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The vast central area of the U.S., into Canada, is a landscape of low, flat to rolling terrain in the Interior Plains. As it rises towards the Rocky Mountains it transitions into the Great Plains. A typical Great Plains view of such country is shown by a Landsat image of Kansas. But, in various areas, especially in western North and South Dakota and eastern Montana, erosion has produce gullies and small canyons. A scene including part of the Black Hills is illustrative of this.


The Interior Lowlands: The Great Plains

Most people believe they enter the Great Plains as they cross into Kansas, Nebraska, and other states along that general longitude. From the geomorphologist's and geographer's viewpoint, the Great Plains is arbitrarily set further west in these states, where lowlands elevations begin to rise to their maximum ascension at the Rocky Mountain Front. Say "Great Plains" and typically the first thought is agriculture - this region is often called the "Bread Basket of the U.S." because wheat is the dominant crop. Here is a space image that shows an area of the Great Plains almost totally occupied by farmlands:

Natural color ASTER image of square fields and circular irrigation in the eastern Great Plains.

Another mental picture of the Great Plains is that of natural (wild) grasslands which are almost synonimous with the term "prairie", such as depicted here:

Prairie grasslands

So, as our journey continues to the west, the terrain slowly rises in elevation and local hilly surfaces, often with low scarps, begin to appear. This Landsat-1 image is typical of the farmlands in central Kansas. This August. 1973 scene shows fields that contained now harvested winter wheat in blue and spring wheat and other crops such as alfalfa in red. The area contains mostly Tertiary sedimentary rocks. Much of the water is obtained from the vast underground aquifer known as the Ogallala formation (it is being rapidly depleted by overwithdrawal).

Typical Great Plains scene, imaged by Landsat-1

Enlargement of the above scene, to show the details of the farmland plots.

In this next scene, acquired in October, 1972 we are now over the Great Plains of southwestern Kansas. During fall and winter, the ground has a grayish-brown look that intensifies even further to the west in Colorado. This is also evident in parts of this scene, wherever farm crops have not blotted out their underlying soils (i.e., currently fallow), or the natural surfaces are not converted to agriculture. An example occurs in the lower left corner where the Cimarron River has developed gullied badlands (dendritic drainage) in soft sediments. Note that many farms are square and are often just one mile on a side. These squares correspond to the section divisions in the Township-Range system of land mapping that was adopted in the 19th century in the United States. Near the upper right corner are clusters of circular pivot-irrigation fields, similar to those we showed on page 3-3. These fields lie along the Arkansas River just to the west of the largest town in this part of the state, Garden City.

Landsat MSS image of southwestern Kansas in October, 1972

A Landsat TM image within which is Garden City, Kansas is another typical view of Great Plains farmlands. The time is early Spring when some crops (in red; probably spring wheat) are ready for harvest, other farms remain fallow before planting. The green areas (not a natural color in this false color rendition) are mainly grasslands.

Farmlands around Garden City, Ks; Landsat TM image.

As a generalization, the Great Plains scenes appears similar to some western Interior Lowlands scenes, both of which, are dominated by farmland. On the ground, the Kansas landscape has a more western look because of the semi-desert vegetation, including grasses and sage-like shrubs. There is more red in the eastern (right) half of the image than to the west, becauseof differences in crop type and stage. That is, wheat is more common in the western part of the image, and according to the harvesting schedule, the higher and somewhat cooler western lands had been culled earlier in the Fall.

There are few large cities in the Great Plains. Exceptions are Dallas-Fort Worth, which we examined in Section 4, and Kansas City, MO and Omaha, Nebraska which lie near the boundary between the eastern Great Plains and the Interior Lowlands. Here is a color photograph of Omaha, with Council Bluffs, Iowa across the Missouri River, taken by astronauts onboard the International Space Station:

Omaha, NE and environs in a photograph taken from the ISS.

The two largest cities in Oklahoma appear in this Landsat-1 image. Tulsa is the blue patch in the upper right; Oklahoma City is much harder to see in the lower left. Both oil and agriculture are important in this region, where trees are still fairly common, although giving way on the west side to more western Great Plains vegetation (brush; grasses).

Landsat-1 view of east and central Oklahoma, including Tulsa and Oklahoma City.

Where the western Great Plains extends into Canada, a visually striking difference marks the exact border between that country and the U.S., clearly evident in the scene below. The lower half lies within the farmlands (mostly wheat) of eastern Montana (note the elongate shapes of many farms). But across the border in Alberta, Canadian settlers chose to retain the natural vegetation (grasslands) and devote this land use to grazing of cattle (some farms are seen in the upper right). On the U.S. side, the plains surround two older outliers of igneous rocks, the Bearpaw Mountains (lower right) and the Sweet Grass Hills (center left), both forested.

The U.S.-Canadian border between eastern Montana and Alberta, as seen in a Landsat MSS image.

Most of the northern Interior Lowlands has its topography, vegetation, farm crops, and landscape developed on drifts and tills deposited during the Pleistocene glaciation. The Great Plains in this Landsat-1 scene (in mid-May when vegetation is just emerging) is relatively flat as the overlying till plains is not dissected. Parts of Saskatchewan, Manitoba, and North Dakota are within the scene. However, the Turtle Mountains (elliptical feature) is actually a dissected mesa (of Eocene sandstones) rising about 210 m (700 ft) above the surrounding plains:

The Northern Great Plains.

It is surprising to some, especially after flying over the Interior and Great Plains, that the region from a broader perspective is not flat but often displays rolling terrain and distinct valleys. This is dramatically revealed in this next portrayal - a Heat Capacity Mapping Mission (HCMM; see page 9-8) Nightime Thermal Infrared view of nearly all of northern Kansas, most of Nebraska, and the southwest corner of Iowa. The Missouri (top) and Platte (center) Rivers control the major drainage. The sense of relief is brought about by the tendency of cooler air (darker) to sink into lower terrain at night, producing an effect somewhat like a shaded relief map.

HCMM Night-IR image of a part of the Great Plains about 700 km (430 miles) on a side.

The Great Plains, which grades eastward into the Interior Plains, has a variety of landscapes, including areas that have few farms such as seen above. A typical example of a more diverse scene appears below. Most of the July 4, 1973 Landsat image is in western South Dakota. On the upper left is a portion of the Black Hills, which rise several thousand feet above the rolling terrain whose elevation exceeds 4000 ft (1100 meters). These mountains are so named because from a distance the preponderance of dark evergreens give the Hills a somber appearance. The Black Hills, home of Mount Rushmore and the Homestake Mines in Deadwood, S.D., are a broad domal uplift exposing igneous and metamorphic rocks over most of the interior. Geologists consider the Black Hills to be an offshoot of the Rocky Mountains, which we will encounter on the next page.

Landsat MSS image of the Black Hills, South Dakota Badlands, and part of the Sand Hills of Nebraska. July 4, 1974.

Almost due east is the famous Badlands (bluish-white), an extensively gullied area cut by erosion into soft, easily eroded, often colorful, Tertiary sediments (see figure below). The medium-blue-gray areas are weakly dissected plains with sparse vegetation. This High Plains Tablelands is bounded on its southeast by the forested Pine Ridge escarpment. To the south is a farming region where wheat is the main crop, along with oats, corn, and fodder crop.

Ground view of the soft, eroded Badlands of south-central South Dakota

Here is a perspective view looking west at the eastern side of the Black Hills, made from Landsat and DEM data (note: the dissected high plains in the foreground contain the route taken by the writer [NMS] every day in the summer of 1950 when he worked for the Topographic Branch of the U.S. Geological Survey).

Perspective view of the Black Hills.

The reason that the Black Hills got its name is its general "darkness" owing to a preponderance of dark pine species. This is quite apparent in this Landsat-1 false color image of the Black Hills during wintertime when snow blankets the surrounding plains with snow that is not visible within the Black Hills because the evergreen canopy prevents its exposure:

The Black Hills in winter.

However, nowadays, in the mood of patriotism brought on by 9/11 and Iraq, the Black Hills have taken on a center stage position as we look back to our roots. On the side of a granite mountain south of Rapid City is the famed rock sculptures of the faces of George Washington, Thomas Jefferson, Abraham Lincoln, and Teddy Roosevelt - the Mount Rushmore Memorial - a National Monument. The writer (NMS) feels a personal kinship to this wondrous accomplishment by Gutzon Borglum and his son, Lincoln. I rented a room in 1950 from a Mrs Vincent. One Sunday she asked me to join some guests for breakfast. I was introduced to Lincoln Borglum and his family. Seems the bed I used was also used by Gutzon whenever he was in town as a respite from the construction site. The occasion this Sunday was the dedication of floodlights to illuminate the faces; the guest speaker was the columnist/radio commentator Drew Pearson whom I also met that night when I attended the dedication with the family. I've always treated this occasion as an honor and a lifetime highlight.

Thus, I was pleasantly surprised while cruising the Internet for new material to find a Quickbird image (2.4 meters multispectral combined with a 0.6 m panchromatic image) of Mt. Rushmore and the parklands around it. The DigitalGlobe people kindly made a copy available to me, shown below. I enlarged the area showing the faces of (as I remember) Washington and Jefferson. Most of my heroes are on this cliff (made famous in the movie North by Northwest but I wish that someone would add the faces of Ben Franklin (America's most extraordinary and versatile Founding Father) and Harry Truman (my fellow Missourian who set the stage for the eventual check of Communism). Anyway, here are the images.

Mountain Rushmore, South Dakota, in a 4-meter Quickbird image; courtesy Digital Globe.

Enlargement of two of the Mt. Rushmore faces of U.S. Presidents.

Compare this last image with a ground photo taken through a telescopic lens:

The four Presidents on the Mount Rushmore cliff face, photographed from the ground.

Incidentally, some have questioned the inclusion of Teddy Roosevelt in this quartet. Read his life: perhaps he's not among the greatest (but high up), but few would dispute he is probably the most interesting President owing to his "free spirit" personality.

At the lower right corner of the July 4th Landsat MSS image is the northwest end of the Sand Hills of Nebraska whose dune fields are discernible. The Sand Hills are one of the largest dune fields in the Western Hemisphere. They formed some 10000 years ago by strong winds in the early post-glacial phase of the last major glaciation. Sand produced the longitudinal dunes but were capped by loess (fine-grained silt) which allows some vegetation to grow on the dunes themselves. Water is trapped between dunes to form lakes (some evaporate periodically). We show the western 2/3rds of the dune field in this May 15, 1973 Landsat MSS image (Band 5); the main river is the North Platte, the large water body built by damming this river is Lake McConaughy. A ground photo shows typical landscape within the Hills.

Landsat MSS image of the Sand Hills region of Nebraska.

Among the Sand Hills in Nebraska.

Lets move off flightline to look at two Landsat images of parts of the Great Plains in Texas. The first image if of the Llano Estacado (Staked Plains) in the Panhandle of Texas. The bluish area sites Lubbock, TX. The Ogallala formation (Miocene in age) is capped by up to 10 m of caliche (calcium carbonate formed by precipitation from upwelling groundwater) and is responsible for the low plateau (in brown) which supports mesquite brushland. The greenish areas are mainly undeveloped grasslands. Some oil fields - an offshoot of the West Texas petroleum deposits - are present in the scene.

The Llano Estacado region of the Texas Panhandle.

The southernmost section of the Great Plains is the Edwards Plateau in central Texas. Cretaceous Limestones are the dominant rock type. These have been downcut by stream and wind erosion to form canyonlands and draws in a region of low relief; elevations in this scene range from 600 to 900 m (2000-3000 ft). This is cattle and sheep country rather than farmland. Vegetation is mostly scrub savannah with Junipers and Live Oaks. At the bottom is the Amistead Reservoir formed by damming the Rio Grande. The Pecos River joins it as that river moves south-southeast. Note the canyonland near the left edge of the image.

The Edwards Plateau.

The next scene is not in the Great Plains as such but is topographically and ecologically similar to parts of the southern Great Plains in Texas. The region here lies in the Texas Coastal Plains, built up, as is nearly all the Coastal Plains province running from the southern U.S. to New Jersey, of Miocene to Pleistocene sedimenary rocks deposited when sea level was higher during marine invasion onto the continent. Corpus Christi is found along the side side of the Bay by that name (near top center). Almost the entire Texas coastline is one continuous string of barrier islands, with lagoons and the Intracoastal Waterway to its landward. Best known of these is Padre Island (top) which runs nearly the entire length of this scene. A vast amount of the land south of Corpus Christi was once a huge cattle grazing endeavor, the famed King Ranch, which still exists but has shrunk by sale of some of its holdings.

Landsat MSS of the Texas Gulf Coast and inland Coastal Plains around Corpus Christi, TX.

As the western Great Plains approaches the Rocky Mountains, the topography develops gullies, canyons, and a few mesas or plateaus because of increased downward erosion resulting from the higher elevations. Farms diminish rapidly westward and a semi-desert vegetation cover gives hints of true Western U.S. ecosystems. This image of Southeast Colorado shows these changes:

Landsat-1 scene in southeastern Colorado.

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Primary Author: Nicholas M. Short, Sr. email: nmshort@ptd.net