olelog

RedOrbit regularly posts satellite images of the day. I have the impression that it is mostly more than one image per day. Thank You RedOrbit. They often give new insights in larger geological structures. On 13 February 2008 they posted an image of the Pingualuit Meteorite Crater

The Pingualuit Crater was created 1.4 ± 0.1 million years ago (Pleistocene) by a meteorite impact. The 3.4-km diameter crater rises 160 m above the surrounding tundra and is 400 m deep. On the bottom of the crater, a lake with a measured depth of 267 m, contains some of the purest water in the world. The lake has no inlets or apparent outlets, so the water accumulates from rain and snow and is only lost through evaporation. The residence time of the water in the lake has been estimated at 330 years. It has a salinity level of less than 3 parts per million. In terms of transparency, it is second only to Lake Masyuko in Japan. It is one of the youngest and best-preserved craters in the world.

During World War II (in 1943), the singular landmark was noted by Allied pilots ferrying planes north and eastwards to Europe. Fred Chubb, a diamond prospector, visited the crater in July 1950 and the crater was subsequently identified as the "Chubb Crater". In the summer of 1951, the National Geographic Society and the Royal Ontario Museum lead the first scientific expedition to the crater. In 1968, it was renamed "Cratère du Nouveau-Québec" (New Quebec Crater ) by the Quebec government. Then in 1999, the name was changed to "Pingualuit", which means "where the land rises" in the local Inuit language. The crater and surrounding area is now a Provincial Park. Having a surface area of 1,133.9 km2, this park was officially created on 1 January 2004. The park’s main characteristic is the Pingualuit crater.

Recognising Pingualuit Crater’s unique characteristics - the lake has no surface connection to other surrounding water bodies - a research team from the University of Arkansas collected samples of the lake’s sediments, paying special attention to diatoms. Communities of these single-celled, silica-shelled algae change in response to environmental changes, including changes in climate. Deep within the crater’s lake sediments, the research team found two separate layers of diatoms and other organic material that indicate they were created during relatively warm conditions. The layers probably dated back before the Holocene Epoch — the geologic time period that covers Earth’s history since the end of the Pleistocene Ice Age about 10 thousand years ago. In short, the team’s findings suggested that at two different times before the Holocene Epoch, the area around Pingualuit Crater enjoyed ice-free conditions.

• http://www.unb.ca/passc/ImpactDatabase/images/new-quebec.htm
• http://www.redorbit.com/images/images-of-the-day/img/18878/pingualuit_crater_canada/index.html?source=r_earthiod
• http://www.ottawa.rasc.ca/articles/odale_chuck/earth_craters/pingualuit/index.html
• http://www.bivouac.com/MtnPg.asp?MtnId=4469
• http://www.sciencedaily.com/releases/2007/12/071215212916.htm
• http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17919
• http://dailyheadlines.uark.edu/11974.htm

The 40-km-diameter Mjølnir Crater is one of the best-preserved marine impact craters on Earth. It became interpreted as an impact structure in 1993. The structure is located in the central Barents Sea at latitude 73° 48´N, longitude 29° 40´E below ice-free waters. it is formed by the impact of an asteroid about 142 million years ago.

Drilling of the Mjølnir Crater - in The Mjølnir Scientific Drilling Project - has increased and will further increase our understanding of marine impacts and impact-induced processes along with the post-impact development of the Arctic.

More information about the Mjølnir impact crater is found at http://folk.uio.no/ftsikala/mjolnir/#mjolnir_english