mineral: a solid material of Easth's crust with a definite composition.

Luster: the way light bounces off a mineral's surface.

Streak: the color of the powder left when a mineral is rubbed against a hard, rough surface.

Hardness: how well a mineral resist scratching. 

Cleavage: the tendency of a mineral to break along flat surfaces.

Ore: a mineral containing a useful substance.

Gem: a mineral valued for being rare and beautiful.

Nonrenewable resource: a resource that cannot be replaced within a short period of time or at all.


Earth's Rocks and Soil

Rock: a naturally formed solid in the crust, made up of one or more minerals.

Igneous rock: a rock formed when melted rock material cools and hardens.

Sedimentary rock: a rock made of bits of matter joined together.

Fossil: any remains or imprint of living things of the past.

Metamorphic rock: a rock formed under heat and pressure from another kind of rock.

Humus: decayed plant or animal material in soil.

Pollution: adding any harmful substance to Earth's land, water, or air.

Rock cycle: rocks changing from one form into another in a never-ending series of processes.


Earth's Atmosphere

Renewable resource: a resource that can be replaced in a short period of time.

Ozone layer: a layer of azone gas in the atmosphere that screens out much of the Sun's UV

Fossil fuel: a fuel formed from the decay of ancient forms of life.

Smog: a mixture of smoke and fog.

Acid rain: mousture that falls to Earth after being mixed with wastes from burned fossil fuels.


Earth's Water Supply

Desalination: getting fresh water from seawater.

Water cycle: the continuous movement of water between Earth's surface and the air, changing from liquid to gas to liquid.

Groundwater: water that seeps into the ground into spaces between bits of rock and soil.

Water table: the top of the water-filled spaces in the ground.

Aquifer: an underground layer of rock or soil filled with water.

Spring: a place where groundwater seeps out of the ground.

Well: a hole dug below the water table that water seeps into.

Reservoir: a storage area for freshwater supplies. 


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