TH
8 GRADE SCIENCE
COMPARE AND CONTRAST THE
DIFFERENT LANDFORMS CAUSED BY
EARTH’S EXTERNAL FORCES.
ESS 8.8.4
PLAINS
Plains are large, relatively flat areas
of land.
 Plains found near the ocean are called
coastal plains.
 Flat, grassy areas used to grow crops
or for grazing are also plains.
 Together, these 2 types of plains make
up one-half of all of the land in the
united states.

COASTAL PLAINS
Coastal plains are broad areas along
the ocean’s shore.
 They are often called lowlands because
of their low elevations.
 The Atlantic Coastal Plain stretches
along the east coast of the United
States.
 This area is characterized by low
rolling hills, swamps, and marshes.

Coastal Plains
The Atlantic Coastal Plain isn’t
perfectly flat.
 It has many low hills and valleys that
have been carved by rivers.
 The Atlantic Coastal Plain formed
under water about 70 million years ago
from sediments composed of marine
organisms that fell to the ancient
ocean floor.
 When the sea level dropped, the plain
was exposed.

Coastal Plains
GULF COASTAL PLAIN

Another example is the Gulf Coastal plain.
 It includes the lowlands of the southern United States that
surround the Gulf of Mexico.
 Much of this plain was formed from sediments deposited by the
Mississippi River as it entered the Gulf of Mexico.
Texas Gulf
Coast
Mississippi / Louisiana
Gulf Plains
Interior Plains
A large portion of the interior
Plains is referred to as the Great
Plains.
 They lie between the Mississippi
lowlands and the Rocky
Mountains.
 The Great Plains are flat, grassy,
dry plains with few trees.

Interior Plains
A large portion of the center of the
United States is called the Interior
Plains.
 They extend from the Appalachian
Mountains in the east to the Rocky
Mountains in the west, to the Gulf
Coastal Plain in the south.
 They include the rolling hills of the
Great Lakes area and the central
lowlands around the Missouri and
Mississippi rivers.

Great Plains
They are also called High Plains
because of their elevation.
 They range from 350 meters above sea
level at their eastern border to 1500
meters at their western boundary.
 The Great Plains are covered with
nearly horizontal layers of loose
materials eroded from the Rocky
Mountains.
 Streams deposited these sediments over
the course of the last 28 million years.

CONSTRUCTIVE AND
DESTRUCTIVE FORCES ON LAND
FORMS
ESS 8.8.4
CROWLEY’S RIDGE
CROWLEY’S RIDGE IS A UNIQUE LANDFORM IN
NORTHEAST ARKANSAS, RUNNING FROM
SOUTHERN MISSOURI DOWN TO AROUND
HELENA, ARKANSAS.
 The land in that area is relatively flat.
 This ridge was formed during the great
earthquakes of 1811-1812.
 This is the same quake, along the New
Madrid fault, that made the Mississippi
River change course and even flow
backward for a while!

swamps

Swamps are lowlying areas, that
have standing
water in them.
 They are very
important areas
for certain types
of animals.
canyons
Deltas
A delta is a triangular deposit of
sediment that forms when a stream or a
river slows as it empties into an ocean,
gulf, or lake.
 Eventually, the Mississippi River
reaches the Gulf of Mexico with a
tremendous amount of sediment.
 The water slows down as it hits the
gulf and the sediment spreads out in a
triangular shape, forming the
Mississippi Delta.

TOPOGRAPHIC MAPS
IF YOU WANTED TOI GO HIKING, A
CONIC MAP PROJECTION WOULD GET
YOU TO THE MOUNTAIN, BUT YOU
WOULD NEED A MORE DETAILED MAP
SHOWING THE HILLS AND VALLEYS OF
THAT SPECIFIC AREA.
 A TOPOGRAPHIC MAP SHOWS THE
CHANGES IN ELEVATION OF THE EARTH’S
SURFACE.

TOPOGRAPHIC MAPS

Before starting your hike up the
mountain, you would look at the
contour lines on your
topographic map to see the trails
change in elevation.
 A contour line is a line on a map
that connects points of equal
elevation.
Topographic maps
The difference in elevation
between 2 side by side contour
lines is called the contour
interval.
 If the contour interval was 10
meters, then when you walked
between those 2 lines on the trail,
you would have climbed or
descended 10 meters.

Topographic maps
the closer the contour lines are
together, the steeper the slope will be.
 Contour intervals can be different, but
they will be the same distance on that
map.
 For example, one map may have contour
intervals of 5 meters, while another
map might have contour intervals of
100 meters.

Topographic maps
Some contour lines, called index
contours, are marked with their
elevation.
 If the contour interval is 5 meters,
you can tell the elevation of
other lines around the index
contour by adding or subtracting
5 meters from the elevation
indicated on the index contour.

Topographic maps
Here are some rules to remember when
examining contour lines.
 To decide whether you are looking at a
hill or basin, you can read the
elevation numbers or look for
“hachures”
 Hachures are short lines at right
angles to the contour line that are
used to show depressions.
 These lines point toward lower
elevations.

Topographic maps
Contour lines never cross.
 Contour lines form v’s that point
upstream whenever they cross
streams.

Agents of
Erosion
REVIEW
1. THESE ARE THE LOWLANDS OF THE SOUTHERN UNITED STATES
THAT SURROUND THE GULF OF MEXICO.
 GULF COASTAL PLAIN
 2. THIS IS A TRIANGULAR DEPOSIT OF SEDIMENT THAT FORMS WHEN
A STREAM OR RIVER SLOWS DOWN AND EMPTIES INTO THE OCEAN.
 DELTA
 3. THIS TYPE OF MAP SHOWS THE CHANGES IN ELEVATION OF THE
EARTH’S SURFACE.
 TOPOGRAPHIC
 4. SHORT LINES AT RIGHT ANGLES TO THE CONTOUR LINE THAT ARE
USED TO SHOW DEPRESSIONS.
 HACHURES
 5. LARGE, RELATIVELY FLAT AREAS OF LAND ARE:
 PLAINS
 6. LOW LYING AREAS THAT HAVE WATER STANDING IN THEM AND IS
THE HOME OF VERY MANY ORGANISMS.
 SWAMP

REVIEW
7. CONTOUR LINES NEVER __________.
 CROSS
 8. THE CLOSER THE CONTOUR LINES ARE, THE ___________ THE SLOPE
WILL BE.
 STEEPER
 9. THIS FLAT, GRASSY AREA LIES BETWEEN THE MISSISSIPPI
LOWLANDS AND THE ROCKY MOUNTAINS.
 INTERIOR PLAINS
 10. THIS UNIQUE LANDFORM STRETCHES FROM SOUTHERN MISSOURI
DOWN TO HELENA, ARKANSAS.
 CROWLEY’S RIDGE
 11. SEDIMENTS THAT SLOWLY INCH THEIR WAY DOWN A HILL.
 CREEP
 12. LOOSE MATERIALS OR ROCK LAYERS THAT SLIP DOWN A SLOPE IS
CALLED ________________
 SLUMP

REVIEW
13. THIS IS A LINE ON A MAP THAT CONNECTS POINTS OF EQUAL ELEVETION

CONTOUR LINE

14. THIS STRETCHES ALONG THE EAST COAST OF THE UNITED STATES.

ATLANTIC COASTAL PLAIN
15. THE DIFFERENCE IN ELEVATION BETWEEN 2 SIDE BY SIDE CONTOUR LINES IS
CALLED THE __________.

CONTOUR INTERVAL

16. A THICK MIXTURE OF SEDIMENTS AND WATER FLOWING DOWN A SLOPE.

MUDFLOW

17. A LARGE MOVING MASS OF ICE AND SNOW IS A _______.

GLACIER

18. THE TYPE OF EROSION CAUSED BY GRAVITY IS________.

MASS MOVEMENT

19. VALLEY GLACIERS CAN MAKE A U SHAPED VALLEY OUT OF A V SHAPED
VALLEY

TRUE


REVIEW
20. THESE ARE SHALLOW GROOVES LEFT IN ROCK, CAUSED BY A
GLACIER DRAGGING BIG ROCKS.
 STRIATIONS
 21. THE PROCESS OF BOULDERS BEING LIFTED OUT BY A GLACIER.
 PLUCKING
 22. WHEN WIND BLOWN SEDIMENTS STRIKE ROCKS , _____ OCCURS.
 ABRASION
 23. THESE HAPPEN WHEN LARGE BLOCKS OF ROCK BREAK LOOSE AND
START TUMBLING.
 ROCKSLIDES
 24. WIND BLOWS ACROSS LOOSE SEDIMENTS REMOVING SMALL
PARTICLES SUCH AS CLAY, SILT, AND SAND.
