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Earth Systems

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Earth Systems. Chapter 8. Earth history. What’s here now has been here all along Layers: Core – solid inner, liquid outer Mantle – made of magma Crust – solid rock. Theory of Plate Tectonics. - PowerPoint PPT Presentation
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Earth Systems Chapter 8
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Page 1: Earth Systems

Earth SystemsChapter 8

Page 2: Earth Systems

Earth history•What’s here now has been here all along•Layers:

▫Core – solid inner, liquid outer▫Mantle – made of magma▫Crust – solid rock

Page 3: Earth Systems

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

Page 4: Earth Systems
Page 5: Earth Systems
Page 6: Earth Systems

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

Page 7: Earth Systems
Page 8: Earth Systems

Soil – 4 Distinct parts•Minerals – 45% of ‘typical’ soil•Organic matter – about 5%•Water – about 25%•Air – about 25%

Page 9: Earth Systems

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

Page 10: Earth Systems

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

Page 11: Earth Systems

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

Page 12: Earth Systems

Soil horizons

Page 13: Earth Systems

Soil properties - texture•The percentages by weight of different

sized particles of sand, silt, and clay

Page 14: Earth Systems

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

Page 15: Earth Systems

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

Page 16: Earth Systems

Mining•Some types and rocks and minerals are

vital to modern life•Earth’s chemical composition is variable

in different locations of the crust

Page 17: Earth Systems

Mining…•Ore – concentrated accumulations of

minerals▫Typically contain salt, sand, metals

•Metals – allow electrical and/or heat conduction▫Copper, nickel, aluminum

Page 18: Earth Systems

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)

Page 19: Earth Systems

Mining – subsurface •Used when the resource is more than

100m below Earth’s surface•Usually a horizontal tunnel dug into a

mountainside with vertical shafts•The deepest mines are 2.2 miles deep•Coal, diamonds, gold

Page 20: Earth Systems

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

Page 21: Earth Systems

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

Page 22: Earth Systems

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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