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41-465: The crater is exposed to the surface, rising 160 m (520 ft) above the surrounding tundra , and is 400 m (1,300 ft) deep. The 267 m-deep (876 ft) Pingualuk Lake fills the hollow, and is one of the deepest lakes in North America. The lake also holds some of the purest fresh water in the world, with a salinity level of less than 3 ppm (by comparison, the salinity level of

82-553: A temperate grassland , restricting southern tundra to coastal Antarctica and its islands. The flora and fauna of Antarctica and the Antarctic Islands (south of 60° south latitude) are protected by the Antarctic Treaty . Alpine tundra does not contain trees because the climate and soils at high altitude block tree growth. The cold climate of the alpine tundra is caused by the low air temperatures, and

123-523: A 2007 expedition to the crater which extracted sediment cores from the bottom of the lake, which were filled with fossil pollen , algae , and insect larvae. It was hoped that these finds would yield information about the climate dating back to the last interglacial period 120,000 years ago. Preliminary results show that the upper 8.5 m (28 ft) sediment core contains records of two interglacial periods. Tundra In physical geography , tundra ( / ˈ t ʌ n d r ə , ˈ t ʊ n -/ )

164-552: A distinctively conical shape that radiates from the top of the cones repeating cone-on-cone, at various scales in the same sample. They are only known to form in rocks beneath meteorite impact craters or underground nuclear explosions . They are evidence that the rock has been subjected to a shock with pressures in the range of 2-30 GPa . The effects described above have been found singly, or more often in combination, associated with every impact structure that has been identified on Earth. The search for such effects therefore forms

205-757: A local climate in which at least one month has an average temperature high enough to melt snow (0 °C (32 °F)), but no month with an average temperature in excess of 10 °C (50 °F). The cold limit generally meets the EF climates of permanent ice and snows ; the warm-summer limit generally corresponds with the poleward or altitudinal limit of trees, where they grade into the subarctic climates designated Dfd , Dwd and Dsd (extreme winters as in parts of Siberia ), Dfc typical in Alaska, Canada, mountain areas of Scandinavia , European Russia , and Western Siberia (cold winters with months of freezing). Despite

246-610: A navigational aid. On June 20, 1943, a United States Army Air Force plane on a meteorological flight over the Ungava region of Quebec Province took a photograph that showed the wide crater rim rising up above the landscape. In 1948, the Royal Canadian Air Force covered the same remote area as part of its program of photomapping Canada, though these photographs were not made publicly available until 1950. Ontario diamond prospector Frederick W. Chubb became interested by

287-485: Is a risk of wildfire, such as the 1,039 km (401 sq mi) of tundra which burned in 2007 on the north slope of the Brooks Range in Alaska. Such events may both result from and contribute to global warming. Carbon emissions from permafrost thaw contribute to the same warming which facilitates the thaw, making it a positive climate change feedback . The warming also intensifies Arctic water cycle , and

328-409: Is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: Arctic tundra, alpine tundra , and Antarctic tundra. Tundra vegetation is composed of dwarf shrubs , sedges , grasses , mosses , and lichens . Scattered trees grow in some tundra regions. The ecotone (or ecological boundary region) between

369-453: Is characterized by plants that grow close to the ground, including perennial grasses , sedges , forbs , cushion plants , mosses , and lichens . The flora is adapted to the harsh conditions of the alpine environment, which include low temperatures, dryness, ultraviolet radiation, and a short growing season. Tundra climates ordinarily fit the Köppen climate classification ET , signifying

410-784: Is home to several peoples who are mostly nomadic reindeer herders, such as the Nganasan and Nenets in the permafrost area (and the Sami in Sápmi ). Arctic tundra contains areas of stark landscape and is frozen for much of the year. The soil there is frozen from 25 to 90 cm (10 to 35 in) down, making it impossible for trees to grow there. Instead, bare and sometimes rocky land can only support certain kinds of Arctic vegetation , low-growing plants such as moss, heath ( Ericaceae varieties such as crowberry and black bearberry ), and lichen . There are two main seasons, winter and summer, in

451-508: Is known only from impact structures. Two of the high-pressure polymorphs of titanium dioxide , one with a baddeleyite -like form and the other with a α-PbO 2 structure, have been found associated with the Nördlinger Ries impact structure. Diamond, the high-pressure allotrope of carbon , has been found associated with many impact structures, and both fullerenes and carbynes have been reported. Shatter cones have

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492-630: Is light, evaporation is also relatively minimal. During the summer, the permafrost thaws just enough to let plants grow and reproduce, but because the ground below this is frozen, the water cannot sink any lower, so the water forms the lakes and marshes found during the summer months. There is a natural pattern of accumulation of fuel and wildfire which varies depending on the nature of vegetation and terrain. Research in Alaska has shown fire-event return intervals (FRIs) that typically vary from 150 to 200 years, with dryer lowland areas burning more frequently than wetter highland areas. The biodiversity of tundra

533-698: Is low: 1,700 species of vascular plants and only 48 species of land mammals can be found, although millions of birds migrate there each year for the marshes. There are also a few fish species. There are few species with large populations. Notable plants in the Arctic tundra include blueberry ( Vaccinium uliginosum ), crowberry ( Empetrum nigrum ), reindeer lichen ( Cladonia rangiferina ), lingonberry ( Vaccinium vitis-idaea ), and Labrador tea ( Rhododendron groenlandicum ). Notable animals include reindeer (caribou), musk ox , Arctic hare , Arctic fox , snowy owl , ptarmigan , northern red-backed voles , lemmings ,

574-404: Is similar to polar climate . Alpine tundra is generally better drained than arctic soils. Alpine tundra transitions to subalpine forests below the tree line; stunted forests occurring at the forest-tundra ecotone (the treeline ) are known as Krummholz . Alpine tundra can be affected by woody plant encroachment . Alpine tundra occurs in mountains worldwide. The flora of the alpine tundra

615-538: The Great Lakes is 500 ppm). It is one of the most transparent lakes in the world, with a Secchi disk visible more than 35 m (115 ft) deep. The lake has no inlets or apparent outlets, so the water accumulates solely from rain and snow and is lost only through evaporation. The crater was formed by a meteorite impact 1.4 Ma , as estimated by Ar/Ar dating of impact melt rocks. An analysis of these rocks also revealed planar deformation features as well as

656-541: The Harvard – Smithsonian Center for Astrophysics and reported to the 51st Meteoritical Society in 1988 by Ursula Marvin and David Kring. Boulger returned to the area that summer, along with a research party led by M. A. Bouchard of the University of Montreal . Three years later Canadian geologist Richard A. F. Grieve listed New Quebec among the 130 known terrestrial impact craters. In 1992, Marvin and Kring documented

697-586: The Kerguelen Islands . Most of Antarctica is too cold and dry to support vegetation, and most of the continent is covered by ice fields or cold deserts. However, some portions of the continent, particularly the Antarctic Peninsula , have areas of rocky soil that support plant life. The flora presently consists of around 300–400 species of lichens, 100 mosses, 25 liverworts , and around 700 terrestrial and aquatic algae species, which live on

738-472: The mosquito , and even polar bears near the ocean. Tundra is largely devoid of poikilotherms such as frogs or lizards. Due to the harsh climate of Arctic tundra, regions of this kind have seen little human activity, even though they are sometimes rich in natural resources such as petroleum , natural gas , and uranium . In recent times this has begun to change in Alaska , Russia, and some other parts of

779-602: The areas of exposed rock and soil around the shore of the continent. Antarctica's two flowering plant species, the Antarctic hair grass ( Deschampsia antarctica ) and Antarctic pearlwort ( Colobanthus quitensis ), are found on the northern and western parts of the Antarctic Peninsula. In contrast with the Arctic tundra, the Antarctic tundra lacks a large mammal fauna, mostly due to its physical isolation from

820-565: The atmosphere, creating a feedback cycle that changes climate. The term is a Russian word adapted from the Sámi languages . Arctic tundra occurs in the far Northern Hemisphere , north of the taiga belt. The word "tundra" usually refers only to the areas where the subsoil is permafrost , or permanently frozen soil. (It may also refer to the treeless plain in general so that northern Sápmi would be included.) Permafrost tundra includes vast areas of northern Russia and Canada. The polar tundra

861-411: The chilly atmosphere, but as a rule potential evapotranspiration is extremely low, allowing soggy terrain of swamps and bogs even in places that get precipitation typical of deserts of lower and middle latitudes. The amount of native tundra biomass depends more on the local temperature than the amount of precipitation. Shock metamorphism Shock metamorphism or impact metamorphism describes

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902-493: The climate system activated around 2 °C (3.6 °F) of global warming suggested that at this threshold, permafrost thaw would add a further 0.09 °C (0.16 °F) to global temperatures by 2100, with a range of 0.04–0.16 °C (0.07–0.29 °F) Antarctic tundra occurs on Antarctica and on several Antarctic and subantarctic islands, including South Georgia and the South Sandwich Islands and

943-418: The composition of the meteorite itself. Enrichments of iron, nickel, cobalt, and chromium found in impact melt samples suggest that the meteorite was chondritic in nature. Once largely unknown to the outside world, the lake-filled crater had long been known to local Inuit , who knew it as the "Crystal Eye of Nunavik" for its clear water. World War II pilots often used the almost perfectly circular landmark as

984-566: The crater with Chubb in 1950; it was on this trip that Meen proposed the name "Chubb Crater" for the circular feature and "Museum Lake" for the irregular body of water about 2 mi (3.2 km) north of the crater (now known as Laflamme Lake). Following his return, Meen organized a proper expedition with the cooperation of the National Geographic Society and the Royal Ontario Museum . They travelled to

1025-439: The effects of shock-wave related deformation and heating during impact events . The formation of similar features during explosive volcanism is generally discounted due to the lack of metamorphic effects unequivocally associated with explosions and the difficulty in reaching sufficient pressures during such an event. Planar fractures are parallel sets of multiple planar cracks or cleavages in quartz grains; they develop at

1066-454: The formation of high-pressure polymorphs of various minerals. Quartz may occur as either of its two high-pressure forms, coesite and stishovite . Coesite occasionally occurs associated with eclogites formed during very high pressure regional metamorphism but was first discovered in a meteorite crater in 1960. Stishovite, however, is only known from impact structures. Reidite , the high-pressure scheelite -structure polymorph of zircon ,

1107-655: The grain's crystal structure . PDFs are only produced by extreme shock compressions on the scale of meteor impacts. They are not found in volcanic environments. This form of twinning in quartz is relatively common but the occurrence of close-spaced Brazil twins parallel to the basal plane , (0001), has only been reported from impact structures. Experimental formation of basal-orientated Brazil twins in quartz requires high stresses (about 8 GPa ) and high strain rates, and it seems probable that such features in natural quartz can also be regarded as unique impact indicators. The very high pressures associated with impacts can lead to

1148-488: The increased amounts of warmer rain are another factor which increases permafrost thaw depths. The IPCC Sixth Assessment Report estimates that carbon dioxide and methane released from permafrost could amount to the equivalent of 14–175 billion tonnes of carbon dioxide per 1 °C (1.8 °F) of warming. For comparison, by 2019, annual anthropogenic emission of carbon dioxide alone stood around 40 billion tonnes. A 2018 perspectives article discussing tipping points in

1189-644: The lowest pressures characteristic of shock waves (~5–8 GPa) and a common feature of quartz grains found associated with impact structures. Although the occurrence of planar fractures is relatively common in other deformed rocks, the development of intense, widespread, and closely spaced planar fractures is considered diagnostic of shock metamorphism. Planar deformation features , or PDFs, are optically recognizable microscopic features in grains of silicate minerals (usually quartz or feldspar ), consisting of very narrow planes of glassy material arranged in parallel sets that have distinct orientations with respect to

1230-484: The only subantarctic orchids; the royal penguin ; and the Antipodean albatross . There is some ambiguity on whether Magellanic moorland , on the west coast of Patagonia , should be considered tundra or not. Phytogeographer Edmundo Pisano called it tundra ( Spanish : tundra Magallánica ) since he considered the low temperatures key to restrict plant growth. More recent approaches have since recognized it as

1271-621: The other continents. Sea mammals and sea birds, including seals and penguins, inhabit areas near the shore, and some small mammals, like rabbits and cats, have been introduced by humans to some of the subantarctic islands. The Antipodes Subantarctic Islands tundra ecoregion includes the Bounty Islands , Auckland Islands , Antipodes Islands , the Campbell Island group , and Macquarie Island . Species endemic to this ecoregion include Corybas dienemus and Corybas sulcatus ,

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1312-416: The petrographic analysis of two impact melt samples collected within the crater rim. They presented evidence of shock metamorphism , which is consistent with similar impact crater sites. In 1999, the name was again changed, to "Pingualuit". The crater and the surrounding area are now part of Canada's Pingualuit National Park , created on January 1, 2004. Professor Reinhard Pienitz of Laval University led

1353-413: The polar tundra areas. During the winter it is very cold, dark, and windy with the average temperature around −28 °C (−18 °F), sometimes dipping as low as −50 °C (−58 °F). However, extreme cold temperatures on the tundra do not drop as low as those experienced in taiga areas further south (for example, Russia's, Canada's, and Alaska's lowest temperatures were recorded in locations south of

1394-528: The potential diversity of climates in the ET category involving precipitation, extreme temperatures, and relative wet and dry seasons, this category is rarely subdivided, although, for example, Wainwright, Alaska can be classified ETw and Provideniya, Russia ETs , with most of the rest of the tundra fitting into the ETf subcategory. Rainfall and snowfall are generally slight due to the low vapor pressure of water in

1435-530: The site in a PBY Catalina flying boat in July 1951, landing on nearby Museum Lake. Attempts to find fragments of nickel-iron from the meteorite using mine detectors lent by the US Army were unsuccessful due to the area's granite containing high levels of magnetite . A magnetometer survey did find a magnetic anomaly under the crater's northern rim, however, indicating that a large mass of metal-bearing material

1476-410: The strange terrain shown in the photographs and sought the opinion of geologist V. Ben Meen of the Royal Ontario Museum . Chubb hoped that the crater was that of an extinct volcano , in which case the area might contain diamond deposits similar to those of South Africa . However, Meen's knowledge of Canadian geology tentatively ruled out a volcanic origin. Meen subsequently made a brief trip by air to

1517-444: The subject of habitat conservation programs. In Canada and Russia, many of these areas are protected through a national Biodiversity Action Plan . Tundra tends to be windy, with winds often blowing upwards of 50–100 km/h (30–60 mph). However, it is desert-like, with only about 150–250 mm (6–10 in) of precipitation falling per year (the summer is typically the season of maximum precipitation). Although precipitation

1558-412: The tree line). During the summer, temperatures rise somewhat, and the top layer of seasonally-frozen soil melts, leaving the ground very soggy. The tundra is covered in marshes, lakes, bogs, and streams during the warm months. Generally daytime temperatures during the summer rise to about 12 °C (54 °F) but can often drop to 3 °C (37 °F) or even below freezing. Arctic tundras are sometimes

1599-481: The tundra and the forest is known as the tree line or timberline. The tundra soil is rich in nitrogen and phosphorus . The soil also contains large amounts of biomass and decomposed biomass that has been stored as methane and carbon dioxide in the permafrost , making the tundra soil a carbon sink . As global warming heats the ecosystem and causes soil thawing, the permafrost carbon cycle accelerates and releases much of these soil-contained greenhouse gases into

1640-600: The world: for example, the Yamalo-Nenets Autonomous Okrug produces 90% of Russia's natural gas. A severe threat to tundra is global warming , which causes permafrost to thaw. The thawing of the permafrost in a given area on human time scales (decades or centuries) could radically change which species can survive there. It also represents a significant risk to infrastructure built on top of permafrost, such as roads and pipelines. In locations where dead vegetation and peat have accumulated, there

1681-542: Was buried below the surface. Meen led a second expedition to the crater in 1954. That same year its name was changed to "Cratère du Nouveau-Quebec" ("New Quebec Crater") at the request of the Quebec Geographic Board . An expedition led by James Boulger in 1986 collected a small rock sample from the area surrounding the New Quebec Crater. Petrographic analysis of this sample was conducted at

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