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Tephrochronology
250px, Tephra horizons in south-central Iceland. The thick and light coloured layer at the height of the volcanologist's hands is rhyolitic tephra from Hekla. Tephrochronology is a Geochronology, geochronological technique for dating archaeological, geological and palaeoenvironmental sequences and events by their location between upper and lower layers of tephra (volcanic ejecta) of known date, and for correlating such sequences and events at separate locations between the same layers. The premise of the technique is that each volcanic event produces a "tephra horizon", a layer of ash with a unique chemical "fingerprint" that allows the deposit to be identified across the area affected by fallout. Thus, once the volcanic event has been independently dated, the tephra horizon will act as time marker. It is a variant of the basic geological technique of stratigraphy. The main advantages of the technique are that the volcanic ash layers can be relatively easily identified in many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Tephrochronology Iceland
image:Icelandic tephra.JPG, 250px, Tephra horizons in south-central Iceland. The thick and light coloured layer at the height of the volcanologist's hands is rhyolitic tephra from Hekla. Tephrochronology is a Geochronology, geochronological technique for dating archaeological, geological and palaeoenvironmental sequences and events by their location between upper and lower layers of tephra (volcanic ejecta) of known date, and for correlating such sequences and events at separate locations between the same layers. The premise of the technique is that each volcanic event produces a "tephra horizon", a layer of ash with a unique chemical "fingerprint" that allows the deposit to be identified across the area affected by fallout. Thus, once the volcanic event has been independently dated, the tephra horizon will act as time marker. It is a variant of the basic geological technique of stratigraphy. The main advantages of the technique are that the volcanic ash layers can be relatively e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Tephra Layer
Tephra is fragmental material produced by a Volcano, 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. 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. Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which Paleoecology, paleoenvironmental or Archaeology, archaeological records can be placed. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Geochronology
Geochronology is the science of Chronological dating, determining the age of rock (geology), rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is provided by tools such as paleomagnetism and stable isotope ratios. By combining multiple geochronological (and biostratigraphic) indicators the precision of the recovered age can be improved. Geochronology is different in application from biostratigraphy, which is the science of assigning sedimentary rocks to a known geological period via describing, cataloging and comparing fossil floral and faunal assemblages. Biostratigraphy does not ''directly'' provide an absolute age determination of a rock, but merely places it within an ''interval'' of time at which that fossil assemblage is known to have coexisted. Both disciplines work together hand in hand, however, to the point where they share the same syste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Volcanic Ash
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer to all explosive eruption products (correctly referred to as '' tephra''), including particles larger than 2 mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. The force of the gases shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. Once in the air, ash is transported by wind up to thousands of kilometres away. Due to its wide dispersal, ash can have a number of impacts on society, including animal a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Santorini
Santorini (, ), officially Thira (, ) or Thera, is a Greek island in the southern Aegean Sea, about southeast from the mainland. It is the largest island of a small, circular archipelago formed by the Santorini caldera. It is the southernmost member of the Cyclades group of islands, with an area of approximately and a 2021 census population of 15,480. The municipality of Santorini includes the inhabited islands of Santorini and Therasia, and the uninhabited islands of Nea Kameni, Palaia Kameni, Aspronisi, Anydros, and Christiana. The total land area is . Santorini is part of the Thira regional unit. It is the most active volcanic centre in the South Aegean Volcanic Arc. The volcanic arc is approximately long and wide. The region first became volcanically active around 3–4 million years ago, though volcanism on Thera began around 2 million years ago with the extrusion of dacitic lavas from vents around Akrotiri. One of the largest volcanic eruptions in reco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Laacher See
Laacher See (), also known as Lake Laach or Laach Lake, is a volcanic Volcanic crater lake, caldera lake with a diameter of in Rhineland-Palatinate, Germany, about northwest of Koblenz, south of Bonn, and west of Andernach. It is in the Eifel mountain range, and is part of the East Eifel volcanic field within the larger Volcanic Eifel. The lake was formed by a Plinian eruption approximately 13,000 years Before Present, BP with a Volcanic Explosivity Index (VEI) of 6, on the same scale as the Mount Pinatubo#1991 eruption, Pinatubo eruption of 1991. The Volcanic gas, volcanic discharge observable as mofettas on the southeastern shore of the lake is a sign of Dormant volcano, dormant volcanism. Description The lake is oval in shape and surrounded by high banks. The lava was quarried for millstones from the Roman period until the introduction of iron rollers for grinding grain. The water level has considerable rises and falls as the lake has no natural outlet. On the western side ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Eifel
The Eifel (; , ) is a low mountain range in western Germany, eastern Belgium and northern Luxembourg. It occupies parts of southwestern North Rhine-Westphalia, northwestern Rhineland-Palatinate and the southern area of the German-speaking Community of Belgium. The Eifel is part of the Rhenish Massif; within its northern portions lies the Eifel National Park. The Eifelian stage in geological history is named after the region because rocks of that period reach the surface in the Eifel at the Wetteldorf Richtschnitt outcrop. The inhabitants of the Eifel are known as Eiflers or Eifelers. Geography Location The Eifel lies between the cities of Aachen to the north, Trier to the south and Koblenz to the east. It descends in the northeast along a line from Aachen via Düren to Bonn into the Lower Rhine Bay. In the east and south it is bounded by the valleys of the Rhine and the Moselle. To the west it transitions in Belgium and Luxembourg into the geologically related Ardenn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Vesuvius
Mount Vesuvius ( ) is a Somma volcano, somma–stratovolcano located on the Gulf of Naples in Campania, Italy, about east of Naples and a short distance from the shore. It is one of several volcanoes forming the Campanian volcanic arc. Vesuvius consists of a large volcanic cone, cone partially encircled by the steep rim of a summit caldera, resulting from the collapse of an earlier, much higher structure. The eruption of Mount Vesuvius in 79 AD destroyed the Roman Empire, Roman cities of Pompeii, Herculaneum, Oplontis, Stabiae and other settlements. The eruption ejected a cloud of Volcanic rock, stones, Volcanic ash, ash and volcanic gases to a height of , Volcanic eruption, erupting Lava, molten rock and pulverized pumice at the rate of per second. More than 1,000 people are thought to have died in the eruption, though the exact toll is unknown. The only surviving witness account consists of two letters by Pliny the Younger to the historian Tacitus. Vesuvius has erupted ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Hekla
Hekla (), or Hecla, is an active stratovolcano in the south of Iceland with a height of . Hekla is one of Iceland's most active volcanoes; over 20 eruptions have occurred in and around the volcano since the year 1210. During the Middle Ages, the Icelandic Norse called the volcano the "Gateway to Hell" and the idea spread over much of Europe. The volcano's frequent large and often initially explosive eruptions have covered much of Iceland with tephra, and these layers can be used to date eruptions of Iceland's other volcanoes. Approximately 10% of the tephra created in Iceland in the last thousand years has come from Hekla, amounting to . Cumulatively, the volcano has produced one of the largest volumes of lava of any in the world in the last millennium, around . Etymology In Icelandic language, Icelandic ''Hekla'' is the word for a short hooded cloak, which may relate to the frequent cloud cover on the summit. An early Latin source refers to the mountain as ''Mons chasuble, Cas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Icelandic Tephra
Icelandic refers to anything of, from, or related to Iceland and may refer to: *Icelandic people *Icelandic language *Icelandic orthography *Icelandic cuisine See also * Icelander (other) * Icelandic Airlines, a predecessor of Icelandair * Icelandic horse, a breed of domestic horse * Icelandic sheep, a breed of domestic sheep * Icelandic Sheepdog, a breed of domestic dog * Icelandic cattle Icelandic cattle ( ) are a breed of cattle native to Iceland. Cattle were first brought to the island during the Settlement of Iceland a thousand years ago. Icelandic cows are an especially colorful breed with a wide variety of colours and marki ..., a breed of cattle * Icelandic chicken, a breed of chicken {{disambig Language and nationality disambiguation pages ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Hayes Volcano
Hayes Volcano is a stratovolcano in southwestern Matanuska-Susitna Borough, Alaska, 135 km northwest of Anchorage, that was not discovered until 1975. It is responsible for a series of six major tephra layers in the Cook Inlet region of Alaska. Hayes was mostly destroyed by at least six catastrophic eruptions between 3,400 and 3,800 years ago, and the average volume of these eruptions was 2.4 cubic km. In comparison, the volume of the May 18, 1980 eruption of Mount St. Helens was about 1 cubic km. The eruptions of Hayes Volcano during that time were the most voluminous Holocene eruptions to have occurred in the Cook Inlet region. There is currently no fumarolic activity present. The last eruption of Hayes Volcano occurred roughly 1,200 years ago. It is named after the adjacent Hayes Glacier. Physical setting Hayes Volcano is an ice-shrouded, glacially scoured eruptive center of Quaternary age composed of pyroclastic deposits, volcanic breccia, and lava domes. Althoug ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Palynology
Palynology is the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur in sediments, sedimentary rocks, and even some metasedimentary rocks. Palynomorphs are the microscopic, acid-resistant organic remains and debris produced by a wide variety of plants, animals, and Protista that have existed since the late Proterozoic.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds., 2005, ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. It is the science that studies contemporary and fossil palynomorphs (paleopalynology), including pollen, spores, orbicules, dinocysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter (POM) and kerogen found in sedimentary rocks and sediments. Palynology does not include diatoms, foraminiferans or other organisms with siliceous or calcareous tests. The name of the science and o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
