Kansas is a long, tilted ramp. Its 213,100 km² (82,278 sq mi) rise from about 207 m (679 ft), where the Verdigris River leaves the state near Coffeyville, to 1,231 m (4,039 ft) at Mount Sunflower on the Colorado line, and along the way the land passes through eleven physiographic regions. The main landforms are the glacial hills of the north-east corner, the Osage Cuestas and Ozark Plateau of the south-east, the tallgrass-covered Flint Hills, the sandstone, limestone and chalk belts of the Smoky Hills, the gypsum-laced Red Hills of the south, the Arkansas River Lowlands, and the High Plains that cover the western third. The easiest way to see most of them in one go is to drive Interstate 70, which crosses the state for just over 682 km (424 mi) from Kansas City to Kanorado, gaining about a kilometre of height as it goes.
Kaw Point to Topeka: the glacial corner along the Kansas River
The trip starts low, at Kaw Point in Kansas City, where the Kansas River, known locally as the Kaw, joins the Missouri at 219 m (718 ft). For nearly 121 km (75 mi) north of here, the Missouri River itself forms the state’s north-eastern boundary.
Across the river from the interstate lies the corner of Kansas that the ice sheets reached: the land north of the Kansas River and east of the Big Blue River. Pre-Illinoian glaciers about 600,000 years ago buried the Pennsylvanian and Permian bedrock there under glacial debris, largely loess, and left behind erratic boulders, many of them Sioux Quartzite carried south from the Sioux Falls area of South Dakota. The Kansas River’s course roughly follows the maximum reach of a Pre-Illinoian ice sheet, and it probably began as a channel for meltwater draining along the ice front. Today it meanders 238 km (148 mi) from Junction City to Kaw Point, dropping just 98 m (322 ft), less than 2 ft per mile, through a valley that averages 4.2 km (2.6 mi) wide and reaches 6.4 km (4 mi) between Wamego and Rossville.
Konza Prairie and the Florence roadcuts: I-70 enters the Flint Hills
West of Topeka the road climbs into the Flint Hills, a band of hills and prairie that runs from Marshall and Washington counties on the Nebraska line south into Oklahoma, where the same country is called the Osage Hills. The rocks here were laid down in shallow seas during the Permian period, about 250 million years ago, and many of the limestones carry nodules of chert, or flint. The most prominent chert-bearing layer, the Florence Limestone Member, is about 14 m (45 ft) thick, and it is exposed in the roadcuts that line I-70 in Riley County. Zebulon Pike gave the region its name in 1806 when he wrote in his journal that he “passed very ruff flint hills”.
That flint is why the prairie survived. Settlers could not plough the stony soil, so the land became cattle range, kept open by spring burns, and the Flint Hills now hold the densest coverage of intact tallgrass prairie in North America. Of the roughly 1,000,000 km² (400,000 sq mi) of tallgrass prairie that once covered the continent, less than 5% remains, most of it here. The Konza Prairie Biological Station, 3,487 ha (8,616 acres) owned by Kansas State University and The Nature Conservancy, has its southern boundary right alongside the interstate south of Manhattan; its ground, with limestone outcrops throughout, ranges from 320 to 444 m (1,050 to 1,457 ft). Further south, off the route near Strong City, the Tallgrass Prairie National Preserve has kept a bison herd since 2009.
Junction City to Ellsworth County: sandstone buttes and cannonball concretions
Just east of Junction City the Smoky Hill and Republican rivers meet to form the Kansas River, at about 320 m (1,040 ft). West of Abilene and Salina the interstate leaves the Permian rocks behind and enters the Smoky Hills, a dissected upland that covers nearly all of north-central Kansas. The Smoky Hills are really three belts of hills running south-west to north-east, each matching a different Cretaceous rock: the Dakota Formation sandstone in the east, the Greenhorn Limestone in the middle belt, known as the Blue Hills, and the Niobrara Chalk in the west.
The Dakota sandstone was laid down by rivers on a low coastal plain, and where it caps the land it makes flat-topped buttes. Coronado Heights in Saline County is the best-known of these Smoky Hill Buttes. At Rock City, 5.8 km (3.6 mi) south of Minneapolis in Ottawa County and a short detour north of Salina, about 200 spherical boulders sit on a hillside above the Solomon River. They are calcite-cemented concretions 3 to 6 m (10 to 20 ft) across that weathered out of the softer sandstone around them, and the site is a National Natural Landmark. South of the interstate in Ellsworth County, Mushroom Rock State Park, the smallest state park in Kansas at 2 ha (5 acres), preserves similar concretions perched on pedestals of sandstone; the largest is about 8 m (27 ft) across.
Post rock country and the sinkholes near Russell
Past the Ellsworth–Russell county line the highway follows a ridge between the Smoky Hill River and its tributary, the Saline, running through the turbines of the Smoky Hills Wind Farm. This is the Blue Hills belt, and its signature is a man-made one. The topmost bed of the Greenhorn Limestone, the Fencepost limestone, is a thin, resistant layer that forms a line of bluffs from the Nebraska border near Mahaska about 320 km (200 mi) south-west to near Dodge City. Settlers on this treeless ground quarried it into posts, and the countless stone fence posts along the roads have given the area the name Post Rock Country.
The ground here is not entirely stable. Around Russell, I-70 crosses three active sinkholes, the largest of which, the Crawford Sinkhole, sits at mile 179. Reservoirs such as Wilson Lake and Kanopolis Lake, dammed from the 1940s onward, fill valleys cut into these Cretaceous rocks.
Riga Road to Oakley: the High Plains and the chalk detours
At exit 140, the Riga Road interchange west of Hays, the road climbs out of the Blue Hills onto the High Plains, and the gentle undulations and stone posts give way to open tableland. From here to Colorado the route stays high and unusually level. The High Plains surface is built of non-marine sediment washed east from the Rocky Mountains as they rose during the Cenozoic, including the sands and silts of the Ogallala Formation, a major aquifer under the plains. The western third of the state gets only about 410 mm (16 in) of precipitation a year, and the change from tallgrass to short, dry grassland is visible from the car window.
The flatness hides the most dramatic scenery in the state, because the Smoky Hill River and its tributaries have cut down through the High Plains cover into the Niobrara Chalk beneath. About 18 km (11 mi) south of the interstate near Quinter, Castle Rock is a 21 m (70 ft) chalk pillar that served as a landmark on the Butterfield Overland Despatch route; its tallest spire fell in a thunderstorm in 2001. Further west, 40 km (25 mi) south of Oakley in Gove County, Monument Rocks, also called the Chalk Pyramids, rise up to 21 m (70 ft) as buttes and arches. Their chalk was laid down about 80 million years ago on the floor of the Western Interior Seaway, and they were the first landmark in Kansas chosen as a National Natural Landmark. The chalk has yielded exceptionally preserved fossils of plesiosaurs and mosasaurs. Nearby in Logan County, Little Jerusalem Badlands State Park protects 89 ha (220 acres) of narrow chalk canyons whose white walls have been likened to the walls and winding streets of ancient Jerusalem.
Kanorado and Mount Sunflower: the top of the ramp
Past Colby and Goodland the interstate reaches Kanorado, the last town before Colorado, at about 1,191 m (3,907 ft). The state’s high point lies just south, between Kanorado and Weskan in Wallace County, less than 0.8 km (half a mile) from the Colorado border. Mount Sunflower is not a mountain at all but a slight swell in a cattle pasture, reached by county dirt roads. It sits on a family farm homesteaded in 1906, marked by a sunflower sculpture welded from railroad spikes. The USGS designated it the state’s highest point in 1961. Its summit is about 1,020 m (3,360 ft) above the Verdigris low point, which gives Kansas more relief than 22 other states; a tongue-in-cheek 2003 study declared it “flatter than a pancake”, but by maximum relief it is only the 23rd flattest.
North of the interstate, in the state’s north-west corner, the plains break up again. The Arikaree Breaks are a 3 to 5 km (2 to 3 mi) wide strip of badlands in the Arikaree and Republican river basins, where water has carved ravines and vertical cliffs into loess up to 30 m (100 ft) thick.
What I-70 misses: the Red Hills, Big Basin and the south-east
An east–west interstate skips the southern regions entirely. In Clark, Comanche and Barber counties, the Red Hills, also called the Gypsum Hills, are made of Permian red beds laid down in short-lived playas within an arid closed basin inside the supercontinent Pangaea. Oxidised iron gives them their colour, and the dissolving of gypsum beds below has pocked them with sinkholes. Big Basin near Ashland, a crater-like sinkhole about 1.6 km (1 mi) across and 30 m (100 ft) deep, has no outlet; a short distance east lies Little Basin, with the water-filled St. Jacob’s Well, 26 m (84 ft) wide, on its rim. Mount Nebo, at 744 m (2,441 ft), is among the highest of the Red Hills. Between them and the Flint Hills lie the Arkansas River Lowlands, where the Arkansas River bends for nearly 800 km (500 mi) across the south and west of the state. In the south-east, the Osage Cuestas form a staircase of east-facing limestone escarpments 15 to 61 m (50 to 200 ft) high across twenty counties, the sandstone ridges of the Chautauqua Hills run into Oklahoma, the coal-bearing Cherokee Lowlands roll across Cherokee, Labette, Crawford and Bourbon counties, and a sliver of the Ozark Plateau in Cherokee County exposes the state’s oldest surface rock, Mississippian limestone and chert once mined for lead and zinc around Galena.
For the state’s rivers, climate and counties in more depth, see our full guide to Kansas geography. The shortgrass and tallgrass country along this drive is part of a much bigger story told in our Great Plains guide, and the ecology that survived in the Flint Hills is explained in what a prairie is.