|
Adams Seamount
Adams Seamount (also known as Forty Mile Reef) is a submarine volcano above the Pitcairn hotspot in the central Pacific Ocean about southwest of Pitcairn Island. Geography and geomorphology Adams is part of a field of about 90 seamounts east-southeast away from Pitcairn Island, and the largest of these. Adams lies southeast of another large seamount, Bounty Seamount. Most of these seamounts except for Adams and Bounty are less than high. They were discovered in 1989 by the RV Sonne research ship. It is a conical seamount rising from the sea floor to about or below the surface of the ocean. The total volume of the seamount, whose base has a diameter of about , is about . Adams has two summits, and coral and sand derived from coral has been found on Adams. Given its height, during the last glacial maximum Adams was likely an island. Its slopes are covered by recent lava flows, volcanic debris and hyaloclastite. Lava flows feature aa lava characteristics and lava tubes, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continents of Asia and Oceania in the west and the Americas in the east. At in area (as defined with a southern Antarctic border), this largest division of the World Ocean—and, in turn, the hydrosphere—covers about 46% of Earth's water surface and about 32% of its total surface area, larger than Earth's entire land area combined .Pacific Ocean . '' Britannica Concise.'' 2008: Encyclopædia Britannica, Inc. The centers of both the |
Austral Hotspot
Austral means 'southern', often in reference to the Southern Hemisphere. Austral may also refer to: Businesses *Austral Líneas Aéreas, an Argentine airline * Air Austral, an airline based in Réunion *Austral (bus manufacturer), a defunct Australian bus body manufacturer Education * Austral University, a private university in Argentina *Universidad Austral de Chile, a Chilean traditional university Entertainment venues *Austral Picture Palace, Kilkenny, South Australia *Austral Picture Theatre, Collingwood, Victoria, Australia * Austral Theatre, Naracoorte, South Australia *The Austral, a pub in Rundle Street, Adelaide, South Australia Events *Austral Wheel Race, the world's oldest track bicycle race, held in Victoria, Australia *Australasian Intervarsity Debating Championships, a collegiate debating tournament also known as the "Australs" Places * Austral, New South Wales, a suburb of Sydney, Australia *Austral Islands, the southernmost group of islands in French Polynesi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coral Reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons that support and protect the coral. Most reefs grow best in warm, shallow, clear, sunny and agitated water. Coral reefs first appeared 485 million years ago, at the dawn of the Early Ordovician, displacing the microbial and sponge reefs of the Cambrian. Sometimes called ''rainforests of the sea'', shallow coral reefs form some of Earth's most diverse ecosystems. They occupy less than 0.1% of the world's ocean area, about half the area of France, yet they provide a home for at least 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrothermal
Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with the assistance of. Roderick McKenzie.'' Oxford: Clarendon Press. and θέρμη, ''heat'' ). Hydrothermal circulation occurs most often in the vicinity of sources of heat within the Earth's crust. In general, this occurs near volcanic activity, but can occur in the shallow to mid crust along deeply penetrating fault irregularities or in the deep crust related to the intrusion of granite, or as the result of orogeny or metamorphism. Seafloor hydrothermal circulation Hydrothermal circulation in the oceans is the passage of the water through mid-oceanic ridge systems. The term includes both the circulation of the well-known, high-temperature vent waters near the ridge crests, and the much-lower-temperature, diffuse flow of water through sedim ... [...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] |
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1. It is considered by some to be an interglacial period within the Pleistocene Epoch, called the Flandrian interglacial.Oxford University Press – Why Geography Matters: More Than Ever (book) – "Holocene Humanity" section https://books.google.com/books?id=7P0_sWIcBNsC The Holocene corresponds with the rapid proliferation, growth and impacts of the human species worldwide, including all of its written history, technological revolutions, development of major civilizations, and overall significant transition towards urban living in the present. The human impact on modern-era Earth and its ecosystems may be considered of global si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tholeiite
The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. Rock types of the tholeiitic magma series include tholeiitic basalt, ferro-basalt, tholeiitic basaltic andesite, tholeiitic andesite, dacite and rhyolite. The variety of basalt in the series was originally called ''tholeiite'' but the International Union of Geological Sciences recommends that ''tholeiitic basalt'' be used in preference to that term.Le Maitre ''et al.'' 2002 Tholeiitic rock types tend to be more enriched in iron and less enriched in aluminium than calc-alkaline rock types. They are thought to form in a less oxidized environment than calc-alkaline rocks. Tholeiitic basalt is formed at mid-ocean ridges and makes up much of the oceanic crust. Almost all the basalt found on the Moon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trachyte
Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and alkali metals. It is the volcanic equivalent of syenite. Trachyte is common wherever alkali magma is erupted, including in late stages of ocean island volcanismMacDonald 1983, pp. 51-52 and in continental rift valleys, above mantle plumes,Philpotts and Ague 2009, pp. 390-394 and in areas of back-arc extension. Trachyte has also been found in Gale crater on Mars. Trachyte has been used as decorative building stone and was extensively used as dimension stone in the Roman Empire and the Republic of Venice. Chemical composition Trachyte has a silica content of 60 to 65% and an alkali oxide content of over 7%. This gives it less SiO2 than rhyolite and more (Na2O plus K2O) than dacite. These chemical differences are consistent with the positio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkali Basalt
Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt is characterized by relatively high alkali (Na2O and K2O) content relative to other basalts and by the presence of olivine and titanium-rich augite in its groundmass and phenocrysts, and nepheline in its CIPW norm. Geochemical characterization Alkali basalt is chemically classified as a rock in region B (basalt) of the total alkali versus silica (TAS) diagram that contains nepheline in its CIPW norm. Basalts that do not contain normative nepheline are characterized as sub-alkali basalts, which include tholeiitic basalts and calc-alkaline basalts. Petrography The groundmass of alkali basalt is mainly composed of olivine, titanium-rich augite and plagioclase feldspar and may have alkali feldspar or feldspathoid interstitially, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet, dwarf planet, or natural satellite. It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be distinguished based on its phase (solid crust vs. liquid mantle). The crusts of Earth, Mercury, Venus, Mars, Io, the Moon and other planetary bodies formed via igneous processes and were later modified by erosion, impact cratering, volcanism, and sedimentation. Most terrestrial planets have fairly uniform crusts. Earth, however, has two distinct types: continental crust and oceanic crust. These two types have different chemical compositions and physical properties and were formed by different geological processes. Types of crust Planetary geologists divide crust into three categories based on how and when it formed. Primary crust / primordial crust This is a planet's "original" crust. It forms from solidification of a magma ocean. Towa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Society Hotspot
The Society hotspot is a volcanic hotspot in the south Pacific Ocean which is responsible for the formation of the Society Islands, an archipelago of fourteen volcanic islands and atolls spanning around 720 km of the ocean which formed between 4.5 and <1 Ma. There are currently two main hypotheses concerning the cause of volcanic activity. The conventional view is that the hotspot is underlain by a which has transported hot material from the lower mantle to the surface, creating the chain as the Pacific Plate has moved northwest over the plume. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Pacific Ocean")
.jpg "Click for more on -> Hydrothermal")
