Produced by Gary Martens and Laurie Saikin
Alluvium.--Next to the Loess deposits, in an economical point of view, the alluvium formations are the most important. The valleys and flood plains of the rivers and smaller streams, where these deposits are found, are a prominent feature of the surface geology of the State. All the rivers of the interior, such as the Platte, the Republican, the Niobrara, the Elkhorn, the Blues, the Nemnhas, and their tributaries, have broad bottoms, in the center or on one side of which the streams have their beds. The width of these bottoms seems to be dependent on the character of the underlying rock formation. Where this is soft or yielding the bottoms are broad, but where it is hard and compact, they contract. This is, no doubt, one reason why the bottom on the middle or upper courses of some of the rivers are wider than further down. These broad bottoms, as we have already seen, represent the ancient river beds toward the close of the Loess age. It required many ages to drain the mighty ancient lake bed; and when the present river were first outlined, the greater part of it was yet a vast swamp or bog. But gradually as the continent rose to higher level, the rivers cut deeper and deeper, filling the whole flood plain from bluff to bluff. Not until the drainage of this region was completed, and the continent hat reached nearly to its present level, was the volume of water so much diminished that the rivers contracted their currents and cut new beds somewhere through the present bottoms. The terraces, which are so numerous along many of the river bottoms, indicate the extreme slowness with which the land assumed its present form. The upper terraces were dry bottom when all the rest of the valley was yet a river bed. It is probable that some of these bottoms were excavated during pre-loess times, and were afterward filled up with debris when the continent had reached its lowest level. The great depth of sand and mud at the bottom of the Missouri, being from forty to one hundred feet below low water along the Nebraska line before solid rock is reached, indicates an elevation of this region, when this was accomplished, far greater than it reached at any period during or immediately after Loess times. When this great Loess lake commenced to be drained, the waters naturally took the direction of least resistance, which was the original bed of the river. If the Rocky Mountain system continues to rise, as, it is believed to be doing, at the rate of a few feet to the century, although degradation may be equal to elevation, a time must come in the distant future when the Missouri must again roll over solid rock at its bottom.
As typical of the river bottoms, let us look at the formation of the Platte Valley. The general direction of this great highway from the mountains to the Missouri is from west to east. This valley is from three to twenty miles wide in Nebraska, and over five hundred miles long. All the materials that once filled up this trough, from the top of the highest hills on each side, have been, since the present rivers were outlined, toward the close of the Loess age, transported by the agency of water to the Missouri and the gulf. (See Hayden's report for 1870.) Here, then, are several thousand miles in area of surface entirely removed by denudation. Now the Platte comprises only a fraction of the river bottoms of Nebraska. The Republican alone, for 200miles, has a bottom ranging from three to eight miles in breadth. The combined length of the main bottoms of the Blues, Elkhorns and the Loups would be over a thousand miles, and their breadth ranges from one to ten miles. The Nemahas and the Bows, and portions of the Niobrara, also add a great deal to the area of bottom lands. All these rivers have numerous tributaries, which have valleys in size proportionate to the main rivers, and these more than double the areas of bottom land. The Missouri has also, in some counties, like Dakota and Burt, contributed large areas of bottom land to the soil of the State. These Missouri bottoms in Nebraska are exceptionally high, so that few of them have been overflowed since the settlement of the country. The one element of uncertainty about them is, when located near the river, the danger of being gradually washed away by the undermining action of the water. Sometimes, during flood time, when the current sweeps the bank, it is so insidiously undermined that for several rods in length and many feet in breadth it tumbles into the river. This cutting of the banks is greatest when the river commences to fall.
When we bring into our estimate all the river bottoms or Nebraska, and the tributaries of these rivers, and reflect that all these valleys were formed in the same way, within comparatively modern geological times, the forces which water agencies brought into play almost appall the mind by their very immensity.
Agricultural Value of the Bottom Lands.--So well are the bottom lands of the State distributed that the emigrants can, in most of the counties of the State, choose between them and the uplands for their future home. In some of the counties, like Fillmore, where the bottom lands are far apart, there are many small, modern, dried-up lake beds, whose soil is closely allied to the valleys. Portions of each are sometimes chosen, on the supposition that the bottom lands are best adapted for the growth of large crops of grasses.
But all the years of experience in cultivating uplands and bottoms in Nebraska leave the question of the superiority of the one over the other undecided. Both have their advocates. The seasons, as well as the location, have much to do with the question. Some bottom lands are high and dry, while others are lower, and contain so much alumina that in wet seasons they are difficult to work. On such lands, too, a wet spring interferes somewhat with early planting and sowing. All the uplands, too, which have a loess origin, seem to produce cultivated grass as luxuriantly as the richest bottoms, especially where there is a deep cultivation on old breaking. Again, most of the bottom lands are so mingled with loess materials, and their drainage is so good, that the cereal grains and fruits are as productive on them as on the high lands. The bottom lands are, however, the richest in organic matter. The following analyses of these soils will give a better idea of their physical character. The samples were taken from what are believed to be average soils. The first is from the Elkhorn, the second from the Platte, the third from the Republican and the fourth from the Blue River. The fifth is from an exceptionally wet and sticky soil, about two miles southeast of Dakota City:
================================================================== | No.1. | No.2. | No.3. | No.4. | No.5. ___________________________|_______|_______|_______|_______|______ Insoluble (silicious) | | | | | matter................| 63.07 | 63.70 | 63.01 | 62.99 | 61.03 Ferric oxide...............| 2.85 | 2.25 | 2.40 | 2.47 | 2.82 Alumina....................| 8.41 | 7.76 | 8.36 | 8.08 | 10.52 Lime (carbonate)...........| 7.08 | 7.79 | 8.01 | 7.85 | 7.09 Lime (phosphate)...........| .90 | .85 | .99 | .94 | .98 Magnesia (carbonate).......| 1.41 | 1.45 | 1.39 | 1.40 | 1.38 Potash.....................| .50 | .54 | .61 | .67 | .60 Soda.......................| .49 | .52 | .54 | .58 | .57 Sulphuric acid.............| .79 | .70 | .71 | .79 | .69 Organic matter.............| 14.00 | 13.45 | 13.01 | 13.27 | 13.40 Loss in analysis...........| .50 | .79 | .97 | .96 | .92 |_______|_______|_______|_______|______ Totals..............|100.00 |100.00 |100.00 |100.00 |100.00 ___________________________|_______|_______|_______|_______|______
Soils often, when taken only a few feet apart, vary much in chemical properties, and therefore analyses frequently fail to give a correct idea of their true character. The above analyses, however, show that, chemically, alluvium differs from the loess principally in having more organic matter than alumina, and less silica The depth of the alluvium varies greatly. Sometimes sand and drift materials predominate in the river bottoms, especially in the subsoil; often the alluvium is of unknown depth, and again, in a few feet, the drift pebbles and sand are struck. This is especially the case in a few of the Western valleys. There was a period, of longer or shorter duration, when the bottoms were in the condition of swamps and bogs; andduring this period, the greater part of that organic matter which is a distinguishing feature of these lands accumulated in the surface soil. It would be easy to select isolated spots, where the soil has from 30 to 40 per cent of organic matter; where, in fact, it is semi-peat. When we reflect that this black soil is often twenty feet thick, it is apparent that the period of its formation must have been very long. There are still some few localities where that formative condition has been perpetuated to the present time--as, for example, the bogs that yet exist at the headwaters of the Elkhorn and Logan, along Elk Creek on the Dakota Bottom, and on some of the tributaries of the Republican. All the intermediate stages from perfectly dry bottom to a bog can yet be found. So much has the volume of water been lessened in the rivers of Nebraska, through the influence of geological causes, that there are few places where now, even in flood time, they overflow their banks. The occurrence of great masses of timber on our bottoms, at various depths, in a semi-decayed condition, illustrates through what changes of level they have passed. The deepening of the river channels now going on still further lessen the dangers of overflow.
The Sand Hills.--The sand hills are found in certain sections of the western portion of the State South of the Platte Valley, they run parallel with the river, and are from one-half to six miles in breadth. A few are also found on the tributaries of the Republican. Occasionally, slightly sandy districts are found as far east as the Logan, but they rarely approach even a small hill in magnitude. A few sand ridges are also found on the Elkhorn. North of the Platte, from about the mouth of the Calamus on to the Niobrara, they cover much larger areas. They are also found over a limited area north of the Niobrara. Hayden estimated the area of the sand hills at 20,000 square miles. I estimate them, after examining the whole region carefully at less than half the above, or not more than about eight thousand square miles. They are, indeed, found for 100 miles west from the mouth of the Rapid River, but they are not continuous, and from eight to twenty miles south of the Niobrara there are spots of greater or less extent where the soil seemed to be a mixture of drift and loess, and of high fertility, as is indicated by the character and rankness of the vegetation. Sometimes these hills are comparatively barren, and then again they are fertile enough to sustain a covering of nutritious grasses, so that this region is by no means the barren waste that it has sometimes been represented to be. It has been a favorite range for buffalo antelope and deer. It is now extensively used for stock raising.
A great deal of the vegetation is peculiar to sandy districts. Some of the hills seem to have their loose sands held together by the Ucca angustifolia, which sends it roots down to a great depth. It probably marks a certain stage in their history. After this plant has compacted and given to the sands organic matter, the grasses come in and partially clothe the hills. The materials of these sand-hills are almost entirely sand, pebbles and gravel, of varying degrees of fineness. The sand always predominates. Occasionally it is more or less modified by the presence of the materials, such as lime, potash, soda, alumina and organic matter. These hills are in some places stationary, and so covered by vegetation that their true character is not suspected until closely examined. In other places again, especially in portions of the Loup and Niobrara region. they are so loosely compacted that the wind is ever changing their form and turning them into all kinds of fantastic shapes. The most common appearance is that of a plain, undulating or hilly region, covered with conical hills of drifting sands. The smaller elevations frequently show a striking resemblance to craters. One such curious hill I found south of the Calamua, where the crater-like basin seemed to be compacted at once, and grown over with a species of wire grass. With the increase of rainfall and vegetation, the remodifying effects of the winds disappear. In fact, already the old condition of things has passed away, as in few places do the sands now shift with the winds.
Origin of the Sand Hills.--Some of these sand hills along the Upper Loup and on the Niobrara, where the loess lake did not extend, are the remodified equus beds of the upper Pliocene. Along the Platte they show the line of a current in the old loess lake. At other places, the sand hills are remodified loess materials--the loess with the finer materials washed out. The two deposits so shade into each other that it is often impossible to tell where one begins and the other ends. Many of these hills that, twelve years ago, were barren, are now covered with a vigorous growth of grasses, and not a few are gradually being brought under cultivation. The transformation has been caused by a notable increase of rainfall during the last decade.
Alkali Lands.--Every one in Nebraska will sooner or later hear of the so-called alkali lands. They are not confined to any one geological formation, but are found sometimes on the drift, alluvium, or the loess. They increase in number from the eastern to the western portions of the State. Yet one-half of the counties of the State do not have any such lands, and often there are only a few in a township or county. Where they have been closely examined, they are found to vary a great deal in chemical constituents. Generally, however, the alkali is largely composed of soda compounds, with an occasional excess of lime and magnesia or potash. The following analyses of these soils show how variable they are. The first is taken from the Platte Bottom, south of North Platte; the second, from near Old Fort Kearney; and the third, two miles west of Lincoln.
============================================================ | No.1. | No.2. | No.3. ____________________________________|_______|_______|_______ Insoluble (silicious) matter........| 74.00 | 73.10 | 73.90 Ferric (oxide)......................| 3.80 | 3.73 | 3.69 Alumina.............................| 2.08 | 2.29 | 2.10 Lime (carbonate)....................| 6.01 | 4.29 | 3.90 Lime (phosphate)....................| 1.70 | 1.40 | 1.49 Magnesia (carbonate)................| 1.89 | 1.29 | 1.47 Potash..............................| 1.68 | 1.80 | 3.69 Soda carbonate and bicarbonate......| 5.17 | 7.33 | 4.91 Sodium sulphate.....................| .70 | .89 | .89 Moisture............................| .99 | .98 | .98 Organic matter......................| 1.20 | 2.10 | 2.10 Loss in analysis....................| .78 | .80 | .88 |_______|_______|_______ Totals.......................|100.00 |100.00 |100.00 ____________________________________|_______|_______|_______
The specimens for analysis were not taken from soils crusted over with alkaline matter, but from spots where the ground was covered with a sparse vegetation.
Much of the alkali originated by the accumulation of water in low places. The escape of the water by evaporation left the saline matters behind, and in the case of salt (sodium chloride), which all waters contain in at least minute quantities, the chlorine, by chemical re-actions, separated from the sodium; the latter, uniting with oxygen and carbonic acid, formed the soda compounds. The alkali that exists far down in the soil is also brought up during dry weather by the escaping moisture, and is left on the surface when the water is evaporated.
In cultivating these alkali spots, it is found that wheat rapidly consumes it, and a few crops, with deep plowing, prepares the soil for other crops. In this way, these lands have often been made the most valuable part of the farm.
Hard Pan--Gumbo Soil.--Hard pan, sometimes called gumbo soil, occurs in small patches in a few localities. Sometimes these spots are slightly below the level of the surface, and occasionally shade into what are known as clay and wet lands. They are easily recognized by the paucity of the peculiar blue and wire grasses that cover them. More rarely they are covered by from two to six inches of alluvium, or ordinary upland soil, and only give indications of their presence when an attempt is made at their cultivation. They "bake," and become exceedingly hard when dried. The most compact of these soils are cultivated with difficulty. The following analyses indicate their composition. The first is taken from a specimen on Salt Creek Bottom, and the second from the Lower Nemaha:
==================================================== | No.1. | No.2. ____________________________________|_______|_______ Insoluble (silicious) matter........| 27.11 | 20.67 Ferric (oxide)......................| 4.32 | 2.83 Alumina (clay)......................| 50.11 | 57.30 Lime (carbonate)....................| 8.21 | 9.08 Lime (phosphate)....................| 1.09 | .88 Magnesia (carbonate)................| 1.45 | 1.70 Potassa.............................| 1.98 | .67 Soda ...............................| .83 | 1.80 Organic matter......................| 1.30 | 2.01 Moisture............................| 2.90 | 2.09 Loss in analysis....................| .70 | .87 |_______|_______ Totals.......................|100.00 |100.00 ____________________________________|_______|_______
This analysis shows that these soils contain clay in excess. From many other analyses which I made, only to ascertain the amount of clay that was present, it was found to vary from 15 to 60 per cent. However varied the constituents, all these soils are alike in the large quantity of clay which they contain. Sometimes a little manganese is found in them. It is evident that to redeem them requires the admixture of a considerable quantity of sand. Often the soil below where the hard pan is only a few inches thick, answers this purpose best.
Bad Lands.--In the northwest corner of the State, especially beyond the White Earth River, over a very limited extent of country, the Miocene Tertiary is exposed. Here it has been worn by the erosive agency of water into curious cañons, and into the similitude of grand architectural forms, such as pyramids, castles, etc. The materials are marls, indurated clays, sands, sandstones and thin beds of limestone. Here in the deep cañons, at the foot of stair like projections, the earliest of those wonderful fossil treasures were found, which have been described by Leidy, and which have done so much to revolutionize our ideas of life and especially of Tertiary times. The Indian word translated Bad Lands means a country difficult to travel over. It was also often applied by them to the Sand Hill Region. Though utterly barren when I first visited them, they are now gradually being covered with more or less vegetation, and are rapidly being utilized in places for the pasturage of herds of cattle. Though so unattractive to the utilitarian, I doubt whether any other equal area of Nebraska will be of more benefit to mankind, simply because here we have outlined so wonderfully the old life of Miocene times. These Bad Lands must ever remain a stimulus to geological studies and those grand results which scientific culture produce.
Physical Changes in Modern Geological Times--Timber--.When the Loess epoch was drawing to a close, and portions of the area covered by these deposits were yet in a condition of a bog, the climate was much more favorable than the present for the growth of timber. Rainfall was then much more abundant. In 1868, I found logs, some of which were sixty feet in length, buried in the peat bogs at the head of the Logan, where no timber was then growing within twenty miles They evidently grew on the shores or banks, and, after falling into the bog, they were protected from decay by the antiseptic properties of the peaty waters. Many other facts exist showing the greater prevalence of forests within geologically recent times. It is known that at a comparatively recent period pine forests existed eastward to the mouth of the Niobrara, along the northern line of the State. What caused the disappearance of these forests cannot perhaps be determined with certainty. Some geologists hold that the increasing dryness of the climate caused the disappearance of the old forests. Might not the converse of this be true here as elsewhere, namely, that the destruction of forests inaugurated the dry climate that prevailed when this territory was first explored? It is at least conceivable that the primitive forest received its death-blow in a dry summer by fire through the vandal acts of Indians in pursuit of game or for purposes of war. An old tradition that I once heard from the Omaha Indians points to this conclusion.
It is wonderful how nature here responds to the efforts of men for reclothing this territory with timber. Man thus becomes an efficient agent for the production of geological changes. As prairie fires are repressed and trees are planted by the million, the climate must be still further ameliorated When once there are groves of timber on every section or quarter-section of land in the State, an approach will be made to some of the best physical conditions of Tertiary times. The people of this new State have a wonderful inheritance of wealth, beauty and power in their fine climate and their rich lands, and as they become conscious of this, they will more and more lend a helping hand to the processes of nature for the development and utilization of the material wealth of Nebraska.