Geology topics
Research about North America
Source-linked reports with geographic coverage including North America.
The beginnings of seismology in North America
The study of earthquakes advanced somewhat more slowly in North America than it did in Europe and Japan. J.D. Whitney, professor of geology at Harvard University and former State Geologist of California, studied the Owens Valley, Calif., earthquake of 1872 and reported on it that same year.
Species diversity: Patterns in modern and Miocene foraminifera of the eastern margin of North America
Patterns of foraminiferal species diversity were examined along the eastern margin of North America by utilizing the number of species, S, the information function, H(S), and species equitability, E. The 350 modern samples we studied extended from the Arctic to the Gulf of Mexico at depths ranging from a few meters to more than 5,000 m. In addition, 29 samples from Miocene strata of the Atlantic Coastal Plain and continental shelf were studied. Modern species diversity as measured by S and H(S) generally increases as depth increases and latitude decreases. Some notable exceptions occur, however, which are difficult to explain. For example, species diversity in the Arctic depth interval of 0 to 100 m is as high or higher than that found immediately south of Nova Scotia, in the Gulf of Maine, on Browns and Georges Banks, and even off the Gulf of Mexico deltas. At the moderate depth interval of 100 to 1,000 m, however, the entire margin north of Browns and Georges Banks has lower diversities than that to the south. The highest diversity by far in this depth interval occurs in the northeastern Gulf of Mexico. At the depth interval greater than 1,000 m, the more southern areas studied generally have a higher species diversity than the more northern Cape Cod to Maryland area. An exception to this is the northwestern Gulf of Mexico; this area is also an exception in that species diversity is significantly lower in the deeper waters than in the shallower waters in the same area. The measure of species equitability, E, showed no clear pattern with depth or latitude. This may be so because no simple pattern of species proportions exists or because the sampling was inadequate to measure it. Samples from the Miocene strata show a striking resemblance in species diversity to modern samples at similar depths and latitudes. Our observations indicate that species diversity and equitability have not increased during the last 15 × 10 6 yrs. The fossil and modern data indicate that each environment has its own carrying capacity and that this capacity is reached rather quickly. Although time and environmental stability are undoubtedly important in determining species diversity, as presently defined they are inadequate to explain all observed patterns. Long-term observations in various environments will be required to determine the relative importance of variables that affect species diversity.
Our changing continent
Where were the land areas and oceans of the North American Continent one million years ago, compared to our present geography? Was North America always about the same size and shape as it is today? To answer these questions, we must construct maps of the lands and sea that existed during the past ages. This process of reconstructing ancient geography is called paleogeography (from the Greek word "palaios," meaning ancient).
Duck viral enteritis (duck plague) in North American Waterfowl
Duck Viral Enteritis (DVE) was first recognized in North America in January 1967, when an outbreak occurred in a commercial flock of white Pekin ducks in Suffolk County, Long Island, New York (Leibovitz and Hwang, 1968b). Originally described as a disease of domestic ducks in the Netherlands, DVE has since been reported from India and Belgium. it is also believed to have occurred in China and France (Jansen, 1968). This paper briefly reviews the status of DVE among wild waterfowl in North America and describes some of the characteristic lesions associated with this disease. The paper also mentions some of the work which has been undertaken to learn more about the status of DVE in North America.
Ground water in North America
The fast-growing demands on this natural resource expose a need to resolve many hydrologic unknowns.
North American geologic formation names: Bibliography, synonymy and distribution
No abstract available.
I. Sexual, individual, and geographical variation in leucosticte tephrocotis, II.Geographical variation among North American mammals, especially in respect to size
Having recently had an opportunity (through the kindness of Professor Baird) of studying with some care the magnificent series of skulls of the North American Mammalia belonging to the National Museum (amounting often to eighty or a hundred specimens of a single species), I have been strongly impressed with the different degrees of variability exhibited by the representatives of the species and genera of even the same family. The variation in size, for instance, with latitude, in the Wolves and Foxes is surprisingly great, amounting in some species (as will be shown later) to 25 per cent. of the average size of the species, while in other species of the Ferae it is almost nil . Contrary to the general supposition, the variation in size among representatives of the same species is not always a decrease with the decrease of the latitude of the locality, but is in some cases exactly the reverse, in some species there being a very considerable and indisputable increase southward . This, for instance, is very markedly true of some species of Felis and in Procyon lotor . Consequently, the very generally-received impression that in North America the species of Mammalia diminish in size southward, or with the decrease in the latitude (and altitude) of the locality, requires modification. While such is generally the case, the reverse of this too often occurs, with occasional instances also of a total absence of variation in size with locality, to be considered as forming "the exceptions" necessary to "prove the rule".