The Canadian Shield, also called the Laurentian Shield or the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks. It forms the North American Craton, the ancient geologic core of the North American continent. Glaciation has left the area with only a thin layer of soil, through which exposures of igneous bedrock resulting from its long volcanic history are frequently visible. As a deep, common, joined bedrock region in eastern and central Canada, the shield stretches north from the Great Lakes to the Arctic Ocean, covering over half of Canada and most of Greenland; it also extends south into the northern reaches of the continental United States.
An impact crater is a depression in the surface of a solid astronomical body formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Impact craters are typically circular, though they can be elliptical in shape or even irregular due to events such as landslides. Impact craters range in size from microscopic craters seen on lunar rocks returned by the Apollo Program to simple bowl-shaped depressions and vast, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth.
An impact event is a collision between astronomical objects causing measurable effects. Impact events have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, as the impacting body is usually traveling at several kilometres a second, though atmospheres mitigate many surface impacts through atmospheric entry. Impact craters and structures are dominant landforms on many of the Solar System's solid objects and present the strongest empirical evidence for their frequency and scale.
The Chesapeake Bay impact crater is a buried impact crater, located beneath the mouth of Chesapeake Bay, United States. It was formed by a bolide that struck the eastern shore of North America about 35.5 ± 0.3 million years ago, in the late Eocene epoch. It is one of the best-preserved "wet-target" impact craters in the world.
Manicouagan Reservoir is an annular lake in central Quebec, Canada, covering an area of 1,942 km2 (750 sq mi). The lake island in its centre is known as René-Levasseur Island, and its highest point is Mount Babel. The structure was created 214 (±1) million years ago, in the Late Triassic, by the impact of a meteorite 5 km (3 mi) in diameter. The lake and island are clearly seen from space and are sometimes called the "eye of Quebec". The lake has a volume of 137.9 km3 (33.1 cu mi).
Carswell is an impact structure within the Athabasca Basin of the Canadian Shield in northern Saskatchewan, Canada. It is 39 kilometres (24 mi) in diameter and the age is estimated to be 115 ± 10 million years. The impact structure is exposed at the surface.
Gow is an impact crater in Saskatchewan, Canada. It is 5 km (3 mi) in diameter and the age is estimated to be less than 250 million years. The crater contains a classic crater lake with an island formed by the central uplift. It is the smallest known crater in Canada with an uplift structure.
Lappajärvi is a lake in Finland, in the municipalities of Lappajärvi, Alajärvi and Vimpeli. It is formed in a 23 km (14 mi) wide, partly eroded meteorite impact crater. The lake is part of Ähtävänjoki basin together with Lake Evijärvi that is located downstream (north) of it.
Maple Creek is a subterranean meteorite crater in Saskatchewan, Canada. It is 6 km (3.7 mi) in diameter and the age is estimated to be less than 75 million years. The crater is buried beneath younger sediment and cannot be seen at the surface.
Mistastin crater is a meteorite crater in Labrador, Canada which contains the roughly circular Mistastin Lake. The lake is approximately 16 km (9.9 mi) in diameter, while the estimated diameter of the original crater is 28 km (17 mi). The age of the crater is calculated to be 36.6 ± 2 million years (Eocene).
Steen River is an impact structure in Alberta, Canada. It is 25 km (16 mi) in diameter and the age is estimated to be 91 ± 7 million years. The structure is not exposed at the surface. The original crater was partially eroded prior to burial, and lies under 200 m (660 ft) of sediments.
The Slate Islands are a small archipelago in Lake Superior, Ontario, Canada, about 12 kilometres (7.5 mi) south of the town of Terrace Bay. The island group, consisting of 15 islands in total, was created by a meteorite impact which formed a crater about 32 km (20 mi) wide. In 1985, the Ontario government established the Slate Islands as a natural environment provincial park. The islands are notable for having Ontario's largest herd of boreal woodland caribou.
The Manicouagan or Manicuagan River, often clipped to Manic, is a river in Côte-Nord region of Quebec, Canada. The river originates in the Manicouagan Reservoir and flows approximately 200 kilometres (120 mi) south, emptying into the Saint Lawrence River near Baie-Comeau. The reservoir, also known as Lake Manicouagan, lies within the remnant of an ancient eroded impact crater (astrobleme). It was formed following the impact of a 5 kilometres (3.1 mi) diameter asteroid which excavated a crater originally about 100 km (62 mi) wide, although erosion and deposition of sediments have since reduced the visible diameter to about 72 km (45 mi). The Manicouagan impact structure is the sixth-largest confirmed impact crater known on earth.
The Shiva crater is the claim by paleontologist Sankar Chatterjee and colleagues that the Bombay High and Surat Depression on the Indian continental shelf west of Mumbai, India represent a 500-kilometre (310 mi) impact crater, that formed around the Cretaceous-Paleogene boundary. Chatterjee and colleagues have claimed that this could have contributed to the K-Pg extinction event. Other scholars have questioned the claims, finding that there is no evidence of an impact structure.
The Lac Wiyâshâkimî, also called the Clearwater Lakes in English and Allait Qasigialingat by the Inuit, are a pair of annular lakes and impact structures on the Canadian Shield in Quebec, Canada, near Hudson Bay.
The geography of Saskatchewan is unique among the provinces and territories of Canada in some respects. It is one of only two landlocked regions and it is the only region whose borders are not based on natural features like lakes, rivers, or drainage divides. The borders of Saskatchewan, which make it very nearly a trapezoid, were determined in 1905 when it became a Canadian province. Saskatchewan has a total area of 651,036 square kilometres (251,366 sq mi) of which 591,670 km2 (228,450 sq mi) is land and 59,366 km2 (22,921 sq mi) is water.
The Ottawa-Bonnechere Graben is a geological structure that coincides with a 55 km (34 mi) wide topographic depression extending from near Montréal through Ottawa. It is part of the Saint Lawrence rift system that also includes the seismically active Saguenay graben. This rift valley was formed when the Earth's crust moved downward about a kilometre between two major fault zones known as the Mattawa and Petawawa faults.
The geology of Saskatchewan can be divided into two main geological regions, the Precambrian Canadian Shield and the Phanerozoic Western Canadian Sedimentary Basin. Within the Precambrian shield exists the Athabasca sedimentary basin. Meteorite impacts have altered the natural geological formation processes. The prairies were most recently affected by glacial events in the Quaternary period.
The Tunnunik impact structure, formerly known as the Prince Albert Impact Crater, is a recently confirmed meteorite impact structure. It is located on Prince Albert Peninsula in the northwestern part of Victoria Island[A] in Canada's Northwest Territories.
