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Catastrophic Events Two Categories of Catastrophic Events Weather Related Tornados Hurricanes Flooding Wildfires Tectonic Related Earthquakes Volcanoes Tsunamis Tornado (a.k.a twister, cyclone) Counterclockwise column of rotating air extending from cumulonimbus cloud Per square foot, is the most destructive atmospheric event Rated by wind speed (F1 to F5) Fujita Scale “Tornado season” = April, May, June Tornadoes that form over water are called “waterspouts” Behavior of a tornado is unpredictable Typical tornado will: 1. Occur between 3-7 pm 2. Travel 4 miles 3. Be 300-400 m wide 4. Travel 25-40 mi/hour 5. Have wind speeds up to 300 mi/hr 6. Produce extremely low pressure 7. Be dark due to debris picked up Safety Rules Rule #1: Take immediate action! Move away from tornado’s path Tornado’s path Move away at a right angle Lie flat in nearest ditch, etc. At home seek shelter in basement or under heavy table in middle of house Tornado A violently rotating column of air (vortex), hanging from a cumulonimbus cloud, with circulation that touches the surface of the earth Tornado Facts Tornados can occur almost anywhere in the world Duration: a few minutes Diameter (Avg.): 0.4 km Length of path (Avg.): 6 km Funnel can travel from 0 mph up to ~70 mph, usually travels at 30 mph 99% of all tornados in Northern Hemisphere rotate counterclockwise Texas is #1 for frequency of tornados per year Tornado Myths A highway overpass is a safe place to take shelter under during a tornado Opening windows during a tornado will help balance the pressure between the inside and outside of the house and may prevent destruction of the structure One should seek shelter in the southwest corner of a house or basement. Tornado Oddities Tornados are reported to routinely carry objects many miles and have: sucked the frogs out of a pond and dropped them on a town carried a necktie rack with 10 ties attached 40 miles carried a flour sack 110 miles from a mill Tornados also drive objects into other objects and have: Driven splinters into an iron fire hydrant Driven straw and grass into telephone poles When Tornados Occur Anytime of the year- usually in the spring, summer, and fall Most tornados occur during late spring in the month of May Between the late afternoon and early evening is when most tornados are spawned The most dangerous time for formation during evening hours A typical late afternoon tornado Songer http://www.pitt.edu/~super1/lecture/lec0761/005.htm Where Tornados Occur Tornado Alley covers the Great Plains states Tornado Wind Speed In 1971, Dr. Fujita developed a way of measuring the winds of a tornado. He reasoned that there was a link between wind speed and the damage caused by a tornado. There are 6 categories of tornados (F0 – F5) F0 Category (Weak) winds (40-72) mph , little damage Damage: tree branches snapped, chimneys toppled, signs torn down F3 Category (Strong) winds: (158-206) mph, severe damage Damage: most trees uprooted, trains overturned, roofs torn off, walls demolished F5 Category (Violent) winds: (261- 319) mph, incredible damage; rare Damage: bark peeled off trees, houses lifted off foundations, vehicles travel greater than 100 m through the air Tropical Cyclone Nicknames 1. Atlantic: hurricane 2. SE Asia, Japan: typhoon 3. Australia: willy-willy 4. Indian Ocean: cyclone Tropical Cyclone Rated by wind speed (category 1 to 5) Starts and grows over warm ocean water Composed of bands of thunderstorms spiraling counterclockwise around a low pressure center What is a hurricane? Violent cyclonic storm that develops in the tropical region Wind speeds are > 74 mph Source: http://earthobservatory.nasa.gov/ Newsroom/NewImages/images.php3?img_id=680 What conditions must be present for a hurricane to develop? Source: http://lwf.ncdc.noaa. gov/oa/reports/fran/fran.html Warm ocean temperatures (>80˚ F) up to 60m deep Little to no wind shear Low pressure system at least 5˚ North or South of Equator Rotation caused by winds Characteristics Several hundred miles wide Last many days (even weeks) Winds from 74-200 mi/hr Contains an “eye” a. b. c. d. Small region of low pressure Surrounded by highest winds Calm, peaceful, sunny weather Last for about 1 hour as hurricane passes by Rotation and Pressure In which direction does a hurricane rotate? COUNTERCLOCKWISE Is the barometric pressure inside the hurricane high or low? LOW When is Hurricane Season? st 1 June through November 31st Hurricane Anatomy Source: http://hurricanes.noaa.gov/prepare/structure.htm Inside a Hurricane Comparison of Terms Tropical Disturbance Group of thunderstorms in the tropics that are present for at least 24 hours Tropical Wave lack of circulation, winds <25 mph and every direction Tropical Depression closed circulation but disorganized, winds at least 25 mph Comparison of Terms Tropical Storm Shower and thunderstorm moves over closed circulation, winds greater than 39 mph Hurricane Eye is developed, winds > 74 mph What is the Scale Used to Categorize Hurricanes? Saffir-Simpson Scale Category Max Wind Speed (mph) Min. Surface Pressure (mb) Storm Surge m (ft) 1 74-96 > 980 1-1.7 (3-5) 2 97-111 979-965 1.8-2.6 (6-8) 3 112-131 964-945 2.7-3.8 (9-12) 4 132-155 944-920 3.9-5.6 (1318) 5 > 155 < 920 > 5.7 (>19) Source: http://kids.earth.nasa.gov/archive/hurricane/saffir-simpson.html What causes the damage in a hurricane? Winds Flooding Storm Surge What is a storm surge? Large wall or dome of water that rushes into the coastline as a result of a hurricane making landfall To the right are the areas affected by high storm surges Souce: http://www.wkrg.com/hurricanecenter/surge/SE.jpg Danger from Hurricanes In the US, most people that die from hurricanes are killed by fresh water flooding. Think Back! Fresh water flooding was the number one cause of death in the United States. Do you remember from the graph the number two cause of death by hurricane in the U.S.? THE WIND! Take a look at this piece of wood that was driven into the palm tree. Safety Rules Prepare for high winds Prepare for flooding (greatest source of damage) a. b. Up to 20 in. of rain Flooding by coastal water 3. Prepare for thunderstorms 4. Have on hand stored food, water, blankets, candles, matches, radio, etc. 5. Seek shelter Plate Tectonics What is Plate Tectonics The Earth’s crust and upper mantle are broken into sections called plates Plates move around on top of the mantle like rafts 3 types of Plate Boundaries Divergent Boundaries Convergent Boundaries Transform Fault Boundaries Divergent Boundaries Boundary between two plates that are moving apart or rifting RIFTING causes SEAFLOOR SPREADING Causing Volcanic activity Mid Ocean Ridge Convergent Boundaries Boundaries between two plates that are colliding Creating Subduction Zones Causing Volcanic Activity Volcanoes Magma Deep within the Earth, under tremendous pressure and at great temperatures, rock exists as a hot liquid called magma. This molten rock is found in pockets called magma chambers. Magma Chambers Lava When the magma reaches the surface, it is called lava. In some places, lava can build up to form a cone-shaped mountain. The opening from which lava erupts is the vent. Volcanoes often have more than one vent. Lava Volcanic Eruptions During volcanic eruptions, many rock fragments are blown into the air. The smallest particles are called volcanic dust. (less than 0.25 mm) Volcanic Ash ( 0.25 -5mm) falls to the Earth and forms small rocks. Volcanic bombs (a few cm to several meters) are molten and harden as they travel through the air. Volcanic dust and ash Volcanic Bombs Types of Volcanoes Different types of volcanic eruptions form different types of volcanoes. Cinder cones Shield volcanoes Composite volcanoes Shied volcano Can be 28,000 ft Composite volcano up be 8,000 ft. Cinder volcano Up to 1,000 ft. Volcanic Activity Volcanoes are rather unpredictable. Some erupt regularly, others have not erupted in modern history. Scientists classify them as active, dormant or extinct. Volcano Safety Volcanoes are impossible to control but there are some things you can do to help. Create a disaster plan (emergency plans) Make reinforcing structures Build protective walls that move lava away Evaluate the risk (build in a safer place) Educate yourself about volcanic hazards Have an evacuation plan Listen to warnings Transform Fault Boundaries Boundary between two plates that are sliding past each other EARTHQUAKES along faults San Andreas Fault, CA New Madrid Fault Earthquakes Earthquakes An earthquake is the shaking and trembling that results from the sudden movement of part of the Earth’s crust. The most common cause of earthquakes is faulting. During faulting, energy is released. Rocks continue to move until the energy is used up. Seismic Risk Map of the U.S. Tsunamis Earthquakes which occur on the ocean floor produce giant sea waves called tsunamis. Tsunamis can travel at speeds of 700 to 800 km per hour. As they approach the coast, they can reach heights of greater than 20 meters. Picture of Banda Aceh before and after 2004 Tsunami The Seismograph Invented in 1893 by John Milne, a seismograph detects and measures seismic waves. A weight attached to a spring remains nearly still even when the Earth moves. A pen attached to the weight records any movement on a roll of paper on a constantly rotating drum. The drum moves with the Earth and affects the line. The Seismograph Seismologists Seismologists study earthquakes. They can determine the strength of an earthquake by the height of the wavy line recorded on the paper. The seismograph record of waves is called a seismogram. The Richter scale is used to calculate the strength of an earthquake. The Richter Scale The amount of damage created by an earthquake depends on several factors. The earthquake’s strength The kind of rock and soil that underlie an area The population of the area The kind of buildings in the area The time at which the earthquake occurs Volcano and Earthquake Zones Most major earthquakes and volcanic eruptions occur in three zones of the world. Scientists believe that there is a great deal of movement and activity in the Earth’s crust in these three zones. Ring of Fire One major earthquake and volcano zone extends nearly all the way around the edge of the Pacific Ocean. This zone goes through New Zealand, the Philippines, Japan, Alaska and along the western coasts of North and South America. The San Andreas fault is part of this zone. Mediterranean Zone A second Major earthquake and volcano zone is located near the Mediterranean Zone and extends across Asia into India. Many countries in the zone, including Italy, Greece and Turkey, have violent earthquakes. Many volcanic eruptions also occur in this zone. Mid-Atlantic Ridge Zone The third major earthquake and volcano zone extends through Iceland and to the middle of the Atlantic Ocean. There is under the ocean a long range of volcanic mountains called the Mid-Atlantic Ocean Range. Volcanic Zones