Missouri River

Long ago, a shallow sea covered the middle of North America. It left layers of chalk and mud.

Later, giant sheets of ice came from the north. The river flows along where the ice stopped.

The oldest rocks along the Missouri National Recreational River formed in shallow seas that covered the western interior of North America between 85 and 65 million years ago. They became chalky limestone and shale, and today the river cuts into them, making chalk bluffs.

Much later, during the last ice age, glaciers pushed south across the northern plains. In this region, the river's course marks the southern edge of one of those advances. So the river runs between land the glaciers covered and land they never reached.

According to the National Park Service, the oldest exposed rocks are the chalky Niobrara Formation and the Pierre shale, deposited in shallow seas over the western interior of North America between 85 and 65 million years ago, near the end of the Mesozoic. The underlying sequence runs from the Dakota Formation up through the Graneros Shale, Greenhorn Limestone and Carlile Shale.

The park lies between the glaciated and unglaciated parts of the Missouri Plateau; the river's course marks the southern limit of the Mankato substage of the Wisconsin glaciation here, and younger Quaternary deposits include Peoria Loess, glacial till, terraces and alluvium. The FWS describes the river as the boundary between glaciated ice-age terrain and sediments laid down by an ancient sea.

In one part, the river is still wild. It wiggles and leaves sandbars and little islands.

The sandbars keep shifting.

The Missouri National Recreational River in South Dakota and Nebraska protects the last stretches of the Missouri that are neither channelized nor dammed. Here the river still meanders, leaving a mosaic of sandbars, snags, backwaters, islands and side channels.

Upstream, steep chalkstone bluffs line the river. Downstream, the wide floodplain is made of sandy soil the river has dropped since the ice age.

Authorized on 10 November 1978, the Missouri National Recreational River covers about 19,609 ha in two districts separated by Lewis and Clark Lake, and preserves the last unchannelized and unimpounded segments of the Missouri with native floodplain forest, wetlands and tallgrass and mixed-grass prairie, the NPS says.

The 39-Mile District has steep, dissected chalkstone bluffs; the 59-Mile District is a wide, meandering valley of sandbars, snags, backwaters, islands and tributary channels, on a floodplain of sandy soil deposited since the Pleistocene. The FWS calls it one of the last remnant examples of diverse, high-quality shallow-water habitat in a large river system.

Fish called pallid sturgeon swim in the river. Shorebirds called piping plovers live along it.

Swallows dig nests in the riverbanks.

More than 400 kinds of fish and wildlife live along the Missouri National Recreational River. Protected species there include the pallid sturgeon, a fish, the piping plover, a shorebird, and the scaleshell mussel.

The river's ever-changing banks and bluffs give bank swallows and cliff swallows places to nest. Cottonwood forests, some more than 100 years old, are nesting and resting places for songbirds, and bald eagles nest and spend the winter there.

The NPS lists over 400 fish and wildlife species along the corridor, including the federally protected pallid sturgeon, piping plover and scaleshell mussel; non-native zebra mussels and Asian carp are widespread and outcompete native species. The FWS adds that the western segments still offer shallow-water habitat free of Asian carp, native fish reproduce in sandbar pools, braided channels and backwaters, and mussel diversity is among the highest in the region.

Eroding banks and bluff faces provide nesting for bank and cliff swallows, and cottonwood forests over 100 years old offer nesting and migratory stopover habitat for rare woodland songbirds and nesting and wintering habitat for bald eagles.

Flood water is stronger than it looks. Never walk into flood water.

Give wild birds lots of space.

Flood water is stronger than it looks. The US National Weather Service warns that just 6 inches (15 centimeters) of fast-moving flood water can knock over an adult, so it is never safe to walk or drive into flood water.

PlayOwl's advice: protected birds such as piping plovers live along the river, so give birds plenty of space and follow any posted closures.

The US National Weather Service notes that people underestimate the force of moving water: about 6 inches (15 cm) of fast-moving flood water can knock over an adult and about 12 inches can carry away most cars, so it is never safe to walk or drive into flood water.

On the recreational river, where the FWS lists boating, birding, fishing and hiking among the activities, PlayOwl's own advice is to keep clear of protected birds such as the piping plover and to leave wildlife undisturbed.