Paraglacial

Paraglacial means unstable conditions[1] caused by a significant relaxation time in processes and geomorphic patterns following glacial climates.[2] Rates of landscape change and sediment output from the system are typically elevated during paraglacial landscape response.

When a large mass of ice melts, the newly exposed landscape is free of vegetation and is generally unstable. Often, the retreating glacier is providing the area with high stream discharge, further increasing erosion. The combination of a lack of vegetation, high discharge, and a changing climate (the cause of deglaciation) forces ecological communities, sediment deposition patterns and surface morphology to adjust to the new conditions over time.

Periglacial processes—those that directly involve ice—may be prominent in the early stages of paraglacial landscape response, but the two terms are not synonymous. Many geomorphic processes that don't require freezing conditions—for example fluvial erosion, transport and deposition—are typically involved in paraglacial change.

See also

  • Ballantyne, C.K. (2002) Paraglacial Geomorphology. Quaternary Science Reviews, 21, 1935-2017.
  • Benn, D.I. and Evans, D.J.A., Glaciers and Glaciation, (1998) ISBN 0-340-65303-5 or 0-340-58431-9 (paperback), Section 7.6.
  • Iturrizaga, L. (1999). Typical debris accumulation forms and formations in High Asia. A glacial-history-based concept of the origin of Postglacial debris accumulation landscapes in subtropical high mountains with selected examples from the Hindu Kush, the Karakoram and the Himalayas. In: GeoJournal, Tibet and High Asia V, vol. 47, 277-339.
  • Iturrizaga, L. (2008). Paraglacial landform assemblages in the Hindukush and Karakoram Mountains. In: Geomorphology, 95, Issues 1-2, 27-47.
  • Slaymaker O., 2011. Criteria to distinguish between periglacial, proglacial and paraglacial environments. Quaestiones Geographicae 30(1): 85–94. DOI 10.2478/v10117-011-0008-y

References

  1. ^ Renwick, W.H. 1992: Equilibrium, disequilibrium, and nonequilibrium landforms in the landscape. Geomorphology 5, 265-76
  2. ^ Church, Michael and June M Ryder, Paraglacial Sedimentation: A Consideration of Fluvial Processes Conditioned by Glaciation, GSA Bulletin; October 1972; v. 83; no. 10; p. 3059-3072
Deglaciation

Deglaciation describes the transition from full glacial conditions during ice ages, to warm interglacials, characterized by global warming and sea level rise due to change in continental ice volume. Thus, it refers to the retreat of a glacier, an ice sheet or frozen surface layer, and the resulting exposure of the Earth's surface. The decline of the cryosphere due to ablation can occur on any scale from global to localized to a particular glacier. After the Last Glacial Maximum (ca. 21,000 years ago), the last deglaciation begun, which lasted until the early Holocene. Around much of Earth, deglaciation during the last 100 years has been accelerating as a result of climate change, partly brought on by anthropogenic changes to greenhouse gases.The previous deglaciation took place between approximately 22ka until 11.5ka. This occurred when there was an annual mean atmospheric temperature on the earth that increased by roughly 5 °C, which was also accompanied by regional high-latitude warming that exceeded 10 °C. This was also followed by noteworthy deep-sea and tropical-sea warming, between about 1-2 °C (deep-sea) and 2-4 °C (tropical sea). Not only did this warming occur, but the global hydrological budget also experienced noticeable changes and regional precipitation patterns changed. As a result of all of this, the world's main ice sheets, including the ones located in Eurasia, North America and parts of the Antarctic melted. As a consequence, sea levels rose roughly 120 metres. These processes did not occur steadily, and they also did not occur at the same time.

Discrete debris accumulation

Discrete debris accumulation (DDA) is a non-genetic term in mountain glacial geology to aid identification of non-lithified sediments on a valley or mountain slope or floor. It is intended that the debris accumulation is discrete such that it can be mapped, in the field and/or from aerial or satellite imagery. The origin or formative process may well not be known clearly or be changed by subsequent investigators it is advisable to have a non-genetic field reference so that discussion can then be used to ascertain, if possible, the origin. Mountain areas may currently have glaciers (glacierized) or have had glaciers (glaciated) or be subject to forms of periglacial activity. A moraine would be an easily identified DDA as would an esker. Although scree (talus) is generally easily identified and mapped, these deposits may be modified by ice, avalanches or downlope movement to create essentially new landforms. Many small slope failures and landslides can give the appearance of moraines or protalus ramparts on slopes. After mapping as a DDA, further investigation might draw light on the origin of the feature.

The term was apparently first used by Sven Lukas for a very specific feature in Svalbard.

Independently, it was suggested in the literature in W. B. Whalley and subsequently in Whalley, 2012 as relating to the basic definition and usage as above. This book chapter provides several photographic examples.

The 'cirque infills' described by Hätterstrand et al. (2008) in the Khibiny Mountains, Kola Peninsula could be described as discrete debris accumulations, although their origin is postulated by these authors as being moraine remnants of an ice sheet pushing into these cirques rather than as rock glaciers formed within the cirques.

Geomorphology

Geomorphology (from Ancient Greek: γῆ, gê, "earth"; μορφή, morphḗ, "form"; and λόγος, lógos, "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or near the Earth's surface. Geomorphologists seek to understand why landscapes look the way they do, to understand landform history and dynamics and to predict changes through a combination of field observations, physical experiments and numerical modeling. Geomorphologists work within disciplines such as physical geography, geology, geodesy, engineering geology, archaeology, climatology and geotechnical engineering. This broad base of interests contributes to many research styles and interests within the field.

Gullies on Mars

Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars. They are named for their resemblance to terrestrial gullies. First discovered on images from Mars Global Surveyor, they occur on steep slopes, especially on the walls of craters. Usually, each gully has a dendritic alcove at its head, a fan-shaped apron at its base, and a single thread of incised channel linking the two, giving the whole gully an hourglass shape. They are estimated to be relatively young because they have few, if any craters. A subclass of gullies is also found cut into the faces of sand dunes, that are themselves considered to be quite young. Linear dune gullies are now considered recurrent seasonnal afeatures.Most gullies occur 30 degrees poleward in each hemisphere, with greater numbers in the southern hemisphere. Some studies have found that gullies occur on slopes that face all directions; others have found that the greater number of gullies are found on poleward facing slopes, especially from 30° to 44° S. Although thousands have been found, they appear to be restricted to only certain areas of the planet. In the northern hemisphere, they have been found in Arcadia Planitia, Tempe Terra, Acidalia Planitia, and Utopia Planitia. In the south, high concentrations are found on the northern edge of Argyre basin, in northern Noachis Terra, and along the walls of the Hellas outflow channels. A recent study examined 54,040 CTX images that covered 85% of the Martian surface found 4861 separate gullied landforms (e.g., individual craters, mounds, valleys, etc.), which totaled tens of thousands of individual gullies. It is estimated that CTX can resolve 95% of gullies.This article gives a history of the discovery and research on gullies. As research progresses, the cause of Martian gullies has shifted from recent liquid water to pieces of dry ice moving down steep slopes, but research continues. On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers think that the processes carving the gullies involve liquid water. When the volumes of the aprons are compared to the rest of the gully, it appears that there is much less volume in the apron; hence, much of the material may have contained water and ice that disappeared. However, this remains a topic of active research. Because the gullies are so young, this would suggest that liquid water has been present on Mars in its very recent geological past, with consequences for the potential habitability of the modern surface.

On July 10, 2014, NASA reported that gullies on the surface of Mars were mostly formed by the seasonal freezing of carbon dioxide (CO2), and not by that of liquid water as considered earlier.

Kobuk River

The Kobuk River (also Kooak, Kowak, Kubuk, Kuvuk, or Putnam)

is a river located in the Arctic region of northwestern Alaska in the United States. It is approximately 280 miles (451 km) long. Draining a basin with an area of 12,300 square miles (32,000 km2), the Kobuk River is among the largest rivers in northwest Alaska with widths of up to 1500 feet (460 m) and flow at a speed of 3–5 miles per hour (5–8 km per hour) in its lower and middle reaches. The average elevation for the Kobuk River Basin is 1,300 feet (400 m) above sea level, ranging from near sea level to 11,400 feet (3,475 m). Topography includes low, rolling mountains, plains and lowlands, moderately high rugged mountainous land, and some gently sloped plateaus and highlands. The river contains an exceptional population of sheefish (Stenodus leucicthys), a large predatory whitefish within the salmon family, found throughout the Arctic that spawns in the river's upper reaches during the autumn. A portion of the vast Western Arctic Caribou Herd utilize the Kobuk river valley as winter range.

Lagoon

A lagoon is a shallow body of water separated from a larger body of water by barrier islands or reefs. Lagoons are commonly divided into coastal lagoons and atoll lagoons. They have also been identified as occurring on mixed-sand and gravel coastlines. There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries. Lagoons are common coastal features around many parts of the world.

Lake Tauca

Lake Tauca is a former lake in the Altiplano of Bolivia. It is also known as Lake Pocoyu for its constituent lakes: Lake Poopó, Salar de Coipasa and Salar de Uyuni. The lake covered large parts of the southern Altiplano between the Eastern Cordillera and the Western Cordillera, covering an estimated 48,000 to 80,000 square kilometres (19,000 to 31,000 sq mi) of the basins of present-day Lake Poopó and the Salars of Uyuni, Coipasa and adjacent basins. Water levels varied, possibly reaching 3,800 metres (12,500 ft) in altitude. The lake was saline. The lake received water from Lake Titicaca, but whether this contributed most of Tauca's water or only a small amount is controversial; the quantity was sufficient to influence the local climate and depress the underlying terrain with its weight. Diatoms, plants and animals developed in the lake, sometimes forming reef knolls.

The duration of Lake Tauca's existence is uncertain. Research in 2011 indicated that the rise in lake levels began 18,500 BP, peaking 16,000 and 14,500 years ago. About 14,200 years ago, lake levels dropped before rising again until 11,500 years ago. Some researchers postulate that the last phase of Lake Tauca may have continued until 8,500 BP. The drying of the lake, which may have occurred because of the Bølling-Allerød climate oscillation, left the salt deposits of Salar de Uyuni.

Lake Tauca is one of several ancient lakes which formed in the Altiplano. Other known lakes are Lake Escara, Ouki, Salinas, Lake Minchin, Inca Huasi and Sajsi, in addition to several water-level rises of Lake Titicaca. The identity of these lakes is controversial; Sajsi is often considered part of Lake Tauca, and the lake is frequently divided into an earlier (Ticaña) and a later (Coipasa) phase.

The formation of Lake Tauca depended on a reduction in air temperature over the Altiplano and an increase in precipitation, which may have been caused by shifts in the Intertropical Convergence Zone (ITCZ) and increased easterly winds. It was originally supposed that glacial melting might have filled Lake Tauca, but the quantity of water would not have been sufficient to fill the whole lake. The lake was accompanied by glacial advance, noticeable at Cerro Azanaques and Tunupa. Elsewhere in South America, water levels and glaciers also expanded during the Lake Tauca phase.

Lithalsa

Lithalsa is a frost-induced raised land form in permafrost areas with mineral-rich soils, where a perennial ice lens has developed within the soil. The term sometimes also refers to palsas and pingos.

Mount Meager massif

The Mount Meager massif is a group of volcanic peaks in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada. Part of the Cascade Volcanic Arc of western North America, it is located 150 km (93 mi) north of Vancouver at the northern end of the Pemberton Valley and reaches a maximum elevation of 2,680 m (8,790 ft). The massif is capped by several eroded volcanic edifices, including lava domes, volcanic plugs and overlapping piles of lava flows; these form at least six major summits including Mount Meager which is the second highest of the massif.

The Garibaldi Volcanic Belt (GVB) has a long history of eruptions and poses a threat to the surrounding region. Any volcanic hazard ranging from landslides to eruptions could pose a significant risk to humans and wildlife. Although the massif has not erupted for more than 2,000 years, it could produce a major eruption; if this were to happen, relief efforts would be quickly organized. Teams such as the Interagency Volcanic Event Notification Plan (IVENP) are prepared to notify people threatened by volcanic eruptions in Canada.

The Mount Meager massif produced the largest volcanic eruption in Canada in the last 10,000 years. About 2,400 years ago, an explosive eruption formed a volcanic crater on its northeastern flank and sent avalanches of hot ash, rock fragments and volcanic gases down the northern flank of the volcano. Evidence for more recent volcanic activity has been documented at the volcano, such as hot springs and earthquakes. The Mount Meager massif has also been the source of several large landslides in the past, including a massive debris flow in 2010 that swept down Meager Creek and the Lillooet River.

Periglaciation

Periglaciation (adjective: "periglacial", also referring to places at the edges of glacial areas) describes geomorphic processes that result from seasonal thawing of snow in areas of permafrost, the runoff from which refreezes in ice wedges and other structures. "Periglacial" suggests an environment located on the margin of past glaciers. However, freeze and thaw cycles influence landscapes outside areas of past glaciation. Therefore, periglacial environments are anywhere that freezing and thawing modify the landscape in a significant manner.Tundra is a common ecological community in periglacial areas.

Phaethontis quadrangle

The Phaethontis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Phaethontis quadrangle is also referred to as MC-24 (Mars Chart-24).The name comes from Phaethon, the son of Helios.The Phaethontis quadrangle lies between 30° and 65 ° south latitude and 120° and 180 ° west longitude on Mars. This latitude range is where numerous gullies have been discovered. An old feature in this area, called Terra Sirenum lies in this quadrangle; Mars Reconnaissance Orbiter discovered iron/magnesium smectites there. Part of this quadrangle contains what is called the Electris deposits, a deposit that is 100–200 meters thick. It is light-toned and appears to be weak because of few boulders. Among a group of large craters is Mariner Crater, first observed by the Mariner IV spacecraft in the summer of 1965. It was named after that spacecraft. A low area in Terra Sirenum is believed to have once held a lake that eventually drained through Ma'adim Vallis. Russia's Mars 3 probe landed in the Phaethontis quadrangle at 44.9° S and 160.1° W in December 1971. It landed at a speed of 75 km per hour, but survived to radio back 20 seconds of signal, then it went dead. Its message just appeared as a blank screen.

Sainte-Marguerite River (Sept-Îles)

The Sainte-Marguerite River (French: Rivière Sainte-Marguerite; Saint Margaret River) is a 316 kilometres (196 mi) long river in the Côte-Nord region of Quebec, Canada.

It flows into the Gulf of Saint Lawrence to the west of Sept-Îles.

There are traces of human activity along the river from 4,000 years ago.

Pulp and paper exploitation in the river basin began in the early 20th century, followed by mining.

The river has a large hydroelectric power dam, the Denis-Perron dam, that contains a reservoir that is 140 kilometres (87 mi) long.

Washdyke Lagoon

Washdyke Lagoon is a brackish shallow coastal lagoon approximately 1 kilometre north of Timaru, South Canterbury, New Zealand. The lagoon has drastically reduced in size since 1881 when it was approximately 253 hectares, now it is less than 48 hectares in area (0.48 square kilometres). It is enclosed by a barrier beach that is 3 kilometres long and 3 metres above high tide at its largest point (see Figure 1). The reduced lagoon size is due to the construction of the Timaru Port breakwater which is preventing coarse sediments from reaching and replenishing Washdyke Barrier. This is important as the lagoon and the surrounding 250 hectares are classified as a wildlife refuge and it demonstrates the role human structures have on coastline evolution.

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