Earth Systems Chapter 8 Earth history Whats here now has been here all along Layers: Core solid inner, liquid outer Mantle made of magma Crust solid rock
Theory of Plate Tectonics Crust is divided into plates which move slowly, carried by convection currents in the magma below Where plates are in contact: Divergent plate boundaries moving apart, magma forces its way up Convergent plate boundaries moving together, one plate forced under the other
Transform plate boundaries one plate moving past another Consequences: Fault zones pressure between plates Earthquakes occur when the pressure releases suddenly Ring of Fire areas where volcanoes are common
The rock cycle Igneous rocks form directly from magma Sedimentary rocks form from sediments compressed and solidified Metamorphic rocks either igneous or sedimentary rocks transformed by heat and pressure
Soil 4 Distinct parts Minerals 45% of typical soil Organic matter about 5% Water about 25% Air about 25% Soil Slowly renewable may take from 200-1000 years to form 1 inch
Provides most of the nutrients needed for plant growth Also helps purify water Formation begins when bedrock - the parent material - is broken down by weathering Decomposition helps produce new soil except in the rainforests, where nutrients in the soil are recycled into living organisms very quickly
Weathering and erosion Breaking down of parent material in soil formation Physical: Expansion of freezing water Biological agents ex: tree roots Chemical: CO2 in soil reacts with H2O to form carbonic acid
(H2CO3) Air pollution can also cause acid rain Erosion removal of rock or soil Wind, water, ice Soil properties - horizons Mature soils have developed over a long time and are arranged in a series of horizontal layers; composition
depends on climate, vegetation, and parent material O horizon: organic detritus A horizon: so-called top soil organic material and minerals mixed together E horizon: a zone of leaching found in acidic soils only B horizon: subsoil mainly minerals with very little organic matter C horizon: the least weathered; similar to the parent
material Soil horizons Soil properties - texture The percentages by weight of different sized particles of sand, silt, and clay Soil properties - texture
> 2mm = gravel/stone not actually soil b/c it has no direct value to plants 0.05 2mm = sand (largest soil particles) can be seen easily with the eye 0.002-0.05mm = silt (about the size of flour) barely visible with the eye < 0.002mm = clay (has the greatest surface value) only seen under an electronic microsope
Soil properties - porosity How quickly the soil drains water: sand silt clay Best agricultural soils have a mixture to promote water drainage and retention Sandy soils can cause problems in areas with industrial discharge pollutants move through
them quickly and contaminate groundwater Many landfills are lined with clay to prevent contaminants from leaching into surrounding soil and groundwater Mining Some types and rocks and minerals are vital to modern life Earths chemical composition is variable
in different locations of the crust Mining Ore concentrated accumulations of minerals Typically contain salt, sand, metals Metals allow electrical and/or heat conduction
Copper, nickel, aluminum Mining surface mining Strip mining removal of strips of soil and rock to expose ore Used when the desired ore is relatively close to the surface Mining spoils or tailings unwanted material removed from the surface; usually returned to the hole
Open-pit mining creation of a large hole Resource is close to surface but extends both horizontally and vertically; copper mines Mountain-top removal just like it sounds Placer mining use of river water to separate heavier items (like gold and diamond prospectors)
Mining subsurface Used when the resource is more than 100m below Earths surface Usually a horizontal tunnel dug into a mountainside with vertical shafts The deepest mines are 2.2 miles deep Coal, diamonds, gold Mining - Impacts
Surface Air dust from earth-moving equipment Water contamination of water that percolates through tailings Soil most soil removed from site Biodiversity habitat alteration and destruction Humans decline of air and water quality near mining operation
Mining Impacts Subsurface: Air emissions from fossil fuels used to power mining equipment Water acid mine drainage as well as contamination of water that percolates through tailings Biodiversity road construction fragments
habitats Humans occupational hazards; possibility of chronic lung diseases Mining - Legislation General Mining Act 1872 Allows individuals and companies to recover ores and fuels from federal lands. Contains very few environmental protection
provisions Surface Mining Control and Reclamation Act 1977 Regulates surface mining of coal as well as the surface effects of subsurface mining Land must be minimally disturbed during the mining process and reclaimed after mining is completed
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