Baltic Ice Lake
The Baltic Ice Lake is a name given by geologists to a freshwater lake that evolved in the Baltic Sea basin as glaciers retreated from that region at the end of the last ice age. The lake's existence was first understood in 1894. The lake existed between about 16,000 and 11,700 years ago with well defined evidence from the warming of the Bølling–Allerød Interstadial to the period of cooling called the Younger Dryas before the Holocene, the onset of which is close in time to the end of the ice lake. The lake drained into the raising world ocean on two occasions and when water levels became the same on the second, with a sea level passage in the Billingen region of southern Sweden, it became the Yoldia Sea. Phenomena related to ice lake and sea formation The term lake is used to mean a body of primarily fresh water. A sea is filled with brackish or salt water. In the history of the Baltic Sea, the distinction is not always clear. Salinity has varied with location, depth and ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Billingen
Billingen is the largest of the thirteen mesas in the Swedish county of Västra Götaland, with a maximum altitude of . The mesa extends in a north-southerly direct with a length of and a width of . Billingen is divided into two parts by an east–west valley between Skövde and Varnhem. The mesa plateau is covered with vast forests and moorlands, including the nature reserve Blängsmossen with its unique flora. The limestone at Billingen has been quarried for a long time for concrete manufacturing; diabase is also still quarried there. The mesa, located between the two great lakes Vänern and Vättern, is also a popular nature resort with several nearby hotels, and an annual orienteering tournament is held here. [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Isostasy
Isostasy (Greek wikt:ἴσος, ''ísos'' 'equal', wikt:στάσις, ''stásis'' 'standstill') or isostatic equilibrium is the state of gravity, gravitational mechanical equilibrium, equilibrium between Earth's crust (geology), crust (or lithosphere) and mantle (geology), mantle such that the crust (geology), crust "floats" at an elevation that depends on its thickness and density. This concept is invoked to explain how different topographic heights can exist at Earth's surface. Although originally defined in terms of continental crust and mantle, it has subsequently been interpreted in terms of lithosphere and asthenosphere, particularly with respect to oceanic island volcanoes, such as the Hawaiian Islands. Although Earth is a dynamic system that responds to loads in many different ways, isostasy describes the important limiting case in which crust and mantle are in static equilibrium. Certain areas (such as the Himalayas and other convergent margins) are not in isostatic equili ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Boreal (age)
In paleoclimatology of the Holocene, the Boreal was the first of the Blytt–Sernander sequence of north European climatic phases that were originally based on the study of Danish peat bogs, named for Axel Blytt and Rutger Sernander, who first established the sequence. In peat bog sediments, the Boreal is also recognized by its characteristic pollen zone. It was preceded by the Younger Dryas, the last cold snap of the Pleistocene, and followed by the Atlantic, a warmer and moister period than our most recent climate. The Boreal, transitional between the two periods, varied a great deal, at times having within it climates like today's. Subdividing the Boreal Subsequent to the original Blytt-Sernander scheme, the first stage of the Boreal was divided off as a Pre-boreal transitional phase, followed by the Boreal proper. Some current schemes based on pollen zones also distinguish a pre-Boreal (pollen zone IV), an early Boreal (pollen zone V) and a late Boreal (pollen zone VIa, ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Henrik Munthe
Henrik Vilhelm Munthe (1 November 1860 – 15 August 1958) was a Swedish geologist. Biography Munthe became a student in 1882 and in 1892 a doctor of philosophy and associate professor of geology at Uppsala University, where he was acting professor of mineralogy and geology in 1894–96. In 1898 he was appointed and in 1899 regular geologist at the Swedish Geological Survey (SGU). In the years 1904-13 he was secretary of the Geological Society in Stockholm. Munthe received the title of professor in 1917. He was elected to the Royal Swedish Academy of Sciences in 1928. His research centered on the Quaternary geology of the Baltic Sea region, nevertheless he did also some contributions on the Silurian stratigraphy of Västergötland and Gotland. Having begun his career using bicycles to survey the terrain Munthe continued to advocate using bicycle well after survey by car had become commonplace. A Gotlänning ("Gotlander") by birth Munthe's dialect is reported to have been Gotlä ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Dendrochronology
Dendrochronology (or tree-ring dating) is the scientific method of chronological dating, dating tree rings (also called growth rings) to the exact year they were formed in a tree. As well as dating them, this can give data for dendroclimatology, the study of climate and atmospheric conditions during different periods in history from the wood of old trees. Dendrochronology derives from the Ancient Greek (), meaning "tree", (), meaning "time", and (), "the study of". Dendrochronology is useful for determining the precise age of samples, especially those that are too recent for radiocarbon dating, which always produces a range rather than an exact date. However, for a precise date of the death of the tree a full sample to the edge is needed, which most trimmed timber will not provide. It also gives data on the timing of events and rates of change in the environment (most prominently climate) and also in wood found in archaeology or works of art and architecture, such as old pane ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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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]   |
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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]   |
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Askja
Askja () is an active volcano situated in a remote part of the central highlands of Iceland. The name Askja refers to a complex of nested calderas within the surrounding Dyngjufjöll mountains, which rise to , ''askja'' meaning ''box'' or ''caldera'' in Icelandic. Geography The Askja central volcano is in diameter and is associated with the Askja volcanic system which has a long fissure swarm that extends north from beneath the Vatnajökull glacier towards the north coast of Iceland. The Hrúthálsar area which is to the north-east is now usually regarded as part of the system. The outer caldera of Askja, representing a prehistoric eruption, is about in area, and there is evidence of other later caldera-forming events within it. These include the main summit caldera, that is about in diameter, to its north-east the diameter Kollur caldera, and the 1875 Öskjuvatn caldera with a diameter of about . The main crater floor lies at about . The central volcano region i ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Before Present
Before Present (BP) or "years before present (YBP)" 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 1January 1950 as the commencement date (epoch) of the age scale, with 1950 being labelled as the "standard year". 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 account for when using radiocarbon dating for dates of origin that may fall after this year. 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 s ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Varve
A varve is an annual layer of sediment or sedimentary rock. The word 'varve' derives from the Swedish word ''varv'' whose meanings and connotations include 'revolution', 'in layers', and 'circle'. Of the many rhythmites in the geological record, varves are one of the most important and illuminating in studies of past climate change. Varves are amongst the smallest-scale events recognised in stratigraphy. An annual layer can be highly visible because the particles washed into the layer in the spring when there is greater flow strength are much coarser than those deposited later in the year. This forms a pair of layers—one coarse and one fine—for each annual cycle. Varves form only in fresh or brackish water, because the high levels of salt in normal sea water coagulate the clay into coarse grains. Since the saline waters leave coarse particles all year, it is nearly impossible to distinguish the individual layers in salt waters. Indeed, clay flocculation occurs at high ioni ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Iron(II) Sulfide
Iron(II) sulfide or ferrous sulfide (Br.E. sulphide) is one of a family of chemical compounds and minerals with the approximate chemical formula, formula . Iron sulfides are often iron-deficient non-stoichiometric. All are black, water-insoluble solids. Preparation and structure FeS can be obtained by the heating of iron and sulfur: :Fe + S → FeS FeS adopts the nickel arsenide structure, featuring octahedral molecular geometry, octahedral Fe centers and trigonal prismatic sulfide sites. Reactions Iron sulfide reacts with hydrochloric acid, releasing hydrogen sulfide: :FeS + 2 HCl → FeCl2 + H2S :FeS + H2SO4 → FeSO4 + H2S In moist air, iron sulfides oxidize to hydrated ferrous sulfate. Biology and biogeochemistry Iron sulfides occur widely in nature in the form of iron–sulfur proteins. As organic matter decays under low-oxygen (or Hypoxia (environmental), hypoxic) conditions such as in swamps or Dead zone (ecology), dead zones of lakes and oceans, sul ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Invertebrates
Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum Vertebrata, i.e. vertebrates. Well-known phyla of invertebrates include arthropods, molluscs, annelids, echinoderms, flatworms, cnidarians, and sponges. The majority of animal species are invertebrates; one estimate puts the figure at 97%. Many invertebrate taxa have a greater number and diversity of species than the entire subphylum of Vertebrata. Invertebrates vary widely in size, from 10 μm (0.0004 in) myxozoans to the 9–10 m (30–33 ft) colossal squid. Some so-called invertebrates, such as the Tunicata and Cephalochordata, are actually sister chordate subphyla to Vertebrata, being more closely related to vertebrates than to other invertebrates. This makes the "invertebrates" paraphyletic, so the term has ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |