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Blueschist on Île de Groix, France Photomicrograph of a thin section of blueschist facies metamorphosed basalt, from Sivrihisar, Turkey. Blueschist (/ ˈ b l uː ʃ ɪ s t /), also called glaucophane schist, is a metavolcanic rock [1] that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures (200–500 °C (392–932 °F ...
It is a grey basalt similar to Victorian bluestone, quarried near Timaru in the South Island. Bluestone from near Kokonga in Central Otago is also widely used, and is the main construction material (often with facing of Oamaru stone , a local compact limestone) in many of the notable historic buildings in the southern South Island, most of ...
However, some ocean island basalt locations coincide with plate boundaries like Iceland, which sits on top of a mid-ocean ridge, and Samoa, which is located near a subduction zone. [ 2 ] In the ocean basins, ocean island basalts form seamounts , [ 3 ] and in some cases, enough material is erupted that the rock protrudes from the ocean and forms ...
Flood basalts on Vancouver Island form a geologic formation called the Karmutsen Formation, which is perhaps the thickest accreted section of an oceanic plateau worldwide, exposing up to 6,000 m (20,000 ft) of basal sediment-sill complexes, basaltic to picritic pillow lavas, pillow breccia, and thick, massive basalt flows.
The island Lítla Dímun in the Faroes. The Faroe Islands lie on the Eurasian Plate between Scotland, Norway and Iceland. The islands are of volcanic origin and are made up of three layers of basalt, with the top and bottom layers resembling each other. The age of this rock is between 54 and 58 million years, with the oldest material at the ...
Metamorphic rocks are exposed near Stromness and Yesnaby on Mainland and on Graemsay. [1] Most of the basement consists of granitic gneisses and later minor intrusions.These rocks are similar to those exposed in northern Caithness and have been correlated with the Loch Eil Group of the late Proterozoic Loch Ness Supergroup sequence.
The breakup of Gondwana in the Mesozoic Era led to the formation of a large number of minor crustal fragments, including the Falkland Islands. At first, the fragment containing the islands separated from the southeastern part of Africa on a section that would become Antarctica and later rotated by almost 180°.
It is made of solid rock, mostly basalt and granite. The crust that lies below sea level is known as the oceanic crust, while on land it is known as the continental crust. The former is thinner and is composed of relatively dense basalt, while the latter is less dense and mainly composed of granite.