Transcript The Effects of 8 Catastrophic Events that Impact Earth

The Effects of 8 Catastrophic
Events that Impact Earth
7th Grade Science
PGMS
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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.
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?
A drought is a lack of precipitation over a long
period of time, usually a season or more, that
results in a water shortage causing adverse
impacts on vegetation, animals and or people
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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 moisture
Hydrological - 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.California
2.Texas
3.Colorado
4.Washington
5.Idaho
6.Oregon
7.Arizona
8.Utah
9.New Mexico
10.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, Missouri
December 1811, morning
Richter magnitude: Estimated 8
Damage: 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 IKE
September 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.
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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.)