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D'Entrecasteaux Ridge
The d'Entrecasteaux () Ridge (DER) is a double oceanic ridge in the south-west Pacific Ocean, north of New Caledonia and west of Vanuatu Islands. It forms the northern extension of the New Caledonia– Loyalty Islands arc, and is now actively subducting in the Vanuatu subduction zone under the Vanuatu/New Hebrides arc. The subduction of the DER is responsible for the anomalous morphology of the central part of New Hebrides arc whose movement more closely matches the north-east direction of the subducting Australian Plate (the rest of the New Hebrides arc rotate west in front of the southward expanding North Fiji Basin). The name honours French naval officer Antoine Bruni d'Entrecasteaux, explorer of the south-west Pacific in the late 18th century. Geological setting The DER extends north from the New Caledonia ridge to the New Hebrides/Vanuatu Trench and thus separates the North Loyalty Basin ( ) to the south from the West Santos Basin ( bsl) to the north. The DER has a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oceanic Ridge
A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin. The production of new seafloor and oceanic lithosphere results from mantle upwelling in response to plate separation. The melt rises as magma at the linear weakness between the separating plates, and emerges as lava, creating new oceanic crust and lithosphere upon cooling. The first discovered mid-ocean ridge was the Mid-Atlantic Ridge, which is a spreading center that bisects the North and South Atlantic basins; hence the origin of the name 'mid-ocean ridge'. Most oceanic spreading centers are not in the middle of their hosting ocean basis but regardless, are traditionally called mid-ocean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seamount
A seamount is a large submarine landform that rises from the ocean floor without reaching the water surface (sea level), and thus is not an island, islet, or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to in height. They are defined by oceanographers as independent features that rise to at least above the seafloor, characteristically of conical form.IHO, 2008. Standardization of Undersea Feature Names: Guidelines Proposal form Terminology, 4th ed. International Hydrographic Organization and Intergovernmental Oceanographic Commission, Monaco. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea. During their evolution over geologic time, the largest seamounts may reach the sea surface where wave action erodes the summit to form a flat surface. After they have subsided and sunk below the sea surface, such flat-top ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial planet, rocky planet or natural satellite, moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of volcanism on Venus, Venus, which cover ~80% of the surface, are basaltic; the lunar mare, lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars. Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geology Of New Caledonia
The geology of New Caledonia includes all major rock types (igneous rock, igneous, Sedimentary rock, sedimentary, and Metamorphic rock, metamorphic), which here range in age from ~290 million years old (Ma) to recent. Their formation is driven by alternate plate collisions and rifting. The Mantle (geology), mantle-derived Eocene Peridotite Nappe is the most significant and widespread unit (labelled as "Ophiolites" and coloured in bright green in Fig. 1). The igneous unit consists of ore-rich ultramafic rocks Thrust fault, thrust onto the main island. Mining of valuable metals from this unit has been an economical pillar of New Caledonia for more than a century. New Caledonia is located on the Indo-Australian Plate and the largely submerged continent of Zealandia. After New Zealand, it is the second-largest subaerial landmass, and the northernmost part of this continent. As shown on the map, the landmass is elongated in a NW-SE orientation, which is similar to the distribution patte ... [...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 magma series, 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, Basaltic andesite, tholeiitic basaltic andesite, 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 magnesium and 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 m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eocene
The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes from the Ancient Greek (''Ēṓs'', 'Eos, Dawn') and (''kainós'', "new") and refers to the "dawn" of modern ('new') fauna that appeared during the epoch.See: *Letter from William Whewell to Charles Lyell dated 31 January 1831 in: * From p. 55: "The period next antecedent we shall call Eocene, from ήως, aurora, and χαινος, recens, because the extremely small proportion of living species contained in these strata, indicates what may be considered the first commencement, or ''dawn'', of the existing state of the animate creation." The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isoto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
New Hebrides
New Hebrides, officially the New Hebrides Condominium () and named after the Hebrides in Scotland, was the colonial name for the island group in the South Pacific Ocean that is now Vanuatu. Native people had inhabited the islands for three thousand years before the first Europeans arrived in 1606 from a Spanish expedition led by Portuguese navigator Pedro Fernandes de Queirós. The islands were named by Captain James Cook in 1774 and subsequently colonised by both the British and the French. The two countries eventually signed an agreement making the islands an Anglo-French condominium that provided for joint sovereignty over the archipelago with two parallel administrations, one British, one French. In some respects, that divide continued even after independence, with schools teaching in either one language or the other. The condominium lasted from 1906 until 1980, when New Hebrides gained its independence as the Republic of Vanuatu. Politics and economy The New Hebrides ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oceanic Trench
Oceanic trenches are prominent, long, narrow topography, topographic depression (geology), depressions of the seabed, ocean floor. They are typically wide and below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about of oceanic trenches worldwide, mostly around the Pacific Ocean, but also in the eastern Indian Ocean and a few other locations. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of below sea level. Oceanic trenches are a feature of the Earth's distinctive plate tectonics. They mark the locations of convergent boundary, convergent plate boundaries, along which lithosphere, lithospheric plates move towards each other at rates that vary from a few millimeters to over ten centimeters per year. Oceanic lithosphere moves into trenches at a global rate of about per year. A trench marks the position at which the flexed, subduction, subducting slab (geology), slab begins to d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The name Oligocene was coined in 1854 by the German paleontologist Heinrich Ernst Beyrich from his studies of marine beds in Belgium and Germany. The name comes from Ancient Greek (''olígos'') 'few' and (''kainós'') 'new', and refers to the sparsity of Neontology, extant forms of Mollusca, molluscs. The Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period. The Oligocene is often considered an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Major chang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende. Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Geology of Mars, Martian crust. The name ''andesite'' is derived from the Andes mountain range, where this rock type is found in abundance. It was first applied by Christian Leopold von Buch in 1826. Description Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" because it has 18% fewer modern marine invertebrates than the Pliocene has. The Miocene followed the Oligocene and preceded the Pliocene. As Earth went from the Oligocene through the Miocene and into the Pliocene, the climate slowly cooled towards a series of ice ages. The Miocene boundaries are not marked by distinct global events but by regionally defined transitions from the warmer Oligocene to the cooler Pliocene Epoch. During the Early Miocene, Afro-Arabia collided with Eurasia, severing the connection between the Mediterranean and Indian Oceans, and allowing the interchange of fauna between Eurasia and Africa, including the dispersal of proboscideans and Ape, hominoids into Eurasia. During the late Miocene, the conn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
