Hiawatha Glacier is a glacier in northwest

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

, with its terminus in

Inglefield Land Inglefield Land is an unglaciated area along the northwestern coast of Greenland. It was named after English explorer Edward Augustus Inglefield. History Inglefield Land is noted for its archaeological sites, which show evidence of occupation by ...

. It was mapped in 1922 by

Lauge Koch Lauge Koch (5 July 1892 – 5 June 1964) was a Danish geologist and Arctic explorer. Biography Lauge Koch was born in 1892 to Karl and Elisabeth Koch. His development as a scientist was greatly influenced by his father's second cousin Johan Pet ...

, who noted that the glacier tongue extended into Lake Alida (near

Foulk Fjord Foulk Fjord is a fjord in Avannaata municipality in northwestern Greenland. Geography Located near Reindeer Point, the fjord is about wide and several miles long with cliffs on each side. Brother John's Glacier terminates at the eastern end of ...

). Hiawatha Glacier attracted attention in 2018 because of the discovery of a

crater Crater may refer to: Landforms *Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet *Explosion crater, a hole formed in the ground produced by an explosion near or below the surfac ...

beneath the surface of the

ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at Las ...

in the area. A publication noted in 1952 that Hiawatha Glacier had been retreating since 1920. __TOC__

Impact structure

In November 2018, a study revealed the existence of a large () circular depression beneath Greenland's ice sheet in the Hiawatha Glacier region—up to a kilometre below the surface of the ice. The

bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...

within the region of this structure consists of 1.985 to 1.740 billion year old

Paleoproterozoic The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6 Ga), is the first of the three sub-divisions (eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's ...

felsic In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted with mafic rocks, whi ...

igneous Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...

rocks and

paragneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...

. From an interpretation of the crystalline nature of the underlying rock, together with chemical analysis of sediment washed from the crater, the impactor was argued to be a metallic asteroid with a diameter in the order of . A volume of approximately of rock would have been either vaporized or melted. Such an impact would have continued to melt ice flowing into the crater for an as-of-yet undetermined period post-impact. If an impact origin for the crater is confirmed, it would be one of the twenty-five largest known impact craters on Earth. Shortly after the crater was discovered, researchers suggested that the impact could have occurred as late as ~12,800 years ago, leading some to associate it with the

Younger Dryas impact hypothesis The Younger Dryas impact hypothesis (YDIH) or Clovis comet hypothesis is a speculative attempt to explain the onset of the Younger Dryas (YD) as an alternative to the long standing and widely accepted cause due to a significant reduction or shut ...

. However, a 2022 study using

argon–argon dating Argon–argon (or 40Ar/39Ar) dating is a radiometric dating method invented to supersede potassiumargon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measurements, while the newer ...

combined with

uranium–lead dating Uranium–lead dating, abbreviated U–Pb dating, is one of the oldest and most refined of the radiometric dating schemes. It can be used to date rocks that formed and crystallised from about 1 million years to over 4.5 billion years ago with routi ...

of shocked zircon crystals in impact melt rocks found in

outwash An outwash plain, also called a sandur (plural: ''sandurs''), sandr or sandar, is a plain formed of glaciofluvial deposits due to meltwater outwash at the terminus of a glacier. As it flows, the glacier grinds the underlying rock surface and ca ...

less than 10 km downstream of the glacier pushed the estimate back to around 57.99 ± 0.54 million years ago, during the late

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

. In February 2019, a NASA glaciologist discovered a possible second impact crater buried under ice in northwest Greenland. Though the newly found impact sites in northwest Greenland are only 183 km apart, at present they do not appear to have formed at the same time. If the second crater, which has a width of over 35 km, is ultimately confirmed as the result of a meteorite impact, it will be the 22nd largest impact crater found on Earth.

References

External links

International Team, NASA Make Unexpected Discovery Under Greenland Ice
NASA/Video
Massive crater under Greenland's ice points to climate-altering impact in the time of humans
Video
Discovering a massive meteorite crater
Docu/Video {{Impact cratering on Earth Impact craters of Greenland Glaciers of Greenland

Impact structure

See also

References

External links