(i) A valley is made deeper by a stream of water (or) a river as it flows from the high land.
(ii) The valleys are either 'U' shaped or 'V' shaped.
(iii) The glacier debris get deposited in the low lying areas. So glaciers do not form deep narrow valleys.

(i) Yes, weathering a pre-requisite in the formation of soil.
(ii) The rock materials in due course of time are weathered further to form soil.
(iii) Soil is a mixture of disintegrated rock material.

Moraine:
(i) Landforms formed by the glacial deposits of valley (or) continental glaciers are termed as moraines.
(ii) They are of various shapes and sizes, like ground, terminal and lateral moraines, etc.
Drumlin: Drumlins are deposits of glacial moraines that resemble giant inverted teaspoons (or) half cut eggs.
Esker: Long narrow ridges composed of boulders gravel and sand deposited by streams of melting water which run parallel to a glacier are called eskers.

These are valleys eroded by tributary glacier and that hangs over the main valley

The course of a river is divided into
(i) The Upper course - V shaped valleys, gorges
(ii) The middle course - Alluvial fans, flood plains
(iii) The lower course - Delta and Estuary
Associated land forms
i) Water falls - The upper course
ii) Ox bow lakes - The middie course
iii) Deltas - The lower course

Biological weathering occurs due to the penetration and expansion of plant roofs, earth worms, burrowing animals (rabbits, rats) and same human activities.

(i) Weathering is the disintegration and decomposition of materials of the earth's crust by their exposure to atmosphere.
(ii) The nature and magnitude of weathering differs from place to place and region to region.

Some of the erosional landforms of sea waves are sea cliff, sea cave, arch, stack, beach, bar and spit and wave cut platform.
Sea Cave: Prolonged wave attack on the base of a cliff erodes rock materials, which result in the formation of caves.
Sea Arch: When two caves approach one another from either side of a headland and unite, they form an arch. e.g., Neil Island, Andaman and Nicobar.
Sea Stack: Further erosion by waves ultimately leads to the total collapse of the arch. The seaward portion of the headland will remain as a pillar of rock known as stack. Eg the Old man of Hoy in Scotland.
Sea Cliffs: Sea cliffs are steep rock faces formed when sea waves dash against them. The rocks get eroded to form steep vertical walls.
Wave Cut Platforms: Flat surface found at the foot of sea cliffs are called as wave-cut platforms. Wave cut platform is also referred as beach, shelf, terrace and plain.

Rivers generally originate from mountains and end In a sea or lake. The whole path that a river
flows through is called its course. The course of a river is divided into:
(i) The upper course
(ii) The middle course and
(iii) The lower course
(i) The Upper Course: Erosion is the most dominant action of river in the upper course. In this course, a river usually tumbles down the steep mountain slopes. The steep gradient increases the velocity and the river channel performs erosion with great force to widen and deepen its valley; The land' features carved by a river in its upper course are V-shaped valleys, gorges, canyons, rapids, potholes, spurs, and waterfalls.
(ii) The Middle Course: The river enters the plain in its middle course. The volume of water increases with the confluence of many tributaries and thus increases the load of the river. Thus, the predominant action of a river is transportation. Deposition also occurs due to the sudden decrease in velocity. The river in the middle course develops some typical landforms like alluvial fans, flood plains, meanders, ox-bow lakes etc.,
(iii) The Lower course: The river, moving downstream across a broad, level plain is leaded with debris, brought down from its upper and middle courses. Large deposits of sediments are found at the level bed and the river, splits into a number of channels called distributaries. The main work of the river here is deposition and it develops typical landforms like delta and estuary.

(i) The river channels of the upper course has more energy gradiant then the channels of lower course.
(ii) As the river flows in the lower course it corrodes sideways and makes it wider.

(i) Limestone is made up of Calcium Carbonate.
(ii) It dissolves in water easily.
(iii) So during rainfall the water at the joints and fractures of the limestone seeps easily underground.
(iv) So the underground water is more common than the surface run off.

(i) As the desert are with little or no rainfall, wind is the only gradational agent.
(ii) Mechanical weathering is the dominant activity as there are limited plants.

GLACIERS:
(i) A Glacier is a large mass of ice that moves slowly over the land from its place is called River of ice.
(ii) A large mass of ice creates pressure at its bottom and generates heat due to this it melts and starts to move.
TYPES OF GLACIER:
(i) Glaciers are broadly divided into two types based on the place of occurrance such as continental glacier and valley glacier.
CONTINENTAL GLACIER:
(i) This sheets of ice that covers vast areas of a continent is called continental Glacier.
VALLEY GLACIERS:
(i) The glacier which takes its origin from a snow covered mountain range is known Valley Glacier.