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USGS2009

Gap Analysis -A geographic approach to planning for biological diversity

The Mission of the Gap Analysis Project (GAP) is to promote conservation by providing broad geographic information on biological diversity to resource managers, planners, and policy makers who can use the information to make informed decisions. As part of the National Biological Information Infrastructure (NBII) —a collaborative program to provide increased access to data and information on the nation’s biological resources--GAP data and analytical tools have been used in hundreds of applications: from basic research to comprehensive state wildlife plans; from educational projects in schools to ecoregional assessments of biodiversity. The challenge: keeping common species common means protecting them BEFORE they become threatened. To do this on a state or regional basis requires key information such as land cover descriptions, predicted distribution maps for native animals, and an assessment of the level of protection currently given to those plants and animals. GAP works cooperatively with Federal, state, and local natural resource professionals and academics to provide this kind of information. GAP activities focus on the creation of state and regional databases and maps that depict patterns of land management, land cover, and biodiversity. These data can be used to identify “gaps” in conservation--instances where an animal or plant community is not adequately represented on the existing network of conservation lands. GAP is administered through the U.S. Geological Survey. Through building partnerships among disparate groups, GAP hopes to foster the kind of collaboration that is needed to address conservation issues on a broad scale.

GAP Bulletin↗
USGS2009

Applications of a broad-spectrum tool for conservation and fisheries analysis: Aquatic gap analysis

Natural resources support all of our social and economic activities, as well as our biological existence. Humans have little control over most of the physical, biological, and sociological conditions dictating the status and capacity of natural resources in any particular area. However, the most rapid and threatening influences on natural resources typically are anthropogenic overuse and degradation. In addition, living natural resources (i.e., organisms) do not respect political boundaries, but are aware of their optimal habitat and environmental conditions. Most organisms have wider spatial ranges than the jurisdictional boundaries of environmental agencies that deal with them; even within those jurisdictions, information is patchy and disconnected. Planning and projecting effects of ecological management are difficult, because many organisms, habitat conditions, and interactions are involved. Conservation and responsible resource use involves wise management and manipulation of the aspects of the environment and biological communities that can be effectively changed. Tools and data sets that provide new insights and analysis capabilities can enhance the ability of resource managers to make wise decisions and plan effective, long-term management strategies. Aquatic gap analysis has been developed to provide those benefits. Gap analysis is more than just the assessment of the match or mis-match (i.e., gaps) between habitats of ecological value and areas with an appropriate level of environmental protection (e.g., refuges, parks, preserves), as the name suggests. Rather, a Gap Analysis project is a process which leads to an organized database of georeferenced information and previously available tools to examine conservation and other ecological issues; it provides a geographic analysis platform that serves as a foundation for aquatic ecological studies. This analytical tool box allows one to conduct assessments of all habitat elements within an area of interest. Aquatic gap analysis naturally focuses on aquatic habitats. The analytical tools are largely based on specification of the species-habitat relations for the system and organism group of interest (Morrison et al. 2003; McKenna et al. 2006; Steen et al. 2006; Sowa et al. 2007). The Great Lakes Regional Aquatic Gap Analysis (GLGap) project focuses primarily on lotic habitat of the U.S. Great Lakes drainage basin and associated states and has been developed to address fish and fisheries issues. These tools are unique because they allow us to address problems at a range of scales from the region to the stream segment and include the ability to predict species specific occurrence or abundance for most of the fish species in the study area. The results and types of questions that can be addressed provide better global understanding of the ecological context within which specific natural resources fit (e.g., neighboring environments and resources, and large and small scale processes). The geographic analysis platform consists of broad and flexible geospatial tools (and associated data) with many potential applications. The objectives of this article are to provide a brief overview of GLGap methods and analysis tools, and demonstrate conservation and planning applications of those data and tools. Although there are many potential applications, we will highlight just three: (1) support for the Eastern Brook Trout Joint Venture (EBTJV), (2) Aquatic Life classification in Wisconsin, and (3) an educational tool that makes use of Google Earth (use of trade or product names does not imply endorsement by the U.S. Government) and Internet accessibility.

Gap Analysis Bulletin↗
USGS1919

Gravel deposits of the Caddo Gap and De Queen quadrangles, Arkansas

Several thick deposits of gravel are widely distributed along the north edge of the Gulf Coastal Plain, of which a narrow belt is embraced in the southern parts of the Caddo Gap and De Queen quadrangles, Ark. This belt is shown on Plate I, and its location is shown on figure 5, a key map of this region. It comprises parts of Pike, Howard, and Sevier counties and a narrow strip of Hemp- stead County, in southwestern Arkansas, and a strip along the east edge of McCurtain County, in southeastern Oklahoma. The gravels are of Lower Cretaceous, Upper Cretaceous, and Quaternary age, and are composed mainly of pebbles of novaculite (a variety of chert) derived from the Arkansas novaculite exposed in the Ouachita Mountain region, which is north of the Gulf Coastal Plain. They are used in making concrete, in ballasting railroads, and in the construction of wagon roads. Very small quantities of pebbles are also used in the washing plant of the Kimberlite Diamond Mining & Washing Co., at Murfreesboro, to assist in the disintegration of the altered peridotite which carries the diamonds. Interest in possible American sources of flint pebbles or substitutes therefor to be used in tube mills, in which minerals, ores, cement materials, and clinker are extensively ground in this country, has been aroused since the beginning of the present world war. This interest is due to the partial interruption of imports of flint pebbles from Denmark and France, which have supplied most of the pebbles used in this country. The main reasons for the preparation of this report are to present a description of the gravels under discussion and to indicate the possibility of their use in tube mills. The information for this report is the result of detailed field studies in the Caddo Gap and De Queen quadrangles by the authors in 1908 and 1911 and by the senior author in 1912 and 1916. Mr. E, D. Mesler rendered valuable assistance in 1912. Much of the information is abstracted from the De Queen-Caddo Gap folio, which is nearing completion.

Arkansas, Oklahoma↗
USGS1983

Plutonic rocks of Jurassic age in the Alaska-Aleutian Range batholith: Ghemical variation and polarity

Plutonic rocks of Jurassic age exposed on the eastern, or Pacific, side of the Alaska–Aleutian Range batholith represent the roots of a magmatic arc generally considered to have been generated in response to northwest-directed subduction. These rocks form a compositionally continuous calc-alkaline suite that ranges from hornblende gabbro through quartz monzonite. Tonalite and quartz diorite are the dominant rock types. Trend-surface analysis was used to examine the geographic variation of major oxides and a few simple oxide ratios for 102 samples from widely separated localities. Statistical tests indicate that most of the trends, although weak, are real. The direction of slope of the trends is approximately normal to the Jurassic magmatic arc K 2 O and SiO 2 increase toward the east-southeast; the other oxides increase toward the west-northwest. The K 2 O trend accounts for about 19% of the variance in the data and is significant at > 99.9% level of confidence. If the chemical trends reflect the approximate geometry of a paleosubduction zone, the polarity of the Jurassic magmatic arc is to the northwest. That is, the paleosubduction zone was on the northwest side of the arc, and subduction was directed toward the southeast. The paleosubduction zone is on the opposite side of the arc from the position that has generally been assumed, indicating that the Jurassic plutonic rocks were not generated in response to classical Andean-type convergent plate margins. The magmatic arc may have formed in an intra-ocean environment, and subsequently has been rafted northward and accreted to this part of the northern Pacific rim during the late Mesozoic. Middle and Upper Jurassic clastic sediments underlying Cook Inlet to the southeast, and derived from the magmatic arc, are classified as backarc deposits, rather than as an arc-trench gap sequence.

Geological Society of America Bulletin↗
USGS2005

Unusually low rates of slip on the Santa Rosa Range fault zone, northern Nevada

The Santa Rosa Range fault zone (SRRFZ) is one of the most topographically prominent normal fault systems in the northern Basin and Range province of the western United States. It has been assigned high rates of vertical slip by others and has been identified as a possible site of the future extension of the central Nevada seismic belt (CNSB). We use detailed trench mapping and luminescence dating to estimate displacements and timing of the last several large-magnitude paleoearthquakes on the southern part of the SRRFZ at a trench site near Orovada, Nevada. Coseismic vertical displacements ranged from 1 to 2.8 m for each of the last four events. Luminescence ages provide time limits for the last three events of 125-155 ka, 90-108 ka, and 11-16 ka. These data yield recurrence intervals of 17-65 k.y. and 74-97 k.y. and an elapsed time of 11-16 k.y. since the youngest event. Slip-rate determinations at the Orovada site are complicated by multiple fault strands, but rates calculated from a variety of data are surprisingly low (0.01-0.16 mm/yr), given the topographic prominence of the Santa Rosa Range. A lack of compelling patterns in a comparison of paleoseismic parameters indicate that the SRRFZ is no more likely a location for a large-magnitude earthquake than previously identified seismic gaps or along faults that lie directly north of the CNSB.

Bulletin of the Seismological Society of America↗
USGS2020

Mild displacements of boulders during the 2019 Ridgecrest Earthquakes

Strong seismic waves from the July 2019 Ridgecrest, California, earthquakes displaced rocks in proximity to the M 7.1 mainshock fault trace at several locations. In this report, we document large boulders that were displaced at the Wagon Wheel Staging Area (WWSA), approximately 4.5 km southeast of the southern terminus of the large M 6.4 foreshock rupture (hereafter “the large foreshock”) and 9 km southwest of the nearest approach of the M 7.1 mainshock surface rupture. Some boulders appear to have slid along essentially flat surfaces, which suggest that dynamic stresses overcame the coefficient of friction. Other boulders appear to have rocked within their sockets. In both cases, we use simple mechanical models to estimate total peak dynamic accelerations between 0.5 and 1g⁠, commensurate with modified Mercalli intensity 9. It is unclear if the strongest shaking at this location occurred during the large foreshock or the M 7.1 mainshock. The inferred accelerations are higher than predicted mainshock ground motions at WWSA, although local high accelerations could have been generated by path, site, or source effects. Gaps between boulders and their sockets are easily visible in the immediate aftermath of earthquakes and provide a quick indication of strong shaking. More importantly, the gaps quickly fill with surficial organic debris, including seeds and leaves of the year, that quickly become entombed. Boulders may thus potentially be extracted to examine gap fillings associated with past earthquakes, providing a new datable paleoseismic method.

California↗
USGS1990

Ammonites and some characteristic bivalves from the Upper Cretaceous Frontier Formation, Natrona County, Wyoming

The Frontier Formation in Natrona County, Wyoming, consists of two or three members of mostly shallow-water marine shale, siltstone, and sandstone. From oldest to youngest, these units are the Belle Fourche Member, the informal member of Emigrant Gap, and the Wall Creek Member. The members are separated by disconformities, and locally the Wall Creek Member rests on the Belle Fourche Member. Molluscan fossils are present in all the members, but only the Wall Creek Member contains a great variety of species. Ammonites and inoceramid bivalves are most important in zoning the Frontier Formation. Seven of the twelve established ammonite zones of middle and late Cenomanian age in the Western Interior can be recognized in the Belle Fourche Member. Two zones of middle Turonian age are present in the member of Emigrant Gap, and three zones of late Turonian age are present in the Wall Creek Member.

Wyoming↗
USGS1978

Predicting earthquakes along the major plate tectonic boundaries in the Pacific

In an article in the last issue of the Earthquake Information Bulletin ("Earthquakes and Plate Tectonics," by Henry Spall), we saw how 90 percent of the world's earthquakes occur at the margins of the Earth's major crustal plates. however, when we look at the distribution of earthquakes in detail, we see that a number of nearly aseismic regions, or seismic gaps, can be found along the present-day plate boundaries. Why is this? And can we regard these areas as being more likely to be the sites for future larger earthquakes than those segments of the plate boundaries that have ruptured recently.

Earthquake Information Bulletin (USGS)↗
USGS1978

Amplitude of foreshocks as a possible seismic precursor to earthquakes

In recent years, we have made significant progress in being able to recognize the long-range pattern of events that precede large earthquakes. For example, in a recent issue of the Earthquake Information Bulletin, we saw how the pioneering work of S.A. Fedotov of the U.S.S.R in the Kamchatka-Kurile Islands region has been applied worldwide to forecast where large, shallow earthquakes might occur in the next decades. Indeed, such a "seismic gap" off the coast of Alaska was filled by the 1972 Sitka earthquake. Promising results are slowly accumulating from other techniques that suggest that intermediate-term precursors might also be seen: among these are tilt and geomagnetic anomalies and anomalous land uplift. But the crucial point remains that short-term precursors (days to hours) will be needed in many cases if there is to be a significant saving of lives.

Earthquake Information Bulletin (USGS)↗