Missouri. Altogether, about 850 m., or considerably more than half of the entire boundary, is water-front: about 560 m. along the Mississippi, about 208 m. along the Missouri, and about 100 m. along the St Francis and Des Moines. The length of the state from north to south, disregarding the St Francis projection southward, is 282 m.,[1] the width from west to east varies from 208 to 308 m., and the total area is 69,420 sq. m., of which 693 sq. m. are water surface.
Physical Features.—Missouri has three distinct physiographic divisions: a north-western upland plain, or prairie region; a lowland, in the extreme south-east; and, between these, the Missouri portion of the Ozark uplift. The boundary between the prairie and Ozark regions follows the Missouri river from its mouth to Glasgow, running thence south-westward, with irregular limits, but with a direct trend, to Jasper county at the south-east corner of Kansas; and the boundary between the Ozark and embayment regions runs due south-west from Cape Girardeau.
1. The prairie region embraces, accordingly, somewhat more than “northern” Missouri—i.e. the portion of the state north of the Missouri river—and somewhat more than a third of the state. It is a beautiful, rolling country, with a great abundance of streams; more hilly and broken in its western than in its eastern half. The elevation in the extreme north-west is about 1200 ft. and in the extreme north-east about 500 ft., while the rim of the region to the south-east, along the border of the Ozark region, has an elevation of about 900 ft. The larger streams have valleys 250 to 300 ft. deep and sometimes 8 to 10 m. broad, 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 is skirted throughout the length of the state by contours of 400 to 600 ft. elevation.
2. The Ozark region is substantially 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 about Ste Genevieve county to Barry county on the Arkansas border; the contour levels falling with decided regularity in all directions below this crest. High rocky bluffs that 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, mark where that river cuts the Ozark ridge, which, across the river, is continued by the Shawnee Hills in Illinois. The elevations of the crest in Missouri (the highest portion of the uplift is in Arkansas) vary from 1100 to 1600 ft. This second physiographic region comprehends 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 Upland and the Springfield Upland.[2] 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 1800 ft.), in Iron county and Cedar Gap Plateau (1683 ft.), in Wright county. Few localities have an elevation exceeding 1400 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.
3. The third region, the lowlands of the south-east, has an area of some 3000 sq. m. 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 m. 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 open-trough valleys bordered by hills in their upper courses and canyons in their lower courses; others, notably the Gasconade, exhibit 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.[3]
Caves, chiefly of limestone formation, occur in great numbers in and near the Ozark Mountain region in the south-western 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 south-east of the centre of Stone county. The entrance is through a large sink-hole at the top of Roark Mountain, from which there is a passage-way to an open chamber. This extraordinary hall-like room is about 350 ft. long and about 125 ft. wide, has bluish-grey limestone walls, and an almost perfectly vaulted roof, rising from 100 to 195 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.” Jacob's Cavern (q.v.), near Pineville, McDonald county, disclosed on exploration skeletons of men and animals, rude implements, &c. Crystal Cave, near Joplin, Jasper county, has its entire surface lined with calcite crystals and scalenohedron formations, from 1 ft. 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 m. north-east of Rolla, Phelps county, Hannibal Cave (in Ralls county, about 1 m. south of Hannibal), which has a deep pool containing many eyeless fish; and various caverns in Miller, Ozark, Greene and Parry counties.
Geology.—The geological history of the state covers the period from Algonkian to late Carboniferous time, after which there is a gap in the record until Tertiary time, except that there was apparently a temporary depression of the north-western and south-western corners in the Cretaceous age. Northern Missouri is covered with a mantle of glacial deposits, generally thick, although in the stream valleys of the north-east the bed-rocks are widely exposed. The southern limit of these glacial deposits is practically the bluffs bordering the Missouri river, except for a narrow strip along the Mississippi below St Louis. These Pleistocene deposits include bouldery drift, loess, terrace deposits and alluvium. The till is generally less than 5 ft. and rarely more than 40 ft. deep, but in some localities it reaches a thickness of 200 ft., or even more. Modified drift and erratics were also widely deposited. The loess, however—reddish-brown, buff or grey in colour, according to the varying proportions of iron oxide—is almost everywhere spread above the drift. It is exposed in very deep cuts along the bluffs of the Missouri. Southern Missouri is covered, generally speaking, with residuary rocks. The embayment region is of Tertiary origin, containing deposits of both neocene and eocene periods. Regarding now the outcrops of bed-rock, there are exposures of Algonkian (doubtful, and at most a mere patch on Pilot Knob), Archean, Cambrian, Ordovician, Silurian, Devonian, sub-Carboniferous and Carboniferous. The St François Mountains and the neighbouring portion of the Ozark region are capped with Archean rocks. All the rest of the Ozark region except the extreme south-western corner of the state is Cambro-Ordovician. Along the margin of this great deposit, on the Mississippi river below St Louis and along the northern shore of the Missouri near its mouth, is an outcrop of Silurian. Parallel to this in the latter locality, and lying also along the Mississippi near by to the north, as well as in the intervening country between the two rivers, are strips of Devonian. Both this and the Silurian are mere fringes on the great area of Cambro-Ordovician. Next, covering the north-eastern and south-western corners of the state, and connecting them with a narrow belt, are the lower Carboniferous measures (which also appear in a very narrow band along the Mississippi for some distance below St Louis), The western edge of these follows an irregular line from Schuyler county, on the northern border, to Barton county, on the western border, of the state, but with a great eastward projection north of the Missouri river, to Montgomery county. This line defines the eastern limit of the Coal Measures proper, which cover a belt 20 to 80 m. in width. Finally, to the west of these, and covering the north-western corner of the state, are the upper coal measures. Thus the state is to be conceived, in geological history, as gradually built up around an Archean island in successive seas, the whole of the state becoming dry land after the post-Carboniferous uplift. Until the post-Mesozoic uplift of the Rocky Mountain region the north-western portion of the state drained westward.
Fauna.—Excepting the embayment region, Missouri lies wholly
within the Carolinian area of the Upper Austral life-zone; the- ↑ Counting the St Francis projection the length is 328 m.
- ↑ Both the Ozark region and the prairie region are divided by minor escarpments into ten or twelve sub-regions.
- ↑ There has been some controversy as to whether this condition is due to the elevation and corrosion of original flood-plain meanders after their development in a past base-level condition—which theory is probably correct—or to the natural, simultaneous lateral and vertical cut of an originally slightly sinuous stream, under such special conditions of stream declivity and horizontal bed strata (conditions supposed by some to be peculiarly fulfilled in this region) as would be favourable to the requisite balance of bank cutting and channel incision.
