Drumlin

A drumlin, from the Irish word droimnín ("littlest ridge"), first recorded in 1833, in the classical sense is an elongated hill in the shape of an inverted spoon or half-buried egg[1] formed by glacial ice acting on underlying unconsolidated till or ground moraine. Swarms of drumlins create a landscape which is often described as having a 'basket of eggs topography'.[2]

Drumlins around Horicon Marsh in Wisconsin
Drumlins around Horicon Marsh, Wisconsin, in an area with one of the highest concentration of drumlins in the world. The curved path of the Laurentide Ice Sheet is evident in the orientation of the various mounds.
Puerto Williams, Chili
Elongate and forested drumlins south of Puerto Williams, Chile. Flow direction here was at time of formation from west to east (left to right on picture).
Drowned drumlin in Clew Bay
Drowned drumlin in Clew Bay, Ireland

Morphology

Drumlins occur in various shapes and sizes,[3] including symmetrical (about the long axis), spindle, parabolic forms, and transverse asymmetrical forms; their long axis is parallel to the direction of movement of the formative flow at the time of formation.[4]

Drumlins are typically 1 to 2 km (0.6–1.2 mi) long, less than 50 m (160 ft) high and between 300 to 600 metres (1,000–2,000 ft) wide. Drumlins generally have a length:width ratio of between 1:2 and 1:3.5, with the questionable assumption that more elongate forms correspond to faster ice motion. That is, since ice flows in laminar flow, the resistance to flow is frictional and depends on area of contact; elongate, subglacial landforms produced by ice would represent relatively slow flow rates.

Occurrence

Drumlins and drumlin clusters are glacial landforms composed primarily of glacial till. They form near the margin of glacial systems, and within zones of fast flow deep within ice sheets, and are commonly found with other major glacially-formed features (including tunnel valleys, eskers, scours, and exposed bedrock erosion).[5]

Drumlins are often in drumlin fields of similarly shaped, sized and oriented hills. Many Pleistocene drumlin fields are observed to occur in a fan-like distribution.[6] The Múlajökull drumlins of Hofsjökull are also arrayed in a splayed fan distribution around an arc of 180°.[7]

Composition

Drumlins may comprise layers constituting clay, silt, sand, gravel and boulders in various proportions; perhaps indicating that material was repeatedly added to a core, which may be of rock or glacial till. Alternatively, drumlins may be residual, with the landforms resulting from erosion of material between the landforms. The dilatancy of glacial till was invoked as a major factor in drumlin formation.[8] In other cases, drumlin fields include drumlins made up entirely of hard bedrock (e.g. granite or well-lithified limestone).[9] These drumlins cannot be explained by the addition of soft sediment to a core. Thus, accretion and erosion of soft sediment by processes of subglacial deformation do not present unifying theories for all drumlins—some are composed of residual bedrock.

Formation

There are two main theories of drumlin formation:[10] constructional, in which they form as sediment is shaped, for example by subglacial deformation; and remnant/erosional, which proposes that drumlins form by erosion of material from an unconsolidated bed. A hypothesis that catastrophic sub-glacial floods form drumlins by deposition or erosion challenges conventional explanations for drumlins.[11] It includes deposition of glaciofluvial sediment in cavities scoured into a glacier bed by subglacial meltwater, and remnant ridges left behind by erosion of soft sediment or hard rock by turbulent meltwater. This hypothesis requires huge, subglacial meltwater floods, each of which would raise sea level by tens of centimetres in a few weeks. Studies of erosional forms in bedrock at French River, Ontario, Canada provide evidence for such floods.

The recent retreat of a marginal outlet glacier of Hofsjökull in Iceland[12] exposed a drumlin field with more than 50 drumlins ranging from 90 to 320 m (300–1,050 ft) in length, 30 to 105 m (100–340 ft) in width, and 5 to 10 m (16–33 ft) in height. These formed through a progression of subglacial depositional and erosional processes, with each horizontal till bed within the drumlin created by an individual surge of the glacier.[7] The above theory for the formation of these Icelandic drumlins best explains one type of drumlin. However, it does not provide a unifying explanation of all drumlins. For example, drumlin fields including drumlins composed entirely of hard bedrock cannot be explained by deposition and erosion of unconsolidated beds.[9] Furthermore, hairpin scours around many drumlins are best explained by the erosive action of horseshoe vortices around obstacles in a turbulent boundary layer.[13][14]

Erosion under a glacier in the immediate vicinity of a drumlin can be on the order of a meter's depth of sediment per year, with the eroded sediment forming a drumlin as it is repositioned and deposited.[15]

Soil development on drumlins

Recently formed drumlins often incorporate a thin "A" soil horizon (often referred to as "'topsoil'" which accumulated after formation) and a thin "Bw" horizon (commonly referred to as "'subsoil'"). The "C" horizon, which shows little evidence of being affected by soil forming processes (weathering), is close to the surface, and may be at the surface on an eroded drumlin. Below the C horizon the drumlin consists of multiple beds of till deposited by lodgment and bed deformation. On drumlins with longer exposure (e.g. in the Lake Ontario drumlin field in New York State) soil development is more advanced, for example with the formation of clay-enriched "Bt" horizons.[7]

Examples of drumlins

Drumlinfield large
Drumlin field in Western New York state. The drumlins align with glacial flow.

Europe

The retreat of Icelandic glacier Múlajökull, which is an outlet glacier of Hofsjökull, recently exposed a 50 drumlin cluster, which serves as the basis for improved understanding of drumlin formation.[7]

A Passing Steam train - geograph.org.uk - 350110
A steam train on the Downpatrick and County Down Railway in the drumlin belt of Ulster near Downpatrick in County Down, Northern Ireland.

The literature also documents extensive drumlin fields in England, Scotland and Wales,[15] Switzerland,[16] Poland, Estonia (Vooremaa), Latvia, Sweden, around Lake Constance north of the Alps, County Leitrim, County Monaghan, County Mayo and County Cavan in the Republic of Ireland, County Fermanagh, County Armagh and County Down in Northern Ireland, Germany, Hindsholm in Denmark, Finland and Greenland.[17][15]

North America

The largest drumlin fields in the world formed beneath the Laurentide Ice Sheet and are found in Canada—Nunavut, the Northwest Territories, northern Saskatchewan, northern Manitoba, northern Ontario and northern Quebec.[18] Drumlins are common in central New York (between the south shore of Lake Ontario and Cayuga Lake),[19][20] the lower Connecticut River valley, eastern Massachusetts, the Monadnock Region of New Hampshire, Michigan (central and southern Lower Peninsula),[21] Minnesota,[22][15] the Puget Sound region of Washington state,[23] and Wisconsin. Drumlins, which are usually found in swarms or large groups, occur in every Canadian province and territory. Swarms of thousands of drumlins are found in Southern Ontario (along eastern end of Oak Ridges Moraine near Peterborough, as well as areas to the west near Dundas and Guelph[24]), Central-Eastern Ontario (Douro-Dummer), the Thelon Plan of the Northwest Territories, Alberta, southwest of Amundsen Gulf in Nunavut and West Lawrencetown, Nova Scotia.[25] The majority of those observed in North America were formed during the Wisconsin glaciation.

Asia

Drumlins are found at Tiksi, Sakha Republic, Russia.[15]

South America

Extensive drumlin fields are found in Patagonia,[15] for example near Punta Arenas Carlos Ibáñez del Campo Airport and on Navarino and Gable Island in the Beagle Channel.

Antarctica

In 2007, drumlins were observed to be forming beneath the ice of a West Antarctic ice stream.[26]

Africa

Discovery of the Namibian drumlins was reported in 2019.

See also

References

  1. ^ Menzies(1979) quoted in Benn, D.I. & Evans, D.J.A. 2003 Glaciers & Glaciation, Arnold, London (p431) ISBN 0-340-58431-9
  2. ^ http://geoschol.com/counties/CAVAN_GEOLOGY.pdf
  3. ^ Spagnolo, Matteo; Clark, Chris D.; Hughes, Anna L.C.; Dunlop, Paul; Stokes, Chris R. (2010). "The planar shape of drumlins". Sedimentary Geology. 232 (3–4): 119–129. Bibcode:2010SedG..232..119S. doi:10.1016/j.sedgeo.2010.01.008.
  4. ^ Spagnolo, M.; Clark, C.D.; Hughes, A.L.C.; Dunlop, P.; Stokes, C.R. (2010). "The planar shape of drumlins". Sedimentary Geology. 232 (3–4): 119–129. Bibcode:2010SedG..232..119S. doi:10.1016/j.sedgeo.2010.01.008.
  5. ^ Shaw, J.; Kvill, D. (1984). "A glaciofluvial origin for drumlins of the Livingstone Lake area, Saskatchewan". Canadian Journal of Earth Sciences. 21 (12): 1442–1459. Bibcode:1984CaJES..21.1442S. doi:10.1139/e84-150.
  6. ^ Patterson, C.J.; Hooke, R.L. (1995). "Physical environment of drumlin formation". Journal of Glaciology. 41 (137): 30–38. Bibcode:1995JGlac..41...30P. doi:10.1017/S0022143000017731.
  7. ^ a b c d Johnson, M. D.; Schomacker, A.; Benediktsson, I. O.; Geiger, A. J.; Ferguson, A.; Ingolfsson, O. (2010). "Active drumlin field revealed at the margin of Mulajokull, Iceland: A surge-type glacier". Geology. 38 (10): 943–946. Bibcode:2010Geo....38..943J. doi:10.1130/G31371.1.
  8. ^ Smalley, I.J., Unwin, D.J. 1968. The formation and shape of drumlins and their distribution and orientation in drumlin fields. Journal of Glaciology 7, 377-390
  9. ^ a b Lesemann, J., Brennand, T.A., 2009. Regional reconstruction of subglacial hydrology and glaciodynamic behaviour along the southern margin of the Cordilleran Ice Sheet in British Columbia, Canada and Northern Washington State, USA. Quaternary Science Reviews 28, 2420–2444.
  10. ^ Yu, Peter; Eyles, Nick; Sookhan, Shane (2015). "Automated drumlin shape and volume estimation using high resolution LiDAR imagery (Curvature Based Relief Separation): A test from the Wadena Drumlin Field, Minnesota". Geomorphology. 246: 589–601. Bibcode:2015Geomo.246..589Y. doi:10.1016/j.geomorph.2015.07.020.
  11. ^ Shaw, J., 2002. The meltwater hypothesis for subglacial bedforms. Quaternary International 90, 5-22.
  12. ^ A satellite image of the region of Hofsjökull where drumlin growth has been observed (see 64°39′25″N 18°41′41″W / 64.65694°N 18.69472°W). The drumlins can be observed between pools of water.
  13. ^ Paik, J., Escauriaza, C., Sotiropoulos, F., 2007. On the bimodal dynamics of the turbulent horseshoe vortex system in a wing-body junction. Physics of Fluids, 19, 045107 1-20.
  14. ^ Shaw, J., 1994. Hairpin erosional marks, horseshoe vortices and subglacial erosion. Sedimentary Geology 92, 169-283.
  15. ^ a b c d e f Clark, C.D.; Anna L.C. Hughes; Sarah L. Greenwood; Matteo Spagnolo; Felix S.L. Ng (2009). "Size and shape characteristics of drumlins, derived from a large sample, and associated scaling laws" (PDF). Quaternary Science Reviews. Elsevier Ltd. 28 (7–8): 677–692. Bibcode:2009QSRv...28..677C. doi:10.1016/j.quascirev.2008.08.035.
  16. ^ Fiore, J. (2007). "Quaternary subglacial processes in Switzerland: geomorphology of the plateau and seismic stratigraphy of western Lake Geneva". Terre & Environnement. University of Geneva. 69: 169. Archived from the original on 2013-12-02.
  17. ^ O'Dwyer, Barry; Crockford, Lucy; Jordan, Phil; Hislop, Lindsay; Taylor, David (2013). "A palaeolimnological investigation into nutrient impact and recovery in an agricultural catchment". Journal of Environmental Management. 124: 147–155. doi:10.1016/j.jenvman.2013.01.034. ISSN 0301-4797. PMID 23490624.
  18. ^ Shaw, J., Sharp, D., Harris, J., 2010. A flowline map of glaciated Canada based on remote sensing data. Canadian Journal of Earth Sciences. 47, 89-101.
  19. ^ Kerr, Michael; Nick Eyles (2007). "Origin of drumlins on the floor of Lake Ontario and in upper New York State". Sedimentary Geology. Elsevier. 193 (1–4): 7–20. Bibcode:2007SedG..193....7K. doi:10.1016/j.sedgeo.2005.11.025.
  20. ^ "RootsWeb.com Home Page". freepages.genealogy.rootsweb.ancestry.com. Archived from the original on 27 November 2016. Retrieved 29 April 2018.
  21. ^ Kehew, Alan E.; Esch, John M.; Kozlowski, Andrew L.; Ewald, Stephanie K. (2012). "Glacial landsystems and dynamics of the Saginaw Lobe of the Laurentide Ice Sheet, Michigan, USA". Quaternary International. 260: 21–31. Bibcode:2012QuInt.260...21K. doi:10.1016/j.quaint.2011.07.021.
  22. ^ Toimi Uplands Subsection Archived 2016-10-21 at the Wayback Machine of the Northern Superior Uplands, Ecological Classification System. Minnesota Department of Natural Resources, 2016.
  23. ^ Goldstein, Barry (1994). "Drumlins of the Puget Lowland, Washington State, USA". Sedimentary Geology. Elsevier. 91 (1–4): 299–311. Bibcode:1994SedG...91..299G. doi:10.1016/0037-0738(94)90136-8.
  24. ^ "Archived copy". Archived from the original on 2016-03-04. Retrieved 2015-12-14.CS1 maint: archived copy as title (link)
  25. ^ Gray, Charlotte; The Museum Called Canada: 25 Rooms of Wonder, Random House, 2004 ISBN 978-0-679-31220-8
  26. ^ Smith, A.M.; Murray, T.; Nicholls, K.W.; Makinson, K.; Aðalgeirsdóttir, G.; Behar, A.E.; Vaughan, D.G. (2007). "Rapid erosion, drumlin formation, and changing hydrology beneath an Antarctic ice stream". Geology. 35 (2): 127–130. Bibcode:2007Geo....35..127S. doi:10.1130/G23036A.1.

Further reading

  • Easterbrook, Don J. (1999). Surface Processes and Landforms, 2nd Edition. Upper Saddle River, New Jersey: Prentice Hall. pp. 347–350. ISBN 0-13-860958-6.
  • Grotzinger, John; Jordan, Tom (2010). Understanding Earth; 6th Edition. New York, NY: W.H. Freeman and Company. p. 586. ISBN 978-1-4292-1951-8.
  • Tarbuck, Edward J.; Frederick K. Lutgens (2002). Earth: An Introduction to Physical Geography. Upper Saddle River, New Jersey: Prentice Hall. pp. 347–350. ISBN 0-13-092025-8.
  • Trenhaile, Alan (2007). Geomorphology: A Canadian Perspective. Don Mills, Ontario: Oxford University Press. pp. 183–6. ISBN 978-0-19-542474-4.

External links

Annahilt

Annahilt / Anahilt (from Irish: Eanach Eilte) is a village and civil parish in north County Down, Northern Ireland. It is 7.5 miles (12 kilometres) south of Lisburn, and about 14 miles south-west of Belfast, on the main road between Ballynahinch and Hillsborough. In the 2001 Census the village had a population of 1,148. Annahilt has a distinctive drumlin setting, with a small wooded estate on a ridge to the west, and panoramic views on the approaches to the village.

Annahilt's has a primary school, shop(a mace, hair dressers and part-time post office), a Scout Hall, an Orange Hall, a residential care home and a park. There is a business park to the north, on the Glebe Road. Annahilt also has a three-star caravan site, known as the 'Lakeside View Caravan Park', on the Magheraconluce Road.

Arvagh

Arvagh (Irish: Ármhach, meaning "Battlefield") or Arva, is a town in County Cavan, Ireland, on the shores of Garty Lough and overlooked by Bruse Mountain. It is located on the junction of the R198 and R203 regional roads.

It is a scenic town situated in the centre of the drumlin belt. It lies on the border of Counties Longford and Leitrim and is famous as the town where the three provinces of Ulster, Leinster and Connacht meet, being located about 3 km southeast of the tripoint.

As of 2016, the town had a population of 411.

Bumpkin Island

Bumpkin Island, also known as Round Island, Bomkin Island, Bumkin Island, or Ward's Island, is an island in the Hingham Bay area of the Boston Harbor. In 1902, Albert Burrage, a Boston philanthropist, had a summer hospital opened on the island for children with physical disabilities. During World War I the island was used by the U.S. Navy. Starting around 1940, the island was used as a facility for polio patients. However, the hospital closed during World War II and burned down in 1945. Since 1996, it is part of the Boston Harbor Islands National Recreation Area. The island has an area of 30 acres (120,000 m2), plus an intertidal zone of a further 31 acres (130,000 m2). It is composed of a central drumlin with an elevation of 70 feet (21 m) above sea level, surrounded by a rock-strewn shoreline. A sand spit, exposed at low tide, connects the eastern end of the island to Sunset Point in Hull.On weekends and summer weekdays, Bumpkin Island is accessible by a shuttle boat to and from Georges Island, which connects from there with ferries to Boston and Quincy.

Clew Bay

Clew Bay (Irish: Cuan Mó) is a natural ocean bay in County Mayo, Republic of Ireland. It contains Ireland's best example of sunken drumlins. The bay is overlooked by Croagh Patrick to the south and the Nephin Range mountains of North Mayo. Clare Island guards the entrance of the bay. From the southwest part of the bay eastwards are Louisburgh, Lecanvey, Murrisk, and Westport; north of Westport is Newport, and westwards from there lies Mulranny, gateway to Achill. From the south side of the bay, between Clare Island and Achill, Bills Rocks can be seen.

Corleggy Cheese

Corleggy Cheeses is an Irish farmhouse making a selection of cheese in County Cavan. It was started by Silke Cropp in 1985 using milk from her own goat herd. Today Corleggy make a variety of different cheese from goat's milk, sheep's milk and cow's milk sourced from local farmers.

Dexter Drumlin

Dexter Drumlin, formerly known as Kilbourn Hill, is a 311-foot (95 m) drumlin and a 38-acre (15 ha) open space reservation in Lancaster, Massachusetts. The reservation includes a small tributary of the Nashua River and is managed by The Trustees of Reservations. It is characterized by managed, open fields and offers scenic views of surrounding rural Lancaster.

Drumbo

For the musician who has gone by this name, see John French.Drumbo (from Irish: Druim Bó, meaning "ridge of the cow") is a small village, townland and civil parish in County Down, Northern Ireland. It is about 6 miles (10 km) south of Belfast city centre, 3 miles (5 km) east of Lisburn and 3 miles (5 km) west of Carryduff. It is in the historic barony of Castlereagh Upper.The townland has an area of 1,274 acres (516 ha). The 2001 Census recorded the village's population as 408.

The village is set on the edge of a ridge where the drumlin country of County Down starts to descend into the Lagan Valley. It is laid out around a junction of routes meeting at the front of the Presbyterian Church, which is a listed building. The current church building is beside the site of the medieval parish church, the foundations of which can be seen in the graveyard, as can the lower half of the truncated Drumbo round tower, a scheduled historic monument. The round tower was originally built here to take advantage of the panoramic views over the Lagan Valley. At the time of the tower's construction, these views would have been useful in spotting oncoming Viking raiders. The tower formed part of a monastery.

The area is designated in the DOE(NI) area development plan as an 'area of outstanding scenic amenity value'. The village lies on the southern edge of the Lagan Valley Area of Outstanding Natural Beauty, while the northern part of the townland lies within it.The present village has expanded to the south-east along the ridge away from the church and graveyard, with much of the built form developing in the late 20th century. The church buildings still occupy a prominent site in the middle of the settlement. Drumbo functions as a small service centre and facilities include Drumbo Presbyterian Church and Hall, a community hall and a playground and playing fields at Front Road.

A feature in the heart of the village is a wrought iron pump with a distinctive double wheel crank mounted at the junction. This forms the centre of the village adjacent to the presbyterian church, round tower and village hall. Directly opposite this pump is the building which was for many years the post office for the village. A short distance South of this a blacksmith's foundry operates.

Drumlin (band)

Drumlin is a Canadian contemporary folk/pop band. Siblings Dal, Anya, Kassia and Liam Gilbert have been playing together for over a decade. They are multi-instrumental songwriters and celebrators of Nova Scotia's heritage music. This young classically trained band first gained national recognition working with song fragments from folklorist Helen Creighton's collection. Drumlin's music has classical Irish overtones and a modern pop flavour.

Glacial Drumlin State Trail

The Glacial Drumlin State Trail is a multipurpose rail trail in the Midwestern United States. It stretches 52 miles from Waukesha, Wisconsin (near Milwaukee) to Cottage Grove, Wisconsin (near Madison). The trail travels through or near the Wisconsin cities of Cottage Grove, Deerfield, London, Lake Mills, Jefferson, Helenville, Sullivan, Dousman, Wales, and Waukesha. In Lake Mills, Wisconsin it crosses the Rock Lake on one of its many old railroad bridges. The trail was opened in 1986 and follows the old Chicago and North Western Railway track.The name refers to a drumlin, a glacial landform very common in the area.

Great Brewster Island

Great Brewster Island is one of the outer islands in the Boston Harbor Islands National Recreation Area, situated some 9 miles (14 km) offshore of downtown Boston. The island has a permanent size of 18 acres (73,000 m2), plus an intertidal zone of a further 49 acres (200,000 m2). Unlike the other outer islands, which are low-lying outcroppings of bedrock, Great Brewster is a drumlin which reaches a height of over 100 feet (30 m) above sea level. It has vegetation cover consisting of Apple Trees, Pear Trees, Sumac, Beach Roses, Grasses and Common Reeds, together with a large Gull colony. The birds are aggressive during nesting season and access by humans, which is by private boat only, is discouraged during that time.Like the neighbouring islands of Little Brewster, Middle Brewster and Outer Brewster, Great Brewster Island is named after William Brewster, the first preacher and teacher for the Plymouth Colony. In 1891, in

what was considered a radical action for the time, four women spent two weeks on the island and documented their visit. More recently the island has been home to summer cottages for local families and for soldiers who manned an observation post as part of the Brewster Islands Military Reservation during World War II. The military post included 90 mm rapid-fire guns, searchlight stations, and a command post that aided in controlling the harbor’s minefield.

Halifax Peninsula

The Halifax Peninsula is a community and planning area located in the urban core of municipal Halifax, Nova Scotia. Halifax Peninsula is home to Downtown Halifax, the financial and economic heart of the municipality, which was also the site of the original settlement and town of Halifax. The town of Halifax was founded by the British government under the direction of the Board of Trade and Plantations under the command of Governor Edward Cornwallis in 1749. Geographically, the Halifax Peninsula is a Canadian peninsula in central Nova Scotia.

Interglacial

An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene interglacial began at the end of the Pleistocene, about 11,700 years ago.

Kame

A kame is a glacial landform, an irregularly shaped hill or mound composed of sand, gravel and till that accumulates in a depression on a retreating glacier, and is then deposited on the land surface with further melting of the glacier. Kames are often associated with kettles, and this is referred to as kame and kettle topography. The word kame is a variant of comb (kame, or kaim is the Old Scottish word for comb), which has the meaning "crest" among others. The geological term was introduced by Thomas Jamieson in 1874.According to White, "kames were formed by meltwater which deposited more or less washed material at irregular places in and along melting ice. At places the material is very well washed and stratified; at others it is more poorly washed, with inclusions of till masses that fell from ice but were covered before they were completely washed. Kame gravels thus tend to be variable and range from fine to coarse grained and even to cobbly and boulder."With the melting of the glacier, streams carry sediment to glacial lakes, building kame deltas on top of the ice. However, with the continuous melting of the glacier, the kame delta eventually collapses onto the land surface, furthering the "kame and kettle" topography.

Kame terraces are frequently found along the side of a glacial valley and are stratified deposits of meltwater streams flowing between the ice and the adjacent valley side. These kame terraces tend to look like long flat benches, with a lot of pits on the surface made by kettles. They tend to slope downvalley with gradients similar to the glacier surface along which they formed, and can sometimes be found paired on opposite sides of a valley.

Kames are sometimes compared to drumlins, but their formation is distinctively different. A drumlin is not originally shaped by meltwater, but by the ice itself and has a quite regular shape. It occurs in fine-grained material, such as clay or shale, not in sands and gravels. And drumlins usually have concentric layers of material, as the ice successively plasters new layers in its movement.

Kettle (landform)

A kettle (kettle hole, pothole) is a depression/hole in an outwash plain formed by retreating glaciers or draining floodwaters. The kettles are formed as a result of blocks of dead ice left behind by retreating glaciers, which become surrounded by sediment deposited by meltwater streams as there is increased friction. The ice becomes buried in the sediment and when the ice melts, a depression is left called a kettle hole, creating a dimpled appearance on the outwash plain. Lakes often fill these kettles; these are called kettle hole lakes. 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.

Lapham Peak Unit, Kettle Moraine State Forest

Lapham Peak is a Wisconsin state park located in the Kettle Moraine State Forest. It is just south of Delafield and seven miles (11 km) west of Waukesha. The park entrance is two miles (3 km) north of the Glacial Drumlin State Trail.

Leath Cuinn and Leath Moga

Leath Cuinn (Conn's Half) and Leath Moga (Mugh's half) are legendary ancient divisions of Ireland.

Leath Cuinn was the island north of the Esker Riada (east-west drumlin belt from Dublin to Galway Bay). Conn Cétchathach, for whom this division is named, was a retrospective ancestor of the Connachta and Uí Néill dynasties.

Ireland's legendary ancient division into Leath Cuinn (Conn's Half) and Leath Moga (Mugh's half) resulted from the battle of Maigh Nuadad in 123 A.D. Conn, defeated by Eoghan Mor (also known as Mug Nuadat), was forced to accede to the division of Ireland into two halves:

The North - taking in Connacht, Ulster and Meath - would be Conn's Half

The South - taking in Munster, Osraighe and Leinster - would be Eoghan's Half.To solidify the arrangement, Conn's daughter, Sadhbh was married to Ailill Aulom, son of Eoghan.

The Eoganacht dynasty in Munster claimed, as descendants of Oiloill Olum, the historical right as overkings of Leath Moga (i.e. overlordship of Leinster as well as Munster) in the early medieval age, a claim disputed by the Ui Neill.

In the twelfth century, the north-south division of Ireland was used as a basis for the new division of dioceses in Ireland at the Synod of Ráth Breasail.

List of National Natural Landmarks in Washington

There are 18 National Natural Landmarks in the U.S. state of Washington, out of nearly 600 National Natural Landmarks in the United States.

Ward Reservation

The Charles W. Ward Reservation is a 704-acre (285 ha) open space reserve located in Andover and North Andover, Massachusetts, 20 miles (32 km) north of Boston. The reserve, managed by the land conservation non-profit organization The Trustees of Reservations, is notable for its open drumlin hilltops and vistas encompassing Boston and Salem. The Ward Reservation offers 13 miles (21 km) of trails and former woods roads available for hiking, horseback riding, mountain biking, and cross country skiing; it is also a link in the 200-mile (320 km) Bay Circuit Trail system.

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.

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