del dine oplevelser ved Isua Grønland
share your experiences at Isua Greenland
The remote 3.7-3.8 billion year old rock sequence at Isua represents the oldest known and most complete fragment of early Archaean crust, making it one of the prime astrobiological destinations on our planet. A large variety of rocks - including Banded Iron Formation (BIF), conglomerates and a variety of volcanics - lie exposed to scientists interested in studying conditions on the early Earth. The Isua rocks form a 1-3 km thick, ~35 km long arcuate belt opening towards the north. The western and eastern limbs of the arc are separated in the center by a large lake, fed by melt water from the spectacular ice-sheet that covers most of Greenland and forms the eastern and northern boundary of the Isua belt. A 1-hour helicopter trip through steep-sided fiords to the west brings you to the nearest airport, at the town of Nuuk. Stock up on food, or enjoy a beer with local fisherman and try to stay out of fights at one of Nuuk�s many pubs.
Unfortunately, the majority of Isua rocks have been affected by severe changes in pressure and temperature - or metamorphism - following their deposition ~3.7 billion years ago. Another complication to their interpretation is widespread deformation through faulting and folding. However, most geologists agree that the Isua rocks were deposited on the surface of primordial oceanic crust, under a deep liquid-water ocean. Keep an eye out for pillow-basalt: ancient lava that cooled rapidly when it first came into contact with colder ocean water. Of particular interest to astrobiologists is whether the Isua rocks contain evidence of life. Although no undisputed fossils have been found at Isua, some workers argue that 13C/12C isotope ratios of graphite in some sedimentary rocks at Isua provide evidence for biological fractionation. Such claims are hard to validate without the presence of sedimentary limestone co-existing with the supposedly biogenic graphite. Active research is continuing to try to find other proxies for life in the most ancient surface rocks on our planet.
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