The Acasta Gneiss is a rockoutcrop of Archaeantonalitegneiss in the Northwest Territories, Canada. It is the oldest known crustal rock outcrop in the world. The Acasta Gneiss is named for the nearby Acasta River east of Great Slave Lake some 350 km north of Yellowknife. The rock exposed in the outcrop formed just over four billion (4 x 109) years ago; an age based on radiometric dating of zircon crystals. Sedimentary, volcanic, plutonic, metamorphic rock types of North America. ... Outcrop is a geological term referring to the appearance of bedrock exposed at the surface of the Earth. ... The Archean is a geologic eon; it is a somewhat antiquated term for the time span between 2500 million years before the present and 3800 million years before the present. ... Tonalite is an igneous, plutonic (intrusive) rock, of felsic composition, with phaneritic texture. ... Banded gneiss with dike of granite orthogneiss Gneiss is a common and widely distributed type of rock formed by high grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. ... Motto: None Other Canadian provinces and territories Capital Yellowknife Largest city Yellowknife Commissioner Tony Whitford Premier Joe Handley (Consensus government - no party affiliations) Area 1,346,106 km² (3rd) Land 1,183,085 km² Water 163,021 km² (12. ... ... Template:Hide = Motto: Template:Unhide = Multum In Parvo (Much In Little) City of Yellowknife, Northwest Territories, Canadas Location. ... Radiometric dating is a technique used to date materials based on a knowledge of the decay rates of naturally occurring isotopes, and the current abundances. ... Zircon is a mineral belonging to the group of nesosilicates. ...
In 2003 a team from the Smithsonian Institute collected a four-tonne boulder of Acasta Gneiss for display outside the National Museum of the American Indian in Washington, D.C. The Smithsonian castle, as seen through the garden gate. ... National Museum of the American Indian in Washington D.C., viewed from the northeast Interior view looking down toward the entrance. ... ...
The Acasta outcrop is found in a remote area of the Tlicho land settlement. The Tli Cho (Tłįchǫ) First Nation, formerly known as the Dogrib, are an Aboriginal Canadian people living in the Northwest Territories (NWT). ...
External links
Ancient rock begins pilgrimage to museum
ANCIENT CONTINENT OPENS WINDOW ON THE EARLY EARTH Science, December 17,1999
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks.
Gneisses that are metamorphosed igneous rocks or their equivalent are termed granite gneisses, diorite gneisses, etc. However, depending on their composition, they may also be called garnet gneiss, biotite gneiss, albite gneiss, etc. Orthogneiss designates a gneiss derived from an igneous rock, and paragneiss is one from a sedimentary rock.
A coarse-grained gneiss, probably originated from metamorphism of igneous granite, whith characteristics elliptic or lenticular feldspaths, normally microcline, contrasting with the ribbon shape of the quartz, biotite and magnetite clusters.
Feeds |
Contact