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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.



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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.


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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
 rays.

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.


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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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