Valley

Valley: A valley is a geological feature situated between two hills or ridges, formed due to lateral erosion by rivers or glaciers.

‘V’-shaped Valley: Resembling the letter V, this type of valley is commonly found in mountainous regions. The innermost contour line represents the lowest part of the V-shaped valley, with a very small gap between its two sides. Contour lines increase uniformly in value outward from this point.

‘U’-shaped Valley: Formed by intense lateral erosion from glaciers at high altitudes, a U-shaped valley has a wide, flat bottom and steep sides, resembling the letter U. The innermost contour line shows a wide gap between its two sides, with contour values increasing uniformly outward.

Gorge: Gorges are deep and narrow river valleys with steep sides, formed in high-altitude areas where vertical erosion by rivers is dominant. On maps, gorges are represented by closely-spaced contour lines, with the innermost contour showing a small gap between its two sides.

Spur: A spur is a protrusion of land extending from higher ground into lower areas. On maps, spurs are represented by V-shaped contours, with the apex of the V pointing towards the lower ground.

Cliff: Cliffs are steep or nearly perpendicular landforms. On maps, cliffs are identified by closely-spaced contour lines that merge into one another.

Waterfall and Rapids: A waterfall is a sudden descent of water from a considerable height in a riverbed, often accompanied by rapids upstream or downstream. On maps, waterfalls are depicted by contour lines that merge into one another, while rapids are shown by relatively distant contour lines.

Steps for Drawing a Cross-section

Here are the steps to draw cross-sections of various relief features from their contours:

1. Draw a straight line cutting across the contours on the map and label it as AB.
2. Place a strip of white paper or graph along the AB line.
3. Mark the position and value of every contour that intersects the line AB.
4. Choose a suitable vertical scale, like ½ cm = 100 meters, to draw horizontal lines parallel to each other and equal to the length of AB. Ensure that there are enough lines to accommodate all contour lines.
5. Mark the appropriate values corresponding to the contour values along the vertical scale of the cross-section, starting with the lowest value represented by the contours.
6. Align the edge of the marked paper with the horizontal line at the bottom of the cross-section so that AB of the paper corresponds to AB of the map, and mark the contour points.
7. Draw perpendicular lines from the AB line, intersecting contour lines, to the corresponding line at the base of the cross-section.
8. Connect all the marked points on different lines at the base of the cross-section smoothly to complete the drawing.

Topographical Map Notes: Topographical Map is an important topic in CBSE Class 11 Geography. Chapter 5 Geography covers mountains, valleys, and other land features. They use lines called contour lines to show how high or low the land is. Topographical maps also include human-made things like roads and buildings. We can use these maps to understand the land better, find our way around, and plan cities. They help us see how people and nature interact with each other on the Earth’s surface. These notes help us understand and use topographical maps effectively.

All the important topics have been compiled in CBSE Notes Class 11 Geography Chapter 5: Topographical Map.