What are the various differences between a high rocky coast and a low sedimentary coast in terms of processes and landforms?

1. Landforms:

(i) Landforms are small to moderate patches of Earth’s surface which collectively form a Landscape.

(ii) Different geomorphic processes make a Landform’s own physical characteristics.

(iii) Terms such as Youth, mature and old depict the lifespan of a landform.

2. Running water:

(i) Running water is considered to be the most important geographic agent in degrading land.

(ii) There are two main components of running water:

(a) Overland flow as sheet

(b) Linear flow as stream

(iii) Stream channels turn gentle as continued erosion decreases its velocity and facilitates active deposition and as a result hills and valleys are reduced to plains.

(iv) The $3$ stages of landscapes developing in running water regimes are Youth, Mature and Old stage.

(v) Youth:

(a) At this stage streams are few with poor integration and no or very narrow floodplains.

(b) Waterfalls and rapids may exist where local hard rock bodies are exposed.

(vi) Mature:

(a) At This stage streams are plenty with good integration with wider floodplains.

(b) The divides in the streams become sharp and swamps and marshes disappear.

(vii) Old:

(a) Divides are broad and flat with smaller tributaries and streams meander freely over vast floodplains.

3. Erosional Landforms due to Rivers:

(i) Valley:

(a) Starts as a small rill which eventually deepens and forms a valley.

(b) We can identify valleys on the basis of their shape and dimensions.

(c) The type of rock determines the type of valley which will be formed.

(d) Sedimentary rocks are responsible for the formation of Canyons whereas George forms on hard rocks.

(ii) Potholes and Plunge Pools:

(a) Formation of a pothole takes place due to stream erosion and by the abrasion of rock fragments.

(b) These depressions get deep as the stones and pebbles deposit in them and get rotated by the flowing water.

(c) Plunge pools are the deep and large holes found at the base of a waterfall.

(iii) Incised or Entrenched Meanders:

(a) Sinuous or meandering courses form due to active lateral erosion and streams flowing over gentle slopes.

(b) Meandering courses can be found over delta plains and floodplains as genten stream gradients could be found there.

(c) When streams cut through the hard rocks and form very deep and wide meanders, Such meanders are called incised or entrenched meanders.

(iv) River terraces:

(a) When vertical erosion occurs by streams to their own depositional floodplain, formation of river terraces takes place which may or may not have alluvial cover.

(b) Previous river beds can be identified if a number of these terraces are found at different altitudes.

(c) Parried terraces are river terraces at the same height on either side of a river.

4. Depositional Landforms due to Rivers:

(i) Alluvial Fans:

(a) Usually very coarse load is carried by mountain streams and it's too heavy to be carried over gentle gradient, so it deposits as a low to high cone known as alluvial fan.

(b) It’s the reason for the formation of distributaries as streams change their path along the alluvial fans.

(c) Low cones with gentle slopes are found in humid regions whereas high cones with steep slopes in Arid and Semi-arid regions.

(ii) Deltas:

(a) River carries load which is dumped into sea, if dumped not far enough or spread evenly it accumulates as a low cone which are called Deltas.

(b) Deposits are well separated with clear hierarchy as the hard and rough materials settle at the bottom and fine elements line clay and silt gets carried away in the sea.

(c) Deltas continue to grow as the river's distributaries increase in length.

(iii) Floodplains, Natural levees and Point Bars:

(a) Floodplains are a major landform of river deposits where large sized deposits at the bottom and fine sized components like clay, sand and silt carried away my slow moving water and deposits over bed.

(b) River bed formed of river deposits is active floodplain whereas, floodplains above the bank is inactive floodplain which contains two types of deposits i.e.Channel Deposits and Flood Deposits.

(c) Floodplains formed in a delta are called Delta plains.Some important landforms associated with this are Natural levees and Point Bars.

(d) Natural levees are low, linear and parallel ridges of coarse deposits found along the banks of large rivers.

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

(iv) Meanders:

(a) It's rare for a river to flow linear in a flood or delta plain, instead loop-like channel patterns are formed known as meanders.

(b) Meander is a channel not a landform because:

• 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.
•  Coriolis force acting on the fluid water deflecting it like it deflects the wind.

(c) Slight irregularities along the bank gradually form small curvatures which deepens due to erosion and deposition.

(d) The concave bank has undercutting and shows steep scarps that’s why it is also known as a cut-off bank whereas, The convex bank has active deposits and has a long, gentle profile which is why it is also known as slip-off bank.

(e) When loop[s grow deep, it gets cut-off at inflection point due to erosion and forms ox-bow lakes.

5. Groundwater:

(i) After going down to some depth vertically, the water flows under the ground horizontally through the bedding planes and joints.

(ii) The downward flow of water causes erosion in rocks.

(iii) Developing landforms remain unaffected by movement of groundwater and no physical or mechanical removal of materials is noticed.

(iv) The chemical process of solution and precipitation deposition develop varieties of landforms actively found in limestones or dolomites.

(v) Any landform created by action of groundwater on limestone by process of solution and deposition is called Karst topography.

6. Erosional Landforms due to Groundwater:

(i) Pools, sinkholes, lapies, limestone pavements:

(a) After the process of solution on limestones, small to medium sized rounded depressions called shallow holes are formed.

(b) Sinkholes are very common in karst areas. It is a funnel shaped structure with circular opening at top with sizes varying from a few metres to a hectare.

(c) Sometimes, they may also form the roof of an underground cave and may also collapse paving way for cave opening (collapse sinks). The term Doline can be used to refer to a collapse sink.

(d) When the surface of limestone is eaten away by pits or trenches, it forms Ridges or Lapies. The lapie field may even turn into smooth Limestone pavements.

(ii) Caves:

(a) When the water percolates down through the joints and moves horizontally through bedding planes, the limestone dissolves creating wide gaps called caves.

(b) Caves having two openings are called tunnels.

7. Depositional landforms due to Groundwater:

(i) As the water carrying calcium carbonate evaporates, it gets settled over rough rock surfaces.

(ii) Stalactites, Stalagmites and Pillars:

(a) The hanging structures from the roof of the cave are known as stalactites. They are broader at bases and get narrower at the ends.

(b) Stalagmites rise from the bottom floor of the cave.

(c) Pillars and columns are formed by the fusion of stalactites and stalagmites.

8. Glaciers:

(i) Ice masses moving in bulk over land as sheets or flowing down from the slopes of mountains passing through valleys are called glaciers.

(ii) Their movement speed is quite slow.

(iii) They cause severe damage to un-weathered rocks and may reduce high mountains into low hills.

9. Erosional Landforms due to Glaciers:

(i) Cirque:

(a) Cirques are most commonly found on the heads of glaciated mountains.

(b) These are deep, long and wide basins like structures with very steep concave.

(c) The lakes formed after the glacier disappears are known as Cirques.

(ii) Horns and Serrated Ridges:

(a) The erosion of cirque walls leads to formation of horns.

(b) Progressive erosion leads to narrowing of division between cirque side walls which turn into serrated ridges.

(iii) Glacial valleys/Troughs:

(a) These are U-shaped structures with broad floors and smooth-steep sides.

(b) Very deep glacial troughs filled with seawater are known as fjords(fiords).

(c) These valleys can contain littered debris with swampy appearance.

10. Depositional landforms due Glaciers:

(i) The debris dropped by the melting glaciers is known as glacial till.

(ii) The amount of rock debris carried by melt-streams is washed down and deposited known as outwash deposits.

(iii) Moraines:

(a) Moraines are the depositions of glacial tills in the form of long ridges.

(b) Lateral moraines are formed along the sides parallel to glacial valleys.

(c) Moraines are of two types - Ground moraines and Medial moraines.

(iv) Eskers:

(a) The rock debris flown by the stream settle in the valley of ice beneath the glacier and after the ice melts, it can be found as a sinuous ridge called esker.

(v) Outwash plains:

(a) The plains at the foot of the glacial mountains are covered with glacial-fluvial deposits which join to form outwash plains of gravel, silt and clay.

(vi) Drumlins:

(a) Drumlins are mainly composed of glacial till, gravel and sand which have a smooth oval shape.

(b) Their length reaches to about $1 \mathrm{km}$ and their height measures to about $30 \mathrm{m}$.

(c) The blunter and steeper end of a Drumline is called the stoss while the other end is called the tail.

11. Waves and Currents:

(i) The changes taking place across a coast varies hugely, while some seasons show erosion, another may show deposition.

(ii) The coastal landform depends on $3$ factors which are:

(a) Waves

(b) Configuration of land and sea floor

(c) Nature of the coast

(iii) There are mainly $2$ types of coasts, given that the sea level remains constant which are:

(a) High, rocky coasts

(b) Low, smoothe coasts.

12. High Rocky Coasts:

(i) While the coastline smoothly merges into water, the hillsides drop off sharply into the water.

(ii) Wave-cut platforms are formed due to the constant pounding of waves on the cliff.

(iii) Bars are the submerged features which when shown above the water are called barrier bars.

(iv) Spit is formed when a barrier bar gets keyed up to the headland of a bay. A lagoon is formed when barrier bars and spits form at the mouth of a bay and block it.

13. Low Sedimentary Coasts:

(i) Bars, barrier bars, spits, and lagoons when the bottom sediments broken by waves get churned and move readily.

(ii) Coastal plain gets formed from swamps and swamps are formed from lagoons.

(iii) Storm, tsunami and large rivers bring about drastic changes to them.

14. Erosional Landforms near coast:

(i) Cliffs, Terraces, Caves and Stacks:

(a) Erosion is a dominant shore process in wave-cut cliffs and terraces.

(b) A wave cut terrace is one in which the elevation is above the average height of the waves.

(c) Sea stacks are the temporary features which are the resistant masses of rocks, originally parts of hill or cliff.

15. Depositional Landform near the Coast:

(i) Beaches and Dunes:

(a) Beaches are the temporary features which are formed due to the excessive deposition of land carried by the streams and rivers or from wave erosion.

(b) Shingle beaches contain excessive small pebbles and even cobbles while other beaches generally are made up of sand sized matter.

(c) Long ridges parallel to the coastline which are formed by the deposition of sands lifted and winnowed from over the beach surfaces are called sand dunes.

(ii) Bars Barriers and Spits:

(a) An off-shore bar is a ridge of sand and shingle formed in the sea in the off-shore zone almost parallel to the coast.

(b) A barrier bar is formed due to excess addition of sand on an exposed off-shore bar. Barrier bars then get keyed up to one end of the bay and are called spits.

(c) A lagoon is a small opening of the bay into the sea left behind because of the gradual extension of barriers, bars and spits at the mouth of the bay.

(d) A coastal plane may develop over a lagoon because of their gradual filling up by sediments coming from the land or the beach with the help of wind.

16. Winds:

(i) Due to the excessive heating up of the air just above the dry and barren floors of a desert, it results in the formation of winds because of the upward movement of the air creating turbulence, eddies, updrafts and downdrafts.

(ii) Turbulence is also created because of the movement of wind along the surface of the desert with great speeds. It also leads to storm winds.

(iii) The causes of wind are Deflation, Abrasion and Impact.

(iv) Rain / sheet wash also play a significant role along with the wind in moving weathered debris in deserts.

17. Erosional Landforms due to Wind:

(i) Pediments and Pediplains:

(a) Pediments are the gently inclined rocky floors present close to the mountains at their foot which are formed due to the erosion of the mountain front.

(b) A remnant of the mountain called inselberg is formed due to the extension of pediments backwards at the expense of the mountain front through parallel retreat of slopes.The mountain gets reduced and the high relief in desert areas is reduced to low featureless plains called pediplains

(ii) Playas:

(a) Formation of planes takes place by deposition of sediments over a basin surrounded by mountains and hills around and along it but to the drainage towards the centre.

(b) Playas are the temporary deposition formed because of sufficient water being drained on the plane forming shallow lakes called playas.

(c) Alkali flats are the playa plains covered up by salts.

(iii) Deflation Hollows and Caves:

(a) Deflation hollows are shallow depressions created due to the blowing out of a weathered mantle by persistent movement of wind in one direction.

(b) Caves are formed due to the deepening and wider fitting of certain blow outs.

(iv) Mushroom, Table and Pedestal Rocks:

(a) Many rock-outcrops are prone to easily getting wind deflated leaving behind remnants of resistant rocks polished beautifully to form the shape of a mushroom.

(b) When the top of these rocks is broad they look like a table top.

(c) Sometimes, the remnants stand out like pedestals.

18. Depositional Landforms due to Wind:

(i) Sorting of materials takes place depending on different sizes of grains and the velocity of the wind.

(ii) This leads to proper sorting of grains when the depositional landforms are formed by wind.

(iii) Sand Dunes:

(a) Sand dune formation best takes place in hot dry deserts.

(b) Importance of obstacles initiating the formation of sand dunes are equally important.

(c) There are a great variety of sand dune forms based on their shape and size namely - Barchan, Parabolic, Seif, Longitudinal, Transverse.

(d) The shape and the size of these dunes are mostly not fixed. Only in rare cases will the dunes stabilise near human habitations.