Changing Earth Rev 4.14.05

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Transcript Changing Earth Rev 4.14.05

The Changing Earth
Researched and produced by
Mrs. Terri Reed, 5th Grade Teacher
Brookhollow Elementary
Lufkin, Texas
The Changing Earth
The Earth was formed billions of years
ago, but it’s continuously changing.
Some changes happen quickly, while
others can take years to appear.
Earthquakes change the
earth quickly.
When the earth’s plates
move with great force,
waves of energy move
through the ground.
Deep cracks can appear
in the ground after an
Damaged cities
Earthquakes can
cause major damage
to cities.
Earthquakes can trigger giant waves called
This is Surtsey, the newest
island in the world. Located
off Iceland, it formed from
1963 to 1967.
The Hawaiian islands, also
formed by volcanoes, took
thousands of years to form.
Volcanoes can change
the world quickly or
They are formed when
magma (hot rock)
pushes up through
cracks in the earth’s
Volcanoes form and
change islands and
Mount St. Helens, Washington
Mount St. Helens, a volcano in Washington State,
erupted on May 18, 1980. The picture on the left
was taken before the eruption. The picture on the
right was taken afterwards.
Volcano damage
Weathering and erosion
Changes by weathering and erosion occur more
Rocks are broken down by strong winds, heavy rains,
ice, rushing water and even growing plants in a
process called weathering.
After rock is weathered, it is moved to other places
by wind, water and ice. This is called erosion.
Weathering by ice
The unique cones and towers in Utah’s Bryce Canyon
were formed by ice freezing and thawing. When
water freezes, it expands and can break rock. When
the ice melts, it leaves behind a changed rock.
Bryce Canyon in winter
Bryce Canyon in summer
Weathering by plants
Rocks can be split by a plant! The roots of
this tree have grown into the rock.
When the water,
wind or ice drops (or
deposits) sediment,
this is called
In this picture, the
river not only carried
sand and rocks, it
also carried pieces
of wood and a tree!
Deposition forms deltas
As rivers flow down
stream, they erode
rocks and soil.
The sediment is
deposited at the
mouth of the river,
forming a triangleshaped landform
called a delta.
The Nile River Delta as
seen from outer space.
Deposition forms sand dunes
Dunes are formed by
sand accumulating
around any object that
serves as an obstacle to
the wind.
The Great Sand Dunes
in Southern Colorado
were formed from wind
erosion and deposition.
Waves pound shorelines
day after day. Over
time, they carry away,
or erode the rocks and
sediment (sand, gravel
and crushed shells) on
the shore.
Waves deposit the
sediment at other
places and build up
sandbars or islands.
Padre Island is
actually a long
sandbar that hugs
the southeastern
coast of Texas.
Sea cliffs
Sea cliffs are landforms
that result from water
Over a long period of
time, the bottom of a
cliff may be slowly worn
away by waves.
Overhanging rocks may
break off the top of the
cliff and fall into the
Sea stacks
Sea stacks are all that remain of a sea cliff that was
eroded away by waves.
The Grand Canyon
The Grand Canyon,
more than 1500m
(5000 ft) deep, was
produced by water
erosion probably within
the past 5 million years.
It was carved by the
Colorado River across
the Colorado Plateau.
Rocky Mountains
The Rocky Mountains
have been weathered
by rain, wind and ice.
During the Ice Age,
snows accumulated on
the mountains, forming
glaciers that moved
down the valleys.
Weathering by streams
Terra Tomah in the Rocky and rivers cut canyons
and deep gorges
through the ranges, and
continues today.
A plateau is a flat-topped tableland with
steep sides. These landforms are also
changed by wind, streams and glaciers.
Buttes and Mesas
When plateaus wear away, they become buttes or
This is a butte in Monument Valley, a Navajo Nation
tribal park located between the border of Arizona and
Millions of years of
wind erosion
resulted in unique
landforms called
This picture was
taken in Arches
National Park, Utah.
This is a wave cave that formed when waves
pounded against soft places in a sea side cliff.
This is a limestone cave located in “Natural Bridge
Caverns” near New Braunfels, Texas.
It formed over millions of years as water filtered
through soil and cracks in the rocks, then mixed with
carbon dioxide to dissolve the rock.
Valleys formed by rivers
Rivers carry stones and
rocks in its water. The
force of the water and
the grinding of rocks
and stones cut down
into the river bed and
carve out a valley.
As rivers erode and
deposit sediments, they
form valleys with steep
sides, resulting in a Vshape.
Glaciers are huge
collections of ice that
change the earth as
they slide down
They carry rocks, sand
and clay and deposit
them along the way.
This is a glacier in
Valleys formed by glaciers
Valleys shaped by glaciers tend to have
slower sloping sides, resulting in a U-shape.
Wind erosion
Wind erosion carries away valuable topsoil and
reduces land's ability to produce crops. This
causes problems for farmers.
The Dust Bowl
In the 1930s, a long
dry spell, combined
with poor farming
practices, caused
dust storms and soil
This is a photograph
of a "black blizzard“
— a dust storm
Stratford, Texas, on
April 18, 1935.
Good farming practices can prevent erosion
Land covered with plants is
protected against wind and
water erosion.
Farmers need to avoid
cutting their crops too short.
Rows of trees planted next
to fields, called shelterbelts,
reduce wind erosion and
conserve soil moisture.
Terraced fields offer protection
Farmers all over the world use terraced fields to
catch rainwater and hold soil on sloping land.
This picture shows a rural area of Vietnam.
Effects of beach erosion
Erosion along
beaches can cause
serious problems for
homes located along
Washaway Beach
Washaway Beach
on Cape Shoalwater
in Washington State
has been eroding an
average of 100 feet
per year for a
Plants slow beach erosion
Plant roots hold soil in place and slow
erosion at the water’s edge.
Rock walls prevent erosion
Man-made rock
walls are frequently
used to prevent
shoreline erosion.
However, these
structures may harm
plants and animals
who live in the area.
Deforestation and erosion
This is a rain forest in
Costa Rica that has been
destroyed by humans.
The stream valley is
eroding because there is
no longer a good root
system to anchor the
topsoil or decaying plant
matter to replenish its
If the cycle continues,
the area may eventually
resemble a desert.
The future earth …
Earth is changing at this moment. How do
you think it will look in the future?
By studying volcanoes, earthquakes,
weathering, erosion and deposition, you can
make an accurate prediction.
Paolo Koch/Photo Researchers, Inc
Dust storm approaching Stratford, Texas Dust bowl surveying in Texas
Image ID: theb1365, Historic C&GS Collection
Location: Stratford, Texas
Photo Date: April 18, 1935
Credit: NOAA George E. Marsh Alb
S.E. Cornelius/Photo Researchers, Inc$department/deptdocs.nsf/all/agdex3524?opendocument terraced field in Vietnam 4/4/05
Scott Foresman Science for Texas (3rd, 4th and 5th grade textbooks)
“Discovery Works” by HoughtonMifflin Science
“The Earth,” by Dr. Rainer Koethe; Tessloft Publishing
Compton’s Interactive Encyclopedia; 1999; the Learning Co.
Microsoft Encarta Encyclopedia 2002
“Icebergs and Glaciers,” by Seymour Simon; William Morrow & Co., Inc, New York; 1987]
STS 76-719-053 - March, 1996 sea stack volcano damage damaged house tsunami
TEKS covered
3.6 B The student is expected to identify that the surface of the Earth can be
changed by forces such as earthquakes and glaciers.
4.10 A The student is expected to identify and observe effects of events that
require time for changes to be noticeable including erosion, weathering and
4.11 B The student is expected to summarize the effects of the ocean on land.
5.11 A The student is expected to identify and observe actions that require time
for changes to be measurable, including erosion, weathering & flow.
5.12 A The student is expected to interpret how land forms are the result of a
combination of constructive and destructive forces such as deposition of
sediment and weathering.