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27-648: The Caroline plate was first proposed as a distinct plate by Weissel & Anderson 1978 . A separate terrane with its own tectonic history, the Caroline plate has been considered part of the Pacific plate because of sparse seismicity and low velocities along its boundaries. It includes the West and East Caroline basins and the inactive Eauripik Rise separating them, but neither the Caroline Islands nor

54-587: A larger plate, and is relatively buoyant due to thickness or low density. When the plate of which it was a part subducted under another plate, the terrane failed to subduct, detached from its transporting plate, and accreted onto the overriding plate. Therefore, the terrane transferred from one plate to the other. Typically, accreting terranes are portions of continental crust which have rifted off another continental mass and been transported surrounded by oceanic crust, or they are old island arcs formed at some distant subduction zones. A tectonostratigraphic terrane

81-627: A separate plate in the past. The boundary along its eastern side, the Mussau Trench, must have been an important boundary since magnetic anomalies on the Caroline plate are Oligocene but those on the Pacific plate Cretaceous. There are indications of spreading in the Caroline Sea 34–27 Ma. If the Caroline plate moved with the Pacific plate there should be clear evidences of a corresponding subduction beneath New Guinea, of which there

108-436: Is a fault-bounded package of rocks of at least regional extent characterized by a geologic history that differs from that of neighboring terranes. The essential characteristic of these terranes is that the present spatial relations are incompatible with the inferred geologic histories. Where terranes that lie next to each other possess strata of the same age, they are considered separate terranes only if it can be demonstrated that

135-527: Is a planet's "original" crust. It forms from solidification of a magma ocean. Toward the end of planetary accretion , the terrestrial planets likely had surfaces that were magma oceans. As these cooled, they solidified into crust. This crust was likely destroyed by large impacts and re-formed many times as the Era of Heavy Bombardment drew to a close. The nature of primary crust is still debated: its chemical, mineralogic, and physical properties are unknown, as are

162-407: Is also an older usage of the term terrane , which described a series of related rock formations or an area with a preponderance of a particular rock or rock group. A tectonostratigraphic terrane did not necessarily originate as an independent microplate , since it may not contain the full thickness of the lithosphere . It is a piece of crust that has been transported laterally, usually as part of

189-495: Is debated. The anorthosite highlands of the Moon are primary crust, formed as plagioclase crystallized out of the Moon's initial magma ocean and floated to the top; however, it is unlikely that Earth followed a similar pattern, as the Moon was a water-less system and Earth had water. The Martian meteorite ALH84001 might represent primary crust of Mars; however, again, this is debated. Like Earth, Venus lacks primary crust, as

216-496: Is needed to create tertiary crust, and Earth is the only planet in the Solar System with plate tectonics. Earth's crust is a thin shell on the outside of Earth, accounting for less than 1% of Earth's volume. It is the top component of the lithosphere , a division of Earth's layers that includes the crust and the upper part of the mantle . The lithosphere is broken into tectonic plates that move, allowing heat to escape from

243-716: Is the boundary of the Caroline plate with the North Bismarck plate , which is believed to be a relic plate currently moving with the Pacific plate. Beyond the North Bismarck plate to the south is an area with currently actively independently moving microplates such as the South Bismarck plate , the Solomon Sea plate and the Woodlark plate . The Caroline plate moves at velocities very close to those of

270-632: Is virtually none. The Ayu Trough is a slow spreading zone that opened 15 Ma. Before about 6 million years ago as the Ontong Java Plateau and Indo-Australian plate collided the Bismarck Sea was initially formed as a back-arc basin behind the New Britain arc, and after the collision, a transpressional zone developed in what is now the west Bismarck Sea, associated with subduction of the Caroline plate and North Bismarck plate at

297-710: The Caroline Ridge . It is subducting under the Bird's Head and the plates or blocks associated with the present Australian plate along the New Guinea Trench to the south. The boundary with the Philippine Sea to the west has two segments: the southern segment, the Ayu Trough was spreading at a rate of 8 mm/yr c.  25–2 Ma but has been slowing down since. The northern segment,

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324-529: The Palau and southern Yap trenches, is not an active subduction zone as indicated by the lack of active volcanoes . The Caroline- Pacific boundary is a complex, evolving system partly and potentially developing into a subduction zone. The south-east boundary, along the Manus Trench , is a convergent boundary, but in the absence of active volcanoes and earthquakes, is not a subduction zone at present. This

351-473: The adiabatic rise of mantle causes partial melting. Tertiary crust is more chemically-modified than either primary or secondary. It can form in several ways: The only known example of tertiary crust is the continental crust of the Earth. It is unknown whether other terrestrial planets can be said to have tertiary crust, though the evidence so far suggests that they do not. This is likely because plate tectonics

378-925: The crust is the outermost solid shell of a 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. Planetary geologists divide crust into three categories based on how and when it formed. This

405-925: The orogenic belt where they had eventually ended up. It followed that the present orogenic belt was itself an accretionary collage, composed of numerous terranes derived from around the circum- Pacific region and now sutured together along major faults. These concepts were soon applied to other, older orogenic belts, e.g. the Appalachian belt of North America.... Support for the new hypothesis came not only from structural and lithological studies, but also from studies of faunal biodiversity and palaeomagnetism . When terranes are composed of repeated accretionary events, and hence are composed of subunits with distinct history and structure, they may be called superterranes . Africa Asia Taiwan Tibet Australasia Europe Fennoscandia North America South America Crust (geology) In geology ,

432-482: The Caroline Ridge, however, is, although of uncertain origin, made of oceanic crust and probably the product of a hotspot. The presence of a trench and indications of subduction beneath the Pacific plate is suggestive but the absence of island arcs, which could be expected from substantial subduction in the past, makes the development along this boundary unclear. The Caroline plate was, under all circumstances,

459-468: The New Guinea Trench. Terrane In geology , a terrane ( / t ə ˈ r eɪ n , ˈ t ɛr eɪ n / ; in full, a tectonostratigraphic terrane ) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured " to crust lying on another plate. The crustal block or fragment preserves its distinctive geologic history, which is different from

486-606: The Pacific plate and its age of formation and current status as an independent plate are uncertain. There is a very slow rate of spreading between the Caroline and Philippine plates but the Caroline plate apparently moved together with both the Philippine and New Guinea plates during the Neogene. The Caroline Ridge, to the north, meets the Caroline plate at the Sorol Trough at which there some evidence of oblique extension;

513-413: The ability of crustal fragments to "drift" thousands of miles from their origin and attach themselves, crumpled, to an exotic shore. Such terranes were dubbed " accreted terranes " by geologists . Geologist J. N. Carney writes: It was soon determined that these exotic crustal slices had in fact originated as "suspect terranes" in regions at some considerable remove, frequently thousands of kilometers, from

540-423: The crust ranges between about 20 and 120 km. Crust on the far side of the Moon averages about 12 km thicker than that on the near side . Estimates of average thickness fall in the range from about 50 to 60 km. Most of this plagioclase-rich crust formed shortly after formation of the Moon, between about 4.5 and 4.3 billion years ago. Perhaps 10% or less of the crust consists of igneous rock added after

567-453: The entire planet has been repeatedly resurfaced and modified. Secondary crust is formed by partial melting of mostly silicate materials in the mantle, and so is usually basaltic in composition. This is the most common type of crust in the Solar System. Most of the surfaces of Mercury, Venus, Earth, and Mars comprise secondary crust, as do the lunar maria . On Earth secondary crust forms primarily at mid-ocean spreading centers , where

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594-463: The formation of the initial plagioclase-rich material. The best-characterized and most voluminous of these later additions are the mare basalts formed between about 3.9 and 3.2 billion years ago. Minor volcanism continued after 3.2 billion years, perhaps as recently as 1 billion years ago. There is no evidence of plate tectonics . Study of the Moon has established that a crust can form on a rocky planetary body significantly smaller than Earth. Although

621-428: The geologic evolutions are different and incompatible. There must be an absence of intermediate lithofacies that could link the strata. The concept of tectonostratigraphic terrane developed from studies in the 1970s of the complicated Pacific Cordilleran orogenic margin of North America , a complex and diverse geological potpourri that was difficult to explain until the new science of plate tectonics illuminated

648-491: The igneous mechanisms that formed them. This is because it is difficult to study: none of Earth's primary crust has survived to today. Earth's high rates of erosion and crustal recycling from plate tectonics has destroyed all rocks older than about 4 billion years , including whatever primary crust Earth once had. However, geologists can glean information about primary crust by studying it on other terrestrial planets. Mercury's highlands might represent primary crust, though this

675-416: The interior of Earth into space. A theoretical protoplanet named " Theia " is thought to have collided with the forming Earth, and part of the material ejected into space by the collision accreted to form the Moon. As the Moon formed, the outer part of it is thought to have been molten, a " lunar magma ocean ". Plagioclase feldspar crystallized in large amounts from this magma ocean and floated toward

702-444: The surface. The cumulate rocks form much of the crust. The upper part of the crust probably averages about 88% plagioclase (near the lower limit of 90% defined for anorthosite ): the lower part of the crust may contain a higher percentage of ferromagnesian minerals such as the pyroxenes and olivine , but even that lower part probably averages about 78% plagioclase. The underlying mantle is denser and olivine-rich. The thickness of

729-409: The surrounding areas—hence the term "exotic" terrane. The suture zone between a terrane and the crust it attaches to is usually identifiable as a fault . A sedimentary deposit that buries the contact of the terrane with adjacent rock is called an overlap formation . An igneous intrusion that has intruded and obscured the contact of a terrane with adjacent rock is called a stitching pluton . There

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