Proceeding westward, the Appalachian Plateau topography gradually gives way to gentle rolling hills and then (in central Ohio) to flat lands converted principally to farms and urban areas. This is the beginning of the vast Interior Plains of North America, shown first as a single-colored geographic pattern and then in a detailed map which names its subdivisions:
Geographers subdivide the Interior Plains into the Interior Lowlands and the Great Plains on the basis of elevation. The Lowlands are mostly below 1500 feet above sealevel whereas the Great Plains to the west are higher, rising in Colorado to around 5000 feet. The Lowlands, then, are confined to parts of Minnesota, Iowa, Michigan, Ohio, Indiana, Tennessee and Kentucky. Missouri and Arkansas have regions of Lowlands elevations but in the Ozarks (within the Interior Highlands) are higher. Those familiar with the topography of eastern Ohio may be confused by this; that region is hilly but its rocks are horizontal and are an extension of the Appalachian Plateau.
The Interior Plains are largely coincident with the vast Mississippi River Drainage System (other major components are the Missouri and Ohio Rivers), as seen in this map. These rivers have for tens of millions of years been eroding downward into the mostly horizontal sedimentary rocks of Paleozoic, Mesozoic, and Cenozoic ages. The modern Mississippi River system has developed during the Pleistocen Epoch of the Cenozoic Era.
The largest geographic feature in the central U.S. is the group of five Great Lakes, several being in the Lowlands, seen here in this meteorological satellite image:
From left to right (west to east), the lakes are Lake Superior, Lake Michigan, Lake Huron (Georgian Bay is its eastern section), to its south, Lake Erie, then Lake Ontario. Only Lake Michigan lacks a border with Canada. The Great Lakes are the largest complex of freshwater lakes that were scoured out by glacial gouge during the Pleistocene continental ice advance over North America.
The first image depicting Interior Lowlands landforms is just west of the transition between Appalachian-controlled topography and the Interior or Central Lowlands. The scene is that of Cleveland (blackish area on the shore), Lake Erie with partially melted ice in March of 1973, the widespread farmlands (note their distinctive criss-cross pattern) of northern Ohio and southern Ontario, and low hills and lakes (mostly from the last glacial retreat).
Cleveland, Ohio lies astride the southeastern shores of Lake Erie. Here is the central city imaged at 4 meters by IKONOS on April 26, 2000:
Typical of the Interior Lowlands is the region around Chicago, Illinois, shown in this Landsat MSS scene.
The underlying rock type in the Illinois part of the Interior Province is limestone, but nearly all of the surface here is controlled by glacial deposits. The rich soils from these materials promote farming, of which corn, soybeans, and oats make up the major crops. Most of fields in this scene are rectangular, and many now are fallow (tan-colored) after harvesting. Trees cluster along the banks of rivers such as the Illinois, Des Plaines, and Kankakee that stand out among the farms.
Chicago sits along the southwest tip of Lake Michigan, one of the five Great Lakes. All of them originated as basins cut by glacial scouring and, in places, from damming by moraines. Gary, Indiana is the blue area at the southern tip of the Lake.
Chicago itself appears in these two astronaut photos, one taken in daytime, the other at night:
Chicago is the second largest city in the United States. It has numerous suburban towns, many being well known and in the news. Two maps are needed to show the full metropolitan area:
The Chicago Loop (named for the rectangular track layout of elevated trains) reaches to Lake Michigan in the dense central downtown which is visible as blue tones, while much of the surrounding metropolitan areas are expressed by the reds denoting trees in suburban settings. Look in the image for features near the waterfront and compare with those in this aerial oblique photo of that area:
Another major Great Lakes city lies almost due east of Chicago. Detroit, Michigan is built along the Detroit River which connects Lake Ontario at its northwest end with Lake St. Clair above a peninsula in Canada on which Windsor is situated across river from Detroit. Both cities are shown in this aerial view:
This Landsat-7 ETM+ subscene shows part of this metropolitan complex of nearly 8 million people in natural color.
At the other extreme in population (~16000) is Sault Ste. Marie, at the east end of Michigan's Upper Peninsula. It is one of the oldest towns in the Upper Midwest, tracing its founding to the late 1600's. The term "Sault" is French for cataracts (waterfalls along the St. Mary River):
Wisconsin has several larger cities that one thinks of offhand: Madison, Green Bay, and Milwaukee. Madison is the state capital and the site of the main campus of the University of Wisconsin:
As an emblem of Wisconsin, we have selected a very remarkable small city of about 100000: Green Bay, which is the smallest city to support an NFL team, the Packers - perennial powerhouses that play their football in an often frigid open stadium (Lambeau Field) filled with dedicated and loud fans.
Here is Milwaukee, astride Lake Michigan, from space:
Both Wisconsin and Minnesota have a very large number of lakes developed both by glacial scouring and by water in depressions within the till cover. In Wisconsin, one large lake of reknown is Winnebago:
Part of southeastern Wisconsin never experienced thick ice cover during the Pleistocene, so that after melting no tills or drift were deposited. This is known as the "Driftless Area" near Lacrosse. As photographed from the Space Shuttle, the more irregular dissected topography of this terrain is set apart from its surroundings.
Another area within the glaciated part of the Interior Lowlands is southern Minnesota. In the next scene, farmland with many glacial lakes is predominant. But, Minneapolis and St. Paul just to its east appear (blue patches near top center) along a part of the upper reaches of the Mississippi River (whose headwaters begin to the northwest) that make that mighty stream much narrower in this part of its course. The Minnesota River joins the Mississippi from the southwest; the St. Croix River to the east forms the border there with Wisconsin which then continues southward along the Mississippi. Two Landsat images:
Here are two more Landsat images. The first shows Minneapolis-St.Paul in late winter when almost no vegetation is blooming. The second is an odd false color rendition in which the image is tilted to give a perspective view:
A map of the Twin Cities:
This is Minneapolis and then St.Paul as seen from the air:
Now, let's backtrack a bit and go south and east. In the center of Indiana is its capital, Indianapolis seen here from space and from a ground perspective:
While many sports fans may think first of the Indianapolis Colts, once a year, on Memorial Day in May, Indianapolis is the sports capital of the USA. The famed Indianapolis 500 - for racing cars - is run on that day. Here is the track seen from space.
Now, let's move still further south, first along the Ohio River, which in some places marks the southern boundary of Pleistocene glaciation. First, look at these scenes of Cincinnati, OH., with the conspicuous stadium for the Cincinnati Bengals and the Cincinnati Reds:
Further down the Ohio River is the city of Louisville, Kentucky. Once a year it is the center of attention during the running of the Kentucky Derby (a horse race). The track is near the lower right of this SPOT Image; with an enlarged aerial view beneath:
In Tennessee, the Lowlands continue, as evident in this full Landsat scene. At its southeast (lower right) is the edge of the Cumberland Plateau (assigned to the Appalachian province and equivalent to the Allegheny Plateau); its prominent west-facing scarp continues both southward and into Ohio east of Columbus. Nashville is near the edge of the Nashville Dome, a gentle upwarp of sedimentary rocks (mostly limestones); its broad outline is elliptical, and is indicated by forests (evident in the image) that selectively concentrate on soils from certain sedimentary units.
Nashville, Country Music's capital, lies on the Cumberland River:
The Mississippi River services the heartland of the U.S. One of the major urban areas along this river is St. Louis, MO (seen first on page 4-2). Here it is again, extending from St. Charles on the west to the cities of Illinois including East St. Louis and Bellevue and the conspicuous Horseshoe Lake (an oxbow meander).
This Quickbird image shows the downtown area of St. Louis, with its main landmarks being the Arch, and football and baseball stadiums.
Most of the Mississippi River drainage passes through various parts of its vast drainage system within the Interior Plains. But the Lower Mississippi from southernmost Missouri southward is emplaced on a part of the Gulf Coastal Plains known as the Mississippi Embayment (an inflow of marine waters starting about 75 million years ago which deposited thick sediments in a structural trough). In this Landsat-1 view we see the state of Mississippi on the right and Louisiana on the left (along the west bank of the active river). Here, in the Greenville, MS area) the meandering Mississippi River has cut a floodplain about 80 km (50 miles) wide. The forested uplands bedrock to the right consists in part of Eocene sedimentary rocks covered by windblown glacial dust (loess).
Jackson, Mississippi is the capital of the state, seen in this satellite image and from the ground at night:
(One wonders what might happen to Jackson if the prominent dam on the Yockinookany River were to experience at catastrophic failure?)
Baton Rouge, on the east bank of the Mississippi River, is the capital of Louisiana and the home of the Louisiana State University, whose Tigers are a perennial power in college football:
The states immediately west of the Mississippi River are considered part of the Interior Lowlands. But, not all of the Interior Plains is flat and low. Some high hills/low mountains occur. The broadest of these lies within southern Missouri and northern Arkansas and is known both as the Interior Highlands and Ozark Plateau. The Landsat scene below is mostly in Arkansas. The darker red area near the middle of the image is the Boston "Mountains", which are actually a dissected plateau of horizontal (mostly Pennsylvanian in age) strata, with relief up to 300 m (1000 ft).
North of the Boston Mountains is the Ozark Plateau. This plateau is actually a broad, gentle dome with its Paleozoic sedimentary rocks only slightly inclined. This map shows the subdivisions of the Ozarks:
Erosion has produced the Ozark Mountains, seen next. These are technically not true mountains since their rocks are unfolded. At the heart of the Ozarks are the St. Francois Mountains; streams have cut through the sedimentary rocks exposing the granite basement at an outcrop called the Elephant Rocks:
Elephant Rock State Park is about 15 miles from Arcadia, Missouri, outside of which the writer's (NMS) grandparents had a second home. From its north side, I could view Pilot Knob. This conical mountain (elevation 1445 ft) was visible from the Mississippi River 40 miles to the east. The mountain was unique in that it consists of a plug of igneous rocks punched through the surrounding sedimentary rocks. This igneous intrusion contains enriched iron deposits that were mined starting in the 1800s.
Pilot Knob gives its name to a large Civil War battle on September 27, 1864, in which more than 1200 were casualties. The Confederates under Gen. Price won the battle after Union Gen. Ewing ordered Fort Davidson to be blown up.
South of the Ozarks, and part of the Interior Highlands, are the Ouachita Mountains in central Arkansas. These mountains are highly deformed into closed folds. They are part of the Appalachian system of late Paleozoic age. Here is an ASTER image of part of the Ouachitas; below that is a ground scene:
The southern half of Arkansas is part of the Mississippi Embayment, an extension of the Coastal Plains. The state capital, Little Rock, is just south of the Ozarks:
Another state in the westernmost Interior Lowlands is Iowa, sometimes placed specifically in the Central Lowlands subprovince. Most of the state is underlain by Paleozoic rocks (limestones common) covered by Pleistocene till deposits. The capital city is Des Moines, in the center of Iowa:
In the Southeast part of the state is Iowa City, home of the University of Iowa, as shown in this IKONOS image:
During the 19th Century in that period when tens of thousands of Americans followed Horace Greeley's dictum "Go West, young man!", the jumping off places for Prairie Schooners to start their trek across the Great Plains were at the end of eastern rail lines at Kansas City and St. Joseph on the Missouri River at the west end of that state. Here is a space image of the Kansas City area:
Here is a closer look at part of the city with apartment high rises:
This oblique aerial view shows the downtown part of Kansas City: