Geology and Natural Hazards

The Spheres of the Environment 2

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Chemical composition of the earth 4

Convection currents are believed to cause Plate Tectonics 5

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Earth's tectonic plates 7

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

9 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 (SiO 2 ) diamond (C) rock salt (NaCl) 10

quartz feldspar hornblende mica 11

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 12

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) 13

quartz feldspar hornblende mica GRANITE Igneous Rock 14

Sedimentary Rocks form from deposition and consolidation Sedimentary rocks include: sandstone and shale limestone that precipitated from oceans or seas 15

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 17

granite schistlimestone marble shale slate sedimentary igneous metamorphic 18

The chemical and physical breakdown of rocks into their component minerals or elements Weathering: 19

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 radiation plant photosynthesis 20

The Spheres of the Environment 21

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 22

Natural hazards are generally rare, but normal, natural events. Natural hazards only become disasters if people are present. 23

Earthquakes Earthquakes are shock waves that result when large masses of rock in the earth's crust move relative to each other; Tsunamis can result from earthquakes Volcanoes Volcanoes 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 Instability Occurs in many places; includes: landslides, rockfalls, slumps 24

25 Some earthquakes since the 1500’s and deaths associated with them DateLocationMagnitudeFatalities 1556China~ 8~800, IranUnknown~200, Columbia/Ecuador8.81, San Francisco7.83, China8.6200, Kento, Japan7.9143, Tsinghai, China7.9200, Kamchatka, Russia9.0unknown 1957Andreanof Is., Alaska9.1unknown 1960Chile9.55, Prince William Sound, Alaska Tangshan, China7.5> 255, Kobe, Japan6.95, Olympia, Washington Afghanistan6.110, Sumatra9.0?? or >250,000

Kobe, Japan,1995; magnitude

Issaquah, February 2001; magnitude

Bam, Iran December 2003 magnitude

Earthquake of magnitude 9.0 strikes NW Sumatra, December 2004 This is the largest earthquake since the 1964 Prince William Sound, Alaska earthquake. 29

30 Tsunami at Phuket, Thailand

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Mt. St. Helens 32

California hillside and English coast 33

Barrier Island coast Impacts of a jetty on beach sand deposition and erosion 34

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. Wildfire Coastal storm surges Drought (1988 drought – est. cost of 39 Billion $) Hail 35

Mississippi River, Davenport Iowa,

Hurricane Andrew, before hitting the Florida coast and its aftermath 37

Deaths Estimated deaths and damages caused by hurricanes since 1900 Damage in Billions of Dollars 38

Severe weather, such as tornadoes 39

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Canberra, ACT, Australia,

Estimated deaths from natural hazards during 1960 to

Estimated deaths from natural hazards during 1960 to 2000 (tropical storm) (earthquake) (flood) (slides) (volcano) 850, ,000 60,000 50,000 36,000 43

The earth is complex and old (~4.5 by) Earth’s crust differs from its core Plate tectonics reorganizes the earth’s surface- - As does the rock cycle (the interchange of three kinds of rocks: igneous metamorphic sedimentary 44

The earth is dynamic--natural hazards occur Hazards include: earthquakes, tsunamis volcanoes, landslides hurricanes and other storms floods, wildfires Hazards only become disasters when people are involved 45

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