The modern Missouri River, glaciers and man have all contributed to the character of the land at Cross Ranch State Park. Today, only small glimpses can be seen of the underlying sandstones and shales that formed on the bottom of a vast inland sea covering this area some 70 million years ago. Except at the base of deep ravines and at one place along the river's edge, these ancient rocks are buried by sand, gravel and silt brought by the river.
The Missouri itself owes its character and development to the glaciers which covered all but the southwestern corner of the state. This immense expanse of glacial ice blocked the original north-eastward flow of the Missouri, forcing it to cut a new channel to the south. As the glacier melted, huge quantities of water carried sand and gravel scoured from the land, and these sediments were deposited in the bed of the glacial river. After the glaciers were completely melted, there was far less sediment-carrying water in the Missouri, causing the river to cut into its old bed. Today, the modern floodplain lies as much as 50 feet below terrace remnants of the old glacial floodplain.
Change the river and you change the land, and man has had a hand in doing that as well. The creation of Garrison Dam, and other man-made dams upriver, has eliminated the normal flooding pattern of the basin.
Nowhere is there more convincing evidence of the influence of the river on the land of the park than it its vegetation. Of the trees occurring on the floodplain, only cottonwood and willow are able to grow on the bare, newly deposited point bars. They are classic pioneer species; neither can germinate and grow within an established forest. The park and adjacent nature preserve contain the largest remaining tract of floodplain woodland on this free-flowing stretch of the Missouri, encompassing nearly 1,500 acres.
If cottonwood-willow communities remain uneroded, they mature into forests which provide habitat suitable for other tree species. Green ash, box elder and American elm seedlings are shade tolerant, and as years pass will replace the aging cottonwoods. Bur oak is less common on the lower floodplain, but it is well represented on some of the oldest terraces and common in many ravines leading to the river.
The vegetation of these forests varies between the open canopy of cottonwoods compared to the more closed canopy of elm and ash. Common shrubs and woody vines of elm and ash forests include buckbrush, poison ivy, chokecherry, Juneberry, woodbine and wild grape. Buffaloberry, red osier dogwood and Wood's rose occur in cottonwood forests.
Some species show a preference for a particular forest type. Field horsetails and wild licorice are common in cottonwood stands while you are liable to find Virginia wildrye, sedges, bedstraw and other species in stands of green ash and American elm.
The diversity of wildlife species which inhabit the park will amaze and delight visitors of all ages.
The park and nature preserve are home to a wide variety of animal life, and with patience and a keen eye hikers will be rewarded with sightings of deer, wild turkeys, hawks, an occasional bobcat, or, at certain times of the year, a bald eagle.
A comprehensive list of bird species can be found on the Cross Ranch Bird Checklist, which is also available in printed format by contacting the park.
The river sandbars provide habitat for Canada geese and migrating whooping cranes, and nesting for the least tern. The whooping crane and the least tern are both on the endangered species list. Another bird one is likely to see on sandbars is the piping plover, a threatened species.
The native prairie areas of the Cross Ranch provide cover for burrowing owls, chestnut-collared longspur and Sprague's pipit.