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94-710: Eastwind Ridge was mapped by the United States Geological Survey (USGS) from ground surveys and Navy air photos. It was named by the United States Advisory Committee on Antarctic Names (US-ACAN) in 1964 for the USCGC Eastwind , an icebreaker in several American convoys into McMurdo Sound since the 1958–59 season. Download coordinates as: 76°34′00″S 161°00′00″E  /  76.5666667°S 161°E  / -76.5666667; 161 A peak to

188-535: A characteristic fabric . All three types may melt again, and when this happens, new magma is formed, from which an igneous rock may once again solidify. Organic matter, such as coal, bitumen, oil, and natural gas, is linked mainly to organic-rich sedimentary rocks. To study all three types of rock, geologists evaluate the minerals of which they are composed and their other physical properties, such as texture and fabric . Geologists also study unlithified materials (referred to as superficial deposits ) that lie above

282-485: A petrographic microscope , where the minerals can be identified through their different properties in plane-polarized and cross-polarized light, including their birefringence , pleochroism , twinning , and interference properties with a conoscopic lens . In the electron microprobe, individual locations are analyzed for their exact chemical compositions and variation in composition within individual crystals. Stable and radioactive isotope studies provide insight into

376-568: A changing world". The agency's previous slogan, adopted on its hundredth anniversary, was "Earth Science in the Public Service". Since 2012, the USGS science focus has been directed at topical "Mission Areas" that have continued to evolve. Further organizational structure includes headquarters functions, geographic regions, science and support programs, science centers, labs, and other facilities. The USGS regional organization aligns with

470-434: A definite homogeneous chemical composition and an ordered atomic arrangement. Each mineral has distinct physical properties, and there are many tests to determine each of them. Minerals are often identified through these tests. The specimens can be tested for: A rock is any naturally occurring solid mass or aggregate of minerals or mineraloids . Most research in geology is associated with the study of rocks, as they provide

564-593: A federal survey agency, in part to inventory the vast lands added to the United States by the Louisiana Purchase in 1803 and the Mexican–American War in 1848. The USGS was authorized on March 3 in a last-minute amendment to an unrelated bill that charged the new agency with the "classification of the public lands, and examination of the geological structure, mineral resources, and products of

658-449: A lack of accuracy and detail in comparison to older generation maps based on aerial photo surveys and field checks. As the digital databases were not designed for producing general-purpose maps, data integration can be a problem when retrieved from sources with different resolutions and collection dates. Human-made features once recorded by direct field observation are not in any public domain national database and are frequently omitted from

752-627: A length of less than a meter. Rocks at the depth to be ductilely stretched are often also metamorphosed. These stretched rocks can also pinch into lenses, known as boudins , after the French word for "sausage" because of their visual similarity. Where rock units slide past one another, strike-slip faults develop in shallow regions, and become shear zones at deeper depths where the rocks deform ductilely. The addition of new rock units, both depositionally and intrusively, often occurs during deformation. Faulting and other deformational processes result in

846-452: A means to provide information about geological history and the timing of geological events. The principle of uniformitarianism states that the geological processes observed in operation that modify the Earth's crust at present have worked in much the same way over geological time. A fundamental principle of geology advanced by the 18th-century Scottish physician and geologist James Hutton

940-626: A new way to view their entire digitized collection of over 178,000 maps from 1884 to 2006. The site is an interactive map of the United States that allows users to search or move around the map to find the USGS collection of maps for a specific area. Users may then view the maps in great detail and download them if desired. In 2008 the USGS abandoned traditional methods of surveying, revising, and updating topographic maps based on aerial photography and field checks. Today's U.S. Topo quadrangle (1:24,000) maps are mass-produced, using automated and semiautomated processes, with cartographic content supplied from

1034-410: A non-metric scale virtually unique to the United States. Each of these maps covers an area bounded by two lines of latitude and two lines of longitude spaced 7.5 minutes apart. Nearly 57,000 individual maps in this series cover the 48 contiguous states , Hawaii , U.S. territories , and areas of Alaska near Anchorage , Fairbanks , and Prudhoe Bay . The area covered by each map varies with

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1128-608: A number of fields, laboratory, and numerical modeling methods to decipher Earth history and to understand the processes that occur on and inside the Earth. In typical geological investigations, geologists use primary information related to petrology (the study of rocks), stratigraphy (the study of sedimentary layers), and structural geology (the study of positions of rock units and their deformation). In many cases, geologists also study modern soils, rivers , landscapes , and glaciers ; investigate past and current life and biogeochemical pathways, and use geophysical methods to investigate

1222-846: A number of water-related programs, notably the National Streamflow Information Program and National Water-Quality Assessment Program. USGS Water data is publicly available from their National Water Information System database. The USGS also operates the National Wildlife Health Center , whose mission is "to serve the nation and its natural resources by providing sound science and technical support, and to disseminate information to promote science-based decisions affecting wildlife and ecosystem health. The NWHC provides information, technical assistance, research, education, and leadership on national and international wildlife health issues." It

1316-684: A result, some have noted that the U.S. Topo maps currently fall short of traditional topographic map presentation standards achieved in maps drawn from 1945 to 1992. The Hydrologic Instrumentation Facility (HIF) has four sections within its organizational structure; the Field Services Section which includes the warehouse, repair shop, and Engineering Unit; the Testing Section which includes the Hydraulic Laboratory, testing chambers, and Water Quality Laboratory;

1410-451: A sedimentary rock. Sedimentary rocks are mainly divided into four categories: sandstone, shale, carbonate, and evaporite. This group of classifications focuses partly on the size of sedimentary particles (sandstone and shale), and partly on mineralogy and formation processes (carbonation and evaporation). Igneous and sedimentary rocks can then be turned into metamorphic rocks by heat and pressure that change its mineral content, resulting in

1504-499: A single environment and do not necessarily occur in a single order. The Hawaiian Islands , for example, consist almost entirely of layered basaltic lava flows. The sedimentary sequences of the mid-continental United States and the Grand Canyon in the southwestern United States contain almost-undeformed stacks of sedimentary rocks that have remained in place since Cambrian time. Other areas are much more geologically complex. In

1598-478: A towing tank, jet tank, pipe flow facility, and tilting flume. In addition, the HIF provides training and technical support for the equipment it stocks. The Engineering Group seeks out new technology and designs for instrumentation that can work more efficiently, be more accurate, and or be produced at a lower cost than existing instrumentation. HIF works directly with vendors to help them produce products that will meet

1692-644: A variety of USGS Report Series that include preliminary results, maps, data, and final results. A complete catalog of all USGS publications is available from the USGS Publications Warehouse. In the mid-1800s, various states set up geological survey institutions; e.g., the Kentucky Geological Survey , established in 1854. In 1879, a report from the National Academy of Sciences prompted Congress to set up

1786-400: A variety of applications. Dating of lava and volcanic ash layers found within a stratigraphic sequence can provide absolute age data for sedimentary rock units that do not contain radioactive isotopes and calibrate relative dating techniques. These methods can also be used to determine ages of pluton emplacement. Thermochemical techniques can be used to determine temperature profiles within

1880-419: Is a branch of natural science concerned with the Earth and other astronomical objects , the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth sciences , including hydrology . It is integrated with Earth system science and planetary science . Geology describes the structure of the Earth on and beneath its surface and

1974-514: Is a partnership-driven program that teams scientific researchers with natural and cultural resource managers to help fish, wildlife, waters, and lands across the country adapt to climate change . The National CASC (NCASC), based at USGS headquarters in Reston, Virginia, serves as the national office for the CASC network, while eight regional CASCs made up of federal-university consortiums located across

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2068-422: Is accomplished in two primary ways: through faulting and folding . In the shallow crust, where brittle deformation can occur, thrust faults form, which causes the deeper rock to move on top of the shallower rock. Because deeper rock is often older, as noted by the principle of superposition , this can result in older rocks moving on top of younger ones. Movement along faults can result in folding, either because

2162-460: Is an intimate coupling between the movement of the plates on the surface and the convection of the mantle (that is, the heat transfer caused by the slow movement of ductile mantle rock). Thus, oceanic parts of plates and the adjoining mantle convection currents always move in the same direction – because the oceanic lithosphere is actually the rigid upper thermal boundary layer of the convecting mantle. This coupling between rigid plates moving on

2256-433: Is horizontal). The principle of superposition states that a sedimentary rock layer in a tectonically undisturbed sequence is younger than the one beneath it and older than the one above it. Logically a younger layer cannot slip beneath a layer previously deposited. This principle allows sedimentary layers to be viewed as a form of the vertical timeline, a partial or complete record of the time elapsed from deposition of

2350-616: Is important for mineral and hydrocarbon exploration and exploitation, evaluating water resources , understanding natural hazards , remediating environmental problems, and providing insights into past climate change . Geology is a major academic discipline , and it is central to geological engineering and plays an important role in geotechnical engineering . The majority of geological data comes from research on solid Earth materials. Meteorites and other extraterrestrial natural materials are also studied by geological methods. Minerals are naturally occurring elements and compounds with

2444-483: Is mapped at this scale in quadrangles measuring 1° by 1°. USGS topographic quadrangle maps are marked with grid lines and tics around the map collar which make it possible to identify locations on the map by several methods, including the graticule measurements of longitude and latitude, the township and section method within the Public Land Survey System , and cartesian coordinates in both

2538-484: Is primarily accomplished through normal faulting and through the ductile stretching and thinning. Normal faults drop rock units that are higher below those that are lower. This typically results in younger units ending up below older units. Stretching of units can result in their thinning. In fact, at one location within the Maria Fold and Thrust Belt , the entire sedimentary sequence of the Grand Canyon appears over

2632-568: Is that "the present is the key to the past." In Hutton's words: "the past history of our globe must be explained by what can be seen to be happening now." The principle of intrusive relationships concerns crosscutting intrusions. In geology, when an igneous intrusion cuts across a formation of sedimentary rock , it can be determined that the igneous intrusion is younger than the sedimentary rock. Different types of intrusions include stocks, laccoliths , batholiths , sills and dikes . The principle of cross-cutting relationships pertains to

2726-529: Is the agency primarily responsible for surveillance of H5N1 avian influenza outbreaks in the United States. The USGS also runs 17 biological research centers in the United States, including the Patuxent Wildlife Research Center . The USGS is investigating collaboration with the social networking site Twitter to allow for more rapid construction of ShakeMaps. ShakeMaps are an interactive tool allowing users to visually observe

2820-523: Is used for geologically young materials containing organic carbon . The geology of an area changes through time as rock units are deposited and inserted, and deformational processes alter their shapes and locations. Rock units are first emplaced either by deposition onto the surface or intrusion into the overlying rock . Deposition can occur when sediments settle onto the surface of the Earth and later lithify into sedimentary rock, or when as volcanic material such as volcanic ash or lava flows blanket

2914-585: The Geological Survey , is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology , geography , geology , and hydrology . The agency was founded on March 3, 1879, to study the landscape of the United States, its natural resources , and the natural hazards that threaten it. The agency also makes maps of extraterrestrial planets and moons based on data from U.S. space probes . The sole scientific agency of

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3008-599: The State Plane Coordinate System and the Universal Transverse Mercator coordinate system . Other specialty maps have been produced by the USGS at a variety of scales. These include county maps, maps of special interest areas, such as the national parks , and areas of scientific interest. A number of Internet sites have made these maps available on the web for affordable commercial and professional use. Because works of

3102-634: The UCERF California earthquake forecast. As of 2005, the agency is working to create a National Volcano Early Warning System by improving the instrumentation monitoring the 169 volcanoes in U.S. territory and by establishing methods for measuring the relative threats posed at each site. The USGS also operates five volcano observatories throughout the nation: the Alaska Volcano Observatory in Anchorage, Alaska (on

3196-506: The bedrock . This study is often known as Quaternary geology , after the Quaternary period of geologic history, which is the most recent period of geologic time. Magma is the original unlithified source of all igneous rocks . The active flow of molten rock is closely studied in volcanology , and igneous petrology aims to determine the history of igneous rocks from their original molten source to their final crystallization. In

3290-512: The geochemical evolution of rock units. Petrologists can also use fluid inclusion data and perform high temperature and pressure physical experiments to understand the temperatures and pressures at which different mineral phases appear, and how they change through igneous and metamorphic processes. This research can be extrapolated to the field to understand metamorphic processes and the conditions of crystallization of igneous rocks. This work can also help to explain processes that occur within

3384-570: The magnetic field at magnetic observatories and distributes magnetometer data in real time. The USGS collaborates with Canadian and Mexican government scientists, along with the Commission for Environmental Cooperation , to produce the North American Environmental Atlas , which is used to depict and track environmental issues for a continental perspective. The USGS operates the streamgaging network for

3478-402: The mantle below (separated within itself by seismic discontinuities at 410 and 660 kilometers), and the outer core and inner core below that. More recently, seismologists have been able to create detailed images of wave speeds inside the earth in the same way a doctor images a body in a CT scan . These images have led to a much more detailed view of the interior of the Earth, and have replaced

3572-442: The 15-minute series, was once used to map the contiguous 48 states at a scale of 1:62,500 for maps covering the continental United States, but was discontinued during the last quarter of the twentieth century. Each map was bounded by two parallels and two meridians spaced 15 minutes apart—the same area covered by four maps in the 7.5-minute series. The 15-minute series, at a scale of 1:63,360 (one inch representing one mile), remains

3666-440: The 1960s, it was discovered that the Earth's lithosphere , which includes the crust and rigid uppermost portion of the upper mantle , is separated into tectonic plates that move across the plastically deforming, solid, upper mantle, which is called the asthenosphere . This theory is supported by several types of observations, including seafloor spreading and the global distribution of mountain terrain and seismicity. There

3760-439: The 30 x 60-minute quadrangle series. Each of these quadrangles covers the area contained within 32 maps in the 7.5-minute series. The 1:100,000 scale series is unusual in that it primarily employs the metric system . One centimeter on the map represents one kilometer of distance on the ground. Contour intervals , spot elevations, and horizontal distances are also specified in meters. The final regular quadrangle series produced by

3854-424: The Earth, such as subduction and magma chamber evolution. Structural geologists use microscopic analysis of oriented thin sections of geological samples to observe the fabric within the rocks, which gives information about strain within the crystalline structure of the rocks. They also plot and combine measurements of geological structures to better understand the orientations of faults and folds to reconstruct

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3948-484: The Grand Canyon in the southwestern United States being a very visible example, the lower rock units were metamorphosed and deformed, and then deformation ended and the upper, undeformed units were deposited. Although any amount of rock emplacement and rock deformation can occur, and they can occur any number of times, these concepts provide a guide to understanding the geological history of an area. Geologists use

4042-980: The Information Technology Section which includes computer support and the Drafting Unit; and the Administrative Section. The HIF was given national responsibility for the design, testing, evaluation, repair, calibration, warehousing, and distribution of hydrologic instrumentation. Distribution is accomplished by direct sales and through a rental program. The HIF supports data collection activities through centralized warehouse and laboratory facilities. The HIF warehouse provides hydrologic instruments, equipment, and supplies for USGS as well as Other Federal Agencies (OFA) and USGS Cooperators. The HIF also tests, evaluates, repairs, calibrates, and develops hydrologic equipment and instruments. The HIF Hydraulic Laboratory facilities include

4136-523: The National GIS Database. In the two years from June 2009 to May 2011, the USGS produced nearly 40,000 maps, more than 80 maps per work day. Only about two hours of interactive work are spent on each map, mostly on text placement and final inspection; there are essentially no field checks or field inspections to confirm map details. While much less expensive to compile and produce, the revised digital U.S. topo maps have been criticized for

4230-725: The U.S. Department of the Interior Unified Interior Regions: USGS operates and organizes within a number of specific science programs, facilities, and other organizational units: The Earthquake Hazards Program monitors earthquake activity worldwide. The National Earthquake Information Center (NEIC) in Golden, Colorado , on the campus of the Colorado School of Mines detects the location and magnitude of global earthquakes. The USGS also runs or supports several regional monitoring networks in

4324-662: The U.S. Department of the Interior, USGS is a fact-finding research organization with no regulatory responsibility. It is headquartered in Reston, Virginia , with major offices near Lakewood, Colorado ; at the Denver Federal Center ; and in NASA Ames Research Park in California. In 2009, it employed about 8,670 people. The current motto of the USGS, in use since August 1997, is "science for

4418-473: The U.S. government are in the public domain , it is also possible to find many of these maps for free at various locations on the Internet. Georeferenced map images are available from the USGS as digital raster graphics (DRGs) in addition to digital data sets based on USGS maps, notably digital line graphs (DLGs) and digital elevation models (DEMs). In 2015, the USGS unveiled the topoView website,

4512-726: The U.S., U.S. Pacific Islands, and U.S. Caribbean deliver science that addresses resource management priorities of the states within their footprints. Since 1962, the Astrogeology Research Program has been involved in global, lunar , and planetary exploration and mapping . In collaboration with Stanford University , the USGS also operates the USGS-Stanford Ion Microprobe Laboratory, a world-class analytical facility for U-(Th)-Pb geochronology and trace element analyses of minerals and other earth materials. USGS operates

4606-933: The USGS Center for Coastal Geology) has three sites, one for the Atlantic Ocean (located in Woods Hole, Massachusetts ), one for the Pacific Ocean (located in Santa Cruz, California ) and one for the Gulf of Mexico (located on the University of South Florida's St. Petersburg campus). The goal of this department is to conduct research in geology, mapping, hydrology, biology, and related sciences; evaluate hazards associated with floods, droughts, hurricanes, subsidence, human activity, and climate change; map

4700-474: The USGS is the 1:250,000 scale topographic series. Each of these quadrangles in the conterminous United States measures 1 degree of latitude by 2 degrees of longitude. This series was produced by the U.S.  Army Map Service in the 1950s, prior to the maps in the larger-scale series, and consists of 489 sheets, each covering an area ranging from 8,218 square miles (21,285 km ) at 30° north to 6,222 square miles (16,115 km ) at 49° north. Hawaii

4794-520: The USGS to rely on donations of time by civilian volunteers in an attempt to update its 7.5-minute topographic map series, and USGS stated outright in 2000 that the program was to be phased out in favor of The National Map (not to be confused with the National Atlas of the United States produced by the Department of the Interior , one of whose bureaus is USGS). An older series of maps,

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4888-494: The United States under the umbrella of the Advanced National Seismic System (ANSS). The USGS informs authorities, emergency responders, the media, and the public, both domestic and worldwide, about significant earthquakes. It maintains long-term archives of earthquake data for scientific and engineering research. It also conducts and supports research on long-term seismic hazards . USGS has released

4982-912: The United States, with over 7400 streamgages . Real-time streamflow data are available online. As part of the Water Resources Research Act of 1984, the State Water Resources Research Act Program created a Water Resources Research Institute (WRRI) in each state, along with Washington DC, Puerto Rico, the US Virgin Islands, and Guam. Together, these institutes make up the National Institutes for Water Resources (NIWR). The institutes focus on water-related issues through research, training and collaboration. The National and regional Climate Adaptation Science Centers (CASCs)

5076-537: The beginning of the 20th century, advancement in geological science was facilitated by the ability to obtain accurate absolute dates to geological events using radioactive isotopes and other methods. This changed the understanding of geological time. Previously, geologists could only use fossils and stratigraphic correlation to date sections of rock relative to one another. With isotopic dates, it became possible to assign absolute ages to rock units, and these absolute dates could be applied to fossil sequences in which there

5170-1200: The campus of Alaska Pacific University ), the California Volcano Observatory in Menlo Park, California , the Cascades Volcano Observatory (covering volcanoes in Idaho , Oregon , and Washington ) in Vancouver, Washington , the Hawaiian Volcano Observatory in Hilo, Hawaii , and the Yellowstone Volcano Observatory (covering volcanoes in Arizona , Colorado , Montana , New Mexico , Utah , and Wyoming ) in Yellowstone National Park , Wyoming. The USGS Coastal and Marine Science Center (formerly

5264-499: The cirque that it barely makes any contribution to the west end of the Towle Glacier and arcuate supraglacial moraines remain drifting within the cirque. So named by a 1989-90 NZARP field party to describe the sluggish ice flow of this cirque. 76°36′S 160°30′E  /  76.600°S 160.500°E  / -76.600; 160.500 . A rocky ridge at the west side of Chattahoochee Glacier. It extends northward from

5358-422: The continental United States, though only for use by members of its defense forces). The next-smallest topographic series, in terms of scale, is the 1:100,000 series. These maps are bounded by two lines of longitude and two lines of latitude. However, in this series, the lines of latitude are spaced 30 minutes apart and the lines of longitude are spaced 60 minutes, which is the source of another name for these maps;

5452-515: The creation of topographic gradients, causing material on the rock unit that is increasing in elevation to be eroded by hillslopes and channels. These sediments are deposited on the rock unit that is going down. Continual motion along the fault maintains the topographic gradient in spite of the movement of sediment and continues to create accommodation space for the material to deposit. Deformational events are often also associated with volcanism and igneous activity. Volcanic ashes and lavas accumulate on

5546-437: The crust, the uplift of mountain ranges, and paleo-topography. Fractionation of the lanthanide series elements is used to compute ages since rocks were removed from the mantle. Other methods are used for more recent events. Optically stimulated luminescence and cosmogenic radionuclide dating are used to date surfaces and/or erosion rates. Dendrochronology can also be used for the dating of landscapes. Radiocarbon dating

5640-420: The distribution and severity of Shaking resulting from Earthquakes. The USGS produces several national series of topographic maps which vary in scale and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest (both in terms of scale and quantity) and best-known topographic series is the 7.5-minute, 1:24,000 scale, quadrangle ,

5734-483: The east part of Eastwind Ridge. Mapped by USGS from ground swveys and Navy air photos. Named by US-ACAN in 1964 for Captain Joseph Naab, Jr., USCG, commanding officer of the icebreaker Eastwind during 1961 and 1962. 76°37′S 160°51′E  /  76.617°S 160.850°E  / -76.617; 160.850 . A glacial cirque on the south wall of Eastwind Ridge immediately west of Mount Naab. Icefalls at

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5828-570: The fault is a normal fault or a thrust fault . The principle of inclusions and components states that, with sedimentary rocks, if inclusions (or clasts ) are found in a formation, then the inclusions must be older than the formation that contains them. For example, in sedimentary rocks, it is common for gravel from an older formation to be ripped up and included in a newer layer. A similar situation with igneous rocks occurs when xenoliths are found. These foreign bodies are picked up as magma or lava flows, and are incorporated, later to cool in

5922-403: The faults are not planar or because rock layers are dragged along, forming drag folds as slip occurs along the fault. Deeper in the Earth, rocks behave plastically and fold instead of faulting. These folds can either be those where the material in the center of the fold buckles upwards, creating " antiforms ", or where it buckles downwards, creating " synforms ". If the tops of the rock units within

6016-483: The folds remain pointing upwards, they are called anticlines and synclines , respectively. If some of the units in the fold are facing downward, the structure is called an overturned anticline or syncline, and if all of the rock units are overturned or the correct up-direction is unknown, they are simply called by the most general terms, antiforms, and synforms. Even higher pressures and temperatures during horizontal shortening can cause both folding and metamorphism of

6110-404: The formation of faults and the age of the sequences through which they cut. Faults are younger than the rocks they cut; accordingly, if a fault is found that penetrates some formations but not those on top of it, then the formations that were cut are older than the fault, and the ones that are not cut must be younger than the fault. Finding the key bed in these situations may help determine whether

6204-579: The geological history of the Earth as a whole. One aspect is to demonstrate the age of the Earth . Geology provides evidence for plate tectonics , the evolutionary history of life , and the Earth's past climates . Geologists broadly study the properties and processes of Earth and other terrestrial planets. Geologists use a wide variety of methods to understand the Earth's structure and evolution, including fieldwork , rock description , geophysical techniques , chemical analysis , physical experiments , and numerical modelling . In practical terms, geology

6298-598: The head provide the main ice flow into the Towle Glacier . One of the nautical names in Convoy Range. The name was applied by a 1989-90 NZARP field party to describe the fastest flowing tributary to Towle Glacier. 76°38′S 160°45′E  /  76.633°S 160.750°E  / -76.633; 160.750 . The westernmost cirque on Eastwind Ridge which is connected to the "dead" western terminus of Towle Glacier. So little ice from Eastwind Ridge enters

6392-423: The internal composition and structure of the Earth. Seismologists can use the arrival times of seismic waves to image the interior of the Earth. Early advances in this field showed the existence of a liquid outer core (where shear waves were not able to propagate) and a dense solid inner core . These advances led to the development of a layered model of the Earth, with a lithosphere (including crust) on top,

6486-464: The later end of the scale, it is marked by the present day (in the Holocene epoch ). The following five timelines show the geologic time scale to scale. The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon. The second timeline shows an expanded view of the most recent eon. In a similar way, the most recent era is expanded in

6580-488: The latitude of its represented location due to convergence of the meridians. At lower latitudes, near 30° north, a 7.5-minute quadrangle contains an area of about 64 square miles (166 km ). At 49° north latitude, 49 square miles (127 km ) are contained within a quadrangle of that size. As a unique non-metric map scale, the 1:24,000 scale naturally requires a separate and specialized romer scale for plotting map positions. In recent years, budget constraints have forced

6674-454: The lowest layer to deposition of the highest bed. The principle of faunal succession is based on the appearance of fossils in sedimentary rocks. As organisms exist during the same period throughout the world, their presence or (sometimes) absence provides a relative age of the formations where they appear. Based on principles that William Smith laid out almost a hundred years before the publication of Charles Darwin 's theory of evolution ,

6768-497: The mantle and show the crystallographic structures expected in the inner core of the Earth. The geological time scale encompasses the history of the Earth. It is bracketed at the earliest by the dates of the first Solar System material at 4.567 Ga (or 4.567 billion years ago) and the formation of the Earth at 4.54 Ga (4.54 billion years), which is the beginning of the Hadean eon  – a division of geological time. At

6862-405: The matrix. As a result, xenoliths are older than the rock that contains them. The principle of original horizontality states that the deposition of sediments occurs as essentially horizontal beds. Observation of modern marine and non-marine sediments in a wide variety of environments supports this generalization (although cross-bedding is inclined, the overall orientation of cross-bedded units

6956-545: The mission needs of the USGS. For instrument needs not currently met by a vendor, the Engineering Group designs, tests, and issues contracts to have HIF-designed equipment made. Sometimes HIF will patent a new design in the hope that instrument vendors will buy the rights and mass-produce the instrument at a lower cost to everyone. USGS researchers publish the results of their science in a variety of ways, including peer-reviewed scientific journals as well as in one of

7050-535: The national domain". The legislation also provided that the Hayden , Powell , and Wheeler surveys be discontinued as of June 30, 1879. Clarence King , the first director of USGS, assembled the new organization from disparate regional survey agencies. After two years, King was succeeded by John Wesley Powell . Geology Geology (from Ancient Greek γῆ ( gê )  'earth' and λoγία ( -logía )  'study of, discourse')

7144-465: The newest generation digital topo maps, including windmills, mines and mineshafts, water tanks, fence lines, survey marks, parks, recreational trails, buildings, boundaries, pipelines, telephone lines, power transmission lines, and even railroads. Additionally, the digital map's use of existing software may not properly integrate different feature classes or prioritize and organize text in areas of crowded features, obscuring important geographic details. As

7238-600: The north of Mount Naab at the northeast end of Eastwind Ridge. Named in association with Eastwind Ridge after Captain R.D. Schmidtman, United States Coast Guard (USCG), commander of the icebreaker USCGC Eastwind in the Ross Seas Ship Group in Operation Deep Freeze , 1960. 76°35′00″S 161°02′00″E  /  76.5833333°S 161.0333333°E  / -76.5833333; 161.0333333 A cirque between Mount Schmidtman and Mount Naab at

7332-431: The northeast end of Eastwind Ridge. Iceflow from Eastwind Ridge is insufficient to carry surficial moraine away into Fry Glacier and moraines lie in a tangled eddy. So named by New Zealand Geographic Board (NZGB) which also considered the name Eddy Cirque. 76°36′S 160°56′E  /  76.600°S 160.933°E  / -76.600; 160.933 . A mountain, 1,710 metres (5,610 ft) high, which surmounts

7426-621: The northwest end of the Convoy Range. Mapped by the USGS from ground surveys and Navy air photos. Named in 1964 by US-ACAN after the USS Wyandot, a cargo vessel in the American convoy to McMurdo Sound in several years beginning with the 1955–56 season. [REDACTED]  This article incorporates public domain material from websites or documents of the United States Geological Survey . United States Geological Survey The United States Geological Survey ( USGS ), founded as

7520-469: The onshore and offshore geologic framework; assess mineral resources and develop techniques for their discovery; assess water resources and develop an understanding of the impact of human activities and natural phenomena on hydrologic systems; assess links between biodiversity, habitat condition, ecosystem processes and health; and develop new technologies for collection and interpretation of earth science data. The USGS National Geomagnetism Program monitors

7614-413: The primary record of the majority of the geological history of the Earth. There are three major types of rock: igneous , sedimentary , and metamorphic . The rock cycle illustrates the relationships among them (see diagram). When a rock solidifies or crystallizes from melt ( magma or lava ), it is an igneous rock . This rock can be weathered and eroded , then redeposited and lithified into

7708-428: The primary topographic quadrangle for the state of Alaska (and only for that particular state). Nearly 3,000 maps cover 97% of the state. The United States remains virtually the only developed country in the world without a standardized civilian topographic map series in the standard 1:25,000 or 1:50,000 metric scales, making coordination difficult in border regions (the U.S. military does issue 1:50,000 scale topo maps of

7802-569: The principles of succession developed independently of evolutionary thought. The principle becomes quite complex, however, given the uncertainties of fossilization, localization of fossil types due to lateral changes in habitat ( facies change in sedimentary strata), and that not all fossils formed globally at the same time. Geologists also use methods to determine the absolute age of rock samples and geological events. These dates are useful on their own and may also be used in conjunction with relative dating methods or to calibrate relative methods. At

7896-423: The processes that have shaped that structure. Geologists study the mineralogical composition of rocks in order to get insight into their history of formation. Geology determines the relative ages of rocks found at a given location; geochemistry (a branch of geology) determines their absolute ages . By combining various petrological, crystallographic, and paleontological tools, geologists are able to chronicle

7990-428: The rocks. This metamorphism causes changes in the mineral composition of the rocks; creates a foliation , or planar surface, that is related to mineral growth under stress. This can remove signs of the original textures of the rocks, such as bedding in sedimentary rocks, flow features of lavas , and crystal patterns in crystalline rocks . Extension causes the rock units as a whole to become longer and thinner. This

8084-433: The simplified layered model with a much more dynamic model. Mineralogists have been able to use the pressure and temperature data from the seismic and modeling studies alongside knowledge of the elemental composition of the Earth to reproduce these conditions in experimental settings and measure changes within the crystal structure. These studies explain the chemical changes associated with the major seismic discontinuities in

8178-532: The southwestern United States, sedimentary, volcanic, and intrusive rocks have been metamorphosed, faulted, foliated, and folded. Even older rocks, such as the Acasta gneiss of the Slave craton in northwestern Canada , the oldest known rock in the world have been metamorphosed to the point where their origin is indiscernible without laboratory analysis. In addition, these processes can occur in stages. In many places,

8272-550: The subsurface. Sub-specialities of geology may distinguish endogenous and exogenous geology. Geological field work varies depending on the task at hand. Typical fieldwork could consist of: In addition to identifying rocks in the field ( lithology ), petrologists identify rock samples in the laboratory. Two of the primary methods for identifying rocks in the laboratory are through optical microscopy and by using an electron microprobe . In an optical mineralogy analysis, petrologists analyze thin sections of rock samples using

8366-407: The surface of the Earth and the convecting mantle is called plate tectonics . The development of plate tectonics has provided a physical basis for many observations of the solid Earth . Long linear regions of geological features are explained as plate boundaries: Plate tectonics has provided a mechanism for Alfred Wegener 's theory of continental drift , in which the continents move across

8460-488: The surface of the Earth over geological time. They also provided a driving force for crustal deformation, and a new setting for the observations of structural geology. The power of the theory of plate tectonics lies in its ability to combine all of these observations into a single theory of how the lithosphere moves over the convecting mantle. Advances in seismology , computer modeling , and mineralogy and crystallography at high temperatures and pressures give insights into

8554-479: The surface, and igneous intrusions enter from below. Dikes , long, planar igneous intrusions, enter along cracks, and therefore often form in large numbers in areas that are being actively deformed. This can result in the emplacement of dike swarms , such as those that are observable across the Canadian shield, or rings of dikes around the lava tube of a volcano. All of these processes do not necessarily occur in

8648-742: The surface. Igneous intrusions such as batholiths , laccoliths , dikes , and sills , push upwards into the overlying rock, and crystallize as they intrude. After the initial sequence of rocks has been deposited, the rock units can be deformed and/or metamorphosed . Deformation typically occurs as a result of horizontal shortening, horizontal extension , or side-to-side ( strike-slip ) motion. These structural regimes broadly relate to convergent boundaries , divergent boundaries , and transform boundaries, respectively, between tectonic plates. When rock units are placed under horizontal compression , they shorten and become thicker. Because rock units, other than muds, do not significantly change in volume , this

8742-407: The third timeline, the most recent period is expanded in the fourth timeline, and the most recent epoch is expanded in the fifth timeline. Horizontal scale is Millions of years (above timelines) / Thousands of years (below timeline) Epochs: Methods for relative dating were developed when geology first emerged as a natural science . Geologists still use the following principles today as

8836-615: Was datable material, converting the old relative ages into new absolute ages. For many geological applications, isotope ratios of radioactive elements are measured in minerals that give the amount of time that has passed since a rock passed through its particular closure temperature , the point at which different radiometric isotopes stop diffusing into and out of the crystal lattice . These are used in geochronologic and thermochronologic studies. Common methods include uranium–lead dating , potassium–argon dating , argon–argon dating and uranium–thorium dating . These methods are used for

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