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The Effects of 8 Catastrophic Events that Impact Earth

7th Grade SciencePGMS

Student Directions….

• Turn to each corresponding page of flipbook.• Circle the type of cause for this event.• Write in Benefits of each event.

– Each Event benefits earth in some way. How?– Do not write “NONE” for benefits.

• Write down Safety Ideas for each event.

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VOLCANO

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HOW VOLCANOES FORM

• When pressure from gases within the magma becomes too great, an eruption occurs.

• Once the volcano erupts, the Earth moves to a state of equilibrium until pressures build again

• Eruptions can be slow and fairly quiet or violently explosive.

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VOLCANO—MAIN FEATURES

• A volcano is a vent in the Earth which allows molten rock (magma) to escape to the surface.

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IMPACT OF VOLCANOS

• New land can be created by volcanoes but there can also be great destruction to the environment and human habitats.

• Hazards include searing hot, poisonous gases, lava and pyroclastic flows, landslides, mudflows, earthquakes, increased fire hazard, explosions, rockslides, flash flooding, and tsunamis.

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IMPACT OF VOLCANOS

• Volcanic ash is very fine glassy rock fragments.

• It can affect breathing, contaminate water supplies, collapse roofs, disrupt machinery, and cause jet engines to fail while flying.

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VOLCANO--NEGATIVE EFFECTS• When a volcano erupts, people may be killed. When Mount St. Helens

erupted, 57 people died, even though the mountain is in an area of low population density and there was lots of warning about its eruption. Land may be destroyed. In Hawaii, the lava flows from Kilauea burns roads, houses, fields, crops, and fences. Entire species may be eliminated in an area because the eruption either killed them or destroyed their habitat. The larger species of animals and the forests of Mount St. Helens were very badly affected by the most recent eruption. Erosion can produce scars which continue to grow as more soil is washed from the naked land after an eruption kills the forests, scrubs, and grasses. The ash and gas may cloud the atmosphere so that it is hard to breath, and the sunlight cannot get through. In 1815, a volcano (Tambora) produced so much ash and sulfur that it circled the globe. It was called the Year Without a Summer, because the weather never did warm up that year. Tourists may stay away because they are afraid of another eruption or because the natural beauty of the area has been damaged. These are all negative consequences of a volcanic eruption.

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BENEFITS OF VOLCANOS• Many peoples around the world continue to live near volcanoes

because the eruptions produce wonderful soil for growing crops. Most of the surface of the North American continent itself was produced by the eruption of volcanoes over millions of years. The atmosphere of the Earth got much of its components from the eruption of volcanoes. Even tourism can be positively affected. Pompeii is a very popular tourist site because of the information preserved there by the eruption of Vesuvius. Mount St. Helens has more visitors each year now than it did before the explosion, despite the destruction to its natural beauty.

• Generally in the short time frame, volcanoes are destructive; however, in the longer frame of time, they are a vital and necessary part of the Earth as we know it. Without volcanic eruptions, the life we know on the Earth today would not exist.

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VOLCANOES

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Mount Tambora--

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Crater Lake, Oregon

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DROUGHT

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What is a drought?

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Where do droughts occur?

•Most occur in hot areas like Texas, California, Nevada, Australia, and Mexico.

•In the US, most are likely to occur in the Midwest and South because of the heat waves and deserts

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Types of Drought

Meteorological - lack of precipitation

Agricultural - low soil moistureHydrological - lack of water in watersheds,river systems, and reservoirs

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Negative Effects

• Plants may die leaving soil exposed to winds that can carry away topsoil

• Animals may dehydrate and die• People in undeveloped areas may die from

dehydration• 55% of crop failures in the US are due to lack

of water

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Texas Drought Monitor

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Lake Travis 2007

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Lake Travis, Aug. 2011

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Wildfires

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What is a wildfire?

A wildfire is an uncontrolled fire.

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How do they start?

•humans cause 90% of wildfires through campfires left unattended, burning of debris, discarded cigarettes, and arson

•lightning•accumulation of leaves, twigs, trees and

underbrush that can heat up and ignite•arson (intentional setting of a fire )

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Wildfire Facts• Wind has the biggest impact on a wildfire.• crown fires are spread by wind moving quickly

across the tops of trees that are on fire • one of the largest fires ever was in 1825 in Maine

and Canada; it burned over 3 million acres• a really large wildfire can cause its own weather

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Top States Prone to Wildfires 1.California2.Texas3.Colorado4.Washington5.Idaho6.Oregon7.Arizona8.Utah9.New Mexico10.Nevada

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Wildfires—Main Features

• Wildfires can spread slowly from burning material along the forest floor or spread rapidly by wind causing it to jump along the tops of trees.

• Drought conditions, wind, high temperatures, and low humidity are conditions that help wildfires spread.

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Wildfire Impact

• A wildfire can destroy millions of acres of forest. • Watersheds can have all the vegetation burned

off leaving the area prone to erosion.• Animals may become endangered due to

habitat destruction. • The economic losses can impact humans if fire

sweeps through an inhabited area.• New plant growth comes back quickly to a

burned area.

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Bastrop State Park, TX

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Bastrop State Park, TX, 2011

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EARTHQUAKE

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EARTHQUAKE –MAIN FEATURES

• An earthquake is the vibration of the Earth’s surface that occurs after a release of energy in the crust.

• This release of energy can be caused by a volcanic eruption or movement of segments of the crust (faults), or plate tectonic collisions.

• The crust may bend and as the stress builds and exceeds the strength of the rock, break, and snap into a new position.

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EARTHQUAKE—MAIN FEATURES

• This process releases pressures in the crust and the Earth’s crust reaches equilibrium again.

• Seismic waves are created when the crust breaks.

• The waves travel outward from the source of the earthquake at various speeds, depending on what material they move through.

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IMPACT OF EARTHQUAKES

• Earthquakes can open large cracks in the ground causing standing bodies of water such as ponds or lakes to disappear.

• Land of either side of the fault can rise, lower, move away or toward each other.

• Earthquakes can cause damage to the environment by liquefaction of the ground, landslides, avalanches, fires, or tsunamis.

• The main impact to humans is property damage and loss of life.

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Worst in US History

• New Madrid, MissouriDecember 1811, morningRichter magnitude: Estimated 8Damage: Cracks opened in the ground; some islands disappeared from middle of Mississippi River; felt in Washington, D.C.

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New Madrid effects: Landslide

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Cleburne, TX 2009

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TSUNAMI

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HOW TSUNAMI FORMS

• Tsunamis are ocean waves produced by earthquakes, volcanic eruptions, meteorite impact, or underwater landslides.

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TSUNAMI—MAIN FEATURES

• Tsunamis are a series of waves that can travel between 450-600 mph in the open ocean.

• Ships in the open ocean would not feel the tsunamis because the wavelength would be hundreds of miles long and have amplitude of only a few feet.

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TSUNAMI—MAIN FEATURES

• As the tsunami wave approaches the coast, its speed decreases and its amplitude increases.

• Basically, it gets slower and taller. From the starting point of the tsunamis, the waves travel outward in all directions.

• As the waves approach the coast, the time between each wave varies from 5-90 minutes.

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TSUNAMI—MAIN FEATURES

• The first wave is usually not the largest or most destructive.

• Often the waters will pull back before the wave arrives.

• They are not v-shaped or rolling waves. Tsunamis often come ashore as a rapidly rising turbulent surge of debris filled water.

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WHERE TSUNAMIS OCCUR

• Tsunamis often come ashore as a rapidly rising turbulent surge of debris filled water.

• The waves can travel upstream in coastal estuaries and rivers.

• Tsunamis can occur during any season and at any time of day or night.

• Areas of risk are less than 25 ft. above sea level and within one mile of shore.

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IMPACT OF TSUNAMIS

• Impact includes drowning, flooding, contamination of drinking water, loss of habitat or human homes, fires from broken gas lines, etc.

• Both the environment and humans can suffer extreme damage from tsunamis.

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Tsunami wave hits Japan.

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Japan coastline

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HURRICANE

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HOW HURRICANES FORM• Hurricanes start out as tropical storms (tropical• cyclones). • Moist, warm air above the ocean rises and cools

forming clouds. • Air from the oceans surfaces rushes into the

space caused by the upward motion of the warm air.

• This air begins to spiral upward causing wind. When the winds reach a constant speed of 74 mph or more it is upgraded to a hurricane.

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HURRICANE—MAIN FEATURES

• Hurricane winds blow in a spiral around a calm center called an eye.

• The eye can be up to 30 miles wide and the storm can be 400 miles in diameter.

• A single hurricane may last a week or more and travel the length of the East Coast.

• A hurricane can have torrential rains, high winds, and a storm surge as it approaches land.

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WHERE HURRICANES OCCUR

• On average, ten tropical storms develop over the Atlantic Ocean, the Caribbean Sea, or

• the Gulf of Mexico each year. • About six of these develop into hurricanes.

Many of these storms remain over the ocean.

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IMPACT OF HURRICANES

• Most deaths from hurricanes are due to flooding.

• Winds can drive ocean water up the mouth of rivers.

• Flooding can trigger mudslides or landslides. Tornadoes can be spawned by hurricanes.

• Economic costs and habitat loss is common.

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HURRICANE IKESeptember 18, 2008—Gentle waves lap the shore near beach houses (top) on Texas'Gentle waves lap the shore near beach houses (top) on Texas' Bolivar Peninsula on September 9, 2008—just a few days before Hurricane Ike rolled into Galveston Bay. An aerial photo of the same shoreline taken by the U.S. Geological Survey on September 15 (bottom) illustrates the dramatic destruction the strong Category 2 storm wrought on the coastal community. Yellow arrows mark the same distinguishing features in both images. Unprotected by a seawall like the one built on nearby Galveston Island, homes along Bolivar's edge were among the hardest hit by Ike's massive 10- to 15-foot (3- to 4.6-meter) storm surge.

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TORNADO

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HOW TORNADO FORMS

• Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east.

• Thunderstorms develop in warm, moist air ahead of eastward moving cold fronts while the cold, dry air is behind it to the west.

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HOW TORNADOS FORM

• These thunderstorms often produce large hail, strong winds and tornadoes.

• Along the mountains, tornado producing thunderstorms can form as the air flows up the slope to higher land areas.

• Tornadoes can form to the right and in front of the path a hurricane takes as it comes on land.

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TORNADO—MAIN FEATURES

• A tornado is a violently rotating column of air extending from a thunderstorm to the ground.

• The most violent tornadoes have wind speeds of 250 mph or more.

• Damage paths can be in excess of one mile wide and 50 miles long.

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TORNADO—MAIN FEATURES

• Tornadoes may appear transparent until the dirt and debris it picks up gives it color.

• Two or more tornadoes may form at the same time.

• A waterspout is a weak tornado that forms over water. – If the waterspout moves over the land it

becomes a tornado.

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WATERSPOUT???

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Where Tornados Occur

• Tornadoes are most likely to occur between 3 and 9 p.m., but have been known to occur at all hours of the day or night.

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IMPACT OF TORNADOS

• The high winds from the tornado and the hail from the thunderstorm cause the most damage.

• Tornadoes can destroy buildings and vehicles, kill humans and animals, uproot trees, and scour the soil off the ground down to the rock.

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Joplin, MO May 2011

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Joplin, MO May 2011

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FLOOD

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HOW FLOODS FORM

• A flood is an overflowing of water onto land that is normally dry.

• A flood can be caused by intense or long term precipitation from thunderstorms, hurricane storm surges, or melting snow and ice.

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FLOOD—MAIN FEATURES

• Floods can last from a few minutes to months.

• The amount of flooding is controlled by the amount of water that builds up as well as how porous the soil is and the amount of water already in the soil.

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WHERE FLOODS OCCUR

• Humans have altered the landscape in several ways.

• The greatest impact results from paving the ground for housing, roads, and parking lots.

• Neither asphalt nor concrete is porous.– All the precipitation that falls becomes runoff

• Most of the world’s population lives near the coast or on floodplains.

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IMPACT OF FLOODS

• Floods can cause loss of life, disease, property loss or damage, contamination of drinking water, and destruction of crops and livestock.

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Ft Worth, TX 2007

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Damaged crops

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Flood damage.

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Turn Around, Don’t Drown.

Benefits of All of these Catastrophic Events:

• Earth’s way of maintaining equilibrium• Pressures or imbalances equalize through

these processes.

• (YOUR flipbooks should contain these sentences in your “Benefits Lists” in addition to notes you took during class.)