The acasta Gneisses is a Tonalite Gneiss type of rock. by john madkiff on Prezi
The oldest rocks on Earth found so far are the Acasta Gneisses in by a number of radiometric dating methods and the consistency of the. The Acasta Gneiss is a tonalite gneiss in the Slave craton in Northwest Territories , Canada. However, the dating method used did not involve similar radiometric dating of zircon crystals and it remains somewhat contentious whether the. Gneiss is a widely distributed type of metamorphic rock. Also, using a radiometric dating technique, researchers have identified the Acasta.
Jeff is extremely knowledgeable and enthusiastic about geology, and in the course of cramming a semester's worth of geology into the two hour lab, he mentioned that he had in his office one of the oldest rocks in the world: After finishing his talk about the rock cycle, and as everyone began examining the variety of rock types spread out on lab tables in several rooms, Jeff brought out the chunk of ancient gneiss for everyone to see.
Found on an island in the extreme and very isolated northern regions of Canada's Northwest Territories, the Acasta gneiss has been radiometrically dated to be upwards to 4.
That's a number that's not very easy to comprehend. The Earth itself is estimated to be just a half-billion years older, so the Acasta gneiss pronounced nice is some of the very earliest crustal rock still existing on Earth's ever-changing surface.
Gneiss - New World Encyclopedia
For a rock unit to withstand 4 billion years of the rock cycle - where the forces of erosion and plate tectonics are constantly at work wearing down, reworking and remelting rocks - that's quite a feat if you think about it. To give you a better idea of the vast amount of time we're talking about here, let's first reduce it to a more comprehendible time-frame. You'd still be watching it inwhen non-avian dinosaurs suddenly go extinct about three-and-a-half weeks before the end of the video. We modern humans wouldn't appear for the first time until sometime in the show's last couple hours.
Acasta gneiss outcrop location: The exposure is about miles north of the town of Yellowknife in Canada's Northwest Territories.
The ancient gneiss is named after the Acasta River, located east of Great Bear Lakewhere the outcrop was first found in the s.
The exposure is about kilometers miles from Yellowknifeso the only practical way to get there is by float plane. Composed mostly of the minerals quartz and feldsparthe Acasta gneiss was formed during the Hadeanthe earliest eon in Earth's history.
Its composition leads geologists to surmise that it was probably formed from highly metamorphosed granite subjected to unimaginable heat and pressure.
The exact origin of that granite is unknown, but its presence indicates continental crust and surface water were probably already present in those very ancient times. Answering Creationist Claims Part 9b - Evidence for a 4. It occurs in igneous, metamorphic, and sedimentary rocks. Zircons are able to survive geologic processes such as transport, erosion, even metamorphism recrystallizationare chemically inert and they have much to tell about the geologic processes that occurred in history.
While this is still under debate within the scientific community, it nevertheless provides an exciting point of view. Note the oscillatory zoning in the outer rim. Image by John W.
Acasta Gneiss - Wikipedia
The Acasta Gneiss Complex - 4. Dated to be at about 4.
A zircon dated 4. On the weight of evidence from other studies in the area, I would still consider that 3. The Nuvvuagittuq greenstone belt Dammit, why is it so hard to pronounce? Nevertheless, should overwhelming evidence arise for the 4.
Evidence from Meteorites Despite being so old, rocks and minerals still do not tell us when was the formation of the Earth.