Geomorphology

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Dunes of Erg Awbari (Idehan Ubari) in the Sahara desert region of the Wadi Al Hayaa District, of the Fezzan region in southwestern Libya. Credit: Luca Galuzzi.

Geomorphology is the science and study of landforms. These are often changed over time. The forces affecting landforms are an aspect of geophysics, geochemistry, ecology, or evolutionary geomorphology.

Rocky-object science[edit]

Present-day Earth topography and bathymetry at 15-minute horizontal resolution. Credit: Plumbago.

Def. an area of ground that is a part of the Earth's solid surface is called land.

Visuals[edit]

This is a landscape painting. Credit: Martin Johnson Heade.

Def. a "portion of land or territory which the eye can comprehend in a single view, including all the objects it contains"[1] is called a landscape.

Def. each continuous surface of a landscape that is observable in its entirety and has consistence of form or regular change of form is called a landform.

Theoretical geomorphology[edit]

The beach-dune system shows the nearshore zone back-beach environment and the formation of an incipient foredune and established foredune. Credit: Craig R. Sloss, Michael Shepherd & Patrick Hesp.
The geomorphological expressions and their characteristic wind flow patterns are for (a) saucer blowouts and (b) trough blowouts. Credit: Hesp & Hyde.
The geomorphological expressions and characteristics of (a) foredune, blowouts, and parabolic dunes, and (b) the main coastal dunes in relation to relative wind velocity and landward progradation. Credit: Bird.
This shows a pitted outwash plain with kames and a couple kettle lakes. Credit: Ron Schott, Bakersfield College.

"The size and morphology of coastal dunes is dependent on the complex interaction between controlling winds, sediment supply, and the geomorphology of the nearshore and beach environment."[2]

The diagram on the right shows the beach-dune system [with] the nearshore zone back-beach environment and the formation of an incipient foredune and established foredune."[2]

"Secondary dunes are the result of the subsequent modification of the "primary dune" by continued aeolian processes, and are generally located further inland, separated from nearshore processes (Davies 1980). The main secondary dunes include blowouts, parabolic dunes, and transgressive dunefields [image on the left and second right]."[2]

"The wind flow structure in a blowout may be very complex and highly turbulent. Generally, the wind flow is locally accelerated through the blowout and a high speed jet is formed. Thus, wind speeds in the blowout are significantly greater than outside the blowout and this leads to high rates of sand erosion and transport (Carter et al. 1990, Hesp & Hyde 1996, Hesp 1999). Winds remove sand from the deflation basin and the lateral walls and transport it downwind. The erosional walls are then over-steepened and slumping occurs. This causes the erosional walls to retreat, widening the blowout and supplying sediment to the deflation basin, which is then subsequently transported to the depositional lobe. The wind flow is maximised up the axis of the blowout (middle of the deflation basin) towards the depositional lobe. It experiences rapid flow deceleration over the lobe crest, depositing sediment in a radial fashion over the depositional lobe [shown in the images on the right, left and second right]. Deflation basins tend to continue to erode until a base level such as water table level or a more consolidated surface is reached (e.g., old soil profiles, an indurated sediment layer), or a lag surface where coarser materials such as pebbles, shell, or pumice may have been concentrated. Many blowouts become larger over time and may evolve into parabolic dunes [see the two images on the right]."[2]

Def. "the study of the character and origin of landforms"[3] is called geomorphology.

A variety of landforms occasionally occur juxtaposed in a landscape. Theoretical geomorphology is an effort to explain or describe a common cause for these landforms.

The second image on the left is a model for the landforms that may occur as a glacier retreats or is melted. Landforms to be expected from a retreating glacier include an outwash plain, one or more terminal moraines from repeated retreats or meltings, recessional moraines (an earlier and surged over terminal moraine), kames, an esker, a drumlin field, and a pro-glacial lake in a ground moraine.

When such an assemblage of landforms is discovered, it is reasonable to assert that they were formed by a past glacier that may no longer be present.

Mountain ranges[edit]

Himalaya mountain range is photographed from the International Space Station. Credit: NASA.
The Andes are the world's longest mountain range. Credit: Robert Morrow.

Def. a "series of adjoining mountains, often in a line"[4] is called a mountain range.

Summit lines[edit]

A summit line in the Uinta Mountains. Credit: Marli Miller.

"Coming to the geomorphology of the study area, it must be observed that the [Campano–Lucano Apennines] CLA constitute a markedly asymmetric mountain belt whose summit line is shifted towards the inner belt margin."[5]

Mountains[edit]

Low winter sun reflects off Skopphornet and Sunnmøre alps (Sykkylven) in Norway. Credit: "color line".

Def. a "large mass of earth and rock, rising above the common level of the earth or adjacent land, usually given by geographers as above 1000 feet in height (or 304.8 metres), though such masses may still be described as hills in comparison with larger mountains"[6] is called a mountain.

Seamounts[edit]

Bathymetric shows details of the Davidson Seamount. Credit: NOAA.
Multibeam image is of the Ely Seamount in the Gulf of Alaska. Credit: Jason Chaytor and Randall Keller, Oregon State University and NOAA.

Def. a "mountain that rises from the floor of the ocean and does not breach the water's surface"[7] is called a seamount.

Def. a submarine mountain is called a seamount.

Arêtes[edit]

This is an image of Punta dell'Alp from monte Pelvo. Credit: F Ceragioli.

Def. a "very thin ridge of rock"[8] is called an arête.

"An earlier [...] glacial episode, herein termed the Altonah Glaciation, is indicated by an extensive lateral moraine beyond the mouth of Yellowstone canyon as well as moraines in Lake Fork and Uinta River canyons. At higher elevations, alpine glacial landforms, including cirques, rock glaciers, arêtes, and hanging valleys are ubiquitous."[9]

"Arêtes and cols are most common in the south-central and southwestern Uinta Mountains, where accumulation areas of glaciers were largest and the development of ice caps that drained into multiple valleys was common. In the south-central Uintas, the most prominent arêtes have more than 450 m of relief and are more than 10 km in length. In the southeastern Uintas, rounded unglaciated divides locally termed “bollies” are more common than narrow arêtes. Examples of these features include broad divides that separate glacial valleys in the headwaters of Dry Fork and Ashley Creeks [...]."[9]

Horns[edit]

The Matterhorn is located on the border between Switzerland and Italy, towering over the Swiss town of Zermatt and the Italian town of Breuil-Cervinia in the Val Tournanche. Credit: Stan Shebs.
Storen is the third highest peak in Norway. Credit: Tore Røraas.

Def. a "pointed, mountain peak, typically pyramidal in shape, bounded by the walls of three or more cirques."[10] is called a horn.

Def. "a peak [that] has four symmetrical faces"[10] is called a Matterhorn.

Buttes[edit]

The (vertical)-De Chelly Sandstone is upon 'skirts' of the Organ Rock Formation. Credit: Jon Sullivan.

Def. "an isolated hill with steep sides and a flat top"[11] is called a butte.

Guyots[edit]

3-D depiction of Bear Seamount is with Physalia Seamount in the background. Credit: NOAA.

Def. a "flat-topped seamount"[12] is called a guyot.

Hills[edit]

The Chocolate Hills are a natural geological formation of hills in Bohol, Phillippines. Credit: P199.

Def. an "elevated location smaller than a mountain"[13] is called a hill.

Def. a naturally raised area of land, not as high or craggy as a mountain is called a hill.

Roche moutonnée[edit]

This is an example of roche moutonnée. Credit: Insider.
The Lembert Dome in Yosemite National Park, California, is an exceptionally large roche moutonnée. Credit: Michael Hambrey.

Def. an "elongated, rounded, asymmetrical, bedrock knob produced by glacier erosion"[10] is called a roche moutonnée.

"It has a gentle slope on its up-glacier side and a steep- to vertical-face on the down-glacier side."[10]

"The Lembert Dome in Yosemite National Park [imaged on the left], California, is an exceptionally large roche moutonnée. It clearly demonstrates ice flow from right to left."[14]

Drumlins[edit]

This is Shaded Relief Imagery, derived from the US Geological Survey National Elevation Dataset for Wayne County, NY USA. Credit: USGS and Pollinator.
This is a drumlin in the Midwest USA. Credit: Daniel Chapman.

Def. an "elongated hill or ridge of glacial drift"[15] is called a drumlin.

The image on the right is Shaded Relief Imagery from the U.S. Geological Survey to emphasize the relative relief and parallelism of the small hills in Wayne County, New York, USA, south of Lake Ontario.

The image on the left shows one drumlin in the Midwest USA. The ice apparently approached from the larger end and traveled along the length of the drumlin.

Moraines[edit]

A lateral moraine on a glacier joining the Gorner Glacier is left of center. Credit: Adrian Pingstone.
Lateral and terminal moraines of a valley glacier are shown. Credit: Natural Resources Canada, Terrain Sciences Division, Geological Survey of Canada.
The image shows Little Ice Age end moraines for the glacier. Credit: Ó. Ingólfsson.

"Lateral and terminal moraines of a valley glacier, Bylot Island, Canada [are shown in the image at the left]. The glacier formed a massive sharp-crested lateral moraine at the maximum of its expansion during the Little Ice Age. The more rounded terminal moraine at the front consists of medial moraines that were created by the junction of tributary glaciers upstream."[16]

Def. "a mound, ridge, or other distinct accumulation of glacial till"[16] is called a moraine.

Def. "a ridge-shaped moraine deposited at the side of a glacier and composed of material eroded from the valley walls by the moving glacier"[16] is called a lateral moraine.

Def. "a ridge-shaped moraine deposited at the [terminus] of a glacier and composed of material eroded from the valley walls by the moving glacier"[16] is called a terminal moraine.

Hummocky terranes[edit]

This is hummocky sea ice in the Gulf of Finland on the coast of Estonia. Credit: Petrov Victor.
Patterned ground to the west of Mugi hill on Mount Kenya. Credit: Mehmet Karatay.
This is a hummocky moraine, part of the the 1890 Brúarjökull end moraine complex. Credit: Ólafur Ingólfsson.
These big lumps in the ground are called thufur. Credit: Reinhold Richter.
Small hummocks (termed nebkha) formed by sand deposition within discrete plants on the backshore at Dona Juana dunefield, Mexico. Credit: Craig R. Sloss, Michael Shepherd & Patrick Hesp.

Def. a "ridge or hill of ice in an ice field" or a "small hill; a hillock; a knoll"[17] is called a hummock.

On the right is hummocky ice on the coast of Estonia in the Gulf of Finland.

On the left is patterned ground to the west of Mugi hill on Mount Kenya. The hummocks are caused by repeated freezing of the ground in a process known as frost heaving.

Part of the the 1890 Brúarjökull end moraine complex is on the second right. It is also hummocky terrane on a larger scale.

Def. "perennial hummocks formed in either the active layer in permafrost areas, or in the seasonally frozen ground in non-permafrost areas, during freezing of the ground"[16] is called thufur.

"Driftwood sometimes forms the focus for the initial accumulation of dune sand, but vegetation is the most common roughness element that contributes to the formation of incipient dunes [such as the small] hummocks (termed nebkha[in the third image on the right]) formed by sand deposition within discrete plants on the backshore at Dona Juana dunefield, Mexico."[2]

Kames[edit]

The diagrams compare and contrast glacial stagnation and melting with a kame and kettle topography. Credit: Adrian Hall, University of St Andrews, Scotland.
This is a vaguely cone-shaped kame that is not very tall. Credit: Katie Quirk.

Def. a "round hill or short ridge of sand or gravel deposited by a melting glacier"[18] is called a kame.

Def. "a hill or hummock composed of stratified sand and gravel laid down by glacial meltwater"[19] is called a kame.

"Kames are amongst the most varied landforms resulting from deposition by glacial meltwater. A kame (Scots kaim a hill) may occur as an isolated hill but more generally each kame is one mound in a low-lying terrain of many hummocks, terraces, ridges and hollows. Kames often occur in association with kettle holes in kame and kettle topography. Eskers may also occur between the kames. Meltwater channels may be cut into and between the kames. These associations indicate that kames are formed close to ice margins in situations where there are large volumes of both meltwater and debris."[19]

"The sediments inside kames are often exposed by quarrying. Bedded and sorted sand and gravel predominates but often sharp lateral variations are apparent in the calibre of the material, indicating rapid changes in flow velocity. Small details may reveal much about the events during deposition. The sloping beds of delta foresets indicate sand deposition in a pond or lake. Sands clasts, rounded blocks of now-loose sand, show that beds of saturated sands were frozen prior to transport. Beds of sand and gravel may be displaced by faults or rucked by folds, signs that the sides of the kame may have slumped after deposition or that ice has pushed forward again. Some kames are capped by till, indicating a late readvance of ice or deposition in a pond beneath the ice. Ice wedge casts on the surface of the kame point to the development of permafrost during and after ice retreat."[19]

"Kames form in the chaotic zone of melting ice, water and oozing sediment close to the ice margin. Virtually any hollow within the decaying front may fill with water and receive sediment - crevasses, moulins and larger cavities. As the ice melts, the kame begins to emerge as a hump but its side are saturated and no longer supported by ice and so slumping is possible. Buried blocks of ice melt slowly to leave water-filled kettle holes."[19]

Eskers[edit]

This particular esker may have been laid down just before the ice sheet stopped moving and began to melt for the last time. Credit: Hunter.

"Normally this kind of landform [in the image on the right from Northern Manitoba, Canada] would be wiped out as the ice sheet shifts and the meltwater streams change course. This particular esker must have been laid down just before the ice sheet stopped moving and began to melt for the last time."[20]

Dunes[edit]

These are dunes of Nambia. Credit: GIRAUD Patrick.
A modern foredune and relict foredunes form a foredune plain at Cape San Blas, Florida. Credit: Patrick Hesp.
Blow outs are forming in a foredune on the Sunshine Coast of southeast Queensland. Credit: Craig R. Sloss.
Parabolic dunes have formed in southern California. Credit: K. Adelman.
The image shows the lower 45 kilometers of the Tsauchab River. Credit: ISS Expedition 22 crew.
The image shows the Namib-Naukluft National Park is full color. Credit: NASA/GSFC/MITI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.
Transgressive dunefield displays typical transverse dunes at Veracruz, Mexico. Credit: M. Martinez.
The dune sea of the Namib Desert. The crests of the dunes are aligned in a marked northwest-southeast orientation. The dunes act as obstacles, causing the winds to be deflected significantly to the right, in effect reorienting the southerly wind to become a southwesterly wind. Credit: ISS Crew Earth Observations experiment and the Image Science & Analysis Group, Johnson Space Center.
Dune 45 is so called because it lies 45 km past Sesriem on the road to Sossusvlei. Credit: Harald Süpfle.

Def. a "ridge or hill of sand piled up by the wind"[21] is called a dune.

Def. "dunes with a sand supply derived primarily from the beach"[2] are called primary dunes.

Def. dunes "in which vegetation plays a major role (i.e., impedes downwind transport) in the development of the dune"[2] are called impeded primary dunes.

Def. dunes which "develop at the rear of the backshore environments (landward of the active beach) and generally comprise shore-parallel, convex, symmetrical to asymmetrical dune ridges"[2] are called foredunes.

Def. "the initial dunes which accumulate above the high spring tide mark and form due to the presence of some roughness element at the rear of the beach that rapidly reduces wind flow velocities, resulting in sediment accumulation"[2] are called incipient foredunes.

Def. incipient foredunes that survive severe storm events "and grow to become larger"[2] are called established foredunes.

Def. incipient foredunes that survive severe storm events, become "stable as a new incipient foredune develops to seaward"[2] are called relict foredunes.

"If the sediment supply is adequate, a new incipient dune may form seaward of the established foredune, resulting in the established foredune being relatively isolated from the sediment supply. The isolation of the dune, coupled with coastal progradation, can result in the development of successive foredunes that may eventually form a wide foredune plain [image on the left]."[2]

"A modern foredune and relict foredunes [are] forming a foredune plain at Cape San Blas, Florida [in the image on the left]. Note that bars are migrating alongshore, attaching to the beach and providing new sediment to both prograde the beach and build new foredunes."[2]

"Once initiated, the subsequent development of a blowout depends on the size of the initial airflow constriction, the height and width of the dune in which the blowout is developing, the degree and type of vegetation cover, the magnitude of regional winds and the degree of exposure to winds from various directions. The morphology of blowouts is characterised by a deflation (erosional) basin floor or depression, lateral erosional walls, and a downwind depositional lobe [the images in theoretical geomorphology and on the second left]."[2]

"Continued transport of sand through blowouts often results in the development of parabolic dunes. These consist of an actively advancing nose and depositional lobe with two trailing arms that enclose a deflation basin. This produces a characteristic U-shape (i.e., parabolic) or V-shaped dune (Hesp 1999, [image on the third left]). As they develop over a period of time their long axis orientation is closely aligned with that of the dominant wind direction (Bird 2000). Shorter and wider parabolic dunes form where there is a wider range of wind directions (Davis 1980, Bird 2000)."[2]

"Transgressive sand sheets and dunefields are relatively large-scale aeolian sand deposits formed by the downwind and/or alongshore movement of sand over vegetated to semi-vegetated terrain (or transgression of sediment over land; Hesp & Thom 1990). Transgressive sheets are relatively flat to undulating, largely dune-less sheets (like bed sheets), whereas transgressive dunefields comprise various types of dunes on the surface [fourth image on the left]. Transgressive dunefields have also been termed mobile dunes, sand drifts, and migratory dunes. Such dunefields may range from quite small (hundreds of metres in alongshore and landward extent) to very large (many kilometres in extent). They may be largely unvegetated, partially vegetated, or completely vegetated (relict). They may be relatively featureless sandsheets, or comprise a variety of dune types ranging from simple barchans (crescentic shaped dunes with wings pointing downwind), transverse dunes (dunes formed at right angles to the wind), barchanoidal transverse dunes, to parabolic dunes."[2]

"This astronaut photo shows sand heaped up in numerous star dunes, each of them with long arms extending in several directions. Unlike crescent-shaped barchan dunes, which form in areas where winds generally blow from one direction, star dunes are apparently generated where winds are variable. In this part of the Namib Sand Sea, winds are mainly from the south, but easterly winds, channeled along the Tsauchab valley, provide another component. And warm dry winter winds—similar to the Santa Ana winds of California—blow from the northeast."[22]

At right is an image from LandSat 7 of the Namib Desert. "Namib-Naukluft National Park is an ecological preserve in Namibia's vast Namib Desert. Coastal winds create the tallest sand dunes in the world here, with some dunes reaching 980 feet (300 meters) in height."[23]

Crevasse fillings[edit]

This shows a field of melted-out crevasse fillings. Credit: I.Ö.Benediktsson.

"Brúarjökull is the largest outlet glacier of the great Vatnajökull ice cap [in Iceland]. [...] Two large glacial rivers flow from Brúarjökull, Jökulsá á Dal and Kreppa, but numerous smaller rivers and banks drain meltwater from the glacier in spring and summer."[24]

"The present Brúarjökull ice margin is largely inactive (dead), and rapidly downwasting."[24]

As a result of the rapid downwasting, there are fields such as the one shown in the image on the right where the debris that filled crevasses now forms small ridges on the former subglacial surface. Note the pattern of such small ridges on the right and compare this with crevasse images in glaciology.

Levees[edit]

Natural levees along the Bar River. Credit: Sonia Sevilla.
The lava levees of the lava channel are high enough in places to prevent lava overflow. Credit: Brocken Inaglory.

Def. an elongated naturally occurring ridge or "steep bank of a river"[25] is called a levee, or natural levee.

Pāhoehoe Lava flows in the open lava channel (not in a Lava tube) with overflows at both sides. The image on the left was taken at The Big Island of Hawaii. The lava flow is due to July 21, 2007, fissure eruption at Kīlauea volcano. The channel is crusting over with a v-shaped opening pointing upstream. The crusting-over process usually starts at the upstream end, the crust grows downstream for a considerable distance, then the crust founders and sinks opening the channel to crusting over again. The main channel and overflows show perched nature of this kind of lava channels. The picture was taken from a helicopter.

Reefs[edit]

Main sources: Earth/Coral reefs and Coral reefs
Organisms cover every square inch of a coral reef. Credit: Terry Hughes.
Portion of a Pacific atoll (Yap) showing two islets on the ribbon or barrier reef separated by a deep pass betwen the ocean and the lagoon. Credit: NOAA.
Satellite picture is of the Atafu atoll in Tokelau. Credit: NASA Johnson Space Center.

Def. a "chain or range of rocks, sand, or coral lying at or near the surface of the water"[26] is called a reef.

Def. a "mound or hummock of compacted coral skeletons"[27] is called a coral reef.

The image on the left is an island with fringing coral reef off Yap, Micronesia.

Def. a "type of island consisting of a ribbon reef that nearly or entirely surrounds a lagoon and supports, in most cases, one to many islets on the reef platform"[28] is called an atoll.

Cliffs[edit]

This cliff is part of a karst landscape formed by water and plants on calcareous (probably) limestone. Credit: Pavle Cikovac.
An eroded boulder clay cliff is shown. Credit: Eric Jones.
A red cliff along US287 between Lander and Dubois in Wyoming, near Wind Canyon. Credit: Wing-Chi Poon.
Cliffs of Moher is in East, Ireland. Credit: Tobias Helfrich.

The cliff in the image on the right is part of a karst landscape formed by water and plants on calcareous (probably) limestone.

"This photo [on the left] shows clearly why these glacial deposits are called boulder clay, consisting as they are of clay and stones of various sizes up to and including large boulders. Till is another name for boulder clay."[29] The image is of an eroded boulder-clay cliff near to Trefor, Gwynedd, Great Britain.

Def. a "vertical (or nearly vertical) rock face"[30] is called a cliff.

Promontories[edit]

East side of the Freshwater Steps promontory is at the western end of Egmont Bight, Dorset, U.K. Credit: JimChampion.
Sròn a' Chorra Bhuilg, a typical Nose, is above Creagbheiteachain in Glen Scaddle. Credit: LHOON.

Def. a "high point of land extending into a body of water, headland; cliff"[31] is called a promontory.

Headlands[edit]

Beachy Head is in East Sussex, England. Credit: Ian Stannard from Southsea, England.

Def. a "bit of coastal land that juts into the sea"[32] is called a headland.

Capes[edit]

Cape Canaveral, Florida, and the NASA John F. Kennedy Space Center are shown in this near-vertical photograph. Credit: NASA.

Def. a "piece or point of land, extending beyond the adjacent coast into a sea or lake"[33] is called a cape.

Peninsulas[edit]

Cape Verde in Dakar is considered by some to be a peninsula. Credit: NASA.

Def. a "piece of land projecting into water from a larger land mass"[34] is called a peninsula.

Glaciers[edit]

Main sources: Rocks/Glaciers and Glaciers
Briksdalsbreen is a part of the Jostedalsbreen glacier in Norway. Credit: Donarreiskoffer.

Def. "a mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer"[16] is called a glacier.

Fans[edit]

An alluvial fan blossoms between the Kunlun and Altun mountain ranges in east Turkestan. Credit: NASA/GSFC/METI/Japan Space Systems, and U.S./Japan ASTER Science Team.

Def. a "cone-shaped heap of alluvium deposited by a river"[35] is called an alluvial fan.

"A vast alluvial fan [in the image on the right] blossoms across the desolate landscape between the Kunlun and Altun mountain ranges that form the southern border of the Taklimakan Desert in China's XinJiang Province. The left side is the active part of the fan, and appears blue from water currently flowing in the many small streams. The image was acquired May 2, 2002, covers an area of 56.6 x 61.3 km, and is centered near 37.4 degrees north, 84.3 degrees east."[36]

Salt glaciers[edit]

The diapirs, or salt plugs, in this image are a few of over 200 similar features scattered about this part of the Zagros Mountains in southern Iran. Credit: NASA/GSFC/METI/Japan Space Systems, and U.S./Japan ASTER Science Team.

"The diapirs, or salt plugs, in this image are a few of over 200 similar features scattered about this part of the Zagros Mountains in southern Iran. This region of folded rocks is the result of the collision between the Asian landmass and the Arabian platform. The deeper underlying deposits of salt have been reformed into ascending fluid-like, plastic plumes of salt. In some places these plumes have pushed through the overlying rock units, like toothpaste extruding from a tube, and are now visible as darkish irregular patches. Gravity has caused the salt to flow into adjacent valleys; the resulting tongue-shaped bodies, more than 5 km long, resemble glaciers, with arcuate ridges separated by crevasse-like gullies and with steep sides and fronts. The darker tones are due to clays brought up with the salt, as well as the probable accumulation of airborne dust. This ASTER perspective view [on the right] was created by draping a band 3-2-1 (RGB) image over an ASTER-derived DEM (2x vertical exaggeration), was acquired on August 10, 2001, and is located at 27.4 degrees north latitude and 54.6 degrees east longitude."[37]

Terraces[edit]

These wave-cut terraces are on San Clemente Island, California. Credit: Dan Muhs, USGS.

"Wave-cut terraces on San Clemente Island, California [are shown in the image on the right]. Nearly horizontal surfaces, separated by step-like cliffs, were created during former intervals of high sea level; the highest terrace represents the oldest sea-level high stand. Because San Clemente Island is slowly rising, terraces cut during an interglacial continue to rise with the island during the following glacial interval. When sea level rises during the next interglacial, a new wave-cut terrace is eroded below the previous interglacial terrace. Geologists can calculate the height of the former high sea levels by knowing the tectonic uplift rate of the island."[38]

Ice scours[edit]

Def. "a narrow ditch on a seabed caused by the movement of pack ice"[39] is called an ice scour.

Iceways[edit]

Def. a "linear channel eroded through bedrock by the passage of glacial ice"[40] is called an iceway.

Cols[edit]

Mont Blanc massif - Graian Alps has several cols in its summit-line. Credit: Francofranco56.

Def. a "dip between mountain peaks in a summit-line"[41] is called a col.

Cirques[edit]

This show a cirque on Cirque Mountain in the Torngat Mountains, Newfoundland, Canada. Credit: Hazen Russel, Natural Resources Canada, Terrain Sciences Division, Geological Survey of Canada.

"A cirque is a bowl-shaped rock valley on the side of a mountain, often with a glacier or permanent snowfield in it. The glacier makes the cirque, by grinding an existing valley into a rounded shape with steep sides."[20]

Valleys[edit]

Newlands Valley image is taken from the slopes of Dale Head looking downstream, with Skiddaw in the distance. Credit: Richard Webb.

Def. an "elongated depression between hills or mountains"[42] is called a valley.

V-shaped valleys[edit]

This is a V-shaped valley. Credit: Daniel Chapman.

V-shaped valleys are a product of erosion from steep drainage by streams or rivers.

U-shaped valleys[edit]

This shows the Noatak River and Glacial Valley - Aerial View. Credit: U.S. Fish and Wildlife Service.
The image shows a U-shaped glacial valley. Credit: Rob Gamesby.

"As corrie [cirque] glaciers leave their source regions and descend down old river valleys they can make huge changes to the landscape. One of the major change they make is to the V-shaped valleys characteristic of the upper reaches of river valleys. The glaciers basically alter this V shape into a U, by creating a steep sided, wide valley in the shape of the letter U. They are formed by a valley glacier that moves down the valley because of gravity."[43]

"As the glacier moves down the valley it plucks the rock from beneath and those rocks then rub against the bed of the valley, eroding it further. This deepens and widens the valley. At the front end of the glacier it acts like a bulldozer, shifting and removing soil, plucking rock from interlocking spurs and truncating them. This creates Truncated Spurs, which are interlocking spurs without the land that interlocks! Originally, truncated spurs are created as a river erodes the upper valley it cuts down into the rock and meanders in and out of the surrounding rock. During glaciations this rock is removed by descending ice sheets."[43]

Canyons[edit]

This is a view of the Grand Canyon in Arizona, USA. Credit: Mike Buchheit.

On the right is an example of a river canyon, specifically the Grand Canyon in Arizona, USA.

Def. a "valley, especially a long, narrow, steep valley, cut in rock by a river"[44] is called a canyon, or a river canyon.

Def. a deep gorge is called a canyon.

Gorges[edit]

Def. a narrow valley between hills or mountains is called a gorge.

Def. a "deep narrow passage with steep rocky sides; a ravine"[45] is called a gorge.

Gulfs[edit]

Def. a deep ravine, chasm, or abyss is called a gulf.

Def. a "hollow place in the earth; an abyss; a deep chasm or basin"[46] is called a gulf.

Plateaus[edit]

This is a line-art drawing illustrating a plateau. Credit: Pearson Scott Foresman.
The mesas of Island in the Sky have plateaus, Canyonlands National Park, as seen from the Needles district. Credit: Qfl247.

Def. a "largely level expanse of land at a high elevation; tableland"[47] is called a plateau.

Plains[edit]

This shows the Konza Prairie Preserve, a tallgrass prairie, in the Flint Hills of northeastern Kansas. Credit: Edwin Olson.

Def. an "expanse of land with relatively low relief"[48] is called a plain.

Outwash plains[edit]

Lómagnú and Skeiðarárjökull are from a bridge over Núpsvötn on 24 November 2007 at 17:00 in Iceland. Credit: Debivort.
This is the outwash plain of Brady Glacier in Alaska's Fairweather Range. Credit: Hunter.

The center image shows the outwash plain on the western edge of Skeiðarársandur from the Vatnajökull icecap. Braided streams carry glacial sediment to the sea.

On the right is an image of the outwash plain in front of Brady Glacier in the Fairweather Range of Alaska.

Valley trains[edit]

This photo shows the valley train further from the glacier margin. Credit: W.H. Johnson.
This photo shows summer meltwater issuing from a glacier on Bylot Island in eastern Canada. Credit: W.H. Johnson.

Def. gravel "and sand [that] are deposited in bars to form a braided channel system "[49] is called a valley train.

The "photo [on the left] shows summer meltwater issuing from a glacier on Bylot Island in eastern Canada."[49]

The "photo [on the right] shows the valley train further from the glacier margin. The interesting pattern shown in the lower left of the photo is patterned ground formed by freezing and thawing of the active layer in a permafrost area."[49]

Flats[edit]

Mudflats in Brewster, Massachusetts, extend hundreds of meters offshore at low tide. Credit: Caliga10.
The image is a plateau and locally a flatland. Credit: web GEEK.

Def. an "area of level ground"[50] is called a flat.

Def. any "land of relatively constant altitude"[51] is called a flatland.

The first image on the right shows mudflats that extend hundreds of meters offshore at low tide.

The second image on the right shows a similar sized flatland where the local trees may be at least two meters high. Here, the flatland is on top of an extended butte often referred to as a plateau.

Ice sheets[edit]

Main sources: Rocks/Ice sheets and Ice sheets
An aerial view atop the Greenland ice sheet shows water converging on the moulin. Credit: Alan Buis.

For ice sheets the central portion is quite flat as shown in the image on the right of the Greenland ice sheet.

Def. "a dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers (12 million acres)"[16] is called an ice sheet.

Steppes[edit]

Steppe of western Kazakhstan is in the early spring. Credit: Carole a.
Approximate extent is of the Eurasian Steppe grasslands ecoregion, and Eurasia cultural region. Credit: Cp6.

Def. a "vast cold, dry grass-plain"[52] is called a steppe.

Tundra[edit]

Tundra is near Dudinka, Krasnoyarsk Krai. Credit: Andreas Hugentobler.
Wrangel Island has tundra. Credit: NOAA.

Def. a cold, "flat and treeless" plain[53]is called a tundra.

Savanna[edit]

A savanna in Africa is occupied. Credit: eismcsquare.

Def. a "tropical grassland with scattered trees"[54] is called a savanna.

Prairie[edit]

Prairie in Alberta, Canada is somewhere between Calgary and Edmonton. Credit: Zeitlupe.

Def. an " extensive area of relatively flat grassland with few, if any, trees"[55] is called a prairie.

Velds[edit]

Swartland Shale Renosterveld is after a major veld fire. Credit: S Molteno.

Def. an "open pasture land or grassland"[56] is called a veld.

Swamps[edit]

Vasyugan Swamp is in western Siberia. Credit: Vadim Andrianov.

Def. a "piece of wet, spongy land; low ground saturated with water; soft, wet ground which may have a growth of certain kinds of trees, but is unfit for agricultural or pastoral purposes"[57] is called a swamp.

Flood plains[edit]

The Paraná River floodplain reaches a width of 11 kilometers. Credit: NASA Astronaut photograph ISS030-E-90012.

Def. an "alluvial plain that may or may not experience occasional or periodic flooding"[58] is called a flood plain.

"The Paraná River appears as a wide, blue strip with the muddy brown water of the smaller Verde River entering from the northwest (top left). An extensive wetland (dark green) occupies most of the left half of this astronaut photograph, and the floodplain reaches a width of 11 kilometers (about 7 miles). The thin line of a road crossing the floodplain also gives a sense of scale. Above the Paraná-Verde confluence (image center), the floodplain is much narrower."[59]

"The floodplain is generated by sediments delivered by both rivers. The evidence for this is that the entire surface is crisscrossed by the wider traces of former Paraná River channels, as well as numerous narrower traces of the Verde. The floodplains along both rivers are bordered by numerous rectangular agricultural fields. The dominant crops along this part of the Paraná River are coffee, corn, and cotton."[59]

"Turbid water, such as that in the Verde River, is common in most rivers that drain plowed agricultural land, as some topsoil is washed into local rivers after rains. A long tendril of brown water extends from the Verde into the main channel of the Paraná, where it hugs the west bank and remains unmixed for many kilometers. This effectively shows the direction of river flow from orbit: right to left for the Paraná, and upper left to image center for the Verde."[59]

Pavements[edit]

Limestone pavement is above Malham Cove in the Yorkshire Dales. Credit: Lupin.
This shows limestone pavement in Haute Savoie, France. Credit: f.corageoud.
Desert pavement is near Barstow, California. Credit: Wilson44691.
The "Tesselated Pavement“ is the result of an orthogonal joint pattern in the rock. Credit: JJ Harrison.
Grooves and striations are on exhumed Permian glacial pavement. Credit: Bahudhara.

Def. a more or less horizontal, hard expanse of bare rock as a surface is called a pavement.

On the right are two images of a limestone pavement which is part of a karst topography.

On the left is a desert pavement in southeastern California.

A pavement such as the one on the second left covered with pieces that are similarly shaped is referred to as a tessellated pavement.

Deltas[edit]

Lena River delta landform at the mouth of the river. Credit: USGS EROS Data Center Satellite Systems Branch.
NASA image of Nile Delta is taken by the MISR instrument on January 30, 2001. Credit: NASA.

Def. "landform at the mouth of a river [shaped like the letter Δ] where it empties into a body of water"[60]

On the right is a Landsat multispectral image of the delta from the Lena River.

The delta of the Nile is on the left.

Continental shelves[edit]

Elevationscale.JPG
This is a global land and undersea elevation map. Credit: National Oceanic and Atmospheric Administration.
Diagram of the continental shelf and slope of the southeastern United States leads down to the ocean floor. Credit: National Oceanic and Atmospheric Administration.

Def. an "area of sea around a land mass where the depth gradually increases before it plunges into the ocean deeps"[61] is called a continental shelf.

Abyssal plains[edit]

The diagram represents an oceanic basin, displaying various features. Credit: Chris_huh.
This diagram shows divisions of the Earth's oceans. Credit: Chris_huh.

Def. "a large expanse of very flat and smooth ocean floor, usually found at depths of 4,600 to 5,500 meters (15,000 to 18,000 feet)"[62] is called an abyssal plain.

Kettles[edit]

Kettle Hole in sandur sediments is in front of the 1890 Brúarjökull surge moraine. Credit: Ó. Ingólfsson.

"Kettle, also called Kettle Hole, in geology, [is a] depression in a glacial outwash drift made by the melting of a detached mass of glacial ice that became wholly or partly buried. The occurrence of these stranded ice masses is thought to be the result of gradual accumulation of outwash atop the irregular glacier terminus. Kettles may range in size from 5 m (15 feet) to 13 km (8 miles) in diameter and up to 45 m in depth. When filled with water they are called kettle lakes. Most kettles are circular in shape because melting blocks of ice tend to become rounded; distorted or branching depressions may result from extremely irregular ice masses."[63]

"Two types of kettles are recognized: a depression formed from a partially buried ice mass by the sliding of unsupported sediment into the space left by the ice and a depression formed from a completely buried ice mass by the collapse of overlying sediment. By either process, small kettles may be formed from ice blocks that were not left as the glacier retreated but rather were later floated into place by shallow meltwater streams. Kettles may occur singly or in groups; when large numbers are found together, the terrain appears as mounds and basins and is called kettle and kame topography."[63]

Geology[edit]

Main source: Geology
This aerial view shows a portion of the San Andreas fault in California. Credit: Robert E. Wallace, USGS USA.

Def. the intellectual and practical activity encompassing the systematic study through observation and experiment of the Earth's physical structure and substance, its history and origin, and the processes that act on it, especially by examination of its rocks, is called geology.

Def. "the study of the planet earth- the materials it is made of, the processes that act on those materials, the products formed, and the history of the planet and its life forms since its origin"[64] is called geology.

Geography[edit]

Main source: Geography
A Robinson projection map of the Earth is displayed in the diagram. Credit: United States Central Intelligence Agency's World Factbook.

Def.

a "study of the physical structure and inhabitants of the Earth"[65] or

a "physical structure of a particular region; terrain"[65] is called geography.

Def. "areal differentiation The varied nature of the earth's surface, as shown by the character, pattern and interrelationship of relief, climate, soil, vegetation, population, political units, etc., thus producing a mosaic of unique and dissimilar units. This is one definition of geography, partic. as propounded by R. Hartshorne."[66] is called geography.

Def. "the arrangement of things on the surface of the earth" is called geography, after A. Hettner.[66]

Def. "the study of the earth's surface in its areal differentiation as the home of Man"[66] is called geography.

Precambrian[edit]

The Canadian Shield is a broad region of Precambrian rock (pictured in shades of red) that encircles Hudson Bay. Credit: Qyd.
A contour map of the thickness of the Earth's crust is numbered in kilometres. Credit: USGS.

Def.

  1. "the time and geology dated before the Phanerozoic"[67] or
  2. the "eon (or supereon) and rock formations dated before 541.0±1.0 million years ago, coinciding with the first appearance of the fossils of hard-shelled animals"[67]

is called the precambrian.

"The Canadian Shield constitutes the largest mass of exposed Precambrian rock on the face of Earth."[68]

It extends "for 8 million square km (3 million square miles)".[68]

At an average depth of 35 km, the Canadian Shield has a volume of about 280 million cubic km.

Hypotheses[edit]

Main source: Hypotheses
  1. A landform may have more than one origin.

See also[edit]

References[edit]

  1. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 Craig R. Sloss, Michael Shepherd & Patrick Hesp (2012). "Coastal Dunes: Geomorphology". Nature Education Knowledge 3 (10): 2. http://www.nature.com/scitable/knowledge/library/coastal-dunes-geomorphology-25822000. Retrieved 2014-11-27. 
  3. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  4. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  5. A. Amato and A. Cinque (December 1999). "Erosional landsurfaces of the Campano–Lucano Apennines (S. Italy): genesis, evolution, and tectonic implications". Tectonophysics 315 (1-4): 251-67. doi:10.1016/S0040-1951(99)00288-7. http://www.sciencedirect.com/science/article/pii/S0040195199002887. Retrieved 2014-11-10. 
  6. "mountain, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2014-12-14. 
  7. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  8. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  9. 9.0 9.1 Benjamin J.C. Laabs and Eric C. Carson (2005). Dehler, C.M., Pederson, J.L., Sprinkel, D.A., and Kowallis, B.J.. ed. Glacial Geology of the Southern Uinta Mountains, In: Uinta Mountain geology. 33. Utah Geological Association. 235-53. http://www.geology.wisc.edu/~davem/abstracts/05-20.pdf. Retrieved 2014-11-08. 
  10. 10.0 10.1 10.2 10.3 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
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  15. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  16. 16.0 16.1 16.2 16.3 16.4 16.5 16.6 Janet Beitler (2014). "Cryosphere Glossary". National Snow and Ice Data Center. Retrieved 2014-09-20. 
  17. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
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  19. 19.0 19.1 19.2 19.3 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  20. 20.0 20.1 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
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  23. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  24. 24.0 24.1 Ó. Ingólfsson (2004). "Brúarjökull Photos". Iceland: Brúarjökull Project. Retrieved 2014-11-26. 
  25. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  26. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  27. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  28. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  29. Eric Jones (2008). "An eroded boulder clay cliff". Geograph.org. Retrieved 2014-12-04. 
  30. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
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  38. Richard Z. Poore, Richard S. Williams, Jr., and Christopher Tracey (2000). "Sea Level and Climate". Reston, Virginia USA: United States Geological Survey. Retrieved 2014-11-22. 
  39. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
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  49. 49.0 49.1 49.2 Richard C. Berg (2014). "Valley Trains". 615 E. Peabody, Champaign, IL 61820 USA: Illinois State Geological Survey. Retrieved 2014-12-11. 
  50. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
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  66. 66.0 66.1 66.2 Francis John Monkhouse (November 30, 2007). A Dictionary of Geography, Second Edition. Transaction Publishers. pp. 378. ISBN 0202361314. http://books.google.com/books?id=9yhhzHMnnyoC&lr=&source=gbs_navlinks_s. Retrieved 2012-05-24. 
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External links[edit]

{{Geology resources}}