1. Earth Systems
Chapter 8

2. Earth history What’s here now has been here all along Layers:
Core – solid inner, liquid outer
Mantle – made of magma
Crust – solid rock

3. 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

6. 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

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

9. 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

10. 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

11. Soil properties - texture
The percentages by weight of different sized particles of sand, silt, and clay

12. 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
mm = 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

13. 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

14. Soil horizons

15. 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

16. Mining Some types of rocks and minerals are vital to modern life
Earth’s chemical composition is variable in different locations of the crust

17. Mining… Ore – concentrated accumulations of minerals
Typically contain salt, sand, metals
Metals – allow electrical and/or heat conduction
Copper, nickel, aluminum

18. 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)

19. Strip mining

20. Open-pit mining

21. Mountaintop removal mining

22. Placer mining - then

23. Placer mining –and now

25. 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

26. Subsurface mining

27. 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

28. 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

29. Acidic water due to mining contamination

30. Black lung disease

31. 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

32. Mining reclamation: before and after