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Bear Rock Formation
Bear Rock (Dene: Kweteniɂaá) is a geologic formation in the Sahtu Region of the Northwest Territories located across the mouth of the Great Bear River from Tulita. Geology Bear Rock is a lithostratigraphic sedimentary outcropping composed primarily of gypsum, dolomite, limestone, and breccia laid down in the Late Silurian to Middle Devonian (422.9 - 385.3 ma) periods. It is a site of karst features including caves and sinkholes, including one that was featured on Fodor's "15 of Canada's Most Stunning Natural Wonders" list. Marine fossils including acanthodians, brachiopods and corals have been found here. Folklore Bear Rock is said to be the rock over which a mythical hero, known to various Dene groups as either Yamoria, Yamozah, or Zhamba Dezha, stretched the skins of giant beavers after he had slain them to stop them from terrorizing the people. It has been a traditional place of prayer and reflection for these indigenous people for generations. 2019 landslide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Bear River
The long Great Bear River, which drains the Great Bear Lake westward through marshes into the Mackenzie River, forms an important transportation link during its four ice-free months. It originates at south-west bay of the lake. The river has irregular meander pattern wide channel with average depth . Historic air photos show no evidence of bank erosion or channel migration in a 50-year period. The low discharge rate is due to small amount of precipitation in watershed area. Maps of Canada Annual Precipitation Great Bear River contained open reaches that had melted out in place over 80 percent of its length in 1972 and 1974. The settlement of Tulita, Northwest Territori ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cave
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea caves, rock shelters, and grottos, that extend a relatively short distance into the rock and they are called ''exogene'' caves. Caves which extend further underground than the opening is wide are called ''endogene'' caves. Speleology is the science of exploration and study of all aspects of caves and the cave environment. Visiting or exploring caves for recreation may be called ''caving'', ''potholing'', or ''spelunking''. Formation types The formation and development of caves is known as '' speleogenesis''; it can occur over the course of millions of years. Caves can range widely in size, and are formed by various geological processes. These may involve a combination of chemical processes, erosion by water, tectonic forces, microorgan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landslides
Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event (such as a heavy rainfall, an earthquake, a slope cut to build a road, and many others), although this is not always identifiable. Causes Landslides occur when the slope (or a portion of it) undergoes some processes that change its condition from stable to unstable. This is essentially due to a decrease in the shear strength o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forest Fire
A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a bushfire( in Australia), desert fire, grass fire, hill fire, peat fire, prairie fire, vegetation fire, or veld fire. Some natural forest ecosystems depend on wildfire. Wildfires are distinct from beneficial human usage of wildland fire, called controlled burning, although controlled burns can turn into wildfires. Fossil charcoal indicates that wildfires began soon after the appearance of terrestrial plants approximately 419 million years ago during the Silurian period. Earth's carbon-rich vegetation, seasonally dry climates, atmospheric oxygen, and widespread lightning and volcanic ignitions create favorable conditions for fires. The occurrence of wildfires throughout the history of terrestrial life invites conjecture t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dene
The Dene people () are an indigenous group of First Nations who inhabit the northern boreal and Arctic regions of Canada. The Dene speak Northern Athabaskan languages. ''Dene'' is the common Athabaskan word for "people". The term "Dene" has two usages. More commonly, it is used narrowly to refer to the Athabaskan speakers of the Northwest Territories and Nunavut in Canada, especially including the Chipewyan (Denesuline), Tlicho (''Dogrib''), Yellowknives (T'atsaot'ine), Slavey (Deh Gah Got'ine or Deh Cho), and Sahtu (the Eastern group in Jeff Leer's classification; part of the Northwestern Canada group in Keren Rice's classification). However, it is sometimes also used to refer to all Northern Athabaskan speakers, who are spread in a wide range all across Alaska and northern Canada. The Southern Athabaskan speakers, however, also refer to themselves by similar words: Diné (Navajo) and Indé (Apache). Location Dene are spread through a wide region. They live in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton. A coral "group" is a colony of very many genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in height. A set of tentacles surround a central mouth opening. Each polyp excretes an exoskeleton near the base. Over many generations, the colony thus creates a skeleton characteristic of the species which can measure up to several meters in size. Individual colonies grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously overnight, often around a full moon. Fertilized eggs form planulae, a mobile early form of the coral polyp which, when matu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brachiopod
Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major categories are traditionally recognized, articulate and inarticulate brachiopods. The word "articulate" is used to describe the tooth-and-groove structures of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic skeletal feature, by which the two main groups can be readily distinguished as fossils. Articulate brachiopods have toothed hinges and simple, vertically-oriented opening and closing muscles. Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachiopods, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acanthodii
Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, which includes living sharks, rays, and chimaeras. Acanthodians possess a mosaic of features shared with both osteichthyans (bony fish) and chondrichthyans (cartilaginous fish). In general body shape, they were similar to modern sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteians ( gars, bowfins). A lower Silurian species, '' Fanjingshania renovata'', attributed to Climatiiformes is the oldest chondrichthyan with known anatomical features. The popular name "spiny sharks" is because they were superficially shark-shaped, with a streamlined body, paired fins, a strongly upturned tail, and stout, largely immovable bony spines supporting all the fins except the tail—hence, "spiny sharks". However ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fossils
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood and DNA remnants. The totality of fossils is known as the ''fossil record''. Paleontology is the study of fossils: their age, method of formation, and evolutionary significance. Specimens are usually considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years old to 4.1 billion years old. Early edition, published online before print. The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils. The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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