Moraine

A moraine is any glacially formed accumulation of unconsolidated glacial debris (regolith and rock) that occurs in both currently and formerly glaciated regions on Earth (i.e. a past glacial maximum), through geomorphological processes. Moraines are formed from debris previously carried along by a glacier and normally consisting of somewhat rounded particles ranging in size from large boulders to minute glacial flour. Lateral moraines are formed at the side of the ice flow and terminal moraines at the foot, marking the maximum advance of the glacier. Other types of moraine include ground moraines, till-covered areas with irregular topography, and medial moraines which are formed where two glaciers meet.

Manang site (54)
The snow-free debris hills around the lagoon are lateral and terminal moraines of a valley glacier in Nepal.

Characteristics

Moraines may be composed of debris ranging in size from silt-sized glacial flour to large boulders. The debris is typically sub-angular to rounded in shape. Moraines may be on the glacier’s surface or deposited as piles or sheets of debris where the glacier has melted.

Formation

Moraines may form through a number of processes, depending on the characteristics of sediment, the dynamics on the ice, and the location on the glacier in which the moraine is formed.[1] Moraine forming processes may be loosely divided into passive and active. Passive processes involve the placing of chaotic supraglacial sediments onto the landscape with limited reworking, typically forming hummocky moraines.[2] These moraines are composed of supraglacial sediments from the ice surface. Active processes form or rework moraine sediment directly by the movement of ice, known as glaciotectonism. These form push moraines and thrust-block moraines, which are often composed of till and reworked proglacial sediment.[3]

Moraine may also form by the accumulation of sand and gravel deposits from glacial streams emanating from the ice margin. These fan deposits may coalesce to form a long moraine bank marking the ice margin.[4]

Several processes may combine to form and rework a single moraine, and most moraines record a continuum of processes.

Ansel Adams - National Archives 79-AA-M02
Moraine in Rocky Mountain National Park, taken by Ansel Adams in 1941
Icy-lake
Moraines around the Icy lake (2709 m.), just below Musala peak (2925 m.) in Rila Mountain, Bulgaria
Moraines Surlej
Lateral moraines of a retreating glacier in Engadin

Types of moraines

Moraines can be classified either by origin, location with respect to a glacier or former glacier, or by shape. The first approach is suitable for moraines associated with contemporary glaciers—but more difficult to apply to old moraines, which are defined by their particular morphology, since their origin is debated. Some moraine types are known only from ancient glaciers, while medial moraines of valley glaciers are poorly preserved and difficult to distinguish after the retreat or melting of the glacier.

Lateral moraines

MorainesLakeLouise
Lateral moraines above Lake Louise, Alberta, Canada.

Lateral moraines are parallel ridges of debris deposited along the sides of a glacier. The unconsolidated debris can be deposited on top of the glacier by frost shattering of the valley walls and/or from tributary streams flowing into the valley. The till is carried along the glacial margin until the glacier melts. Because lateral moraines are deposited on top of the glacier, they do not experience the postglacial erosion of the valley floor and therefore, as the glacier melts, lateral moraines are usually preserved as high ridges.

Glacier.zermatt.arp.750pix
Moraines clearly seen on a side glacier of the Gorner Glacier, Zermatt, Switzerland. The lateral moraine is the high snow-free bank of debris in the top left hand quarter of the picture. The medial moraine is the double line of debris running down the centre-line of the glacier.

Lateral moraines stand high because they protect the ice under them from the elements, causing it to melt or sublime less than the uncovered parts of the glacier. Multiple lateral moraines may develop as the glacier advances and retreats.

Ground moraines

Ground moraine 9004
Ground moraines create irregular, rolling topography

Ground moraines are till-covered areas with irregular topography and no ridges, often forming gently rolling hills or plains. They are accumulated at the base of the ice as lodgment till, but may also be deposited as the glacier retreats. In alpine glaciers, ground moraines are often found between the two lateral moraines. Ground moraines may be modified into drumlins by the overriding ice.

Rogen moraines

Rogen moraines or ribbed moraines are a type of basal moraines that form a series of ribs perpendicular to the ice flow in an ice sheet. The depressions between the ribs are sometimes filled with water, making the Rogen moraines look like tigerstripes on aerial photographs. Rogen moraines are named after Lake Rogen[5] in Härjedalen, Sweden, the landform’s type locality.

Nuussuaq-peninsula-moraines
Medial moraines, Nuussuaq Peninsula, Greenland

End or terminal moraines

Erratics-Cascades-PB110028
Multiple erratics on the terminal moraine of the Okanogan Lobe. Cascade mountains in the background.

End moraines, or terminal moraines, are ridges of unconsolidated debris deposited at the snout or end of the glacier. They usually reflect the shape of the glacier's terminus. Glaciers act much like a conveyor belt, carrying debris from the top of the glacier to the bottom where it deposits it in end moraines. End moraine size and shape are determined by whether the glacier is advancing, receding or at equilibrium. The longer the terminus of the glacier stays in one place, the more debris accumulate in the moraine. There are two types of end moraines: terminal and recessional. Terminal moraines mark the maximum advance of the glacier. Recessional moraines are small ridges left as a glacier pauses during its retreat. After a glacier retreats, the end moraine may be destroyed by postglacial erosion.

Recessional moraine

Recessional moraines are often observed as a series of transverse ridges running across a valley behind a terminal moraine. They form perpendicular to the lateral moraines that they reside between and are composed of unconsolidated debris deposited by the glacier. They are created during temporary halts in a glacier's retreat.[1][6]

Medial moraine

A medial moraine is a ridge of moraine that runs down the center of a valley floor. It forms when two glaciers meet and the debris on the edges of the adjacent valley sides join and are carried on top of the enlarged glacier. As the glacier melts or retreats, the debris is deposited and a ridge down the middle of the valley floor is created. The Kaskawulsh Glacier in the Kluane National Park, Yukon, has a ridge of medial moraine 1 km wide.

The prominent dark streak at the left quarter is forming a medial moraine. This is seen as a mudflat at the water's surface. (Brüggen Glacier, Patagonia)
The prominent dark streak at the left quarter is forming a medial moraine.
This is seen as a mudflat at the water's surface. (Brüggen Glacier, Patagonia)

Supraglacial moraines

Supraglacial moraines are created by debris accumulated on top of glacial ice. This debris can accumulate due to ice flow toward the surface in the ablation zone, melting of surface ice or from debris that falls onto the glacier from valley sidewalls.

Washboard moraines

Washboard moraines, also known as minor or corrugated moraines, are low-amplitude geomorphic features caused by glaciers. The name "washboard moraine" refers to the fact that, from the air, it resembles a washboard.

Veiki moraine

A Veiki moraine is a kind of hummocky moraine that forms irregular landscapes of ponds and plateaus surrounded by banks. It forms from the irregular melting of ice covered with a thick layer of debris. Veiki moraine is common in northern Sweden and parts of Canada.

See also

Colline moreniche del Lago Garda
Moraine of Lake Garda
Geologic features related to moraines
Moraine examples

References

  1. ^ a b Benn, D. I. and Evans, D. J. A. (1998) Glaciers & Glaciation. Oxford University Press, New York, NY.
  2. ^ Kjær, Kurt H.; Krüger, Johannes (2001-10-21). "The final phase of dead-ice moraine development: processes and sediment architecture, Kötlujökull, Iceland". Sedimentology. 48 (5): 935–952. Bibcode:2001Sedim..48..935K. doi:10.1046/j.1365-3091.2001.00402.x. ISSN 1365-3091.
  3. ^ Bennett, Matthew R. (2001-04-01). "The morphology, structural evolution and significance of push moraines". Earth-Science Reviews. 53 (3–4): 197–236. Bibcode:2001ESRv...53..197B. doi:10.1016/S0012-8252(00)00039-8.
  4. ^ Boulton, G. S. (1986-10-01). "Push-moraines and glacier-contact fans in marine and terrestrial environments". Sedimentology. 33 (5): 677–698. Bibcode:1986Sedim..33..677B. doi:10.1111/j.1365-3091.1986.tb01969.x. ISSN 1365-3091.
  5. ^ Möller, P., 2006. Rogen moraine: an example of glacial reshaping of preexisting landforms. Quaternary Science Reviews, 25:362-389
  6. ^ "Moraine." Columbia Electronic Encyclopedia, 6th Edition (2009): 1. Academic Search Complete. EBSCO. Web. 6 Oct. 2010.
  • Easterbrook, D. J. (1999) Surface processes and landforms. (Second Ed). Prentice Hall, Upper Saddle River, New Jersey.
  • Benn, D. I. and Evans, D. J. A. (1998) Glaciers & Glaciation. Oxford University Press, New York, NY.

External links

Chippewa Moraine State Recreation Area

Chippewa Moraine State Recreation Area is a state park unit of Wisconsin, USA, preserving numerous glacial landforms. The abundance and quality of these geological features led to its being included in the Ice Age National Scientific Reserve. The Ice Age National Scenic Trail passes through the park. The park is largely undeveloped, but its modern visitor center serves to interpret the area's geological and biological features. Official documentation alternatively refers to the park as the Chippewa Moraine Ice Age Reserve or the Chippewa Moraine Ice Age National Scientific Reserve. It is located in northwestern Chippewa County.

The Chippewa Moraine Interpretive Center offers exhibits about the area's geology, natural history, and cultural history, as well as naturalist-led programs for school groups. The center is located 7 miles (11 km) east of New Auburn.

Dirt cone

A dirt cone is a type of depositional glacial feature. Dirt cones are not actually made entirely of dirt. They have a core of ice, snow, or firn that gets covered with material and insulated. The material, if it is thick enough, will protect the underlying core from ablation. The thickness of material needed to insulate the core is called the “critical thickness.” If the material is less thick than the critical thickness, it will actually speed up erosion of the core through ablation. This is called “indirect ablation.” The cone would then begin melting and shrinking away.

Dirt cones begin forming in a crevasse or a hollow. Dirt, dust, or moraine deposit material will fall into the crevasse in the glacier and build up over time. At the same time, the surrounding glacier lowers through ablation until the dirt filled crevasse is exposed and the material begins to spread out of top of the glacier. The rest of the glacier continues to lower as the material mound grows higher and taller. Any ice, snow, or firn trapped under the material will be insulated and protected from erosion. It begins forming a conical shape as the sides steepen to an angle that is unstable. Material falls down and protects the sides. The more material is added to the top, the more insulated the core becomes. Over time, it becomes a cone with a layer of material on the outside and a core of ice, snow, or firn on the inside. The material at the top of the cone is generally thicker than the material on the sides of the dirt cone.Cones can also be found on snow patches. Many snow patches contain a certain amount of debris on them, blown in on the wind. Typically, this is a course grained sand or organic material. The sand is quite porous which makes it a poor conductor of heat. During extreme wind events, this sand or organic matter is carried onto the snow patch. The snow lying underneath the porous sand is protected from the heat and does not erode away. The snow not protected by a layer of sand or organic matter begins to erode through ablation. The protected areas accumulate more sand and eventually take on a conical shape. The core of snow is protected from ablation while the surrounding snow patch continues to melt. This is another way dirt cones can form.Even areas with a very small debris load, like Antarctica, can have dirt cones. The dirt cones in Antarctica are formed from the moraine deposit material left behind when a glacier retreats. The material making up these cones can be sorted or unsorted. Sorted moraine material is sorted by water. Sorting refers to the material size. Well-sorted material is all the same size. Unsorted material consists of all different sizes. For instance, there are smaller grained particles, like clay aggregates, next to boulders and gravel. Both sorted and unsorted moraine material is used in Antarctica to make dirt cones. Dirt cones were previously not thought to be formed in Antarctica.Some cones are only be a few centimeters tall, while others can be up to 30 meters high. The larger dirt cones are commonly multiple cones that have fused (melted) together. As an ice sheet or glacier melts and retreats, the cones on the surface are brought together and eventually fuse together. This strengthens the ice core and creates a thicker layer of material on the outside to protect the hardened core from eroding. They can develop in one winter season or they can be a product of several seasons. Sometimes, they form as a single cone or as multiple cones in a ridge on moraine deposits. Generally, there are many cones on a glacier, snow patch, or ice sheet. They may be similar in size and material.

Dirt cones are found all over the globe, in both arctic and temperate regions. They are not limited to one geographic region. They have been seen in Iceland, Alaska, Antarctica, in the Himalayas, Norway, Canada, and Greenland. Many of these cones have been studied and surveyed to better understand their dynamics. All they need to form is debris of some sort and ice.

Kettle (landform)

A kettle (kettle hole, pothole) is a shallow, sediment-filled body of water formed by retreating glaciers or draining floodwaters. The kettles are formed as a result of blocks of ice calving from glaciers and becoming submerged in the sediment on the outwash plain. Another source is the sudden drainage of an ice-dammed lake. When the block melts, the hole it leaves behind is a kettle. As the ice melts, ramparts can form around the edge of the kettle hole. The lakes that fill these holes are seldom more than 10 m (33 ft) deep and eventually become filled with sediment. In acid conditions, a kettle bog may form but in alkaline conditions, it will be kettle peatland.

Kettle Moraine State Forest

The Kettle Moraine State Forest is a state forest in southeastern Wisconsin. The chief feature of the reserve is the Kettle Moraine, a highly glaciated area. The area contains very hilly terrain and glacial landforms, such as kettles, kames and eskers. The 56,000-acre (23,000 ha) forest is divided into two large and three small units, which are spread across a hundred miles.

The forest includes 250 miles (400 km) of hiking trails, almost 100 miles (160 km) of cross-country ski trails, 130 miles (210 km) of equestrian trails, 150 miles (240 km) of snowmobile trails, 75 miles (121 km) of off-road bicycle trails including 30 miles (48 km) of singletrack trail, and 750 campsites.All units include a portion of the Ice Age National Scenic Trail and most units have horse/snowmobile trails. Several areas of trail loops for hiking, biking and skiing can be found in the northern and southern units.

Kettle Moraine Scenic Drive is a 115-mile (185 km) scenic route that winds across southeastern Wisconsin, and through all five forest units.

Moraine-dammed lake

A moraine-dammed lake occurs when the terminal moraine has prevented some meltwater from leaving the valley. Its most common shape is that of a long ribbon (ribbon lake).

Example of moraine dammed lakes include:

Argentina/Chile: General Carrera/Buenos Aires Lake

Chile: Calafquén Lake, Panguipulli Lake

New Zealand: Lake Hāwea, Lake Ohau, Lake Pukaki, Lake Tekapo, Lake Wakatipu, and Lake Wanaka (i.e., almost all large lakes in the South Island)

Switzerland: Lake Zurich

United States: Donner Lake in California, Flathead Lake in Montana, Mille Lacs Lake in Minnesota, Wallowa Lake in Oregon

Wales: Llyn Peris and its twin Llyn Padarn.In the 19th century the Argentine explorer Francisco Perito Moreno suggested that many Patagonian lakes draining to the Pacific were in fact part of the Atlantic basin but had been moraine dammed during the quaternary glaciations changing their outlets to the west. He argued that as originally belonging to the Atlantic basin these lakes should be awarded to Argentina. Most of the lakes situated in the Himalaya of Nepal and Bhutan are also of the moraine dammed type. They may burst at any time. That is why the areas below such lakes have high risk of flooding.

Moraine Cone

Moraine Cone is a cinder cone in northern British Columbia, Canada. It is thought to have last erupted in the Holocene period and is part of the Mount Edziza volcanic complex.

Moraine Hills State Park

Moraine Hills State Park is an Illinois state park on 2,200 acres (890 ha) in McHenry County, Illinois, United States.

Moraine Park Museum and Amphitheater

The Moraine Park Museum and Amphitheater, also known as the Moraine Park Lodge and the Moraine Park Visitor Center, are located in Moraine Park, a glaciated meadow between two moraines in Rocky Mountain National Park.The two structures were built to serve visitors to the park, and are listed on the National Register of Historic Places. The museum was built in 1923 by Imogene Green MacPherson as the center of her private tourist development, and was then known as the Moraine Park Lodge. The National Park Service purchased the property in 1931 and demolished the surrounding cabins in following years. The amphitheater was designed and built in 1935, with the design by the NPS Branch of Plans and Designs and the construction by the Civilian Conservation Corps. The lodge was reworked in 1934-35. Both structures adhere to the National Park Service Rustic design ethic of the time, with stone and log construction.Imogene Green MacPherson first homesteaded the site in Moraine Park in 1903, naming the land "Hillcrest". In 1905, newly married, she expanded with a lodge, dining hall, stable and some cabins for guests. Paying guest began to arrive in 1910. Mrs. MacPherson continued to operate the resort after the death of her husband in 1919, and was involved in the campaign for the establishment of Rocky Mountain National Park. After her death in 1928, her family continued to run the lodge until its purchase by the Park Service.The amphitheater is built about one hundred feet from the lodge, with seating interspersed with trees. A projection booth and screen once existed, but were removed. An elaborate arrangement of stone gutters and culverts provides drainage.

The Moraine Park Lodge adjoins the William Allen White Cabins historic district.

The museum features interactive natural history exhibits, with themes including geologic processes, glaciation, weather and climate, ecosystems, and human impact. The park offers environmental education programs based on similar themes. The lodge building was listed on the National Register of Historic Places on October 8, 1976. The listing was expanded to include the amphitheater on June 15, 2005.

Moraine State Park

Moraine State Park is a Pennsylvania state park on 16,725 acres (6,768 ha) in Brady, Clay, Franklin, Muddy Creek, and Worth townships in Butler County, Pennsylvania, in the United States.

The park's main feature is its man-made lake, Lake Arthur, formed by impounding Muddy Creek, which is 3,225 acres (1,305 ha) and is used for recreational purposes. The surrounding park is used for hiking, bicycling, group camping, picnicking, and hunting. Moraine State Park hosts the annual Regatta at Lake Arthur in August. The park was the location of the 1973 and 1977 National Scout Jamborees. Moraine State Park is at the intersection of Interstate 79 and U.S. Route 422 and shares a border with Jennings Environmental Education Center to the north.

Moraine State Park was chosen by the Pennsylvania Department of Conservation and Natural Resources (DCNR) and its Bureau of State Parks as one of "25 Must-See Pennsylvania State Parks".

Moraine Valley Community College

Moraine Valley Community College is a public community college in Palos Hills, Illinois. Founded in 1967, it is in the Cook County Forest Preserves. The college also operates satellite facilities in Blue Island and Tinley Park, Illinois.

Moraine View State Recreation Area

The Moraine View State Recreation Area is a state park operated by the Department of Natural Resources (DNR) of the U.S. state of Illinois. The 1,687 acre (6.7 km2) recreation area is located near Le Roy, Illinois.

The predecessor of Moraine View, the McLean County Conservation Area, traces its history to 1959. The park was renamed Moraine View State Park in 1975, then Moraine View State Recreation Area in 1995. It is managed for active recreation, including camping, hiking, swimming, boating, hunting and fishing. Camping available includes Class A sites with electricity and nearby modern toilet and shower facilities, to group camps and primitive backpacking sites. Hunters use the park for whitetail deer, pheasant, and wild turkey.

Moraine View was one of eleven state parks slated to close indefinitely on November 1, 2008 due to budget cuts by former Illinois governor Rod Blagojevich. It reopened to the public on February 26, 2009.

Oak Ridges Moraine

The Oak Ridges Moraine is an ecologically important geological landform in the Mixedwood Plains of south-central Ontario, Canada. The moraine covers a geographic area of 1,900 square kilometres (730 sq mi) between Caledon and Rice Lake, near Peterborough. One of the most significant landforms in southern Ontario, the moraine gets its name from the rolling hills and river valleys extending 160 km (99 mi) from the Niagara Escarpment east to Rice Lake. It was formed 12,000 years ago by advancing and retreating glaciers (see geological origins, below). The moraine is currently a contested site in Ontario, since it stands in the path of major urban development (see political action).

Pulju moraine

A Pulju moraine (Swedish: Pulju-morän) is a type of moraine found in northern Finland. Pulju moraines were first identified as distinct moraine type in 1967 by Finnish geologist Raimo Kujansuu who noticed moraines that resembled Veiki moraines as those described by Gunnar Hoppe in 1952 but were smaller. Raimo Kujansuu described Pulju moraines with the following words:

...consists of small hummocks, often only from one to five meters high, or of ridges of the same height and between 50 and 300 meters long, which are situated helter-skelter or in thick clusters running either parallel to the movement or margin of the ice sheet or crossvalleywise. In many spots one also meets with ring ridges, measuring no more than 50 to 150 meters in diameter. The slopes are gentle and the hollows between the ridges are mostly filled with peat.

Together with Veiki moraines Pulju moraines form landscapes of the type "ice-walled lake plains".

Rogen moraine

A Rogen moraine (also called ribbed moraine) is a subglacially (i.e. under a glacier or ice sheet) formed type of moraine landform, that mainly occurs in Fennoscandia, Scotland, Ireland and Canada. They cover large areas that have been covered by ice, and occur mostly in what is believed to have been the central areas of the ice sheets. Rogen moraines are named after Lake Rogen in Härjedalen, Sweden, the landform's type locality. Rogen Nature Reserve serves to protect the unusual area.

The landform occurs in groups that are often closely and regularly spaced. They consist of glacial drift, with till being the most common constituent. The individual moraines are large, wavy ridges orientated transverse to ice flow. Drumlins are often found in close proximity of Rogen moraines, and are often interpreted to be formed at the same time as the Rogen moraines. Although Rogen moraines can span a large range of sizes, the most common distribution seems to be 10–30 metres high, 150–300 metres wide and 300–1,200 metres long.The exact mechanics of Rogen moraine formation are not known, but since the 1970s, several theories on the formation have been proposed:

Megaripples eroded in the basal ice fill during subglacial outburst floods.

Already existing landforms, such as drumlins and flutes or marginal moraines are reshaped due to a ≈90° change in the direction of the ice flow.

Debris-rich basal ice or pre-existing sediments are sheared and stacked, or folded during compressive ice flow.

Sediment sheets become fractured and extended during a transition of the overlying glacier from being cold based ice to warm based.However, it has been suggested that, due to the diversity of morphological characteristics displayed by Rogen moraine, different processes might be able to create the landform. This means that all four of the processes mentioned above might be correct. The different theories that proposed a formation near or at the glacial margin have largely been abandoned. Some of these theories proposed that Rogen moraines had an origin as a series of end moraines, that they formed in association with calving ice termini in glacial lakes, or that Rogen moraines formed in dead-ice, where supraglacial material fell down into crevasses in the ice.

Sevetti moraine

The Sevetti moraine is a particular assemblage of morainic forms found between Partakko and Sevettijärvi in northern Finland. The Sevetti moraines are disposed in trains about 50 km long and 2–3 km wide. They have rugged surfaces.

Tarn (lake)

A tarn (or corrie loch) is a mountain lake, pond or pool, formed in a cirque excavated by a glacier. A moraine may form a natural dam below a tarn.

Terminal moraine

A terminal moraine, also called end moraine, is a type of moraine that forms at the snout (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, and has been pushed by the front edge of the ice, is driven no further and instead is dumped in a heap. Because the glacier acts very much like a conveyor belt, the longer it stays in one place, the greater the amount of material that will be deposited. The moraine is left as the marking point of the terminal extent of the ice.

Veiki moraine

A Veiki moraine (Swedish: Veikimorän) is a type of moraine found in northern Sweden, Finnmark in Norway, and parts of Canada. This moraine is characterized by forming a hummocky landscape of irregular moraine plateaus with elevated rims that are intercalated with ponds. Gunnar Hoppe was the first to define the Veiki moraine concept in 1952, naming it after a locality consisting of two farms located about 10 kilometers north of Gällivare and Malmberget. To the east in Finnish Lapland, a moraine type similar to Veiki moraine but smaller is known as Pulju moraine since 1967.The disposition of the Veiki moraines reflects the last glacier movements before an ice sheet retreats, and their final form is given by the melting of dead-ice and the development and sedimentation of glacial lagoons between dead-ice cored rims during interstadial periods. In the case of the Veiki moraines of Sweden, the interstadial during which the lagoons sedimented is believed to have occurred in the early Weichsel glaciation. Thus, the Veiki moraines of Sweden are a relict landform that has largely survived later glacier action.

Withrow Moraine and Jameson Lake Drumlin Field

The Withrow Moraine and Jameson Lake Drumlin Field is a National Park Service–designated privately owned National Natural Landmark located in Douglas County, Washington state, United States. Withrow Moraine is the only Ice Age terminal moraine on the Waterville Plateau section of the Columbia Plateau. The drumlin field includes excellent examples of glacially-formed elongated hills.

Types
Anatomy
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Volcanic relations
Landforms

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