Geology topics
Research about Maryland
Source-linked reports with geographic coverage including Maryland.
Experimental analysis of methods for measuring small mammal populations
No abstract available.
Picking among pen-reared quail
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Observations on the natural and artificial propagation of the smallmouth black bass, Micropterus dolomieu
Counts of smallmouth black bass nests in the same sections of the South Branch of the Potomac, the Cacapon, and the Shenandoah Rivers are reported over a period of several seasons. The 4‐year record for the South Branch of the Potomac indicates little change in the smallmouth black bass population. The number of nests varied between 50.7 and 73.2 and averaged 58.1 for each mile of stream. The results of fry counts from wild nests showed an average of 2,159 fry in each nest in the South Branch of the Potomac, 2,210 in the Cacapon River, and 1,998 in the Shenandoah River. One important characteristic of natural propagation in these rivers is the simultaneous occurrence of spawning in any section of stream having similar conditions. Evidence is supplied to support the theory that a long, drawn‐out spawning season in artificial ponds is due to annoyance of the brood fish. The importance of attendance by the male fish at the nest is pointed out. Examples in pond culture are given to demonstrate that there are other factors involved in the spawning of smallmouth black bass besides temperature. These factors are annoyance, over‐crowding of the brood fish, and lack of provision for greater individual privacy among the brood bass during their spawning season. In general, productivity of fry apparently increases with age and size of the brood fish.
Protein requirements of bobwhite chicks for survival, growth and efficiency of feed utilization
No abstract available.
Blood parasites of birds of the District of Columbia and Patuxent Research Refuge vicinity
Recently a number of surveys of blood parasites of birds have been made in different parts of this country by different workers, the general purpose of which was to further the knowledge of the distribution and pathogenicity of these protozoa. This paper treats the distribution of parasites found in sampling miscellaneous birds of the District of Columbia and vicinity and contains a preliminary report on the more important phase of the problem of pathogenicity.
Erosion and sedimentation in Chesapeake Bay around the mouth of Choptank River
With the unfolding of geologic knowledge during the last century the processes of denudation, transportation of sediments, and sedimentation have become better understood, and to some extent their relative effects in bringing about the present configuration of the earth's surface have been determined. The nature of these processes has been studied in many parts of the globe, but owing to the large size of the units affected and the slowness of the processes there has been little opportunity to collect quantitative data. Indeed, the data available are very largely conjectural, their degree of accuracy being only that of good guessing. However, with the advent of accurate topographic and hydrographic surveys, the first steps toward actual measurements of some of the many interesting surficial changes that are in progress have been taken, and it only remains for time and additional observations to afford opportunities for comparison. Resurveys, particularly by the United States Coast and Geodetic Survey, of parts of the eastern coast of the United States at different intervals have shown in many places marked changes of both shore line and sea bottom, as on Cape Cod, on Nantucket Island, and in Delaware Bay. Comparisons of this kind have so far been incidental to work in engineering and coast surveying, so that there has been little opportunity for the selection of localities particularly adapted to studies of erosion and sedimentation.
Choptank folio, Maryland
The Choptank quadrangle lies between parallel 38 ° 30' and 39° north latitude and meridians 76° and 76° 30' west longitude. It includes one-fourth of a square degree of the earth's surface and contains 931.51 square miles. From north to south it measures 34.5 miles and from east to west its mean width is 27 miles, as it is 27.1 miles wide along the southern and 26.9 miles along the northern border.
The gabbros and associated hornblende rocks occurring in the neighborhood of Baltimore, Maryland
Considerable attention has been devoted during late years to the metamorphism of igneous rocks, and it can now be regarded as placed beyond reasonable doubt that such rocks may be changed to more or less schistose masses, which often closely resemble crystallized sediments. This possibility has heretofore been largely ignored, owing doubtless to the extensive obliteration of those characteristics which are generally regarded as most typical of eruptive rocks. Schistose or banded structure, however, can now hardly be considered as necessarily an indication of sedimentary origin. The minerals which are most characteristic of the so-called crystalline schists have been repeatedly shown to be derived from the alteration of igneous as well as of aqueous formations. These minerals only represent the final and most stable combination of certain elements under certain conditions, and are quite independent of the earlier combinations in which these elements may have existed. A lava bed and a clay bank, if the two may be supposed to have originally had the same chemical composition, might, under the influence of the same metamorphic agencies, ultimately give rise to the same rock in spite of original differences in structure or mineralogical composition. Stratification may be obliterated by metamorphism, while foliation, or even a banded structure, may, by the same means, be secondarily induced. Neither structure nor mineral composition can be taken as an infallible guide in determining the origin or the age of rocks. The present paper is intended as a contribution to our knowledge of a particular phase of metamorphism in eruptive rocks, i. e., that one which is dependent on the secondary development of hornblende by the paramorphism or pseudomorphism of pyroxene. This is a change the frequency of which renders it of fundamental geological importance. It has already received considerable attention from many eminent geologists, but no locality heretofore studied seems to have afforded opportunities for tracing out every stage in the process of alteration superior to those offered by the area of massive rocks west and northwest of the city of Baltimore. Here, covering a district of over fifty square miles, the unchanged pyroxene rock and its resultant hornblendic equivalent occur in the most intimate relations. Exposures of both rocks in situ are numerous, and the opportunity of following out the gradual transition of one into the other is proportionately great.