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Mazama Ash
The Mazama Ash (formally named the Mazama Member in some areas) is an extensive, geologically recent deposit of volcanic ash that is present throughout much of northern North America. The ash was ejected from Mount Mazama, a volcano in south-central Oregon, during its climactic eruption about 7640 ± 20 years ago when Crater Lake was formed by caldera collapse. The ash spread primarily to the north and east due to the prevailing winds, and remnants of the ash have been identified as far northeast as the Greenland ice sheet.Zdanowicz, C.M., Zielinski, G.A. and Germani, M.S. 1999. Mount Mazama eruption: Calendrical age verified and atmospheric impact assessed. Geology, vol. 27, no. 7, p. 621-624. Because it was deposited throughout a wide area at a known time, the Mazama Ash is an important marker bed for paleoclimatology, paleoecology, and archaeology, as well as for Quaternary geology and stratigraphic correlation.Spano, N.G., Lane, C.S., Francis, S.W. and Johnson, T.C. 2017. Disc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Member (stratigraphy)
A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize it. Units must be ''mappable'' and ''distinct'' from one another, but the contact need not be particularly distinct. For instance, a unit may be defined by terms such as "when the sandstone component exceeds 75%". Lithostratigraphic units Sequences of sedimentary and volcanic rocks are subdivided the basis of their shared or associated lithology. Formally identified lithostratigraphic units are structured in a hierarchy of lithostratigraphic rank, higher rank units generally comprising two or more units of lower rank. Going from smaller to larger in rank, the main lithostratigraphic ranks are Bed, Member, Formation, Group and Supergroup. Formal names of lithostratigraphic units are assigned by geological surveys. Units of formation or hi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeology
Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, sites, and cultural landscapes. Archaeology can be considered both a social science and a branch of the humanities. It is usually considered an independent academic discipline, but may also be classified as part of anthropology (in North America – the four-field approach), history or geography. Archaeologists study human prehistory and history, from the development of the first stone tools at Lomekwi in East Africa 3.3 million years ago up until recent decades. Archaeology is distinct from palaeontology, which is the study of fossil remains. Archaeology is particularly important for learning about prehistoric societies, for which, by definition, there are no written records. Prehistory includes over 99% of the human past, from the Paleolithic until the adven ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Mazama Eruption Timeline
Mount is often used as part of the name of specific mountains, e.g. Mount Everest. Mount or Mounts may also refer to: Places * Mount, Cornwall, a village in Warleggan parish, England * Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, Cornwall, England * Mounts, Indiana, a community in Gibson County, Indiana, United States People * Mount (surname) * William L. Mounts (1862–1929), American lawyer and politician Computing and software * Mount (computing), the process of making a file system accessible * Mount (Unix), the utility in Unix-like operating systems which mounts file systems Displays and equipment * Mount, a fixed point for attaching equipment, such as a hardpoint on an airframe * Mounting board, in picture framing * Mount, a hanging scroll for mounting paintings * Mount, to display an item on a heavy backing such as foamcore, e.g.: ** To pin a biological specimen, on a heavy backing in a stretched stable position for ease of dissection or display ** To ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Superior
Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh water. The northern and westernmost of the Great Lakes of North America, it straddles the Canada–United States border with the province of Ontario to the north and east, and the states of Minnesota to the northwest and Wisconsin and Michigan to the south. It drains into Lake Huron via St. Marys River, then through the lower Great Lakes to the St. Lawrence River and the Atlantic Ocean. Name The Ojibwe name for the lake is ''gichi-gami'' (in syllabics: , pronounced ''gitchi-gami'' or ''kitchi-gami'' in different dialects), meaning "great sea". Henry Wadsworth Longfellow wrote this name as "Gitche Gumee" in the poem ''The Song of Hiawatha'', as did Gordon Lightfoot in his song " The Wreck of the ''Edmund Fitzgerald''". According to oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Core Sample
A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The hole made for the core sample is called the "core hole". A variety of core samplers exist to sample different media under different conditions. More continue to be invented on a regular basis. In the coring process, the sample is pushed more or less intact into the tube. Removed from the tube in the laboratory, it is inspected and analyzed by different techniques and equipment depending on the type of data desired. Core samples can be taken to test the properties of manmade materials, such as concrete, ceramics, some metals and alloys, especially the softer ones. Core samples can also be taken of living things, including human beings, especially of a person's bones for microscopic examination to help diagnose diseases. Methods The compo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenland Ice Sheet Project
The Greenland Ice Sheet Project (GISP) was a decade-long project to drill ice cores in Greenland that involved scientists and funding agencies from Denmark, Switzerland and the United States. Besides the U.S. National Science Foundation (NSF), funding was provided by the Swiss National Science Foundation and the Danish Commission for Scientific Research in Greenland. The ice cores provide a proxy archive of temperature and atmospheric constituents that help to understand past climate variations. The preliminary GISP field work started in 1971 at Dye 3 (), where a 372 meter deep, 10.2 cm diameter core was recovered. After this, annual field expeditions were carried out to drill intermediate depth cores at various locations on the ice sheet. The first was a 398 m core at Milcent and another was a 405 m core at the Crete station in 1974. After working out various logistical and engineering problems related to the development of a more sophisticated drilling rig, drilling to bed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Core
An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ice formed over a range of years. Cores are drilled with hand augers (for shallow holes) or powered drills; they can reach depths of over two miles (3.2 km), and contain ice up to 800,000 years old. The physical properties of the ice and of material trapped in it can be used to reconstruct the climate over the age range of the core. The proportions of different oxygen and hydrogen isotopes provide information about ancient temperatures, and the air trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such as carbon dioxide. Since heat flow in a large ice sheet is very slow, the borehole temperature is another indicator of temperature in the past. These data can be combined to find the climate model ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific Northwest
The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common conception includes the U.S. states of Oregon, Washington (state), Washington, and Idaho, and the Canadian province of British Columbia. Some broader conceptions reach north into Alaska and Yukon, south into northern California, and east into western Montana. Other conceptions may be limited to the coastal areas west of the Cascade Mountains, Cascade and Coast Mountains, Coast mountains. The variety of definitions can be attributed to partially overlapping commonalities of the region's history, culture, geography, society, ecosystems, and other factors. The Northwest Coast is the coastal region of the Pacific Northwest, and the Northwest Plateau (also commonly known as "British Columbia Interi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tephra
Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they remain as tephra unless hot enough to fuse into pyroclastic rock or tuff. Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which paleoenvironmental or archaeological records can be placed. When a volcano explodes, it releases a variety of tephra including ash, cinders, and blocks. These layers settle on the land and, over time, sedimentation occurs incorporating these tephra layers into the geologic record. Often, when a volcano explodes, biological organisms are killed and their remains are buried within the tephra layer. These fossils are later dated by scientists to determine the age of the fossil and its place within the geolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Era
Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the original Anno Domini (AD) and Before Christ (BC) notations used for the same calendar era. The two notation systems are numerically equivalent: " CE" and "AD " each describe the current year; "400 BCE" and "400 BC" are the same year. The expression traces back to 1615, when it first appeared in a book by Johannes Kepler as the la, annus aerae nostrae vulgaris (), and to 1635 in English as " Vulgar Era". The term "Common Era" can be found in English as early as 1708, and became more widely used in the mid-19th century by Jewish religious scholars. Since the later 20th century, BCE and CE have become popular in academic and scientific publications because BCE and CE are religiously neutral terms. They are used by others who wish to be sensit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Before Present
Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date (epoch) of the age scale. The abbreviation "BP" has been interpreted retrospectively as "Before Physics", which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must now account for. In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation RCYBP stands for the explicit "radio carbon years before present". Usage The BP scale is sometimes used for dates established by means other than radiocarbon dating, such as stratigraphy. This usage differs from t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiocarbon Calibration
Radiocarbon dating measurements produce ages in "radiocarbon years", which must be converted to calendar ages by a process called calibration. Calibration is needed because the atmospheric / ratio, which is a key element in calculating radiocarbon ages, has not been constant historically.Taylor (1987), p. 133. Willard Libby, the inventor of radiocarbon dating, pointed out as early as 1955 the possibility that the ratio might have varied over time. Discrepancies began to be noted between measured ages and known historical dates for artefacts, and it became clear that a correction would need to be applied to radiocarbon ages to obtain calendar dates. Uncalibrated dates may be stated as "radiocarbon years ago", abbreviated "ya". The term Before Present (BP) is established for reporting dates derived from radiocarbon analysis, where "present" is 1950. Uncalibrated dates are stated as "uncal BP", and ''calibrated'' (corrected) dates as "cal BP". Used alone, the term BP is amb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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