| Physiographic map of Missouri (Legend) Courtesy USGS |
Missouri, a state near the geographical center of the United States, has three distinct physiographic divisions:
| Table of contents |
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2 Ozark Plateau 3 Mississippi Alluvial Plain 4 Drainage 5 Caves 6 External Links |
The Dissected Til Plains portion of the northern plains region lies in the portion of the state north of the Missouri river, while the Osage plains portion extends into the southwestern portion of the state bordering the Ozark Plateau. Thus the northern plains covers an area slightly more than a third of the state. This region is a beautiful, rolling country, with a great abundance of streams.
It is more hilly and broken in its western half than in its eastern half. The elevation in the extreme northwestern Missouri is about 1,200 ft. and in the extreme northeastern portion about 500 ft., while the rim of the region to the southeast, along the border of the Ozark region, has an elevation of about 900 ft. The vallys for the larger streams are about 250 to 300 ft. deep and
sometimes 8 to 20 miles wide with the country bordering them being the most broken of the region.
The smaller streams have so eroded the
whole face of the country that little of the original surface plain is to be seen. The Mississippi river runs alongside the length of Missouri's eastern side
and is skirted throughout by contours of 400 to 600 ft. elevation.
The elevations of the crest in Missouri
(the highest portions of the Ozarks are in Arkansas) vary from 1,100 to
1,600 ft. This second physiographic region comprises somewhat less
than two-thirds of the area of the state. The Burlington escarpment,
which in places is as much as 250 to 300 ft. in height, runs along
the western edge of the Cambro-Ordovician formations and divides the
region into an eastern and a western area, known respectively to
physiographers as the Salem Plateau and the Springfield Plateau.
Superficially, each is a simple rolling plateau, much broken by erosion
(though considerable undissected areas drained by underground channels
remain), especially in the east, and dotted with hills.
Some of these
are residual outliers of the eroded Mississippian limestones to the west,
and others are the summits of an archaean topography above which
sedimentary formations that now constitute the valley floor about
them were deposited and then eroded. There is no arrangement in
chains, but only scattered rounded peaks and short ridges, with
winding valleys about them.
The highest points in the state are
Tom Sauk Mountain (more than 1,800 ft.), in
Iron county and
Cedar Gap Plateau (1683 ft.), in
Wright county.
Few localities have an elevation exceeding 1,400 ft.
Rather broad, smooth valleys, well degraded hills with rounded summits,
and despite the escarpments generally smooth contours and sky-lines,
characterize the whole of this Ozark region.
The third region, the lowlands of the south-east and part of the Mississippi
Alluvial Plain, has an area of some 3,000 mile2. It is an
undulating country, for the most part well drained, but swampy in its
lowest portions. The Mississippi is skirted with lagoons, lakes and
morasses from Ste. Genevieve to the Arkansas border, and in places
is confined by levees.
The drainage of the state is wholly into the Mississippi, directly or
indirectly, and almost wholly into either that river or the Missouri
within the borders of the state. The latter stream, crossing the state
and cutting the eastern and western borders at or near St Louis and
Kansas City respectively, has a length between these of 430 mile.
The areas drained into the Mississippi outside the state through
the St. Francis, White and other
minor streams are relatively small. The larger streams of the Ozark
dome are of decided interest to the physiographer. Those of the
White system have opentrough valleys bordered by hills in their
upper courses and canyons in their lower courses; others, notably,
the Gasconade, counting the St Francis projection the length is 328 miles.
Both the Ozark region and the northern plain region are divided by minor
escarpments into ten or twelve sub-regions. There are remarkable differences
in the drainage areas of their two sides, with interesting illustrations of
shifting water-partings; and the White, Gasconade, Osage and other rivers
are remarkable for upland meanders, lying, not on flood-plains,
but around the spurs of a highland country.
Caves, chiefly of limestone formation, occur in great numbers in and near
the Ozark Mountain region in the southwestern part of Missouri.
More than a hundred have been discovered in
Stone county alone,
and there are many in Christian,
Greene and McDonald
counties.
The most remarkable is Marble Cave, a short distance
southeast of the center of Stone county. The entrance originally was through
a large sink-hole at the top of Roark Mountain, though now an easier entrance mhas been made. Marble Cave has an extraordinary hall-like room is about
350 ft. long and about 125 ft. wide with bluish-grey limestone walls,
and an almost perfectly vaulted roof, rising from 100 to 295 ft.
Its acoustic properties are said to be almost perfect, and it has been named
the Auditorium. At one end is a remarkable stalagmitic formation of white
and gold onyx, about 65 ft. in height and about 200 ft. in girth, called
the White Throne.
Exploration of Jacob's Cavern, near Pineville, McDonald county, reveled skeletons of men and animals, rude implements.
Crystal Cave, near Joplin, Jasper county, has its entire surface lined with
calcite crystals and scalenohedron formations, from 1 to 2 ft. in length.
Knox Cave, in Greene county, and several caverns near Ozark,
in Christian county, are also of interest. Other caves include Fried's Cave,
about 6 miles northeast of Rolla, Phelps county, Mark Twain Cave
(in Marion county, about 1 mile south of Hannibal), which has a deep pool
containing many eyeless fish; and various caverns in Miller, Ozark,
Greene and Barry counties.Northern Plains
Ozark Plateau
Primarly made up of the Springfiled Plateau and the Salem Plateau, the Ozark region is essentially a low dome, with local faulting and minor undulations, dominated by a ridge or, more exactly, a relatively
even belt of highland that runs from near the Mississippi river about Ste. Genevieve county to Barry county on the Arkansas border.
The contour levels fall with decided regularity in all directions
below this crest. High rocky bluffs rise precipitously on the
Mississippi, sometimes to a height of 150 ft. or so above the water,
from the mouth of the Meramec to
Ste. Genevieve. These mark where that river cuts
the Ozark ridge. Across the Mississippi river, this ridge is continued by the Shawnee Hills in Illinois. Mississippi Alluvial Plain
Drainage
Caves