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Landforms
Geographers study landforms such as mountains, valleys, plains, islands and peninsulas. Today, we will study how landforms are made and how they influence people.
Below Earth's Surface
Below Earth's surface, or curst, is a layer of liquid and a solid core. The planet has seven continents, large landmasses made of Earth's crust. All of Earth's crust rests on 12 plates. These plates are constantly in motion. Geographers call the study of these moving pieces of crust plate tectonics.
All of these plates move at different speeds and in different directions. As they move, they shape Earth's landforms. Plates move in three ways:
They collide (Convergent Plate Boundaries)
They separate (Divergent Plate Boundaries)
They slide past each other (Transform Plate Boundaries)
The energy of colliding plates (Convergent) creates new landforms. When two ocean plates collide, they may form deep valleys on the ocean's floor. When ocean plates collide with continental plates, mountain ranges are formed. Mountains are also created when two continental plates collide.
When plates separate (Divergent), usually on the ocean floor, they cause gaps in the planet's crust. Magma, or liquid rock, rises through the cracks as lava. As it cools, it forms new landforms such as underwater mountains or ridges. Sometimes these mountains rise above the surface of the water and form islands. Hawaii was created this way.
Plates can also slide past each other (Transform). They grind along faults, causing earthquakes.
On Earth's Surface
As landforms are created, other forces work to wear them away. Weathering breaks larger rocks into smaller rocks. Changes in temperature can cause cracks in rocks. Water then gets into the cracks, expands as it freezes, and breaks the rocks. Rocks eventually break down into smaller pieces called sediment to form new landforms, such as river delta.
Another force that wears down landforms is erosion. Erosion takes place when sediment is moved by ice, wind, and/or water.
Landforms Influence Life
Landforms influence where people live. For example, people might want to settle in an area with good soil and water. Climate can cause people to migrate as well as jobs. People do change landforms in many ways. For example, engineers build tunnels through mountains to make roads. Farmers build terraces on steep hillsides to grow crops so that water erosion doesn't wash crops away. The building of water reservoirs and dams also impact the earth, its inhabitants, and wildlife.
Illinois' Landforms
Illinois is bordered by Wisconsin in the north; Lake Michigan, Indiana, and Kentucky in the east; Kentucky and Missouri in the south; and Missouri and Iowa in the west. Since 1842, Illinois has been called the "Prairie State" because the northern portion of our state was once completely covered in this sort of environment, but now, it’s a rare sight. However, there are still places in Illinois where you can enjoy prairie land. Goose Lake Prairie State Park is essentially in our "back yard" offering a many ways for us to experience the prairie. Some geographers divide Illinois into 3 major regions: Central Plains, Shawnee Hills, and the "Egypt" region.
Illinois' Goose Lake Prairie State Park (Jugtown Road, Morris).
The Central Plains region covers almost all of the state and contains fertile land and low hills. It includes the Great Lakes Plain, which runs along Lake Michigan; the elevated Driftless Plains in the northwest; and the Till Plains in the north. The Till Plains are part of the nation’s Corn Belt, named for the fields of corn that grow there. This region contains many moraines, which are a mass of rocks and sediment carried down and deposited by a glacier, typically as ridges at its edges.
Illustration of the making of a moraine.
Photo of a glacier receding after making a moraine.
Illinois highway (McClean County) built over moraines.
The Shawnee Hills region in southern Illinois is a narrow strip of land with higher elevations, rivers, and forests (left below).
Illinois' Gulf Coastal Plain is a hilly area at the state’s southern tip. It’s sometimes nicknamed Egypt because it’s similar to the Egyptian Nile’s fertile delta (right below).
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