Ch 8. Landforms And Their Evolution

Question 1

What is a Landform ?

Answer 1

A landform is a natural or anthropogenic land feature on the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography.

Question 2

What is Geomorphology ?

Answer 2

It deals with the reconstruction of the earth’s surface history through the study of its shapes, the materials it consists of and the processes that shape it

Question 3

What is Sheet erosion ?

Answer 3

Erosion of land due to overland flow of water is called as sheet erosion

Question 4

What are different stages of a river ?

Answer 4

1. Upper course / Stage of youth
2. Middle course / Stage of maturity
3. Lower course / Stage of old

Question 5

Mention few Erosional Landforms ?

Answer 5

Valleys, gorges, canyons and rapids

Question 6

What is a Valley ?

Answer 6

A low area of land between hills or mountains, typically with a river or stream flowing through it.

Question 7

Differentiate Gorge and Canyon ?

Answer 7

A Gorge is a deep valley with very steep to straight sides.

A Canyon is characterised by steep-like side slopes and may be as deep as a gorge

A Gorge is almost equal in width at its top as well as bottom and is formed in hard rocks while a canyon is wider at its top than at its bottom and is formed in horizontal bedded sedimentary rocks

Valley - > Canyon -> Gorge

Question 8

How are Rapids formed ?

Answer 8

Rapids are formed when the stream passes through alternate bands of hard and soft rocks

Question 9

What are Potholes and Plunge pools ?

Answer 9

Circular depression over the rocky beds of hill streams are called as potholes

Plunge pools are wide, deep potholes at the foot of a waterfall

Question 10

Define a Meander

Answer 10

A curvy, wavy river

Question 11

What are River Terraces ? What are paired and unpaired terraces ?

Answer 11

They are surfaces marking old valley floor or flood plains which are resulted due to vertical erosion by the river

When the terraces on either side of hte river have the same height, they are referred to as paired terraces

When the terraces are seen on one side only, with none on the other side or on the other side at a quite a different elevation, they are called unpaired terraces

Question 12

What are Alluvial fans ?

Answer 12

An alluvial fan is a triangle-shaped deposit of gravel, sand, and smaller materials called alluvium. They are formed in the middle course of a river

Question 13

What is a Delta of a river?

Answer 13

Deltas are wetlands that form as rivers empty their water and sediment into another body of water, such as an ocean, lake, or another river.

Question 14

What are Flood plains and Natural leeves ?

Answer 14

Flood plain - an area of low-lying ground adjacent to a river, formed mainly of river sediments and subject to flooding.

Natural leeves - these are embankments formed naturally after a river floods and recedes.

Question 15

What are Meanders and Oxbow Lakes ?

Answer 15

Meander - These are loop like channel patterns formed in the middle stage of the river

Oxbow lakes - the ends of the meander loop come closer. and closer. In due course of time the. meander loop cuts off from the river and. forms a cut-off lake, also called an ox-bow.

Question 16

What are cut-off and slip-off banks in a Meander ?

Answer 16

The concave bank of a meander is called as cut-off bank and the convex bank is called as a slip-off bank

Question 17

What are Braided channels ?

Answer 17

A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars / riverine islands

Question 18

Which is the biggest riverine island in the world ?

Answer 18

Majuli island in Assam

Question 19

What are permeable and impermeable rocks ?

Answer 19

The rocks are called permeable rocks if they allow the water to pass easily, while the rocks that do not allow water to pass through are called impermeable rocks

Question 20

What is Karst Topography ?

Answer 20

Any limestone, dolomite or gypsum area showing typical landforms formed by the solution and deposition process by the action of groundwater is called Karst Topography

Question 21

What is a Saturation zone in Karst topography ?

Answer 21

The zones of permeable and porous rocks completely filled with water are referred to as the Saturation zones

Question 22

What are Springs in Karst topography ?

Answer 22

When the groundwater outflows over the surface under hydraulic pressure through an opening in a rock, these are called as springs

Question 23

What is a Geyser ?

Answer 23

When hot water and steam are released by a spring in the form of fountains or jets at regular intervals, they are called geysers

Question 24

Mention few places where Karst topography is found

Answer 24

Bosnia, Croatia, Southern China, Puerto Rico, Yucatan of Mexico, Florida, Australia, Meghalaya and Siberia

Question 25

What conditions are required for a limestone to develop into a Karst topography ?

Answer 25

1. The limestone formation must contain 80% or more calcium carbonate
2. Complex patterns of joints in limestones
3. Thick strata of limestone (20 feet or more)
4. Moderate rainfall in the region
5. Karst topography does not develop in the deserts

Question 26

What are Swallow holes / Sinkholes ?

Answer 26

By the action of the solution, shallow depressions are formed on the surface of the rocks such as limestone. These depressions are called as Swallow holes / Sinkholes

Question 27

What are Doline / Collapse Sinks ?

Answer 27

Some sinkholes begin their development through the solution, but subsequently collapses due to the presence or hollow under it and becomes a larger sinkhole. Such forms are called Collapse sinks / Doline

Question 28

What are Uvalas in Karst topography ?

Answer 28

When several sinkholes join together to form the valley of sinks, they are called Uvalas (large depression)

Question 29

What are Caverns ?

Answer 29

Caverns are interconnected underground cavities in the bedrock created by the corrosive action of circulating underground water on limestone. Present in Dehradun, Almora, Kotamsar caves of Chhatisgarh

Question 30

What are Stalactites and Stalagmites ?

Answer 30

A stalactite hangs like an icicle from the ceiling or sides of a cavern. A stalagmite appears like an inverted stalactite, rising from the floor of a cavern.