Transcript Changing Earth`s Surface

Changing
Earth’s Surface
4.4
How might a natural disaster affect
Earth’s surface?
• It might. change landforms.
How might a fire alter an environment
and how can the area benefit from a
fire?
• A fire will burn down trees destroying animal
habitats. It can destroy some trees, but will
allow for the germination of other trees.
Some seeds require intense heat in order to
germinate. Some fires prevent larger fires
from occurring when the vegetation is drier.
How can environments change?
• What kinds of natural events cause changes
in an ecosystem?
• Earthquakes
• Floods
• Fire
• Hurricanes
• Tornadoes
• Volcanic eruptions
How can organisms change an
ecosystem?
• They could eat too many of one species,
enter a new ecosystem, or use too many
resources.
Environments are constantly
changing.
• Think about where you live…
• How has your environment changed since
you’ve lived there?
• Have new trees or plants grown? Have
fences been added? Have new houses been
built?
• Things in our environment are change all the
time. What has changed outside our school
even this year???
Environmental changes can be caused
by natural events or by human actions.
• Natural events include:
Earthquakes, storms, volcanoes,
droughts, and other natural disasters
• Natural disasters can happen
suddenly and be very violent.
• Think of an earthquake or a
volcanic eruption. These changes
greatly affect the plants, animals,
and people living where these
disasters occur.
• There is very little that anyone can
do to prevent these natural
disasters from occurring.
Organisms can cause change in an
environment.
• Beavers are a good
example. They build
dams which can
cause flooding, but
the dams can also
be beneficial by
creating new
habitats and food
supplies.
• Large animals such
as an elephant can
cause damage by
trampling trees and
seedlings.
Organisms can cause change in an
environment (continued)
• It’s not just land environments that change.
Aquatic environments can also change.
• Algae could rapidly reproduce and use up
nutrients and oxygen.
• Aquatic organisms can build reefs. These can
create new habitats for other organisms.
Organisms can cause change in an
environment (continued)
• People can cause change in an environment.
• Forests are cut down and destroy animals’
habitats to build roads and neighborhoods.
• People also cause pollution that damages
water, soil, and air quality.
Tsunamis
• What is a tsunami?
• A tsunami is a series of huge
waves caused by an
earthquake or volcanic
eruption beneath the ocean.
Most are started by
earthquakes.
How is plate tectonics related to the
formation of tsunamis?
• Plate movement causes the earthquakes
and volcanic eruptions that create tsunamis.
December 26,
2004
• An earthquake
measuring 9.0 and 9.3
on the Richter scale
occurred in the Indian
Ocean. This triggered a
tsunami that sent a
series of waves
crashing onto the
shorelines of southeast
Asia. This tsunami
destroyed entire
villages and killed
hundreds of thousands
of people.
What causes floods?
• Usually floods are caused by a large amount of rainfall
over a very short period of time.
• Why are floods dangerous?
• The force of rapidly moving floodwater can injure people
and animals, uproot trees and other vegetation, and
destroy or damage homes and property.
How can
people
prevent a river
from
flooding?
• People often build
levees and dams in an
effort to prevent rivers
from overflowing their
banks and flooding the
surrounding areas.
• How can floods
change the landscape
of an area?
• They can erode the
land or deposit large
amounts of mud and
debris.
Floodwater
• Floodwater picks up and carries away tons of mud
and debris.
• Once the water recedes, the mud and debris are
left behind. This mud and debris can bury crops
and other plants, damaging or killing them.
Benefits of a flood
• A flood can benefit future crops. The mud
that is left behind can be nutrient rich and
will renew the soil making it more fertile.
Controlling flood
waters
• In areas where floods are
likely, people try to control the
water’s flow by building dams
or levees.
• A levee is a wall or a large
mound of earth built along a
river to prevent it from flooding.
They raise or extend the banks
of the river so that more water
than usual can flow in the river.
Levees
• A levee can be a good solution
to flooding, but a levee can
also make a river valley
narrower. This can cause
increased flooding farther
downriver.
New Orleans, 2005
• In 2005, a break in a levee caused severe
flooding in New Orleans.
How do earthquakes and landslides
affect habitats?
• Earthquakes can cause a
tremendous amount of damage.
Power lines and gas lines can
be broken causing fires.
• Earthquakes can also cause
changes in landforms. Large
cracks in the ground can open
and shifting ground can cause a
cliff to form in seconds. It can
change a river’s course, drain a
lake, or change the appearance
of the natural and human-made
features of a region.
Landslides
• A factor that contributes to
landslides is the slope of
the land. As the angle of the
slope increases, the slope
becomes too steep to hold
rock and soil.
• Streams can cause slopes
to become very steep. As
the water from the stream
flows through a valley, the
water can cut away rock and
soil until the valley wall
becomes too steep. Waves
can also cause slopes to
become too steep.
Landslides
• A landslide can cause more damage than an
earthquake.
• It can carry buildings down a hillside or bury
highways under debris. Trees can be uprooted
and change a small slope to a steep cliff.
• Tumbling rocks from the landslide can damage
the riverbed by removing plants and killing fish
and other animals.
• Debris can fall into rivers or streams and create
dams, change the course of the water, or cause
flooding.
What are long-term effects of
natural disasters?
• The sudden changes caused by natural
disasters can have long-term effects on Earth
and its habitats.
• A volcanic eruption can send gases and
particles of ash into the air. This debris spreads
into the atmosphere where it can remain for
months or even years.
Natural Disasters can bring positive
changes.
• Volcanoes build new land.
• Floods and landslides can add
to the soil by leaving behind
nutrient-rich mud.
• Volcanic ash can block sunlight
from small plants so that
surrounding trees grown more
quickly.
• New habitats can be formed
and fresh minerals can brought
to the Earth’s surface.
How can living things change their
environments?
• Beavers build dams, creating new habitats;
elephants can trample trees and seedlings;
humans cut down forests and cause
pollution.
Can a natural environmental change cause
more damage than a change caused by
people? Give an example.
• Yes, a natural ecosystem change can cause
more damage than one caused by humans.
• A volcano, for example, can cause more
damage to a local ecosystem than is caused
by building a road.
What information would indicate to scientists
that a tsunami might be about to occur?
• An earthquake or volcanic activity as well as
changes in wave height and length might
indicate to scientists that a tsunami is about
to occur.
How do tsunamis damage habitats
over a wide area?
• Tsunamis damage habitats because they
crash ashore with a powerful force and
submerge large areas of land.
How can floods harm people?
• Floods can damage homes and other
structures, pollute water supplies, and
create dangerous situations in which people
are suddenly surrounded by water. People
and animals can drown.
How can floods affect crops that are
planted near a river?
• Floods can damage or destroy crops that
have been planted, but they can also enrich
the soil for future planting.
How do earthquakes affect wildlife
habitats?
• Earthquakes cause violent shaking that
disturbs animal and plant life. They change
the shape of the landscape by opening
cracks in the ground and moving waterways.
What might happen if a landslide
occurred in a populated area?
• Buildings, including people’s homes, might
be damaged or lost. Roads, power lines, and
water-supply lines might be damaged.
How might an area benefit from a
volcanic eruption?
• Wildfires might clear
out old plant growth,
add nutrients to the
soil, and encourage
new plants to sprout.
How can a natural disaster affect the
climate of an area?
• A natural disaster can affect the climate by
changing the temperature of the air,
changing the depth or location of bodies of
water, adding gases and particles of ash to
the atmosphere, or changing the shape of
the Earth’s surface.