XIV - Minerals & Soil Resources Flashcards
Earth’s major
geological zones
Core
Mantle
Crust
Core
solid center surrounded by molten layer, mostly iron
mantle
solid zone with hot, partly molten "plastic" upper layer known as asthenosphere; rich in iron, silicon, oxygen, & magnesium;
Asthenosphere
“plastic” upper layer
Crust
outermost thin layer, location of mineral resources &soil
Lithospheric/crustal plates
Earth’s outer layers are organized into about a dozen great
pieces
Plate tectonic activity is also know as
Continental drift
Plate tectonic activity is responsible for
current position of continents
Earthquakes & volcanoes are distributed mostly
along tectonic plate boundaries
Boundaries between lithospheric plates can occur
both in oceans and on continents
divergent plate boundaries
formation of new crust
plates move away from one another
mid ocean ridge is an example of
divergent plate boundaries
convergent plate boundaries
One plate get subducted under another plate due to density differences
What are commonly formed along convergent plate boudaries?
Mountain chains
Trenches
Volcanic island arc
Continential crust
makes up land
Oceanic crust
makes up ocean floor
Transform faults
occur where tectonic
plates move in
opposite directions.
Example of transform faults
The San Andreas Fault is a large transform fault along the coast of California.
Weathering
physical & chemical processes in which
solid rock exposed at the earth’s surface is changed to separate solid particles & dissolved material
Weathering is responsible for
Development of soils
Erosion
the process by which earth materials are
transported from one location & deposited in other
locations
What is the most important agent of erosion?
Streams are the most important agent of erosion
Soil erosion
movement of soil components, especially litter & topsoil, from one place to
another
What is the impact of losing topsoil?
losing topsoil makes soil less fertile & less able to
hold water
Soil can be classified as a
potentially renewable resource
How long does it take to form one inch of topsoil?
Typically 200-1000 years
What is the challenge that soil erosion brings?
topsoil is eroding faster than it forms in about one–
third of the world’s cropland
The Dust Bowl of the Great Plains
During the 1930s, a combination of drought & poor soil conservation led to severe
wind erosion of topsoil
Desertification of arid & semiarid lands
results
when land productive drops markedly
Causes of desertification
• overgrazing; • deforestation & devegetation; • surface mining; • poor irrigation techniques; • salt buildup; • farming on unsuitable terrain; • soil compaction by farm machinery
Salinization
results in irrigated cropland where salts build up to levels that decrease yields or prevent cultivation.
Waterlogging
results when excess irrigation water raises the water table & lowers crop productivity.
How does salinization occur?
I-Irrigation water contains small amounts of dissolved salts
II-Evaporation & transpiration leave salt behind
III-salts built up in soil
How does waterlogging occur?
I-Precipitation and irrigation water percolate downward
II-Water table rises
Soil conservation
reducing soil erosion & restoring soil fertility
Soil conservation techniques
Use of organic fertilizer Conservation-tillage farming Contour farming Strip cropping Crop rotation Alley cropping Terracing
Use of organic fertilizer
(manure, “green manure”
= plant matter, & compost) to keep the soil in place
and nutrient-rich
Conservation-tillage farming
minimizes soil
disturbance by use of special tillers or by no–till
methods that inject seeds, fertilizers, & herbicides
in unplowed soil;
Contour farming
follows natural land contours
Strip cropping
maintains strips of different vegetation between crops
Crop rotation
(by planting crops that restore nutrients); &
decrease in use of inorganic fertilizers all help to restore
fertility
Alley cropping
Grows crops between rows of trees
Terracing
Protects steep slopes
Mineral resource
a naturally occurring
concentration of solid, liquid, or gaseous material in or on Earth’s crust that can be processed into useful materials at an affordable cost
Energy resources
coal, oil, natural gas, uranium,
geothermal energy sources
Metallic mineral resources
iron, copper, aluminum…
Ore
metal–yielding material that can be economically
extracted
for metallic mineral resources to be profitable,
they need to be concentrated
copper must be concentrated 86 times,
gold 1,000 times, & mercury 100,000 times the crustal
average
Nonmetallic mineral resources
salt, gypsum, clay,
sand, phosphates, water, & soil
The U.S. Geological Survey (USGS) divides mineral
resources into two broad categories
identified resources
undiscovered resources
identified resources
deposits of a particular
mineral resource that have known location,
quantity, & quality
undiscovered resources
deposits of a particular
mineral resource that are assumed to exist, based
on geologic knowledge & theory, but for which
specific locations, quantities, & quality are
unknown.
Reserves
identified resources that can be extracted economically at current prices using current mining technology
Other resources
are identified & undiscovered resources not classified as reserves.
Strip mining
surface mining in which the upper layer is removed to get at the desired mineral resource
Components in strip mining
Highall Bench Pit Spoil banks Coal seam Overburden
Subsurface mining
involves use of drill holes or tunnels to extract mineral resources that are too deep to be accessible by surface mining
Depletion time
time it takes to use up a certain proportion (usually 80%) of the reserves of a minera
Depletion time can be extended by
recycling, reuse, &
reduction of
consumption.
Some nonfuel minerals for which the U.S. has
essentially no reserves:
manganese, cobalt, tantalum, niobium, platinum,
chromium, nickel, aluminum, tin, antimony,
fluorine, asbestos, vanadium
Some nonfuel minerals for which the U.S. has
reserve deficiency:
mercury, silver, tungsten, sulfur, zinc, gold,
potash
Env’tal effects of mining exploration/extraction
Disturbed land, mining accidents & health hazards, mine waste dumping, oil spills & blowouts, noise, ugliness, heat
Env’tal effects of Mineral processing
Solid wastes: radioactive material, ais, water, and soil pollution, noise, safety and health hazards, ugliness, heat
Env’tal effects of mineral use
Noise, ugliness, thermal water pollution, pollution of air, water, and soil, solid & radioactive wastes, safety & health hazards, heat
Pollution & degradation of water quality by runoff of acids & toxic chemicals from surface & subsurface mining.
Acid drainage
Percolation
Leaching
Runoff
U.S. 1872 Mining Law
Under an 1872 U.S. mining law, any person or
corporation can assume legal ownership of public
land (other than wilderness or park) by filing mining
claims & paying nominal cost for the land (often
$2.50 to $5 per acre).
Limitation of Mining Law
no provision for reclamation of damaged land
environmentalists favor reform of the law to include
the following
- prohibit buying of public land, but allow leasing;
- require environmental impact assessment before leasing;
- set standards for preventing & controlling pollution &
environmental degradation; - make mining companies legally & financially responsible
for environmental cleanup & restoration.
