What defines a back arc region?
The back-arc region is the area behind a volcanic arc. In island volcanic arcs, it consists of back-arc basins of oceanic crust with abyssal depths, which may be separated by remnant arcs, similar to island arcs.
What causes back arc spreading?
A back-arc basin is formed by the process of back-arc spreading, which begins when one tectonic plate subducts under (underthrusts) another. Subduction creates a trench between the two plates and melts the mantle in the overlying plate, which causes magma to rise toward the surface.
What is a back arc spreading center?
: a geological region that forms at a subduction zone when the overriding plate thins and begins to spread out —often used before another noun The hot springs there are not connected at all to the midocean ridge system: they lie on what is called a back-arc spreading center, a geologic feature that occurs not where two …
What is Forearc Ridge?
A forearc is the region between an oceanic trench and the associated volcanic arc. Forearc regions are found at convergent margins, and include any accretionary wedge and forearc basin that may be present.
What are the controls on back-arc deformation?
To briefly summarize, if back-arc deformation and trench motion are dominantly controlled by the abso- lute motion of the upper plate with respect to a more or less fixed trench, we might expect that: (1) upper plate retreat is preferentially associated with back-arc exten- sion and vice-versa for compression; (2) Vd …
How does a forearc basin form?
Forearc basins typically develop along continental margins and island arcs where oceanic plates are subducting beneath the overriding crust.
What is a foreland basin in geology?
[ fôr′lənd ] A low-lying region that is adjacent and parallel to a mountain belt formed as the result of the collision of tectonic plates.
How are island arcs formed?
oceanic arcs form when oceanic crust subducts beneath other oceanic crust on an adjacent plate, creating a volcanic island arc. (Not all island arcs are volcanic island arcs.) continental arcs form when oceanic crust subducts beneath continental crust on an adjacent plate, creating an arc-shaped mountain belt.
What is a strike slip basin?
Strike-slip basins. Strike-slip faults can accommodate localized compression or extension at continental margins, in island arcs, and also within continents. Sedimentary basins commonly develop where the fault kinematics are divergent with respect to the plate vector along strike-slip faults.
What is the difference between a rift basin and a foreland basin?
Foreland basins represent an endmember basin type, the other being rift basins. Space for sediments (accommodation space) is provided by loading and downflexure to form foreland basins, in contrast to rift basins, where accommodation space is generated by lithospheric extension.
What are the four parts of a foreland basin?
(C) Schematic cross-section depicting a revised concept of a foreland basin system, with the wedge-top, foredeep, forebulge and back-bulge depozones shown at approximately true scale.
What boundary causes island arcs?
Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries (such as the Ring of Fire). Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle along the subduction zone.
What is oblique slip fault?
A fault that has a component of dip-slip and a component of strike-slip movement is termed an oblique-slip fault. Nearly all faults will have some component of both dip-slip and strike-slip, so a fault that is classified as oblique requires both dip and strike components to be significant and measurable.
What is cratonic basin?
Summary. Cratonic basins are sites of prolonged, broadly distributed but slow subsidence of the continental lithosphere, and are commonly filled with shallow water and terrestrial sedimentary rocks. They remain poorly understood geodynamically.
What is a Retroarc foreland basin?
Retroarc (Retro) foreland basins, which occur on the plate that overrides during plate convergence or collision (i.e. situated behind the magmatic arc that is linked with the subduction of oceanic lithosphere) Examples include the Andean basins, or Late Mesozoic to Cenozoic Rocky Mountain Basins of North America.
What’s a foreland?
foreland in British English 1. a headland, cape, or coastal promontory. 2. land lying in front of something, such as water.
Why is Hawaii not an island arc?
Not all volcanic chains are island arcs, however, and not all island arcs are “islands”. For example, the Hawaiian Islands are an example of a linear chain of volcanoes in the middle of the Pacific Ocean that is not an island arc.
Is Japan an island arc?
The Japanese island arcs are the best-studied example of an arc-trench system in the western Pacific (Sugimura & Uyeda 1973). The arcs consist of four segments: the western Kuril, Honshu, Ryukyu, and Izu-Bonin (Ogasawara) arcs (Figure 1c).
How island arcs are formed?
Island arcs form when one oceanic plate subducts beneath another. When the ocean basin is closed, or subduction ceases, the volcanoes in the island arc become extinct.
What is the depth of compression in CPR?
The depth of compression is different between adults and children. Since the update to the CPR guidelines in 2015, the depth of chest compressions shifted from 2 inches, to 2-2.4 inches deep. You’ll do these compressions at a rate of 100-120 compressions per minute, on the sternum in the center of the chest.
What is the depth of compression ratio for a child’s chest?
The depth of compression ratio for a child is at least one third the depth of the chest which is about 2 inches or 5 cm. The depth of compression ratio for an adult is at least 2 inches which is 5 cm, all with a rate of 100-120 per minute.
What is the target compression rate for chest compressions?
Allow the chest to fully recoil after each compression. Target compression rate is: The compression to ventilation radio (i.e. 15:2, 30:2) is best defined as 15/30 compressions to 2 seconds pause, to facilitate ventilation. Recommence CPR at 2-3 seconds regardless and do not wait for 2 breaths to be completed.
How do you perform a compression exercise?
Compressions are to be performed with the heel of one hand (2) in the centre of the chest. Utilise the two handed technique (3) with hands positioned in the centre of the chest. Compression depth is approximately ⅓ the depth of the chest.