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Geology and Earth Resources

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A Layered Sphere

• Core – dense, intensely hot metal Mostly Fe and Ni Inner and Outer Core

• Mantle - Hot, pliable layer, less dense O2, Si, Mg Mesosphere (lower mantle) Asthenosphere - warm, ductile, weak, mantle beneath

lithosphere• Crust - Cool, lightweight, floats on mantle. (lithosphere)

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Earth’s Cross Section

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Lithosphere• Divided into plates (about 13 major plates and

several smaller ones).

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Plate Tectonics

• Pangea

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Plate Boundaries • Defined by earthquake data.• Depths of earthquakes indicate types of

boundaries.

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Plate Boundaries• Divergent Boundaries

Oceanic plates move apart Seafloor spreading

- Magma from mantle pushes up and

and out• Convergent Boundaries

2 plates move toward one another and collide- One oceanic plate sinks below the other creating a deep trench- Denser oceanic plate moves underneath continental plate

Creation of long coastal mountain ranges (Andes) Volcanoes form “Ring of Fire”

• Two continental plates colliding mid-continental mountain ranges (Himalayas)

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Plate Boundaries Cont.• Transform Boundaries

Plates slide past each other - Earthquakes

San Andreas Fault

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Earthquakes

• Sudden release of energy in crust creating seismic waves with radiate in all directions from the source (focus)

• Epicenter• Energy dissipates with distance • Caused by:

Rupture of geologic faults Volcanic activity Major human activity

- Mine blasts, nuclear

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Earthquakes

• Types of waves released: P waves-side to side motion

S waves-up and down motion through earth’s crust

• Seismographs-records ground motion P waves arrive faster than S waves Richter scale-scale of magnitude

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Locating the Epicenter of an Earthquake

• P, S and surface waves all start out at same time. • The further you are away from the quake, the

longer the time span between arrival of P and S wave.

• The distance of the seismometer to the earthquake can be determined by the time between the arrival of P wave and arrival of S waves.

• Can tell the distance, but not the direction. • Therefore, multiple sites must be used to find

epicenter.

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Earthquakes

• Earthquakes do not cause injury or death 1988 - Soviet Armenia: magnitude 6.9, 25,000 people

died 1985 - Mexico City: magnitude 8.1, 9500 people 1989 - Loma Prieta, CA: magnitude 7.1, 40 people

died 1995 - Kobe, Japan: magnitude 7, ~6000 people died 2010 – Haiti: magnitude 7.0, over 100,000 people

died ~800,000 small earthquakes of 2.0 or less per year 8.0 occurs about once every 10 years

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Recent World Earthquakes (past 7 days)

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VOLCANOES

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Volcanoes

• Located at plate boundaries Composite, shield, cinder cones, dome

• Result in surface pyroclastic and extrusive igneous rocks

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Eruptions from Volcanoes

• May produce lava rock or ash, molten lava, and/or toxic gases.

• Gases: H2O, CO2, SO2, HCl

• Pressure within magma chamber forces molten magma up through a conduit and out a vent.

• Benefits?

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Eruption of Mount Saint Helens, May 18, 1980

• Most destructive in US history• Located in southwest Washington in the Cascade

Range

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Geological Cycle Geological Cycle

• Geological processes - continually modify the Earth’s surface, destroy old rocks (create soil), create new rocks and add to the complexity of ground conditions. Earth movements are vital to the cycle.

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Rock Types

• Rock Cycle - Cycle of creation, destruction, and metamorphosis. Three major rock classifications:

- Igneous- Sedimentary- Metamorphic

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Rock Cycle

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Igneous Rocks

• Most common type of rock in earth’s crust. Solidified from magma from interior

- Quick cooling-fine grained rocks Basalt

- Slow cooling- coarse-grained rocks

Granite

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Sedimentary Rock

• Deposited materials remaining in one place long enough, or covered with enough material to compact it-will become rock

- Shale, sandstone

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Metamorphic Rock

• Igneous or sedimentary rock that has been subjected to tremendous heat and pressure

- Marble (from limestone)- Quartzite (from sandstone)- Slate (from mudstone and shale)

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Types of Weathering

• Physical-mechanical breakdown of rocks and minerals Caused by water, wind, temp variations Makes rock more vulnerable to further

degradation• Chemical – breakdown of rocks and minerals by

chemical reactions, the dissolving of chemical elements from rocks, or both Natural or man made processes

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Formation of Soils

• From weathering, biological (plants and fungi), chemical (oxidation), and physical (wind, water)

• Soils develop in response to Climate (temperature and moisture) Living organisms (nutrient cycling) Parent Material Topography (drainage, slope, elevation, wind

exposure)

Time

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SoilRenewable or Nonrenewable?

• Soil is created at a rate of 10 tons per hectare (2.5 acres) per year under the best conditions

• Under poor conditions, it can take thousands of years to form that much soil

• Soil is created by natural processes, but we are depleting it at a faster rate than it can be created

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Major Characteristics of Soil• Soil Chemistry• Soil Composition

Particle Size Soil Texture

• Organisms• Soil Horizons

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Soil Chemistry

• pH Best between pH 6-8

- Too acidic-add limestone- Too basic-add organic material

Proper pH directly affects the availability of plant food nutrients

• Nitrogen Stimulates above ground growth Replenished by bacteria (legumes) or fertilizers

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Soil Chemistry

• Phosphorous Helps to provide a strong root system Replenished by fertilizer

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Soil Composition• Particles

Sand (0.05-2 mm), silt (0.02-0.05 mm) and clay (less than 0.02 mm)

• Particle size affects soil characteristics Spaces between sand particles give sandy soil good

drainage and allow aeration. Tight packing of small particles in silt or clay = less

permeable to air and water.• Minerals

humus (sticky brown residue from partially decomposed plants and animals)

- humus creates “structure” -holds materials together

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Soil Organisms

• Activity of organisms living in the soil help create structure and fertility Breaking down the organic material Fungi and bacteria are in the top few cms. Worms and insects add and cycle nutrients in

the soil

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Soil Profiles• Soil profile-stratified horizontal layers

- O Horizon (Organic layer) Leaf litter, partially decomposed organisms.

- A Horizon (Topsoil) Mineral particles mixed with organic material.

- E Horizon (Leached) Depleted of soluble nutrients.

- B Horizon (Subsoil) Often dense texture from accumulating nutrients.

- C Horizon (Parent Material) Weathered rock fragments with little organic

material.

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