The Lac Wiyâshâkimî (the official name, in
French, formerly Lac à l'Eau Claire, a
calque
In linguistics, a calque () or loan translation is a word or phrase borrowed from another language by literal word-for-word or root-for-root translation. When used as a verb, "to calque" means to borrow a word or phrase from another language w ...
of the lake's name, Wiyâšâkamî, in Northern East
Cree, changed form of ''wâšâkamî'' or ''wâšekamî'' in more southerly Cree dialects), also called the Clearwater Lakes in English and Allait Qasigialingat by the
Inuit
Inuit (; iu, ᐃᓄᐃᑦ 'the people', singular: Inuk, , dual: Inuuk, ) are a group of culturally similar indigenous peoples inhabiting the Arctic and subarctic regions of Greenland, Labrador, Quebec, Nunavut, the Northwest Territories ...
,
are a pair of
annular lake
An impact crater lake is a lake inside a depression caused by the impact of a meteor. It is also known as an annular lake in cases where the water body is shaped like a ring, as many impact crater lakes are.
Examples
One of the largest impac ...
s on the
Canadian Shield in
Quebec
Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...
, Canada, near
Hudson Bay.
The lakes are actually a single body of water with a sprinkling of islands forming a "dotted line" between the eastern and western parts. Its name in Cree is due to the clear water it holds. There are actually 25 lakes with names that mean "Clearwater Lake" in the province (26 if the ''Petit lac à l'Eau Claire'' — the Small Clearwater Lake — is included). Collectively, this body of water is the largest, northernmost and the second-largest natural lake in Quebec after
Lake Mistassini
Lake Mistassini () is the largest natural lake by surface area in the province of Quebec, Canada, with a total surface area of approximately and a net area (water surface area only) of . It is located in the Jamésie region of the province, appro ...
.
In 1896, the explorer and geologist
Albert Peter Low
Albert Peter Low (May 24, 1861 – October 9, 1942) was a Canadian geologist, explorer and athlete. His explorations of 1893–1895 were important in declaring Canada's sovereignty over the Arctic, and eventually defining the border between Quebec ...
, a member of the Geological Survey of Canada, provided a probable explanation for the lakes' descriptive Cree name by highlighting the extraordinary clarity and depth of their icy waters.
Impact craters
The Clearwater Lakes occupy the near-circular depressions of two eroded
impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact crater ...
s (
astrobleme
An impact structure is a generally circular or craterlike geologic structure of deformed bedrock or sediment produced by impact on a planetary surface, whatever the stage of erosion of the structure. In contrast, an impact crater is the sur ...
s).
[Robertson, P.B. & Grieve, R.A.F. 1975 Impact structures in Canada: Their recognition and characteristics. Journal of the Royal Astronomical Society of Canada, v. 69, pp. 1-21.] The eastern and western craters are and in diameter, respectively. Both craters were previously believed to have the same age, 290 ± 20 million years (
Permian period
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...
), promoting the long-held idea that they formed simultaneously. According to this doublet impact crater theory initially proposed by
Michael R. Dence and colleagues in 1965, the impactors may have been gravitationally bound as a
binary asteroid
A binary asteroid is a system of two asteroids orbiting their common barycenter. The binary nature of 243 Ida was discovered when the Galileo spacecraft flew by the asteroid in 1993. Since then numerous binary asteroids and several triple a ...
, a suggestion also made by
Thomas Wm. Hamilton in a 1978 letter to ''
Sky & Telescope
''Sky & Telescope'' (''S&T'') is a monthly American magazine covering all aspects of amateur astronomy, including the following:
*current events in astronomy and space exploration;
*events in the amateur astronomy community;
*reviews of astronomic ...
'' magazine in support of the then-controversial theory that asteroids may possess moons
(such as, for example, asteroid
243 Ida
Ida, minor planet designation 243 Ida, is an asteroid in the Koronis family of the asteroid belt. It was discovered on 29 September 1884 by Austrian astronomer Johann Palisa at Vienna Observatory and named after a nymph from Greek mythology. ...
with its satellite Dactyl).
Clearwater East and Clearwater West are both
complex crater
Complex craters are a type of large impact crater morphology.
Above a certain threshold size, which varies with planetary gravity, the collapse and modification of the transient cavity is much more extensive, and the resulting structure is cal ...
s with distinct central peaks. These peaks are caused by the gravitational collapse of crater walls and subsequent rebound of the compressed crater floor. Lake water and sediments cover the central peak of Clearwater East, but bathymetric surveys of the lake floor and core drilling confirm the presence of a peak in its center.
Ordovician
However, repeated
40Ar/39Ar dating of
impact melt rocks from both impact craters suggests that Clearwater East has an age of approximately 460–470 million years, corresponding to the
Middle Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya.
Th ...
time period.
[
]
Permian
Clearwater West was formed 286.2 ± 2.6 million years ago, in the Early Permian.[Bottomley, R.J., York, D., and Grieve, R.A.F. 1990. 40Argon-39Argon dating of impact craters. Proc. 20th Lunar Planet. Sci. Conf., LPI, Houston, pp. 421–431.][Schmieder, M., Schwarz, W. H., Trieloff, M., Tohver, E., Buchner, E., Hopp, J. & Osinski, G. R. 2014]
New 40Ar/39Ar dating of the Clearwater Lake impact structures (Québec, Canada) – Not the binary asteroid impact it seems?
Geochim. Cosmochim. Acta (in press). Both Clearwater impact structures also carry different geophysical (natural remanent magnetization Natural remanent magnetization (NRM) is the permanent magnetism of a rock or sediment. This preserves a record of the Earth's magnetic field at the time the mineral was laid down as sediment or crystallized in magma and also the tectonic movement o ...
) signatures and different geochemical fingerprints of the impacting meteorite in the impact melt
Impact may refer to:
* Impact (mechanics), a high force or shock (mechanics) over a short time period
* Impact, Texas, a town in Taylor County, Texas, US
Science and technology
* Impact crater, a meteor crater caused by an impact event
* Impac ...
of each crater.[Palme, H., Janssens, M.-J., Takahashi, H., Anders, E. and Hertogen, J. 1978. Meteoritic material at five large impact craters. Geochim. Cosmochim. Acta 42, 313–323.]
Micro climate
Because of its size, Lac à l'Eau Claire can affect the local climate, as attested to by the distribution of plant species. Although the lake's shorelines are populated mainly by boreal species, the flora of the central islands in the western basin of the lake is characteristically arctic
The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenland), Finland, Iceland, N ...
, making the islands an arctic enclave.
National park
A vast area surrounding the lakes, Richmond Gulf
Lake Tasiujaq (french: lac Tasiujaq; iu, Tasiujaq, script=Latn (which resembles a lake)) is a large triangular-shaped inland bay located on east side of Hudson Bay just above 56th parallel north in Quebec, Canada. It was formerly known as Richmo ...
(''Lac Guillaume-Delisle''), and Iberville Lake (''Lac D'Iberville'') are part of the Tursujuq National Park, Quebec's largest national park, opened in 2012.[Ministère du Développement durable, de l'Environnement
et des Parcs, ''Provisional Master Plan Parc national des Lacs-Guillaume-Delisle-et-à-l'Eau-Claire'', Quebec, 2008, ]
Online version
)
See also
* Nastapoka arc, an embayment of Hudson Bay 140 km to the west, discredited as an impact crater
Notes
References
External links
Aerial Exploration of the Clearwater West Structure
Aerial Exploration of the Clearwater East Structure
{{Impact cratering on Earth
Impact craters of Quebec
Lakes of Nord-du-Québec
Ordovician impact craters
Permian impact craters
Impact crater lakes