geology and natural hazards. the spheres of the environment 2
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Geology and Natural Hazards
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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
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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
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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
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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
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Kobe, Japan,1995; magnitude 7.2
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Issaquah, February 2001; magnitude 6.827
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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
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California hillside and English coast33
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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
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Mississippi River, Davenport Iowa, 1993 36
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Hurricane Andrew, before hitting the Florida coast and its aftermath
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0
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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
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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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