| A | B |
|---|
| core | inner layer of earth composed of iron and nickel |
| mantle | surrounds earth's core; mostly made of solid rock |
| asthenosphere | plastic region of mantel that flows |
| crust | outer layer of the earth, thinnest layer |
| plates | pieces of the crust |
| lithosphere | crust and rigid portion of mantle |
| plate tectonics | theory explaining plate movement |
| continental drift | continents have split and joined as plates have drifted |
| divergent plate boundary | plates move apart |
| convergent plate boundary | plates move together |
| subduction zone | one plate moves under the other |
| trench | formed at the boundary between two converging plates |
| transform fault | plates move in opposite byt paralle directions |
| erosion | movement of material |
| weathering | breaking down of material |
| mineral resource | concentration of naturally occuring solid, liquid, or gas, in or on the earth;s crust that can be extracted and processed into useful material |
| ore | metal-yielding material that can be extracted; profitable |
| identified resources | deposits of a perticular mineral resource that have a known location, quantity, or quality |
| undiscovered resources | potential supplies of a particular mineral resource that are assumed to exist |
| reserves | identified resources that can be extracted economicaly at current prices using current mining technology |
| subsurface mining | extraction of resources found deep underground |
| surface mining | removing soil, subsoil then extracting deposit that is close to the earth's surface |
| spoil | waste material from mining |
| open-pit mining | removal of minerals by diggin them out of the earth's surface and leaving an open pit |
| dredging | type of surface mining; chain buckets scrape up deposits covered with water; also used to remove sediment from streams and harbors to maintain shipping channels |
| strip mining | surface mining where bulldozers, power shovels, or stripping wheels remove the overburden in strips |
| overburden | layer of soil and rock laying over a deposit |
| depletion time | time it takes to use up a certain proportion of the reserves of a mineral at a given rate of use |
| reserve-to-production ration | number of years that proven reserves of a particular nonrenewable resource will last ar current production rates |
| soil erosion | movement of soil |
| sheet erosion | when surface water moves down a slope and removes sheets or layers of soil |
| rill erosion | surface water forms fast-flowing rivulets that cut small channels in the soil |
| gully erosion | rivulets of fast-flowing water join together and with each succedding rain cut the channesl wider and deeper until they become ditches or gullies |
| desertification | process where the productive potential or arid or semiarid land falss by 10% or more |
| soil conservation | reducing soil erosion and restoring fertility |
| waterlogging | saturation of soil with irrigation water so that water table is close to surface |
| convential-tillage farming | land is plowed and soil is broken up and smoothed to make a planting surface |
| conservation-tillage farming | subsurface soil is broken up without turning over topsoil |
| terracing | used on steep slopes, covert slopes to level areas |
| contour farming | plowing and planting crops in rowws across the sloped contour of land |
| strip cropping | alternating rows of different crops |
| alley cropping or agroforestry | several crops are planted together in strips between trees and shrubs |
| windbreaks/shelterbelts | rows of trees to reduce wind |
| organic fertilizer | animal manure, green manure, compost |
| green manure | fresh or growing green vegetation |
| crop rotation | method to conserve soil nutrients |
