8TH 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

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.

They are also called High Plains because of their elevation. 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 low-lying 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.

Contour lines never cross. Topographic maps Contour lines never cross. Contour lines form v’s that point upstream whenever they cross streams.

Agents of Erosion

5. LARGE, RELATIVELY FLAT AREAS OF LAND ARE: 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.