Here is your brief notes on Youthful Topography



(i) 'V'- Shaped Valley: -

These are formed by vertical erosion or down ward cutting the sign of hectic activity (youthful).

(ii) Water falls, Rapids, Cascades: -

When a river flowing over a hard resistant rock flows over a soft, less resistant rocks by some reason, a scarp face is formed after erosion and it gives rise to waterfall. In hilly terraines, when streams flow down along vertical escarpments, water falls are formed. Also, in case of pre-glaciated terraines, streams flowing over hanging valleys give rise to waterfalls.

If the steepness of the cliff is less; it forms rapids and when water flows along step - like structures, cascades are formed. Mostly, water falls, rapids and cascades are formed due to differential erosion. Niagara fall and Victoria fall are good examples of falls. In India, Gersoppa fall of the Saraswati River is nearly 350 meters. In Orissa, Khandadhar (820 feet) water fall is the best example. Bareipani on Budhabalang has a height above 600 meters.

Canyon and Gorge:

When the valley walls are steep and high in comparison to the width of the channel, the feature is known as gorge. The steep walls are commonly hard and resistant rocks with high / low dips. In some cases, faults or major joints help in down cutting. Gorges with rapids are known as canyons. Good examples are the Grand Canyon of the Colorado River, (a tourist site) the Gilgit Gorge of the Indus River is nearly 7,000 meters deep. The Satkoshia Gorge of the Mahanadi River is famous in Orissa and is about 21 km. long. A canyon section is shown in.

(iii) Potholes:

Commonly, at the foot of falls and rapids, boulders a pebbles, grind the hard rock bed by whirling action of the wat generating holes of different diameter and depth. These are potholes filled with sand and / or heavy materials of the bed.

(iv) Cliffs / Scarps:

Cliffs, scarps are formed due to differential erosion aided by mass wasting and weathering of alternate hard and soft rock.

Mature Topography:

As the fluvial geomorphic cycle proceeds, the 'V' shaped valleys gradually form flat river valleys; water divides become narrower, hills and ridges become sharper with maximum possible relief.

(i) Outlier and Inlier:

In case of homogenous or low folded regions, erosion leaves portions of younger rocks surrounded by older rocks - the land form is outlier. Where, portions of the older rock are exposed due to erosion surrounded by younger rocks, the land form is an inlier.

(ii) Mesa and Butte:

As erosion proceeds, isolated table lands with nearly flat or very gentle slope, survive due to hard resistant cap rocks. These are termed as mesas. Buffets are similar erosion remnants with smaller flat summit area. They have steep sided cliffs. In Koraput district of Orissa mesas and buttes \ are numerous - Panchapatmali, Bafalimali, Sasubohumali etc. are famous mesas which contain bauxite deposits.

(iii) Cuesta and Hog back:

As erosion proceeds in areas underlain by low dipping rocks, the dip slope or resequent slope becomes lower than the slope opposite to dipslope (obsequent slope). The resulting land forms are termed as cuesta. In areas with high dips, resequent slope becomes almost equal to obsequent slope. This type of land forms are termed as hogbacks.

(iv) Homoclinal ridges:

In moderately dipping areas, ridges intermediate between cuesta and hogback are formed, which are termed as homoclinal ridges.

Old Topography: As geomorphic cycle proceeds the entire landscape is subdued and is converted to a gently rolling or almost flat topography with a low MSL.

(i) Peneplain:

As defined by Davis, it is almost a plain formed towards the penultimate stage of a fluvial cycle. It represents a large land ar of low relief with minor irregularities here and there.

(ii) Monadnocks:

In the rolling peneplain the irregularities are in form of minor hillocks studded here and there. These isolated hillocks which have survived the extensive erosion are termed as monadnocks. Paresnath hill is one such hillock in Bihar & Dhauli off Bhubaneswar should be considered that way.

(iii) Flood Plain:

Flood plain is the area on both sides of the river formed by deposits during flood. It is almost a plain land. Within the flood plain, the gently sloping raised features on both sides of the river bed are known as natural levees.

(iv) River Terrace:

The river terraces are remnants of older flood plains or valley floors. Due to rejuvenation, the older valleys are uplifted and the rivers carve their own valleys once again giving rise to terraces. These are marked on both sides of the river or occasionally on one side only. When they occur on both sides the terraces are termed as paired or cyclic.

(v) Deltaic Plain:

The large plain formed by the coalescence of the flood plains of the braided channels or the distributaries within the delta is termed as deltaic plain. Swamps and marshes may exist within the deltaic plain.

(vi) Estuary:

Very often the river meets the sea with a widened mouth through which sea water enters the river and goes back to the sea during high tide and low tide respectively. This portion of the river mouth is the estuary.