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AP Environmental Science Mr. Grant Lesson 21 Earth’s Physical Systems: Matter, Energy, and Geology Geological And Natural Hazards © 2011 Pearson Education, Inc. Objectives: • Define the terms tsunami. • List major types of geological hazards and describe ways to mitigate their impacts. © 2011 Pearson Education, Inc. Define the terms tsunami. Tsunami: An immense swell, or wave, of ocean water triggered by an earthquake, volcano, or landslide, that can travel long distances across oceans and inundate coasts. Japan Tsunami (March 2011) © 2011 Pearson Education, Inc. List major types of geological hazards and describe ways to mitigate their impacts. • The circum-Pacific belt, or “ring of fire”, spawns most of the world’s volcanoes and earthquakes. • Earthquakes result from movement at faults and plate boundaries. We cannot prevent them, but we can build structures and cities in safer ways. • Volcanoes arise from heating by magma at rifts, subduction zones, or hotspots. • Landslides and other forms of mast wasting can occur on small or large scales; damage can be minimized by understanding their risks. • Tsunamis can flood coastlines and cause immense damage. Early warning systems will be key in minimizing future losses. • We often worsen impacts from natural hazards, but we can reduce them through better land use practices. © 2011 Pearson Education, Inc. Geologic and natural hazards • Some consequences of plate tectonics are hazardous • Plate boundaries closely match the circum-Pacific belt - An arc of subduction zones and fault systems - Has 90% of earthquakes and 50% of volcanoes © 2011 Pearson Education, Inc. Earthquakes result from movement • Earthquake = a release of energy (pressure) along plate boundaries and faults • Can be caused by enhanced geothermal systems - Drill deep into rock, fracture it - Pump water in to heat, then extract it • Can do tremendous damage to life and property © 2011 Pearson Education, Inc. Buildings can be built or retrofitted to decrease damage Volcanoes • Volcano= molten rock, hot gas, or ash erupts through Earth’s surface - Cooling and creating a mountain • In rift valleys, ocean ridges, subduction zones, or hotspots (holes in the crust) • Lava can flow slowly or erupt suddenly • Pyroclastic flow: fast-moving cloud of gas, ash, and rock - Buried Pompeii in A.D. 79 © 2011 Pearson Education, Inc. Volcanoes have environmental effects • Ash blocks sunlight • Sulfur emissions lead to sulfuric acid - Blocking radiation and cooling the atmosphere • Large eruptions can decrease temperatures worldwide - Mount Tambora’s eruption caused the 1816 “year without a summer” • Yellowstone National Park is an ancient supervolcano - Past eruptions were so massive they covered much of North America in ash - The region is still geologically active © 2011 Pearson Education, Inc. Landslides are a form of mass wasting • Landslide = a severe, sudden mass wasting - Large amounts of rock or soil collapse and flow downhill • Mass wasting = the downslope movement of soil and rock due to gravity - Rains saturate soils and trigger mudslides - Erodes unstable hillsides and damages property - Caused by humans when soil is loosened or exposed • Lahars = extremely dangerous mudslides - Caused when volcanic eruptions melt snow - Huge volumes of mud race downhill © 2011 Pearson Education, Inc. Mass wasting events can be colossal and deadly © 2011 Pearson Education, Inc. Tsunamis • Tsunami = huge volumes of water are displaced by: - Earthquakes, volcanoes, landslides • Can travel thousands of miles across oceans • Coral reefs, coastal forests, and wetlands are damaged - Saltwater contamination makes it hard to restore them • Agencies and nations have increased efforts to give residents advance warning of approaching tsunamis - Preserving coral reefs and mangrove forests decreases the wave energy of tsunamis © 2011 Pearson Education, Inc. One dangerous tsunami • On December 26, 2004 an earthquake off Sumatra triggered a massive tsunami that hit Indonesia, Thailand, Sri Lanka, India, and African countries - Killed 228,000 and displaced 1–2 million more © 2011 Pearson Education, Inc. We can worsen impacts of natural hazards • We face and affect other natural hazards: floods, coastal erosion, wildfire, tornadoes, and hurricanes • Overpopulation: people must live in susceptible areas • We choose to live in attractive but vulnerable areas (beaches, mountains) • Engineered landscapes increase frequency or severity of hazards (damming rivers, suppressing fire, mining) • Changing climate through greenhouse gases changes rainfall patterns, increases drought, fire, flooding, storms © 2011 Pearson Education, Inc. We can mitigate impacts of natural hazards • We can decrease impacts of hazards through technology, engineering, and policy - Informed by geology and ecology • Building earthquake-resistant structures • Designing early warning systems (tsunamis, volcanoes) • Preserving reefs and shorelines (tsunamis, erosion) • Better forestry, agriculture, mining (mass wasting) • Regulations, building codes, insurance incentives discourage developing in vulnerable areas • Mitigating climate change may reduce natural hazards © 2011 Pearson Education, Inc.