landforms of the earth

geography chapter 5

what are the 3 major types of landforms?

mountains, plateaus, plains.

what are mountains?

• mountain- a very steep land or hill rising to great heights above the land surrounding it.

• classified into 3 main types based on the forces that have formed them - fold mountains, residual mountains, block mountains.

what are fold mountains?

• result of lateral compression of the earth’s crust.

• result of large-scale earth movements caused by stresses in the earth’s crust.

• stresses may be caused by weight of overlying rocks, movements in the mantle, expansion or contraction of some part of the earth etc.

• these stresses subject the rocks to compressive forces, producing wrinkling or folding along the lines of weakness.

give 5 chief characteristics of fold mountains.

1. they form irregular wave-like formations called folds.

2. most of these mountains constitute sedimentary rocks formed due to deposition and consolidation of sediments in shallow oceans.

3. have greater length but are smaller in width.

4. most are found on the margins of continents.

5. associated with volcanic activity, have many active volcanoes.

differentiate between young fold mountains and old fold mountains.

young fold mountains	old fold mountains
have been formed later than old fold mountains.	have been formed long ago much before young fold mountains.
have steep slopes, deep valleys and sharp pointed snow covered peaks.	highly eroded by agents of gradation. gentler slopes, rounded tops /
much higher than old fold mountains.	much lower than young fold mountains.
volcanic activities are common.	rare, but there is evidence of volcanic activities still in them.
himalayas, andes, alps, rockies.	appalachians, urals, aravallis.

what are residual mountains?

• mountains which are subjected to weathering and erosion for a long time, are lowered down and called residual or relict mountains.

• denudation and erosion by natural agents - winds, water, snow, etc. cause the mountains to be lowered but some resistant areas may remain and form residual mountains.

• may also be formed on plateaus that are dissected by rivers.

• also called mountains of denudation. cahracterised by low elevations.

what are block mountains?

• the forces of faulting, AKA epeirogenic forces, lead to formation of block mountains.

• cracks or faults may occur on earth’s crust due to tension. if 2 parallel faults occur, the land between subsides to form a rift valley. if a block rises, it forms a horst or block mountain.

• block mountains which have flattened summits are called horst mountains.

• block mountains are often separated by intervening basins called graben.

what are plateaus?

• plateau is an area of high ground, 500 feet above ground level.

• these uplands have steep slopes on one side. upper part - generally flat and called tableland.

• 2 types - intermontane and volcanic.

what are intermontane plateaus?

• highest and most extensive types on the globe.

• the plateaus surrounded by hills and mountains on all sides are called intermontane plateaus.

• they are formed along with fold mountains.

• tibetan plateau - world’s highest and most extensive plateau.

what are volcanic plateaus?

• volcanic plateaus are formed by numerous volcanic eruptions that slowly build up over time forming a plateau.

• eg. plateau of peninsular india, south african plateau etc.

what are plains?

• a plain is defined as an extensive area of lowland with a level or gently undulating surface.

• 3 types of plains - structural, erosional, depositional.

what are structural plains?

• the plains that are formed due to uplift of subsidience of land are called structural plains.

• diastrophic forces may cause uplift or a portion of land beneath the ocean water or may cause submergence of coastal land under ocean water.

what are depositional plains?

• the plains that are formed by the deposition of materials which have been brought by various agents of transportation are called depositional plains.

  1. river deposition

  2. wind deposition

  3. marine deposition

give 4 points on importance of landforms.

1. they are beautiful sculptures of nature and add to the beauty of the earth.

2. they represent the relief features of the earth. they have an impact on climate, direction of winds, precipitation etc.

3. mountain ranges of the world are the abode of snow and glaciers - thus they are the source of perennial rivers.

4. many kinds of forests are found on slopes of mountains and hills which are home to many animals and plants.

5. such relief features also exist in oceans, thus island groups and coast regions are ideal fishing sites.