Geology and Natural Hazards

The Spheres of the Environment

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Chemical compositionof the earth

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Convection currents are believed to cause Plate Tectonics

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Earth's tectonic plates

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that 200 million years ago there was a single supercontinent called Pangaea that combined all the world's continents in a single landmass? 8

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The Rock Cycle

Rocks are assemblages of minerals. Minerals have a crystalline, repeating arrangements of atoms, and a specific chemical composition Examples of minerals: quartz (SiO2)

diamond (C)rock salt (NaCl)

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quartz

feldspar

hornblende

mica

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The rock cycle includes creation, destruction and metamorphism of rocks

Each of the three rock types can be converted to either of the other types

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Igneous Rocks form from magma (molten rock)

Igneous rocks include:

• volcanic rocks that explosively come to the surface the earth and cool quickly (lava, basalt)

• magma that cools slowly beneath the surface of the earth (granite)

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quartz

feldspar

hornblende

micaGRANITE

Igneous Rock

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Sedimentary Rocks form from deposition and consolidation

Sedimentary rocks include:

• sandstone and shale

• limestone that precipitated from oceans or seas

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sandstone

mudstone

shale

Some Sedimentary Rocks 16

Metamorphic Rocks are rocks that have been altered by heat and pressure to make new rocks

Metamorphic rocks include:

• schist• slate• marble

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granite

schist limestone

marble

shale

slate

sedimentary

igneous

metamorphic

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The chemical and physical breakdown of rocks into their component minerals or elements

Weathering:

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The earth is not a stagnant, unchanging planet--understanding the past environment helps explain the present and the future

The sun and solar system originated about 5 billion years ago (bya) when a gas/dust cloud coalesced

The earth is about 4.5 billion years old; the oceans and atmosphere developed between 3.5 and 4 bya

Since then, oxygen in the atmosphere has increased tremendously due to:

breakdown of water by ultraviolet radiationplant photosynthesis 20

The Spheres of the Environment

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• Humans have always coped with ‘unpredictable’ natural hazards

• Most acts of nature cannot be controlled--we have learned to better predict the occurrence of hazards and mitigate their effects

• Increases in the human population have increased the effects of ‘disasters’ but natural hazards have not changed

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Natural hazards are generally rare, but normal, natural events.

Natural hazards only become disasters if people are present.

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EarthquakesEarthquakes are shock waves that result when large masses of rock in the earth's crust move relative to each other; Tsunamis can result from earthquakesVolcanoesVolcanoes are found at places in the earth's crust where hot, molten rock (magma) wells up to the surface; found at tectonic plate boundaries and hot spots

Land InstabilityOccurs in many places; includes: landslides, rockfalls, slumps

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Some earthquakes since the 1500’s and deaths associated with themDate Location Magnitude Fatalities

1556 China ~ 8 ~800,000

1780 Iran Unknown ~200,000

1906 Columbia/Ecuador 8.8 1,000

1906 San Francisco 7.8 3,000

1920 China 8.6 200,000

1923 Kento, Japan 7.9 143,000

1927 Tsinghai, China 7.9 200,000

1952 Kamchatka, Russia 9.0 unknown

1957 Andreanof Is., Alaska 9.1 unknown

1960 Chile 9.5 5,700

1964 Prince William Sound, Alaska 9.2 125

1976 Tangshan, China 7.5 > 255,000

1995 Kobe, Japan 6.9 5,500

2001 Olympia, Washington 6.8 0

2002 Afghanistan 6.1 10,000

2004 Sumatra 9.0 ?? or >250,000

Kobe, Japan,1995; magnitude 7.2

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Issaquah, February 2001; magnitude 6.827

Bam, IranDecember 2003magnitude 6.6

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Earthquake of magnitude 9.0 strikes NW Sumatra, December 2004This is the largest earthquake since the 1964 Prince William Sound, Alaska earthquake.

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Tsunami at Phuket, Thailand

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Mt. St. Helens32

California hillside and English coast33

Barrier Island coast

Impacts of a jetty on beach sand deposition and erosion

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Tropical cyclones, hurricanes and typhoons are intense storms that develop over warm tropical areas.Tornadoes are a rapidly rotating vortice of air that forms a funnel. When they touch the ground, they can be one of the most deadly natural hazards.

Floods can be nothing more than a normal but not frequent natural occurrence but seem disastrous from a human perspective. Cumulatively, floods are among the most destructive of natural hazards.

WildfireCoastal storm surgesDrought (1988 drought – est. cost of 39 Billion $)Hail 35

Mississippi River, Davenport Iowa, 1993 36

Hurricane Andrew, before hitting the Florida coast and its aftermath

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1900 1910 1920 1930 1940 1950 1960 1970 1980 1990

Deaths

Estimated deaths and damages caused by hurricanes since 1900

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1900 1910 1920 1930 1940 1950 1960 1970 1980 1990

Damage in

Billions of

Dollars

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Severe weather, such as tornadoes

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Canberra, ACT, Australia, 200241

Estimated deaths from natural hazards during 1960 to 2000

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Estimated deaths from natural hazards during 1960 to 2000

(tropical storm)

(earthquake)

(flood)

(slides)

(volcano)

850,000650,000 60,000 50,000 36,000

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The earth is complex and old (~4.5 by)Earth’s crust differs from its corePlate tectonics reorganizes the earth’s surface--As does the rock cycle (the interchange of three kinds of rocks: igneous

metamorphicsedimentary

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The earth is dynamic--natural hazards occurHazards include: earthquakes, tsunamis

volcanoes, landslideshurricanes and other

stormsfloods, wildfires

Hazards only become disasters when people are involved

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