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The Virginia Teacher Volume XVIII MARCH, 1937 No. 3 THE SHENANDOAH VALLEY: and development of age-old mineral re- sources and water supplies. The clues are WHY IT IS WHERE IT IS numerous, but like all clues that lead to the SHENANDOAH Valley—"daughter of deciphering of mysteries, one must under- the stars"—is renowned for its scenic stand how to recognize them and how to beauty, eventful history, spectacular interpret them when they are discovered. caverns, unique Natural Bridge, and excel- About 140 years ago it was first recogniz- lent farms and orchards. Those who live ed in a scientific sense that ordinary process- in the Valley or travel often through it take es working at and near the surface of the most of these features for granted without earth accomplish certain definite far-reach- either wonder or curiosity as to their ori- ing results. It was soon deduced that these gins. Many visitors come and go, and they processes had acted in the same manner, too admire the scenery and the products of producing similar results, throughout geo- the soils, and take them for granted—as they logic eras; for example, the first rains that often do natural features. Some are im- ran vigorously down slopes eroded rocks pressed by the awe-inspiring natural won- and soils just as they do now under similar ders and become inquisitive about them. conditions; or, as waves beat upon coasts Only a few, however, stop to ask Why ? and in times of storm and tear down the weaker How? and When? rocks, so, since time immemorial, have lands Many observers or readers no doubt disappeared gradually into the seas. Thus would be surprised at the statements that at it has been axiomatic for decades that geo- one time there was neither Shnandoah Val- logic agents and processes have always op- ley nor Blue Ridge; that at one time the erated in ways similar to those we can now whole region was an indistinguishable part observe. of a vast plain sloping gently toward the At- All landscapes have been sculptured and lantic; that still earlier the Valley region modeled by geologic processes. Hills, val- was occupied by great mountain ridges; and leys and plains have inscribed in their fea- that in still more remote times it was at the tures records of the processes and the bottom of a huge shallow mediterranean agents that fashioned them out of the rocks basin that was many times inundated by of the earth's crust. Each landscape, like waters from the Atlantic, Arctic, and Gulf the floor of Shenandoah Valley, resembles seas. Strange as it may seem, those are a tapestry of interwoven patterns of ancient facts, recorded indubitably as "current events. The patterns and the details of the events" of past geologic cycles. physiognomies of all topographic features A reviewer once aptly stated, "Science as are full of significance to trained inter- well as fiction has its mysteries, clues, and preters. detectives." Shenandoah Valley had many Each layer of rock in the Valley is literal- geologic mysteries—all long unsolved, some ly a manuscript of contemporary earth his- still to be solved. The detectives are the tory. In it is recorded something of the geologists and engineers, either professional nature of the lands from which the sediment or amateur, who have studied the natural was derived, the agent of transportation, features of the Valley and other regions in the distance of travel, and the environment the search for scientific truths or to make in which the material was deposited. Some some contribution toward the conservation rocks give clues also as to the contemporary 46 THE VIRGINIA TEACHER [Volume 18, No. 3 climates. The fossils-—remains of ancient almost a plain. The most prominent feature plants and animals—in many beds give in- rising above this general level is Massa- dications of the floras and faunas of those nutten Mountain. Here and there low times. More than that, they generally sug- ridges or rounded hills also rise above the gest whether the sediment accumulated on Valley floor. Close inspection shows that land, in lakes, or in seas. They afford reli- the present drainage is well below the gen- able clues also to trace out the extent of ral plain, that the floor itself has been carv- ancient inland seas and their connections ed into a series of ravines and broad valleys with the principal oceans or with seas that with intervening broad flattish uplands a inundated other lands. For example, lime- few hundred feet above the major streams. stone beds in the Valley contain fossil ma- Bordering Shenandoah Valley are two rine shells that are found also in similar prominent mountain ridges, the Blue Ridge rocks in the Arctic and Baltic regions. on the east and North Mountain on the To complete our investigation of data west. From an elevated observation point bearing on the origin of Shenandoah Valley, it will be noted that the crests of these two we should note briefly Certain observable ridges and that of Massanutten Mountain geologic features. The rocks of the Valley have many points at approximately the same are virtually all sedimentary, that is, they altitude. On parts of the adjoining Blue were once particles of sediment derived Ridge, broad flats—such as Big Meadows— directly or indirectly from older rocks. are present. They are now chiefly sandstones, shales, and Shenandoah Valley has specific charac- limestones, that is, cemented and solidified teristics that more or less distinguish it from beds of sand, mud, and limy mud or ooze. other geographic units, either in Virginia or Surficial deposits of boulders, gravel, and in the Appalachian province. They include sand are found in many areas, particularly its general form, topography, altitude, not far from the larger streams. Peculiar drainage, size, and location. Its caverns and masses of limy materials have been deposit- Natural Bridge are in some respects unlike ed in some stream beds and in the large those that occur elsewhere. The rocks, min- caverns. In a few places, bodies of dark- eral resources, soils, and water supplies, colored crystalline rocks are found. These while by no means unique, are nonetheless are masses of molten rock that were forced distinctly characteristic. All of these indi- upward into overlying rocks where they vidualistic features are the result of the cooled and solidified. geologic history of the region, the present Casual observation shows that the strati- end-products of geologic processes operating fied rocks of the Valley are not horizontal— through incomprehensible millenia. Even the position in which the sediments were the climate and the vegetation are to some deposited—but are tilted at gentle to steep extent products of that chain of events. Hu- angles. Closer examination shows that the man activities and history also, so far as beds generally have definite trends to the affected by environment, no doubt have been northeast and the southwest, roughly paral- different in the Valley than they would have lel to the Blue Ridge. In some stream been if the sequence of major geologic gorges and road cuts, complete folds, events had been different or if the geologic arches, or downwarps, can be seen. and topographic features, such as mediter- The topographic features of the Valley ranean seas, high mountains, or a vast coast- at first appear quite diversified, but they can al plain, were those of some former geologic be readily catalogued. Observation from era. some high point, as the Skyline Drive, shows From the evidence recorded in the rocks that the Valley has a broad undulatory floor, and the landscapes of the region, the se- March, 1937] THE VIRGINIA TEACHER 47 quence of events in the geologic panoramas and compressed together, the present con- of Shenandoah Valley can be sketched in glomerates, sandstones and shales of the broad outlines. Many details remain to be Valley and adjacent mountains were form- determined by intensive studies. ed. Some of the sandstones no doubt repre- The first panorama that we may envision sent old sea beaches and some of the shales is that of a broad piedmont plain extending suggest extensive mud flats. At one time the from uplands in what is now Tidewater Vir- southern part of a huge delta spread over ginia westward far into the interior of the the northern part of the Valley area. continent. The records are so meager and During many epochs of the Paleozoic era so obscured by subsequent events and the the marine waters were rather clear. In time elapsed since then so long—some hun- consequence, huge deposits of limy mud and dreds of millions of years—that we can ooze accumulated, formed in part by chemi- never know much about the characteristics cal and biochemical processes in the seas of that ancient land. Earth historians gener- and in part from the shell debris of count- ally think of the region as having a mild to less hordes of shellfish that lived in those temperate climate and as being devoid of seas. Thus we find in Shenandoah Valley vegetation, unless of the most primitive thick limestones alternating with sandstones types. and shales. In the latter part of the era ex- During the Paleozoic era—the time of tensive swamps lay over the area now in "ancient life"—the panorama changes. Rela- the western parts of Augusta and Rocking- tively shallow mediterranean seas very slow- ham counties. The vegetation in those ly invaded an elongate trough that was swamps accumulated and decayed through slowly sinking in respect to sea level. This millenia to produce ultimately the beds of trough extended at times from the Gulf of coal now found between North and Shenan- Mexico area northeastward across the site doah mountains.

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