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38-400: Sombre Lake is the northernmost lake, so named by UK-APC because of the sombre setting of the lake and the proximity of Stygian Cove. Changing Lake is the central lakes. This proglacial lake was named by UK-APC because the lake slowly changes shape and size as the retaining land ice gradually retreats. Moss Lake is the southernmost lake, named by UK-APC because a luxuriant stand of moss covers

76-593: A catastrophic explanation of the geology, ran against the prevailing view of uniformitarianism , and Bretz's views were initially disregarded. The Geological Society of Washington, D.C , invited the young Bretz to present his previously published research at a January 12, 1927, meeting where several other geologists presented competing theories. Another geologist at the meeting, J.T. Pardee , had worked with Bretz and had evidence of an ancient glacial lake that lent credence to Bretz's theories. Bretz defended his theories, which kicked off an acrimonious 40-year debate over

114-510: A comment on the Komatsu analysis, Brian Atwater and colleagues observed substantial evidence for multiple large floods, including mud cracks and animal burrows in lower layers, which were filled by sediment from later floods. Further, evidence for multiple flood flows up sidearms of Glacial Lake Columbia spread over many centuries has been found. They also pointed out that the discharge point from Lake Columbia varied with time, originally flowing across

152-573: A glacial overspill channel created when the water of a proglacial lake rose high enough to breach the lowest point in the containing watershed. Missoula Floods The Missoula floods (also known as the Spokane floods , the Bretz floods , or Bretz's floods ) were cataclysmic glacial lake outburst floods that swept periodically across eastern Washington and down the Columbia River Gorge at

190-643: A newly published topographic map of the Potholes Cataract . Bretz coined the term Channeled Scablands in 1923 to refer to the area near the Grand Coulee , where massive erosion had cut through basalt deposits. Bretz published a paper in 1923 arguing that the Channeled Scablands in Eastern Washington were caused by massive flooding in the distant past. Bretz's view, which was seen as arguing for

228-828: Is a partial list of rivers that had glacial ice dams. The retreating glaciers of the last ice age, both depressed the terrain with their mass and provided a source of meltwater that was confined against the ice mass. Lake Algonquin is an example of a proglacial lake that existed in east-central North America at the time of the last ice age . Parts of the former lake are now Lake Huron , Georgian Bay , Lake Superior , Lake Michigan and inland portions of northern Michigan. Examples in Great Britain include Lake Lapworth , Lake Harrison and Lake Pickering . Ironbridge Gorge in Shropshire and Hubbard's Hills in Lincolnshire are examples of

266-513: The Cordillera Blanca of Peru, where 70% of all tropical glaciers are. Several such lakes have formed rapidly during the 20th century. These lakes may burst, creating a hazard for zones below. Many natural dams (usually moraines ) containing the lake water have been reinforced with safety dams. Some 34 such dams have been built in the Cordillera Blanca to contain proglacial lakes. Several proglacial lakes have also formed in recent decades at

304-644: The Hanford formation , has documented the presence of Middle and Early Pleistocene Missoula flood deposits within the Othello Channels, Columbia River Gorge, Channeled Scabland , Quincy Basin, Pasco Basin, and the Walla Walla Valley . Based on the presence of multiple interglacial calcretes interbedded with flood deposits, magnetostratigraphy , optically stimulated luminescence dating, and unconformity truncated clastic dikes , it has been estimated that

342-465: The Spokane Valley – Rathdrum Prairie immediately downstream of Glacial Lake Missoula, for which several previous estimates had placed the maximum discharge of 17 × 10 m /s and the total amount of water discharged equal to the maximum estimated volume of Lake Missoula (2184 km ). Neglecting erosion effects, their simulated water flow was based on modern-day topography. Their major findings were that

380-548: The 1920s. During the last deglaciation that followed the end of the Last Glacial Maximum , geologists estimate that a cycle of flooding and reformation of the lake lasted an average of 55 years and that the floods occurred several times over the 2,000 years between 15,000 and 13,000 years ago. U.S. Geological Survey hydrologist Jim O'Connor and Spain 's Museo Nacional de Ciencias Naturales scientist Gerardo Benito have found evidence of at least twenty-five massive floods,

418-576: The Channeled Scabland landforms were formed mainly by multiple periodic floods or by a single grand-scale cataclysmic flood from late Pleistocene Glacial Lake Missoula or an unidentified Canadian source continued through 1999. Shaw's team of geologists reviewed the sedimentary sequences of the Touchet beds and concluded that the sequences do not automatically imply multiple floods separated by decades or centuries. Rather, they proposed that sedimentation in

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456-476: The Columbia Gorge would be expected to produce higher flow resistance and correspondingly higher floods. The dating for Waitt's proposed separation of layers into sequential floods has been supported by subsequent paleomagnetism studies, which support a 30–40 year interval between depositions of Mount St. Helens' ash, and hence flood events, but do not preclude an up to 60-year interval. Offshore deposits on

494-526: The Columbia River gorge, it backed up again at the 1 mile (1.6 km) wide narrows near Kalama, Washington . Some temporary lakes rose to an elevation of more than 400 ft (120 m), flooding the Willamette Valley to Eugene, Oregon and beyond. Iceberg-rafted glacial erratics and erosion features are evidence of these events. Lake-bottom sediments deposited by the floods have contributed to

532-606: The Glacial Lake Missoula basin resulted from jökulhlaups draining into Lake Missoula from British Columbia to the north. Further, Shaw's team proposed the scabland flooding might have partially originated from an enormous subglacial reservoir that extended over much of central British Columbia, particularly including the Rocky Mountain Trench , which may have discharged by several paths, including one through Lake Missoula. This discharge, if occurring concurrently with

570-587: The United States, the sudden rupturing of the supporting dam caused glacial lake outburst floods , the rapid and catastrophic release of dammed water resulting in the formation of gorges and other structures downstream from the former lake. Good examples of these structures can be found in the Channeled Scablands of eastern Washington, an area heavily eroded by the Missoula Floods . The following table

608-680: The Waterville Plateau into Moses Coulee, but later, when the Okanagan lobe blocked that route, eroding the Grand Coulee to discharge there as a substantially lower outlet. The Komatsu analysis does not evaluate the impact of the considerable erosion observed in this basin during the flood or floods. However, the assumption that flood hydraulics can be modeled using modern-day topography is an area that warrants further consideration. Earlier narrower constrictions at places such as Wallula Gap and through

646-513: The agricultural richness of the Willamette and Columbia Valleys. Glacial deposits overlaid with centuries of windblown sediments ( loess ) have scattered steep, southerly sloping dunes throughout the Columbia Valley, ideal conditions for orchard and vineyard development at higher latitudes. After analysis and controversy, geologists now believe that there were 40 or more separate floods, although

684-467: The breach of the Lake Missoula ice dam, would have provided significantly larger volumes of water. Further, Shaw and the team proposed that the rhythmic Touchet beds result from multiple pulses or surges within a larger flood. In 2000, a team led by Komatsu simulated the floods numerically with a 3-dimensional hydraulic model. They based the Glacial Lake Missoula discharge rate on the rate predicted for

722-567: The calculated water depth in each flooded location except for the Spokane Valley–Rathdrum Prairie was shallower than the field evidence showed. For example, their calculated water depth at the Pasco Basin–Wallula Gap transition zone is about 190 m, significantly less than the 280–300 m flood depth indicated by high-water marks. They concluded that a flood of ~10 m /s could not have made the observed high-water marks. In

760-657: The catastrophic floods, which he called the Spokane floods , in the 1920s. He was researching the Channeled Scablands in Eastern Washington , the Columbia Gorge , and the Willamette Valley of Oregon . Beginning In the summer of 1922, Bretz conducted field research on the Columbia River Plateau for the next seven years. He had been interested in unusual erosion features in the area since 1910 after seeing

798-593: The coast of Alaska. A similar event takes place after irregular periods in the Perito Moreno Glacier , located in Patagonia . Roughly every four years the glacier forms an ice dam against the rocky coast, causing the waters of the Lago Argentino to rise. When the water pressure is too high, then the giant bridge collapses in what has become a major tourist attraction. This sequence occurred last on 4 March 2012,

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836-406: The cracks, generating more heat, allowing even more water to flow through the cracks. This feedback cycle eventually weakened the ice dam so much that it could no longer support the pressure of the water behind it. It failed catastrophically. This process is known as a glacial lake outburst flood , and there is evidence that many such events occurred in the distant past. As the water emerged from

874-484: The deeper part of the lake. [REDACTED]  This article incorporates public domain material from websites or documents of the United States Geological Survey . This South Orkney Islands location article is a stub . You can help Misplaced Pages by expanding it . Proglacial lake In geology, a proglacial lake is a lake formed either by the damming action of a moraine during

912-459: The end of glaciers on the eastern side of New Zealand's Southern Alps . The most accessible, Lake Tasman , hosts boat trips for tourists. On a smaller scale, a mountain glacier may excavate a depression forming a cirque , which may contain a mountain lake, called a tarn , upon the melting of the glacial ice. The movement of a glacier may flow down a valley to a confluence where the other branch carries an unfrozen river. The glacier blocks

950-652: The end of the last ice age . These floods were the result of periodic sudden ruptures of the ice dam on the Clark Fork River that created Glacial Lake Missoula . After each ice dam rupture, the waters of the lake would rush down the Clark Fork and the Columbia River , flooding much of eastern Washington and the Willamette Valley in western Oregon . After the lake drained, the ice would reform, creating Glacial Lake Missoula again. These floods have been researched since

988-408: The exact source of the water is still being debated. The peak flow of the floods is estimated to be 27 cubic kilometers per hour (6.5 cubic miles per hour). The maximum flow speed approached 36 meters/second (130 km/h or 80 mph). Up to 1.9×10 joules of potential energy were released by each flood (the equivalent of 4,500 megatons of TNT ). For comparison, this is 90 times more powerful than

1026-481: The ice dam and exploded downstream, flowing at a rate 10 times the combined flow of all the rivers of the world. Because such ice dams can re-form, these Missoula Floods happened at least 59 times, carving Dry Falls below Grand Coulee . In some cases, such lakes gradually evaporated during the warming period after the Quaternary ice age. In other cases, such as Glacial Lake Missoula and Glacial Lake Wisconsin in

1064-552: The largest discharging about 10 cubic kilometers per hour (2.7 million m³/s, 13 times that of the Amazon River ). Alternate estimates for the peak flow rate of the largest flood range up to 17 cubic kilometers per hour. The maximum flow speed approached 36 meters/second (130 km/h or 80 mph). Within the Columbia River drainage basin , detailed investigation of the Missoula floods' glaciofluvial deposits , informally known as

1102-425: The largest of the boulders moved by the flood. He estimated the water flow was 9 cubic miles per hour (38 km /h), more than the combined flow of every river in the world. More recent estimates place the flow rate at ten times the flow of all current rivers combined. The Missoula floods have also been referred to as the Bretz floods in honor of Bretz. As the depth of the water in Lake Missoula increased,

1140-440: The most powerful nuclear weapon ever detonated, the 50-megaton " Tsar Bomba ". The cumulative effect of the floods was to excavate 210 cubic kilometres (50 cu mi) of loess, sediment, and basalt from the Channeled Scablands of eastern Washington and to transport it downstream. The multiple flood hypothesis was first proposed by R.B. Waitt Jr. in 1980. Waitt argued for a sequence of 40 or more floods. Waitt's proposal

1178-644: The oldest of the Pleistocene Missoula floods happened before 1.5 million years ago. Because of the fragmentary nature of older glaciofluvial deposits, which have been largely removed by subsequent Missoula floods, within the Hanford formation, the exact number of older Missoula floods, which are known as ancient cataclysmic floods , that occurred during the Pleistocene cannot be estimated with any confidence. Geologist J Harlen Bretz first recognized evidence of

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1216-565: The origin of the Scablands. Both Pardee and Bretz continued their research over the next 30 years, collecting and analyzing evidence that led them to identify Lake Missoula as the source of the Spokane flood and creator of the channeled scablands. After Pardee studied the canyon of the Flathead River , he estimated that flood waters above 45 miles per hour (72 km/h) would be required to roll

1254-410: The pressure at the bottom of the ice dam increased enough to lower the freezing point of water below the temperature of the ice forming the dam. This allowed liquid water to seep into minuscule cracks present in the ice dam. Over a period of time, the friction from water flowing through these cracks generated enough heat to melt the ice walls and enlarge the cracks. This allowed more water to flow through

1292-649: The previous having taken place four years before, in July 2008. About 13,000 years ago in North America, the Cordilleran Ice Sheet crept southward into the Idaho Panhandle , forming a large ice dam that blocked the mouth of the Clark Fork River , creating a massive lake 2,000 feet (600 m) deep and containing more than 500 cubic miles (2,000 km ) of water. Finally this Glacial Lake Missoula burst through

1330-399: The retreat of a melting glacier , a glacial ice dam, or by meltwater trapped against an ice sheet due to isostatic depression of the crust around the ice. At the end of the last ice age about 10,000 years ago, large proglacial lakes were a widespread feature in the northern hemisphere. The receding glaciers of the tropical Andes have formed a number of proglacial lakes, especially in

1368-529: The river, which backs up into a proglacial lake, which eventually overflows or undermines the ice dam, suddenly releasing the impounded water in a glacial lake outburst flood also known by its Icelandic name a jökulhlaup . Some of the largest glacial floods in North American history were from Lake Agassiz . In modern times, the Hubbard Glacier regularly blocks the mouth of Russell Fjord at 60° north on

1406-426: The top of the Touchet beds. The two layers of volcanic ash are separated by 1–10 centimetres (0.4–3.9 in) of airborne nonvolcanic silt. The tephra is Mount St. Helens ash that fell in Eastern Washington. By analogy, since there were 40 layers with comparable characteristics at Burlingame Canyon, Waitt argued they all could be considered to have similar separation in deposition time. The controversy about whether

1444-610: Was based mainly on analysis from glacial lake bottom deposits in Ninemile Creek and the flood deposits in Burlingame Canyon. His most compelling argument for separate floods was that the Touchet bed deposits from two successive floods were found to be separated by two layers of volcanic ash ( tephra ), with the ash separated by a fine layer of windblown dust deposits, located in a thin layer between sediment layers ten rhythmites below

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