Hiawatha Glacier

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Hiawatha Glacier
Hiawatha Glacier.jpg
Land-terminating Hiawatha Glacier (left-center) emerging from its semicircular parent ice lobe, in NW Greenland
Coordinates78°49′N 67°01′W / 78.817°N 67.017°W / 78.817; -67.017Coordinates: 78°49′N 67°01′W / 78.817°N 67.017°W / 78.817; -67.017

Hiawatha Glacier is a glacier in northwest Greenland, near Inglefield Land.[1][2] It was mapped in 1922 by Lauge Koch, who noted that the glacier tongue extended into Lake Alida (near Foulk Fjord).[3] Hiawatha Glacier attracted attention in 2018 because of the discovery of an impact crater beneath the surface of the ice sheet in the area.[4] A publication noted in 1952 that Hiawatha Glacier is retreating since 1920.[5]

Impact crater[edit]

Two views of the Hiawatha crater region—one covered by the Greenland Ice Sheet, the other showing the topography of the rock beneath the ice sheet, including the crater
Hiawatha Glacier Crater
Hiawatha Crater
Hiawatha v45 scene1 4k 5mtopo.1760.tif
A still image showing the ice sheet removed in the region around the Hiawatha Glacier and the bed topography under the ice clearly showing the Hiawatha crater
Impact crater/structure
ConfidenceConfirmed[6]
Diameter31 kilometers (19 mi)
Depth320 meters (1,050 ft)
Impactor diameter1.5 kilometers (0.9 mi)
Ageunknown
Exposedno
Drilledno
Bolide typeIron meteorite
Location
Coordinates78°44′N 66°14′W / 78.733°N 66.233°W / 78.733; -66.233
CountryGreenland
ProvinceAvannaata
Hiawatha Glacier Crater is located in Greenland
Hiawatha Glacier Crater
Hiawatha Glacier Crater
Accessnone

In November 2018, a study revealed the existence of a large impact crater beneath Greenland's ice sheet in the Hiawatha Glacier region—a 31-kilometre-wide (19 mi) circular bedrock depression up to a kilometre below the surface of the ice.[6] The evidence suggests that the crater was created after ice covered Greenland three million years ago, and perhaps as recently as 12,000 years ago.[7][8]

From an interpretation of the crystalline nature of the underlying rock, together with chemical analysis of sediment washed from the crater, the impactor was estimated to be an iron meteorite with a diameter in the order of 1.5 kilometres (0.9 mi). A volume of approximately 20 cubic kilometres (4.8 cu mi) of rock would have been either vaporized or melted. It is one of the twenty-five largest impact craters on Earth.[6]

Cape York meteorite[edit]

The Agpalilik meteorite outside the University of Copenhagen Geological Museum

Before the crater was discovered, the Inuit had found iron meteorites in the region. In 1957 an American surveyor found a 48-kilogram (106 lb) meteorite, and in 1963 Vagn F. Buchwald found the 20-ton Agpalilik meteorite (a fragment of the Cape York meteorite) on a nunatak near Moltke Glacier, which is on the Agpalilik peninsula in the Thule district of northwest Greenland.[9][10]

It has been suggested that the Cape York meteorite is part of the main object responsible for creating the Hiawatha crater. Estimates of the Hiawatha impact's age (which is still being studied), along with other indicators, suggest that the crater may be connected with the so-called Younger Dryas impact hypothesis. However, unless the impact's age is determined with greater precision, which would require drilling one km (3,300 ft) into the ice sheet above the crater to obtain a ice core sample, such a suggestion is considered speculation.[11]

Pleistocene craters[edit]

The Hiawatha crater is estimated to be between 12,000 to 3 million years old[7][8] which is the Pleistocene (11,700 ya to 2.58 Mya) and part of the Pliocene (2.58 to 5.33 Mya). But it is not yet officially in the Earth Impact Database (EID).

The largest confirmed crater in the EID within the last 5 million years, where both size and age are confirmed, is Elgygytgyn (18 km (11 mi)) which is smaller than Hiawatha crater. However, there are larger impact events within these two epochs where either the size or age is uncertain:

Name Location Diameter Age
(million years)
Karakul crater Tajikistan 52 km (32 mi) < 5?[12]
Eltanin impact Pacific Ocean 35 km (22 mi)? 2.5
Australasian strewnfield unknown 30–100 km (19–62 mi)? 0.780
Hiawatha crater Greenland 31 km (19 mi) 2.6 – 0.0117[4]

See also[edit]

References[edit]

  1. ^ Dawes; et al. (2000). "Kane Basin 1999: mapping, stratigraphic studies and economic assessment of Precambrian and Lower Palaeozoic provinces in north-western Greenland" (PDF). p. 11.
  2. ^ "Hiawatha Gletscher: Greenland". Geographical Names. Retrieved November 15, 2018.
  3. ^ Davies, William E.; Krinsley, Daniel B. (1962). "The recent regimen of the ice cap margin in North Greenland" (PDF). International Association of Scientific Hydrology, Commission of Snow and Ice. p. 124.
  4. ^ a b St. Fleur, Niocholas (November 14, 2018). "Ice Age Asteroid Crater Discovered Beneath Greenland Glacier - It is the first impact crater discovered under one of Earth's ice sheets, according to the scientists who found it". The New York Times. Retrieved November 18, 2018.
  5. ^ Børge Fristrup (1952). "Die Klimaänderungen in der Arktis und ihre Bedeutung besonders für Grönland". Erdkunde. doi:10.3112/erdkunde.1952.04.01.
  6. ^ a b c Kjær, Kurt H.; et al. "A large impact crater beneath Hiawatha Glacier in northwest Greenland". doi:10.1126/sciadv.aar8173. Retrieved November 15, 2018.
  7. ^ a b Michelle Starr. "A Massive Geological Surprise Has Been Discovered Under Greenland's Ice Sheet". ScienceAlert. Retrieved November 15, 2018.
  8. ^ a b Brian Clark Howard. "City-size impact crater found under Greenland ice". National Geographic. Retrieved November 16, 2018.
  9. ^ Derek W. G. Sears (2014). "Oral histories in meteoritics and planetary science—XXV: Vagn F. Buchwald". Meteoritics & Planetary Science. 49 (7): 1271–1287. doi:10.1111/maps.12332.
  10. ^ "Discovery of Cape York (Apalilik) Iron Meteorite, Northwest Greenland" (PDF). Meteoritical Bulletin. The Permanent Commission on Meteorites of the International Geological Congress (28): 3. 1963.
  11. ^ "Greenland ice sheet hides huge 'impact crater'". BBC. Retrieved November 15, 2018.
  12. ^ "Kara-Kul". Earth Impact Database. University of New Brunswick. Retrieved 2009-08-15.

External links[edit]