OUTDOOR CORNER: CROWLEY'S RIDGE GIVES `PEAK' INTO MISSOURI'S PAST

Have you ever wondered what southeast Missouri's lowland region looked like around the time the dinosaurs became extinct? It may be hard to imagine, but the area known as the Bootheel was once an upland of at least the same height as the bordering Ozark hills.

Less believable is that the Bootheel was once a 3,000-foot trough which began forming some 60 million years ago (around the time the dinosaurs became extinct). This trough was at the bottom of the Gulf of Mexico, which extended its northern shore to just below Cape Girardeau!

This trough gradually filled with sediments of sand, gravel and clay washed down from the eroding hills of what is now the Midwestern U.S. The Bootheel then underwent a series of uplifts that triggered new changes in the landscape. A clue as to what this region was once like is depicted today by an upland landform called Crowley's Ridge.

Crowley's Ridge begins just below Cape Girardeau and extends south through the Bootheel for some 200 miles, ending at Helena, Ark. Although the ridge averages only 3 to 12 miles across, its height, up to 300 feet above the flat lowland, makes it the most prominent landmark in the Mississippi River valley from Cape Girardeau to the Gulf of Mexico. This ridge is all that remains of once vast uplands.

During the great Ice Age there were periods of massive building and subsequent melting of glaciers that caused enormous meltwaters to scour the Bootheel region. These great floodwaters were carried by the Mississippi and Ohio rivers. The swollen Mississippi traveled along the west half and the Ohio River along the east half of the Bootheel, carving away at the sands and gravels deposited over millions of years.

With the isolation of this prominent landform, plants and animals on Crowley's Ridge became cut off from their normal upland migration routes. Crowley's Ridge, in effect, became much like an island surrounded by sea.

Today, 29 species of plants and five species of animals that live on the ridge are listed as state rare or endangered with three additional plants thought to be eliminated from this region and from Missouri.

Of the various habitats or natural communities on Crowley's Ridge, perhaps the rarest are the seeps and springs which harbor many of the endangered plants and animals. Some of the plants that occur along the seeps and springs in saturated, mucky soil are netted chain fern, yellow fringed orchid, umbrella sedge, black chokeberry, screwstem gentian, large whorled pogonia and marsh blue violet. Also found growing near the seeps and springs are such interesting plants as American beech, American holly, cinnamon fern, royal fern and sphagnum moss.

Two endangered fish are know to be restricted to small springs on Crowley's Ridge. The goldstripe darter, which is more common in southern states, has been found only in one spring run. The other fish, the spring cavefish, lives in a spring issuing from the base of a cliff along the north end of Crowley's Ridge. This nearly blind fish is never common where it occurs in southern Illinois, western Kentucky and Tennessee.

Although the big rivers have had a major influence on the shaping of Crowley's Ridge, in the last few hundred years man's presence has also had an effect. DeSoto was the first white explorer to reach Crowley's Ridge in 1540. He likely followed Indian trails which occupied the high ground, thus avoiding the extensive swamps and marshes of the lowlands.

Today Highway 25 mostly follows this upland route from below Advance to just south of Dexter. The Shawnee, Delaware and Osage Indians occupied Crowley's Ridge until the early 1800's.

Crowley's Ridge was named after Benjamin Crowley, the first white settler on the ridge. In 1821, he crossed the Mississippi River at Cape Girardeau and traveled with his sons along the ridge to an area six miles southwest of Paragould, Ark. It wasn't until the 1830's that settlement on Crowley's Ridge began to increase as emigrants from mainly Kentucky and Tennessee moved onto the ridge, avoiding the nearly impenetrable swamps of the lowlands.

Today much of Crowley's Ridge is occupied with homesites, pastures, small fields, orchards, towns and, especially on the northern end, gravel and sand quarries. But there are still remnants of what the land was once like. Two such areas have been set aside north of Dexter as natural areas that exemplify dry sand forest and seep communities that were once more common on Crowley's Ridge.

Sand forest are restricted in Missouri to Crowley's Ridge and a few smaller sand deposits in the Bootheel's lowlands. On the ridges and upper slopes where the sand soils are well drained, more drought tolerant trees occur. Here, black oak, post oak, white oak, southern red oak, pignut hickory and black hickory can be found growing up to 60 feet tall. American beech, tulip poplar, sweet gum and burr oak grow up to 140 feet high on the lower slopes and valleys where moisture is retained longer.

Crowley's Ridge has changed from what DeSoto first encountered, but there are still areas to explore on this unique ridge with its characteristic plants and animals. You can reach Holly Ridge and Beech Springs natural areas, located in Holly Ridge State Forest, by following state forest signs along a country road north of U.S. 60, 2.5 miles east of Dexter.

Amy Salveter is a natural history regional biologist for the Missouri Department of Conservation.