Landscapes of the Central Great Plains Chapter I Introduction and Geomorphology James S. Aber and Susan W. Aber Emporia State University Emeritus

I.1 Introduction

The Great Plains of North America encompass the vast prairie region between mostly forested lowlands to the east and the Rocky Mountains to the west. Stretching from the Texas Gulf Coast to the Canadian Prairie, the Great Plains span a huge range of environmental and climatic conditions. This description focuses on the central Great Plains, namely Kansas and Nebraska, as well as parts of adjacent states.

This region is the cross roads of the United States, a place of passage east-west as well as north-south. Beginning with the Lewis and Clark Corps of Discovery venture more than two centuries ago, the central Great Plains has served as a transportation corridor extending from the Missouri River westward, first with wagon trains, and then railroads, highways, pipelines, and electrical transmission lines. The central Great Plains has become a resource producing region, including oil and gas, salt, coal, and wind energy.

	Ruts of the Santa Fe Trail date from the mid-1800s and are preserved at Black Jack Park and Ivan Boyd Prairie, Douglas County, northeastern Kansas. Multiple, deep ruts were eroded by the passage of tens of 1000s of heavily loaded cargo wagons and hundreds of 1000s of oxen and mules to pull the wagons. Kite airphoto looking straight down in autumn; taken by ESU students.
	Flat Ridge Wind Farm on the High Plains in Barber County, south-central Kansas. Clipper 2.5 MW turbines stand 420 feet (128 m) above the ground with the blade in the upright position. Mixed land use includes cattle grazing and fields of winter wheat. Kite aerial photograph in the early spring.

Large urban areas have grow up on the margins of the central Great Plains, namely Denver and Colorado Springs to the west and Omaha and Kansas City on the east. A few sizable cities have prospered within the region, such as Wichita, Salina, and Grand Island. Nonetheless, much of the central Great Plains remains thinly populated. Many people live in small cities and towns, and agriculture is the primary land use both for crops and cattle grazing.

	Liberty Memorial, Union Station and Crown Center with the Kansas City, Missouri downtown skyline in the background. The Santa Fe Trail once crossed the foreground. Helium-blimp airphoto by ESU students.
	Town of Marienthal on the High Plains in Wichita County, west-central Kansas. Nearly all the town is visible including grain elevators next to the Kansas & Oklahoma Railroad. Kite aerial photograph.

Landscapes of the central Great Plains are subtle and the prairie vista is long, which give rise to the public perception of a vast, flat, boring territory that is lacking in noteworthy features. In fact, considerable topographic relief exists both regionally and locally. From the junction of the Kansas and Missouri rivers at Kansas City to the High Plains along the Kansas/Colorado border, elevation rises from just above 700 feet (~215 m) to more than 4000 feet (~1220 m). The regional westward elevation gradient across Kansas is, thus, approximately 9 feet per mile (~1.7 m/km).

This broad gently sloping expanse is broken in many places by conspicuous hills, ridges, valleys, and depressions of various types and sizes. Local relief exceeds 300 feet (90 m) in many of these hilly portions, such as the Flint Hills, Smoky Hills, Nebraska Sand Hills, Pine Ridge, and bluffs along deeply incised river valleys. The central Great Plains actually have surprisingly high relief and locally steep slopes in many places, far from the flat stereotype. The region is emerging, in fact, as a destination for ecotourism based on the tallgrass prairie of the Flint Hills and wetlands such as Cheyenne Bottoms and Quivira, the Platte River valley, and the Nebraska Sand Hills, as well as other natural attractions.

	Chalk badlands and meandering (dry) valley of the Smoky Hill River in the background. Little Jerusalem, Logan County, west-central Kansas. Kite aerial photograph.
	Large sand dunes rise above well-watered valleys used for hay production. Nebraska Sand Hills, seen here near Lakeside, Sheridan County.

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I.2 Geomorphology of the central Great Plains

The processes that shape landforms may be categorized as endogenetic or exogenetic. Endogenetic processes are related to plate tectonics and to the surface effects of plate movements, both horizontally and vertically, as well as to other processes originating within the Earth's interior (heat flow, gravity, magnetism). Exogenetic processes develop at or above the surface in the atmosphere, hydrosphere, and biosphere. They involve wind, water, ice, mass movements, or living organisms that modify landforms. Impact of extra-terrestrial materials (meteorites, comets) are also exogenetic processes. The shape or lay of the land is conditioned by three primary geomorphic factors (Aber and Aber 2009).

• Foundation – refers to the nature of geologic materials—bedrock and sediment—that form the surface and subsurface, their composition, texture, fabric, architecture, fluids, mechanical strength, and other physical and chemical attributes.

• Process – refers to the physical, chemical, biological, and/or human actions that shape the surface into landforms. Broadly speaking, processes are either depositional (constructive) or erosional (destructive).

• Time – refers both to the rate at which a process modifies the surface and to the length of time or duration that a process has operated at a site.

Landscapes of the central Great Plains begin with the underlying geologic foundation. Regional geology comprises a thick sequence of sedimentary layers resting nearly horizontally on ancient crystalline basement rock consisting mainly of metamorphic rocks and granite, but nowhere is this basement exposed at the surface. Sedimentary strata were deposited in various marine and terrestrial environments. These sedimentary rocks include Paleozoic, Mesozoic, and Cenozoic formations.

In general, the east is underlain by well-consolidated sedimentary rocks of Paleozoic ages, primarily Pennsylvanian and Permian. In contrast, central and western portions of the region are mostly covered by poorly consolidated to loose sediments of Mesozoic (mainly Cretaceous) and Cenozoic (Neogene) ages. The oldest bedrock exposed at the surface in the central Great Plains is Mississippian limestone (mid-Paleozoic) in the Ozark Plateau, and the youngest consolidated bedrock is the Ogallala Formation of Pliocene-Miocene age, which makes up much of the High Plains.

Generalized geologic map and cross section for Kansas.

Generalized geologic map and cross section for Nebraska.

	Arikaree Breaks is a deeply eroded terrain underlain by thick loess (wind-blown dust) at the northern edge of the High Plains, Cheyenne County, northwestern corner of Kansas. Loess here is up to 20 m (65 feet) thick (Muhs 2010). Kite aerial photograph.
	Small blow-out dunes (foreground) are superimposed on larger transverse dunes, and lakes occupy troughs between transverse dunes. Prairie grass and shallow groundwater stabilize the sand dunes. Nebraska Sand Hills in Cherry County near Valentine. Kite aerial photograph.

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I.3 Bird's-eye view

Many of the scenic locations in Kansas were illustrated with ground photographs by Landes (1935), and erosion of geologic landmarks was documented by Charlton and Merriam (2003), who compared historical photographs with recent pictures taken from the same vantage points. Likewise, Sherow and Charlton (2014) rephotographed the Union Pacific route across Kansas based on Gardner's 1867 photographs.

Castle Rock, a well-known chalk monument in Gove County, west-central Kansas. Photographs taken from the same ground vantage point in 1941 (left), 1997 (middle) and 2001 (right). Rapid disintegration and collapse of the chalk columns are obvious. Adapted from Charlton and Merriam (2003, figs. 4-6).

Most people normally observe the landscape and scenic wonders from ground level, as Castle Rock example, but an entirely new perspective happens when depicted from the bird's-eye view of aerial photography and satellite imagery. Such images reveal spatial patterns and relationships that are difficult, if not impossible, to see on the ground (Aber and Aber 2009). Our primary approach is to utilize geospatial analysis, which involves conventional maps, digital elevation models, aerial photographs, and satellite imagery to visualize and interpret individual landforms and assemblages of landforms that make up the central Great Plains region.

Satellite imagery gives big-picture or synoptic views of landscape assemblages, in other words the megageomorphology (Short and Blair 1986), including distinctive landforms, vegetation cover, and human land-use practices. Conventional aerial photographs provide more detailed imagery of smaller areas on the ground. Digital elevation or terrain models are datasets that portray the land surface devoid of any other features; they complement satellite images and aerial photographs.

	Digital orthophoto quadrangle (DOQ) derived from conventional black-and-white aerial photograph showing a portion of the Gray County Wind Farm, southwestern Kansas. Wind turbines are placed along east-west field boundaries. Dataset obtained from the U.S. Geological Survey, EROS Data Center.
	Shaded-relief digital elevation model for the Gray County Wind Farm vicinity. Elevations range from less than 750 m (darkest gray) to above 850 m (white). The wind farm is located on the drainage divide between the Arkansas River and Crooked Creek at elevations 850-860 m (~2800 feet). Elevation dataset obtained from U.S. Geological Survey.

Small-format aerial photography (SFAP) is a special method to acquire bird's-eye views. SFAP is based on compact cameras to acquire low-height airphotos from manned or unmanned platforms (Warner et al. 1996). Manned platforms include small airplanes and helicopters, ultralight aircraft, gliders, and hot-air balloons. Unmanned platforms in common use are balloons and blimps, model aircraft, kites, and unmanned aerial systems (UAS), commonly known as drones. SFAP has become widely employed in recent years for documenting all manner of natural and human resources (Bauer et al. 1997). The method is relatively low in cost, highly portable, quick to utilize in the field, and especially effective for portraying landscapes (Aber et al. 2019).

Gray County Wind Farm, the first large wind-energy array in Kansas, began operation in 2001. Vestas V47 turbines stand 295 feet (90 m) tall to the tip of upright blades. Green fields are winter wheat on the High Plains upland. Early spring view; kite aerial photograph (Aber and Aber 2012).

We have utilized kites and a small helium blimp for SFAP. Photographs are taken from 100-500 feet (30-150 m) above the ground using radio-controlled and automatic camera rigs. The camera may be tilted (vertical to horizontal) and rotated (360°) in order to provide all possible viewing angles in relation to the ground target and sun position. These aerial views bridge the gap between ground observations and conventional airphotos or satellite images. Manned airplanes and helicopters normally are restricted to heights above 500 feet in the countryside and 1000 feet in urban areas. Unmanned SFAP taken below 500 feet has large scale and exceptionally high spatial resolution that depict ground features in surprising detail (see examples above).

Kite aerial photography. Large delta kite (left) with 19-foot wing span and 20-foot tail. Camera rig (right) hangs from the kite line and is operated by radio-control from the ground.

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I.4 Landscapes of the central Great Plains

Surface features of Kansas showing the major landscape regions and underlying geologic cross section. The map notes the High Plains, Blue Hills Upland, Smoky Hills Upland, Great Bend Prairie, Flint Hills, Osage Plains and Cherokee Lowland. Adapted from Moore (1930).

Landscape regions of Kansas according to Aber and Aber (2009). Based generally on Schoewe (1949) and Wilson (1978) with modifications of some region boundaries and names. Region limits are sharp and well defined in some cases, but may be transitional or gradual in other places. County boundaries shown in maroon.

Topographic regions for Nebraska. Adapted from University of Nebraska-Lincoln, GIS Geology Databases.

Landscape regions of the central Great Plains
Summary of characteristics

Region	Geomorphic agents	Bedrock age and type	Surficial sediment	Landforms	Relief
High Plains	water, wind	Neogene silt, sand, gravel, mortar beds	loess, sand, valley alluvium	broad, flat plain sand dunes	low to high
Pine Ridge	water	Neogene silt, sand, gravel, mortar beds	alluvium in valleys	escarpment, rugged hills	high
Nebraska Sand Hills	wind, water	Neogene silt, sand, gravel, mortar beds	sand	large and small dunes, swales	moderate to high
Arkansas and Platte valleys	water, wind, meltwater	Quaternary silt, sand, gravel	alluvium, sand, loess	dunes, channels, floodplains	low
Red Hills	water	Upper Permian red beds, gypsum	alluvium in valleys	buttes, sinkholes, natural bridges	moderate
Chalk Buttes	water	Upper Cretaceous chalk, limestone	alluvium in valleys, loess	buttes, gentle hills, badlands	moderate to low
Blue Hills	water	Upper Cretaceous shale, limestone	alluvium in valleys	escarpment, gentle hills	high to low
Smoky Hills	water	Lower Cretaceous shale, sandstone	upland gravel, valley alluvium	rugged hills and plains	moderate to low
Flint Hills	water	Permian shale, limestone, chert	upland chert, valley alluvium	escarpments, rugged hills	high to moderate
Glacial Hills	ice sheet, wind, meltwater	Penn. and Permian Lower Cretaceous	till, loess, clay, sand and gravel	spillways and buried valleys	high to moderate
Osage Cuestas	water	Pennsylvanian shale limestone, sandstone	valley alluvium, upland gravel	escarpments and cuestas	moderate to low
Chautauqua Hills	water	Pennsylvanian sandstone, shale	alluvium in valleys	rugged hills	high
Cherokee Lowlands	water	Pennsylvanian coal sandstone, shale	alluvium in valleys	flat plain	low
Ozark Plateau	water	Mississippian limestone, chert	alluvium in valleys	plateau	moderate

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Combined references.

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All text and images © by the authors (2022).