Chapter 14:Geology and Earth

ResourcesBy Karryn Christiansen and

Missy HutchingsDr. Unfried APES 7/8

“Onions have layers. Ogres have layers.”EARTH HAS LAYERS!The core is composed of a dense, intensely hot mass of metal. Solid in the center, more fluid than the outer core

The mantle surrounds the molten outer core and is a hot, pliable layer of rock.

The crust is the outermost layer of the earth and is a cool, lightweight, brittle layer.

The crust is like the ‘skin’ on warm chocolate pudding!

Tectonic Plates!• Upper layer of the mantle has huge convection

currents that break the overlying crust into a mosaic of huge blocks called Tectonic plates!

• Where oceanic plates separate, magma forces up through cracks to form mid-ocean ridges

• When oceanic plates collides with continental landmass, continental plate rides up over the seafloor, so the oceanic plate is subducted, or pushed down into the mantle

• Deep oceanic trenches mark these subduction zones, and volcanoes form where the magma erupts through vents and fissures in the overlying crust

• RING OF FIRE- where the oceanic plates are being subducted under the continental plates and is the source of more earthquakes and volcanic activity than any other place on Earth

Earthquakes

- Caused by the grinding and jerking as plates slide past each other or as they converge or diverge-The continuous movement of plates is causing Southern California to slowly move north towards Alaska-Plate movement varies greatly, from 1cm per year to as much as 18 cm per year at a seafloor spreading zones-Over time continents have moved long distances- Antarctica and Australia were once connected to Africa

In about 30 million years,

Los Angeles will pass San

Francisco!

Minerals• A mineral is a naturally occurring,

inorganic, solid element or compound with a definite chemical composition and a regular internal crystal structure

• Chemical composition and crystal structure categorizes minerals because no two minerals are alike in both of these respects

These minerals are seen under a UV black light, showing their natural beauty

What did the rock and the ruler say to each other?

“You rock!”“You rule!”

Rocks

• A solid, cohesive, aggregate of one or more minerals

• Each rock has a characteristic mixture of minerals, grain sizes, and ways in which the grains are mixed and held together

The Rock Cycle• Cycle of creation,

destruction, and metamorphosis the rock cycle

• Understanding the cycle explains the origin and characteristics of different types of rocks, how they’re shaped, worn away, transported, deposited and altered

• THREE TYPES!

Type 1: Igneous Rocks

• Most common in the earth’s crust• Solidified from magma• Magma extruded from vents cools quickly to

form basalt, rhyolite, andesite, and fine-grained rocks

• Magma cools slowly forms granite, gabbro, and coarse-grained crystalline rocks

Weathering

• Exposure to air, water, changing temperatures, and reactive chemical agents slowly breaks them down in process called weathering

• Mechanical and chemical weathering• Oxidation- combination of oxygen with an

element to form an oxide or hydroxide mineral• Hydrolysis- hydrogen atoms from water

molecules combine with other chemicals to form acids

Sedimentation

• Particles of rock transported by wind, water, ice and gravity

• Deposition of new materials is sedimentation• Deposited material that remains in place long

enough, or is covered with enough material to compact it, may become rock again or Sedimentary Rock

Type 2: Sedimentary Rock

• Includes shale (compacted mud), sandstone (cemented sand), tuff (volcanic ash), and conglomerates (aggregates of gravel, sand, silt, and clay)

• Formed from crystals that precipitate out of, or grow from a solution

• Have distinct layers that show different conditions when they were laid down

Type 3: Metamorphic Rocks

• When preexisting rocks are modified by heat, pressure, and chemical agents- forms metamorphic rock

• Chemical reactions can alter both the composition and structure of rocks as they are metamorphosed

• Examples: marble (from limestone), quartzite (from sandstone), and slate (from mudstone and shale)

Economic Geology and Mineralogy

• Economic mineralogy- study of minerals that are valuable for manufacturing and important to domestic and international commerce

• Most are metal-bearing ores • Very important to human affairs • US public policy has encouraged mining on

public lands as a way of boosting the economy and utilizing natural resources

Metals in the Economy

• Availability of metals have determined technological developments, and economic and political power for individuals and nations

• Often formed in mountainous areas, where heat and pressure of mountain building concentrate ores

• Mineral trade is crucially important to economic and social stability

Nonmetal Minerals

• From silicate minerals to sand, gravel, salts, limestone, and soils.

• Gemstones and precious metals are durable, highly valuable, and easily portable, making them a way to store and transport wealth

• Much of the illegal trade ends up in the $100 billion/year global jewelry trade, two-thirds of which sells in the U.S.

What Happened?

• 2004- a group of Nobel Peace Laureates called on the World Bank to overhaul its policies on lending for resource extractive industries

• Extractive Industries Review appointed by World Bank recommended that areas of high biodiversity should be off-limits for extractive industries

What’s Being Mined?

• Evaporites are mined for halite, gypsum, and potash

• Sulfur deposits are mined mainly for sulfuric acid production

• In the U.S.- sulfuric acid use amounts to more than 200 lbs. per person every year

CASE STUDY!• December 26, 2004- huge undersea

earthquake near Sumatra, Indonesia• Caused by a sudden lurch in the earth’s crust • Triggered a Tsunami (“harbor wave”)• Sumatra- 250,000 residents reported dead or

missing. Millions left homeless• Nature also suffered- like coral reefs or the

turtle nestlings

Environmental Effects of Resource ExtractionMetals from mines are used in our

lights, computers, watches, fertilizers, and carso Can have very severe and social

consequencesWater quality is affected because toxic

substances (ie cyanide) are required to chemically separate metals from the minerals that contain them

Huge amounts of ore must be crushed and washed, leaving water filled with sulfuric acid, arsenic and heavy metals, destroying aquatic ecosystems Nevada uses 230,000 m3 (60 million

gallons) of fresh water daily

Mining can have very serious environmental impacts Many techniques for extracting geologic materials

o Open-pit- extract massive beds of ores and other minerals, but groundwater accumulates at the bottom and a toxic soup results

o Strip- land surface stripped away to expose the coalo Underground- dangerous, tunnels collapse, natural

gas in mines can explode, water seeps in and is contaminated

o Placer- pure nuggets are washed from stream sediment, chokes stream ecosystems with sediment

o Mountaintop removal-long, sinuous ridge-tops are removed by giant shovels to expose horizontal beds of coal

Mining companies go bankrupt due to volatile coal prices and thus leave the clean-up to the public

Case Study

The Centralia Mine Fire firemen of Centralia, Pennsylvania set a fire to trash and the ashes were

washed down with a fire hose fire found its way through a hole in the pit into the abandoned anthracite

underground coal mines repeated efforts to stop the fire failed 1979, the fire broke through an underground barrier and moved under the

town sending dangerous gases into homes and causing the ground itself to collapse

federal government announced in 1983 that it was too costly to distinguish so it was left to burn and still is

Open-pitUnderground Placer

Mountaintop Removal Strip

Mining Methods

Negative Impacts of Processing OresMetals are extracted from ore by heating or with

chemical solvents, releasing large amounts of hazardous toxic materials

Smelting (roasting ore to release metals) is a major source of air pollution

i.e.: near Ducktown, TN in the mid-1800s a 50 mi2 area was covered by a sulfur dioxide cloud released from sulfide ores, leaving a barren land

1930s official cleaning and replanting beganheap-leach extraction- piling crushed ore in huge heaps

and spraying it with a dilute alkaline-cyanide solution, dissolving gold and then taking it to a plant to remove the gold through electrolysis

toxins are left behind in open ponds near earthen dams that are prone to leaking into other waters

Conserving Geologic Resources Less waste to dispose of, less land lost to

mining, and less consumption of money, energy, and water resources

Recycling Extends Geologic Resources Exploiting waste products like

aluminum cans for aluminum saves a lot of money and takes up 1/20 of the energy for

electrolysis2/3 of cans in US are recycled,

hitting shelves in a two month cycle

Metals commonly recycled: gold, silver, copper, lead, iron, and steel

minimills that remelt and reshape scrap/waste are smaller and cheaper to operate than integrated mills that perform every process, saving about $1000 per ton and three times as less energy costs

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Material Energy Savings

Air Pollution Savings

Aluminum 95% 95%

Cardboard 24% -

Glass 5-30% 20%

Paper 40% 73%

Plastics 70% -

Steel 60% -

Environmental Effects of Recycling

New materials can be substituted for old Tradition of change, replacing

stone with bronze, then bronze with iron, then copper, lead, and steel with plastic

For cars, polymers and new alloys are replacing steel and iron, reducing a vehicle’s weight and cost

For electronics and communications technology, ultrahigh-purity glass cables to transmit pulses of light are replacing metal wires carrying electron pulsesGreater efficiency and lower cost

Geological Hazards Geologic forces like earthquakes, volcanic eruptions,

floods, and landslides are thought to have shaped the world through different historic eraso i.e. asteroid 65 million years ago killing the

dinosaursCatastrophic events are dangerous but rare, diseases

such as the bubonic plague in the 1350s and drought-caused famines take a more frequent, thus greater toll

Among natural disasters, floods are the most destructive in human lives while wind storms are for the greatest property damage

Earthquakes can be very destructive Earthquakes are sudden movements

in the earth’s crust that occur along faults (planes of weakness) where one rock mass slides past another oneo Can occur as a creep/seismic slip, or,

friction can prevent rocks from moving and stress builds to produce a sudden quake like the 2004 Sumatran

Epicenter Places like Mexico City and Tokyo,

Japan are prone to earthquakes because they’re built on soft landfill or loose soil

The Richter scale of earthquakes increase by a factor of 10

Earthquakes can be followed by many aftershocks of lesser scale

Descriptor Magnitude Annual average

Great 8 or higher 1

Major 7–7.9 17

Strong 6–6.9 134

Moderate 5–5.9 1,319

Light 4–4.9 c. 13,000

Minor 3–3.9 c. 130,000

Very minor 2–2.9 c. 1,300,000

Frequency of Earthquakes Worldwide

Tsunamis Caused by landslides, earthquakes, and

underwater volcanoesLargest wave was 525 m high, where in 1958 a massive rock avalanche fell into Lituya Fjord in Alaska’s Glacier Bay National Park

US has 6 tsunami warning buoys in the Pacific that are anchored to the sea floor to record the pressure on the floor to relay to ground stations

Volcanoes

Volcanoes and undersea magma vents make up much of earth’s crusto Famous: Mount Vesuvius buried Herculaneum and Pompeii in AD

79Nuees ardentes: glowing clouds, are deadly, denser than air

mixtures of hot gases and asho Can exceed 1,000 C and move 100 km/hro Destroyed St. Pierre on Martinique (Caribbean) in 1902

Volcanoes can erupt centuries apart but can be any secondMudslides can follow volcanoes, where sediments join with

water to spread and damage roads, bridges, and propertyEruptions release large volumes of ash and dust

In 1815 in Tambora, IndonesiaSulfur emissions combine with rain to produce sulfuric acid, cooling earth Mt. Pinatubo in the Philippines in 1991

Landslides are examples of mass wasting mass wasting: mass

movement where geological materials are moved downslope by rockslides, avalanches, or simple slumpingo can be slow and subtle or fast,

dangerous, and obviousroad construction, forest

clearing, agricultural cultivation, and building house on steep slopes increase frequency and damage of landslides

Chapparal fire exposes soil to heavy winter rains, likening a mudslide