Geography - Page 5 of 13

Erosional landforms of groundwater Upsc and features created by it

This article focuses on the work of the Erosional landforms of groundwater.

If the rocks are permeable, thinly bedded, high jointed and cracked, then the water percolates well into it. After the water goes down to some depth vertically, the water under the ground flows horizontally within the bedding places, joints or within the materials themselves.

The downward and horizontal movement of water is the reason behind the erosion of rocks. Physical or mechanical removal of rocks by running groundwater is unimportant in developing landforms.

As a result, the work of groundwater is not seen in all types of rocks. Groundwater’s work is mostly seen in rocks like limestone or dolomites, which are has the presence of Calcium Carbonate in them.

It is by the chemical process of solution and precipitation caused by the groundwater and the surface water, the deposition develops different types of landforms.

The solution process and the precipitation process are active in the limestone and dolomites. These two processes either occur exclusively or interbedded with other rocks.

Any region of limestone or dolomitic that exhibits the landforms produced by the action of groundwater by the processes of solution and deposition is called Karst topography. This is named after the Karst region in the Balkans, which is adjacent to the Adriatic sea, developed such topography, where the region consists of limestone rocks.

Also, the Karst Topography is featured by depositional and erosional landforms.

Erosional landforms of Groundwater

Pools, Lapies, Sinkholes and Limestone Pavement, which are medium to small-sized round to sub-rounded shallow depressions are known as Swallow Holes. The Swallow holes forms on the limestone surface through the solution.

Sinkholes

A Sinkholes are an opening which is almost circular at the top and shaped like a funnel towards the bottom with different sizes from a few square Kilometre to a size of hectares. Its depths also vary from a few metres to thirty metres or more. These Sinkholes are a common thing in Karst Areas or Limestone Areas.

These forms were formed solely by Solution action called Solution Sinks. Others might start as solution forms initially and then if the bottom of the sinkhole forms the roof of a void or cave under the ground, this might leads to collapse, that leaves a large hole opening into a cave or a void bellow called Collapse Sinks.

Collapse Sinks By Tihansky, A.B. – Tihansky, A.B., 1999, Sinkholes, West-Central Florida: U.S. Geological Survey Circular 1182, 121–140 p., accessed March 5, 2015, at https://pubs.er.usgs.gov/publication/cir1182., Public Domain, https://commons.wikimedia.org/w/index.php?curid=51542183

Sometimes, these Sinkholes are with soil mantle and look like shallow water pools and if some steps over them, it would go down similar to quicksands in deserts. The Collapse sinks are also termed Doline.

The solution sinks are more common than the collapse sinks. Sometimes the surface run-off simply runs underneath swallow and sinkholes and runs as underground streams and later it reemerges at distance as downstream from a cave opening.

Valley sinks or Uvalas

Valley Sinks or Uvalas form when the sinkholes and doline merge together due to slumping of materials (rocks) along with their margins or because of the roof collapse of caves, long-narrow to wide trenches.

Slowly, most of the surface of the limestone is eaten away by these pits and trenches that leave extremely irregular with a maze of points, grooves and ridges or lapies.

These ridges or lapies were formed due to differential solution activity along parallel to sub-parallel joints. The lapie fields will eventually turn into something like a smooth limestone pavement.

Caves

In places where there are alternating beds of rocks such as shales, sandstones, quartzites etc with limestone or dolomites in between or in the regions where the limestone is dense, massive and occurring as thick beds, caves formation are prominent.

Along the bedding planes, the water percolates through the cracks, joints, and moves horizontally. Along these bedding planes, where the limestone dissolves, long-narrow to wide gaps form and it is called Caves.

These caves can be a maze of caves at varying elevations. This cave formation at different elevations depends upon the limestone beds and intervening rocks. The cave has opened by which the streams are discharged.

The caves where the opening is present at both ends are called Tunnels.

FAQ

1.how is groundwater erosion differentiated from surface water erosion?

Depositional landforms of river Upsc

Depositional landforms of river

The depositional landforms that formed the running waters of the river are:

Alluvial Fans, Deltas, Floodplains, Natural Levees, and Point Bars, Meanders, Braided Channels

The main work of the river is deposition, bed building, by which it forms the flood plains. When there is a large water flow such as floods, the river cuts the bank and takes straighter, shorter, and new routes.

Alluvial Fans

Alluvial fans are developed when streams running from higher levels break into foot slope plains of low gradients.

Usually, the very coarse load is transported by streams running over mountain slopes. This load grows too heavy for the streams to be carried over gentler gradients and gets dumped and spread as a broad low to high cone-shaped deposit called an alluvial fan.

Usually, the streams which flow over fans are not confined to their original channels for long and shift their position across the fan forming many channels called distributaries.

Alluvial fans in humid areas show normally low cones with a gentle slope from head to toe and they appear as high cones with a steep slope in arid and semi-arid climates.

Also, their Alluvial cone. The alluvial cone is a steep, narrow, cone-shaped alluvial fan. This is where a swift stream rapidly slows down due to an upland stream emerging abruptly into a level plain.

Depositional landforms of river Upsc — Alluvial Fans By en:user:Mikenorton – http://en.wikipedia.org/wiki/Image:Alluvial_fan_01.JPG, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4782727

Deltas

Indus River Delta By NASA, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5989926

Deltas are like alluvial fans but develop at a different location. The load carried by the rivers is dumped and spread into the sea. If this load is not carried away far into the sea or distributed along the coast, it spreads and accumulates as a low cone.

Unlike in alluvial fans, the deposits making up deltas are very well sorted with clear stratification. The coarsest materials settle out first and the finer fractions like silts and clays are carried out into the sea.

As the delta grows, the river distributaries continue to increase in length and the delta continues to build up into the sea.

Floodplains

Deposition develops a floodplain just as erosion makes valleys. Floodplain is a major landform of river deposition. Large-sized materials are deposited first when the stream channel breaks into a gentle slope.

Thus, normally, fine-sized materials like sand, silt, and clay are carried by relatively slow-moving waters in gentler channels usually found in the plains and deposited over the bed and when the waters spill over the banks during flooding above the bed.

A river bed made of river deposits is an active floodplain. The floodplain above the bank is an inactive floodplain. Inactive floodplain above the banks basically contains two types of deposits — flood deposits and channel deposits.

In plains, channels shift laterally and change their courses occasionally leaving cut-off courses that get filled up gradually.

Such areas over flood plains built up by abandoned or cut-off channels contain coarse deposits. The flood deposits of spilled waters carry relatively finer materials like silt and clay. The flood plains in a delta are called delta plains.

Natural Levees

Natural levees and point bars are some of the important landforms found associated with floodplains. Natural levees are found along the banks of large rivers. They are low, linear, and parallel ridges of coarse deposits along the banks of rivers quite often cut into individual mounds.

During flooding as the water spills over the bank, the velocity of the water comes down and large-sized and high specific gravity materials get dumped in the immediate vicinity of the bank as ridges.

They are high nearer the banks and slope gently away from the river. The levee deposits are coarser than the deposits spread by floodwaters away from the river. When rivers shift laterally, a series of natural levees can form.

Point Bars

Point Bar By Jean-Christophe BENOIST – Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=2081218

Point bars are also known as meander bars. They are found on the convex side of meanders of large rivers and are sediments deposited in a linear fashion by flowing waters along the bank.

They are almost uniform in profile and in width and contain mixed sizes of sediments. If they’re more than one ridge, narrow and elongated depressions are found in between the point bars.

Rivers build a series of them depending upon the water flow and supply of sediment. As the rivers build the point bars on the convex side, the bank on the concave side will erode actively.

Meanders

Meaders By Thomas Nugent, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=66434005

In large flood and delta plains, rivers rarely flow in straight courses. Loop-like channel patterns called meanders develop over flood and delta plains. Meander is not a landform but is only a type of channel pattern.

This is because of the propensity of water flowing over very gentle gradients to work laterally on the banks, unconsolidated nature of alluvial deposits making up the banks with many irregularities which can be used by water exerting pressure laterally and Coriolis force acting on the fluid water deflecting it like it deflects the wind.

When the gradient of the channel becomes extremely low, water flows leisurely and starts working laterally.

Slight irregularities along the banks slowly get transformed into a small curvature in the banks; the curvature deepens due to deposition on the inside of the curve and erosion along the bank on the outside.

If there is no deposition and no erosion or undercutting, the tendency to meander is reduced. Normally, in meanders of large rivers, there is active deposition along the convex bank and undercutting along the concave bank.

The concave bank is known as a cut-off bank which shows up as a steep scarp and the convex bank presents a long, gentle profile and is known as a slip-off bank.

As meanders grow into deep loops, the same may get cut-off due to erosion at the inflection points and are left as ox-bow lakes.

Braided Channels

When rivers carry coarse material, there can be selective deposition of coarser materials causing the formation of a central bar which diverts the flow towards the banks; and this flow increases lateral erosion on the banks.

As the valley widens, the water column is reduced and more and more materials get deposited as islands and lateral bars developing a number of separate channels of water flow.

Deposition and lateral erosion of banks are essential for the formation of the braided pattern.

Or, alternatively, when discharge is less and load is more in the valley, channel bars and islands of sand, gravel, and pebbles develop on the floor of the channel and the water flow is divided into multiple threads.

These thread-like streams of water rejoin and subdivide repeatedly to give a typical braided pattern.

Conclusion

This is Ncert’s notes for the topic ‘Depositional landforms of the river’, written Upsc Exam. This article is also useful for Tnpsc and other state service exams. This covers the landforms formed by the deposition of rivers such as natural levees, point bars, braided channels, meanders, etc.

Erosional landforms of River Upsc

The erosional landforms of the river are River Valley Formation, Potholes and Plunge Pools, Incised or Entrenched Meanders, River Terraces, etc.

Valleys

The valley begins as small and narrow rills. The rills then slowly develop into long and wide gullies. Then the gullies get deepened, widened, and rise on becoming valleys.

Based on the dimensions and shape, the Valleys are classified as V-Shaped Valleys, Gorges, Canyons, etc.

V-Shaped Valleys

The V-Shaped Valley is formed by the river erosion over time and its shape is similar to the letter “V“.

V- Shaped Valley - Erosional landforms of river Upsc — V- Shapped Valley – By BorisFromStockdale at the English-language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18215841

Gorge

A Gorge is a narrow, deep valley running between the mountains or hills with very steep to straight sides. It is typically with steep rocky walls and rivers or streams running through it. Also, the canyon is characterized by steep step-like side slopes and might be as deep as the gorge.

It is almost equal in width at the top and as well the bottom. On the other hand, the Canyon is wide at the top than its bottom. Also, the fact, is that Canyon is a type of Gorge.

Gorge – Canyon By chadh – Snake River Canyon, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=46852845

The valley depends on the structure and types of rock on which they form due to the erosion by running water.

For Example – Gorges are formed in Hard rocks and Canyons are formed in the horizontal bedded sedimentary rocks.

Potholes and Plunge Pools

Over the rocky beds of hill-streams, circular depressions called potholes form because of stream erosion aided by the abrasion of rock fragments. Once a small and shallow depression forms, pebbles and boulders get collected in those depressions and get rotated by flowing water and consequently the depressions grow in dimensions.

A series of such depressions eventually join and the stream valley gets deepened. At the foot of waterfalls also, large potholes, quite deep and wide, form because of the sheer impact of water and rotation of boulders.

Such large and deep holes at the base of waterfalls are called plunge pools. These pools also help in the deepening of valleys. Waterfalls are also transitory like any other landform and will recede gradually and bring the floor of the valley above waterfalls to the level below.

Incised or Entrenched Meanders

In streams that flow rapidly over steep gradients, normally erosion is concentrated on the bottom of the stream channel. Also, in the case of steep gradient streams, lateral erosion on the sides of the valleys is not much when compared to the streams flowing on low and gentle slopes.

Because of active lateral erosion, streams flowing over gentle slopes, develop sinuous or meandering courses. It is common to find meandering courses over floodplains and delta plains where stream gradients are very gentle.

But very deep and wide meanders can also be found cut in hard rocks. Such meanders are called incised or entrenched meanders.

Meander loops develop over original gentle surfaces in the initial stages of development of streams and the same loops get entrenched into the rocks normally due to erosion or slow, continued uplift of the land over which they start.

They widen and deepen over time and can be found as deep gorges and canyons in hard rock areas. They give an indication of the status of the original land surfaces over which streams have developed.

River Terraces

River terraces are surfaces marking old valley floor or floodplain levels. They may be bedrock surfaces without any alluvial cover or alluvial terraces consisting of stream deposits.

River terraces are basically products of erosion as they result due to vertical erosion by the stream into its own depositional floodplain.

There can be a number of such terraces at different heights indicating former river bed levels. The river terraces may occur at the same elevation on either side of the rivers in which case they are called paired terraces. When a terrace is present only on one side of the stream and with none on the other side or one at quite a different elevation on the other side, the terraces are called unpaired terraces.

Unpaired terraces are typical in areas of slow uplift of land or where the water column changes are not uniform along both the banks.

The terraces may result due to:

(i) receding water after a peak flow

(ii) change in hydrological regime due to climatic changes;

(iii) tectonic uplift of land;

(iv) sea-level changes in the case of rivers closer to the sea.

Depositional landform of Wind Upsc

Plain formed by Wind Deposition

The two features that are formed by wind deposition are Sand dunes and loess deposits. The dunes are also called Aeolian Landforms. The wind is a good sorting agent. Based on the velocity of the wind, varying sizes of grains are moved along the floor by saltation, or by rolling, carried in suspension.

During this process of transportation, the material gets sorted. The lighter material is carried long, and heavy materials stay grounded.

When the wind slows or begins to die down, based on the sizes of grains and their critical velocities, the grains will begin to settle.

So, in depositional landforms made by wind, good sorting of grains can be found. Since wind is there everywhere and wherever there is a good source of sand and with constant wind directions, depositional features in arid regions can develop anywhere.

Sand Dunes

Dry hot deserts are good places for sand dune formation. Obstacles to initiating dune formation are equally important. There can be a great variety of dune forms.

Crescent-shaped dunes called barchans with the points or wings directed away from wind direction i.e., downwind, form where the wind direction is constant and moderate and where the original surface over which sand is moving is almost uniform.

Parabolic dunes form when sandy surfaces are partially covered with vegetation. That means parabolic dunes are reversed barchans with wind direction being the same.

Seif is similar to barchan with a small difference. Seif has only one wing or point. This happens when there is a shift in wind conditions.

The lone wings of seifs can grow very long and high. Longitudinal dunes form when the supply of sand is poor and wind direction is constant. They appear as long ridges of considerable length but are low in height.

Transverse dunes are aligned perpendicular to the wind direction. These dunes form when the wind direction is constant and the source of sand is an elongated feature at right angles to the wind direction. They may be very long and low in height.

When sand is plenty, quite often, the regular shaped dunes coalesce and lose their individual characteristics. Most of the dunes in the deserts shift and a few of them will get stabilised especially near human habitations.

Conclusion

Deposition landforms of Wind such as a Sand Dune is a mound of sand that is deposited by wind. The landforms vary in size and shape. The Layers of sand and silt which are deposited in the same area are called Loess, it is very fertile.

Deflation hollows and caves in desert Ncert Upsc Notes

Erosional Classification: Deflation hollows and caves are erosional landforms formed by wind action in arid/desert regions.
Deflation Hollow Formation: Weathered mantle over rocks or bare soil is blown out by the persistent movement of wind currents blowing in one direction, creating shallow depressions called deflation hollows or blowouts.
Connection to Oases: In depressions formed where the wind blows away the sand, an oasis is formed when underground water reaches the surface.
Cave Formation Process: Deflation also creates numerous small pits or cavities over exposed rock surfaces. The rock faces suffer from the impact and abrasion of wind-borne sand, first forming shallow depressions called blowouts. Over time, some of these blowouts become deeper and wider until they are fit to be called caves.
Human Significance: These landforms influence human settlement patterns and agriculture in arid regions.

Reference Ncert Documents

https://ncert.nic.in/textbook/pdf/gess203.pdf

https://ncert.nic.in/textbook/pdf/gess207.pdf

https://ncert.nic.in/textbook/pdf/kegy206.pdf

https://ncert.nic.in/textbook/pdf/iest102.pdf

Depositional landforms of sea waves Upsc

Depositional landforms of sea waves

Important depositional landforms of sea waves are sea beaches, bars, barriers, splits, offshore, etc.

Beaches and Dunes

Beaches

Beaches are characteristic of shorelines that are dominated by deposition but may occur as patches along even the rugged shores. Most of the sediment making up the beaches comes from land carried by the streams and rivers or from wave erosion.

Beaches are temporary features. The sandy beach which appears so permanent may be reduced to a very narrow strip of coarse pebbles in some other season. Most of the beaches are made up of sand-sized materials. Beaches are called shingle beaches that contain excessively small pebbles and even cobbles.

Dunes

Just behind the beach, the sands lifted and winnowed from over the beach surfaces will be deposited as sand dunes. Sand dunes forming long ridges parallel to the coastline are very common along low sedimentary coasts.

Depositional landforms of sea waves - Beaches — Beach By Dave Naithani – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18037324

Bars, Barriers and Spits

A ridge of sand and shingle formed in the sea in the off-shore zone (from the position of low tide waterline to seaward) lying approximately parallel to the coast is called an off-shore bar.

An off-shore bar that is exposed due to the further addition of sand is termed a barrier bar. The off-shore bars and barriers are commonly from across the mouth of a river or at the entrance of a bay. Sometimes such barrier bars get keyed up to one end of the bay when they are called spits.

Spits may also develop attached to headlands/hills. The barriers, bars, and spits at the mouth of the bay gradually extend leaving only a small opening of the bay into the sea and the bay will eventually develop into a lagoon.

The lagoons get filled up gradually by sediment coming from the land or from the beach itself (aided by wind) and abroad and wide coastal plain may develop replacing a lagoon. Do you know, the coastal off-shore bars offer the first buffer or defence against storms or tsunamis by absorbing most of their destructive force.

Then come to the barriers, beaches, beach dunes, and mangroves, if any, to absorb the destructive force of the storm and tsunami waves. So, if we do anything which disturbs the ‘sediment budget’ and the mangroves along the coast, these coastal forms will get eroded away leaving human habitations to bear the first strike of the storm and tsunami waves.

Conclusion

This article covers the topic ‘Depositional landforms of sea waves‘ for Upsc.

Cliffs terraces caves and stacks – Erosional landforms of sea Waves Upsc

WAVES AND CURRENTS

Coastal processes are the most dynamic and hence most destructive. Some of the changes along the coasts take place very fast. At one place, there can be erosion in one season and deposition in another. Most of the changes along the coasts are accomplished by waves.

When waves break, the water is thrown with great force onto the shore, and simultaneously, there is a great churning of sediments on the sea bottom. The constant impact of breaking waves drastically affects the coasts. Storm waves and tsunami waves can cause far-reaching changes in a short period of time than normal breaking waves.

As the wave environment changes, the intensity of the force of breaking waves changes. Other than the action of waves, the coastal landforms depend upon:

(i) the configuration of land and seafloor;

(ii) whether the coast is advancing (emerging) seaward or retreating (submerging) landward.

Assuming sea level to be constant, two types of coasts are considered to explain the concept of evolution of coastal landforms:

(i) high, rocky coasts (submerged coasts);

(ii) low, smooth, and gently sloping sedimentary coasts (emerged coasts).

HIGH ROCKY COASTS

Along the high rocky coasts, the rivers appear to have been drowned with the highly irregular coastline. The coastline appears highly indented with the extension of water into the land where glacial valleys (fjords) are present. The hillsides drop off sharply into the water. Shores do not show any depositional landforms initially.

Erosion features dominate. Along high rocky coasts, waves break with great force against the land shaping the hillsides into cliffs. With constant pounding by waves, the cliffs recede leaving a wave-cut platform in front of the sea cliff. Waves gradually minimize the irregularities along the shore.

The materials which fall off, and are removed from the sea cliffs, gradually break into smaller fragments, and roll to roundness will get deposited offshore. After a considerable period of cliff development and retreat when the coastline turns somewhat smooth, with the addition of some more material to this deposit offshore, a wave-built terrace would develop in front of the wave-cut terrace.

As the erosion along the coast takes place a good supply of material becomes available to longshore currents and waves to deposit them as beaches along the shore and as bars (long ridges of sand and/or shingle parallel to the coast) in the nearshore zone.

Bars are submerged features and when bars show up above the water, they are called barrier bars. The barrier bar which gets keyed up to the headland of a bay is called a spit. When barrier bars and spits form at the mouth of a bay and block it, a lagoon forms.

The lagoons would gradually get filled up by sediments from the land giving rise to a coastal plain.

LOW SEDIMENTARY COASTS

Along low sedimentary coasts, the rivers appear to extend their length by building coastal plains and deltas. The coastline appears smooth with occasional incursions of water in the form of lagoons and tidal creeks. The land slopes gently into the water. Marshes and swamps may abound along the coasts.

Depositional features dominate. When waves break over a gently sloping sedimentary coast, the bottom sediments get churned and move readily building bars, barrier bars, spits, and lagoons. Lagoons would eventually turn into a swamp which would subsequently turn into a coastal plain.

The maintenance of these depositional features depends upon the steady supply of materials. Storm and tsunami waves cause drastic changes irrespective of the supply of sediments. Large rivers which bring lots of sediments build deltas along low sedimentary coasts.

The west coast of our country is a high rocky retreating coast. Erosional forms dominate on the west coast. The east coast of India is a low sedimentary coast. Depositional forms dominate on the east coast.

EROSIONAL LANDFORMS

Cliffs, Terraces, Caves, and Stacks

Wave-cut cliffs and terraces are two forms usually found where erosion is the dominant shore process. Almost all sea cliffs are steep and may range from a few m to 30 m or even more. At the foot of such cliffs, there may be a flat or gently sloping platform covered by rock debris derived from the sea cliff behind.

Such platforms occurring at elevations above the average height of waves is called wave-cut terrace. The lashing of waves against the base of the cliff and the rock debris that gets smashed against the cliff along with lashing waves create hollows and these hollows get widened and deepened to form sea caves.

The roofs of caves collapse and the sea cliffs recede further inland. The retreat of the cliff may leave some remnants of rock standing isolated as small islands just off the shore. Such resistant masses of rock, originally parts of a cliff or hill are called sea stacks.

Like all other features, sea stacks are also temporary and eventually, coastal hills and cliffs will disappear because of wave erosion giving rise to narrow coastal plains, and with the onrush of deposits from over the land behind may get covered up by alluvium or may get covered up by shingle or sand to form a wide beach.

FAQ

1.Which is not an erosional feature of sea waves?

Options:

a. Cliff

b. Beach

c. Sea Caves

Answer: Beach is not an erosional feature of sea waves. It is a depositional feature of sea waves.

Glacial depositional landforms and their features Upsc

Glacial depositional landforms

Glacial depositional landforms are formed from the action of glaciers. Most of the Glacial depositional landforms are formed by the movement of large ice sheets.

Most of the famous areas for such glacier landforms are Fennoscandia, Andes, etc.

Formation

The unsorted sediments, unassorted coarse and fine debris are dropped from the glacier melting. This is called Glacial till. The rock fragment in large numbers in the Till is in form of angular or subangular form.

Due to the melting of ice at the bottom, sides, lower ends of the glaciers, the streams are formed. In these streams, small rock debris is carried, washed down, and deposited. Such glacial-fluvial deposits are called Outwash deposits.

Outwash deposits are stratified and assorted. Also, the rock fragments in the outwash deposits are rounded at their edges.

Glacial depositional features

Moraines

Moraine is are the left behind materials by the moving glacier. These materials are usually soil and rocks. The glacier moves all types of boulders, dirt which are built up to form moraines. Moraines are simply long ridges of deposits of glacial till.

Moraines are of four types and are Terminal Moraines, Lateral moraines, medial moraines and Lateral Moraines. Examples of Moraines are the Side Glacier of the Gorner Glacier in Zermatt Switzerland, Kettle Moraine Wisconsin USA, Harbor Hill Moraine in Long Island USA, etc.

Terminal Moraines

Terminal Moraines are found at the endpoint of the glacier. These are long ridges of deposits of glacial till are formed along the sides parallel to the glacial valleys.

In some cases, the lateral moraines and terminal moraine may join and form a horseshoe-shaped ridge.

Lateral Moraines

These moraines are found on either side of the glacier and there can be many lateral moraines. The lateral moraines partly or fully owe their origin to glacio-fluvial waters that push up the material to the sides of the glacier.

Ground Moraines

The ground moraines are rocks of different sizes and types. These are formed when different glacier’s valleys retreat rapidly. This leaves an irregular sheet of till over the valley floors. These deposits differ greatly in thickness and in surface topography.

Medial Moraines

These Moraines are found at the centre of the glacial valley / at the junction between two glaciers flanked by lateral moraines. Medial moraines are imperfectly formed compared to lateral moraines.

In some cases, the ground moraines are indistinguishable from the medial moraines.

Eskers

Eskers are ridges that are made of stones, sands, and gravel. These are deposited by the water which is melted from the glaciers. Eskers are carried by the water through the tunnels underneath or within the glaciers.

Formation of Eskers

During the summer, the glaciers melt and the water flows over the surface of the Ice. Also, the water seeps down along the margin or through holes in the ice. This water accumulates below the glacier and flows like a stream below the glacier.

These streams also flow over the ground that forming ice in its banks. These streams carry coarse materials like boulders, blocks, and other rock debris and make them settle in the valley of ice beneath the glacier.

After the ice melts these coarse materials can be found as a sinuous ridge called Esker.

Outwash Plains

Outwash plains occur in front of melting glaciers. These are deposits of sand and gravel carried by running water. The glacial mountains plain at the foot or beyond the limits of the continental ice sheet are covered with glacio-fluvial deposits.

These glacio-fluvial deposits were in the form of broad flat alluvial fans that may join to form outwash plains of gravel, silt, sand, and clay. The outwash plains are expansive, dominated by braided rivers when glaciers melt.

The outwash plain extends several miles beyond the glacier margin. The outwash plains were often used for specialized kinds of Potato cultivation. Example in Montcalm County. This plain favors plants that grow well in well-drained soil.

Drumlins

Drowned drumlin in Clew Bay Ireland By Brendanconway – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=54447

Drumlins are oval-shaped hills, that are composed of glacial drift that is formed under the glacier or ice sheets. These are aligned in the direction of ice flow.

Drumlins are smooth have the feature of the oval-shaped ridge. It is made of glacial till of gravel and sand. The long axes of drumlins are parallel to the direction of ice movement and measure up to 1 km in length and 30 m or so in height.

One end of the drumlins facing the glacier called the stoss end is blunter and steeper than the other end called the tail. The drumlins form due to the dumping of rock debris below heavily loaded ice through fissures in the glacier or ice sheets. The stoss end gets blunted due to pushing by moving ice.

Thereby, the Drumlins give an indication of the direction of glacier movement.

Conclusion

This is Ncert’s notes for the topic ‘Glacial depositional landforms‘ for Upsc and other state service exams. Due to the deposition actions of the Glaciers, several types of landforms are formed. They are Moraines, Eskers, Outwash Plains, and Drumlins.

Erosional landforms of glacier Upsc

Cirque

Cirques are the most common landforms in glaciated mountains. The cirques quite often are found at the heads of glacial valleys.

The accumulated ice cuts these cirques while moving down the mountain tops. They are deep, long, and wide troughs or basins with very steep concave to vertically dropping high walls at its head as well as sides.

A lake of water can be seen quite often within the cirques after the glacier disappears. Such lakes are called cirque or tarn lakes. There can be two or more cirques one leading into another down below in a stepped sequence.

Horns and Serrated Ridges

Horns form through headward erosion of the cirque walls. If three or more radiating glaciers cut headward until their cirques meet, high, sharp-pointed, and steep-sided peaks called horns form.

The divides between the cirque side walls or headwalls get narrow because of progressive erosion and turn into serrated or saw-toothed ridges sometimes referred to as arêtes with very sharp crest and a zig-zag outline.

“The highest peak in the Alps, Matterhorn and the highest peak in the Himalayas, Everest are in fact horns formed through headward erosion of radiating cirques.“

**Serrated Ridges** By Alpsdake – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11567654

Glacial Valleys/Troughs

Glaciated valleys are trough-like and U-shaped with broad floors and relatively smooth, and steep sides. The valleys may contain littered debris or debris shaped as moraines with a swampy appearance. There may be lakes gouged out of the rocky floor or formed by debris within the valleys.

There can be hanging valleys at an elevation on one or both sides of the main glacial valley. The faces of divides or spurs of such hanging valleys opening into main glacial valleys are quite often truncated to give them an appearance like triangular facets.

Very deep glacial troughs filled with seawater and making up shorelines (in high latitudes) are called fjords/fiords.

depositional landforms of glacier

Transportation and Deposition of Rocks Upsc

Transportation and Deposition of Rocks

Erosion is a natural process by the top layer of soil, rock or material on the surface of earth is removed by transported to another location by means of water, wind etc.

Weathering is an important process, which is part of erosion where is helps in break down of rock into small debris and it does not involve in the movement of the materials.

Erosion is the removal, or transportation process, which involves the acquisition and transportation of rock debris.

Transportation and Deposition of Rocks Upsc By Michael C. Rygel – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=12622448

Role of Geomorphic Agents in Erosion

Depending upon the dynamics of the Geomorphic Agents such as water, glacier, waves, wind, groundwater etc the massive rocks are weathered, that is break up of rocks into smaller fragments or debris.

Abrasion by the rock debris is carried by the Geomorphic agents such as water, glacier, waves, wind etc, and also helps greatly in erosion, transportation and deposition of Rocks.

The erosion degrades the Reliefs and by that, the landscapes are worn down. This makes us understand that weathering helps erosion but it is not a precondition for the erosion to takes places.

The degradational processes include Mass Wasting, Erosion and Weathering. The earth surface undergoes continuous changes and the main reason behind it is Erosion.

Kinetic Energy in Transportation and Deposition of Rocksand deposition of Rocks

Kinetic energy controls denudational processes such as transportation and erosion.

Wind, Water, Glacier, Waves etc brings the earth material by erosion and transportation.

The Geomorphic agent’s such as Wind, Running Water and Glacier are controlled by Climatic conditions. The wind represents the Gaseous form, Running represents the liquid form and glacier represents the solid forms respectively.

Erosion is defined as the application of the kinetic energy related to the agent to the surface of the land along with its moves K.E. = 1/2 m v².

Therefore the energy is available to perform work depends on the mass of the material and the velocity with which it is moving.

Even though the Glacier move very slow, it is more effective than other agents of erosion such as wind. This is because Glacier has tremendous mass and wind is less effective at it is in a gaseous state.

The other two erosional agent such as the waves and the groundwater is not controlled by the climate.

The erosional work of the groundwater is determined much by the lithological character of the region and the work of wave is along the coastal region and it happens along with the interface of lithosphere and hydrosphere.

The Karst topography develops only when the rock is permeable and solution and also there is the availability of water.

The erosional agent’s losses its velocity and thereby the energy on the gentle slopes and material carried by the erosional agents start to settle themselves and it means that the deposition is not actually the work of any agent.

The coarser materials get deposited first and then the finer ones. The depression gets filled up by deposition.

The same erosional agents viz. running water, glaciers, wind, waves, and groundwater also act as aggradational or depositional agents.

FAQ

Which is the gaseous agent of erosion?

Wind is the Gaseous agent of Erosion.

2. why are glaciers such effective agents of erosion and deposition?

This is because Glacier spread out over the surface of land, as it grow and changes the shape of the land. Also they scrape away the surface, erode the rock and its sediment.

The glacier also carry the sediments to one place to another place. Therefore glacier are one of most effective agents of erosion and deposition.