Notes Class 7 Chapter 11 Geography Maharashtra Board

Notes For All Chapters – Geography Class 7

Contour Maps and Landforms

1. Introduction to Contour Maps

• A contour map is a type of map used to show the height, slope, and shape of landforms in a region.
• It represents altitude, relief, and slope through contour lines.
• Contour maps are widely used in geography, engineering, farming, and military planning.

2. Understanding Contour Lines

Contour lines are imaginary lines that join places of equal elevation. They help in visualizing the shape and height of landforms.

Characteristics of Contour Lines:

1. Same Height Representation: Each contour line connects points of the same altitude.
2. No Intersecting: Contour lines never cross each other, as one place cannot have two different elevations.
3. Close Contour Lines: Indicate a steep slope (e.g., mountains, cliffs).
4. Far Apart Contour Lines: Indicate a gentle slope (e.g., plains, river basins).
5. Circular Contour Lines: Represent hills or mountains (smallest circle is the highest peak).
6. V-Shaped Contours: Represent valleys or river courses (V points uphill; river flows in the opposite direction).

3. Purpose and Uses of Contour Maps

Contour maps are useful for many different fields and activities.

Who Uses Contour Maps?

1. Trekkers & Mountaineers: Helps in finding safe and easy routes to climb mountains.
2. Soldiers & Defense Officers: Useful for military strategies, base locations, and troop movement planning.
3. Farmers: Helps in selecting land for farming, irrigation, and preventing soil erosion.
4. Engineers & Town Planners: Used in road construction, drainage system planning, and building development.
5. Environmentalists & Geographers: Helps in studying natural landscapes, soil erosion, and water conservation.

4. Interpreting Slope, Relief, and Elevation

Contour maps help in understanding how land rises or falls in an area.

Types of Slopes:

Steep Slope:

• Contour lines are very close to each other.
• Found in mountains and hilly areas.
• Difficult for construction, farming, and transportation.

Gentle Slope:

• Contour lines are widely spaced.
• Found in plains and plateaus.
• Suitable for agriculture and human settlements.

Flat Land:

• No contour lines or very few contour lines.
• Found in river valleys, plains, and coastal areas.

5. Contour Interval and Importance

• Contour Interval is the difference in height between two consecutive contour lines.
• Helps in determining the steepness or gentleness of a slope.

Contour Interval Variations:

• Large Contour Intervals: Used for mountainous regions where elevation changes rapidly.
• Small Contour Intervals: Used for flat areas and plains where elevation changes slowly.

6. Real-Life Applications of Contour Maps

Contour maps are useful in many fields.

Agriculture and Farming:

• Helps in contour plowing, preventing soil erosion.
• Farmers can plan irrigation systems based on land slope.

Flood and Disaster Management:

• Helps in identifying low-lying areas that are at risk of flooding.
• Government and disaster agencies use contour maps to plan relief measures.

Road and Railway Construction:

• Engineers use contour maps to design roads that avoid steep slopes and landslides.
• Helps in planning tunnels and bridges efficiently.

Military and Defense Operations:

• Soldiers use contour maps for battle strategies and selecting suitable locations for military bases.
• Helps in positioning artillery and planning safe troop movements.

Urban Planning & Construction:

• Used to determine the best locations for houses, schools, hospitals, and industries.
• Helps in planning drainage and water supply systems.

7. Practical Activity: Understanding Contour Maps with a Potato Model

To understand how contour maps represent landforms, a simple experiment can be done using a potato.

Potato Contour Model:

1. Take a large potato and observe its shape.
2. Slice it into different horizontal layers.
3. Draw each layer separately on paper to create a top-view contour map.
4. The topmost slice is the peak, and the outermost slice is the base.

This activity helps in understanding how 3D objects (hills/mountains) are represented in 2D (maps).

8. Identifying Landforms on Contour Maps

Contour maps help in identifying different geographical features:

Hills and Mountains:

• Represented by concentric contour circles with the highest point in the center.
• The smaller the innermost circle, the higher the peak.

Plateaus:

• Broad, flat areas with relatively high elevation.
• Contour lines are widely spaced and have similar heights.

Valleys and Rivers:

• Represented by V-shaped contour lines pointing uphill.
• Rivers flow in the opposite direction of the V-shape.

Cliffs and Escarpments:

• Represented by contour lines that are extremely close together.
• Indicates a very steep, almost vertical slope.

Plains and Lowlands:

• Contour lines are far apart or absent, showing flat terrain.

9. Key Rules for Reading Contour Maps

1. Contour lines never cross each other.
2. The closer the contour lines, the steeper the slope.
3. The farther apart the contour lines, the gentler the slope.
4. Closed circles represent hills; the smallest circle is the highest peak.
5. Contour lines form V-shapes around river valleys, with the tip of V pointing uphill.

10. Summary and Key Points

• Contour maps are special maps that show elevation and landforms using contour lines.
• Contour lines connect points of equal height and help in understanding slopes, elevations, and terrain features.
• Close contour lines = steep slope, widely spaced lines = gentle slope.
• Contour maps are used in farming, engineering, trekking, military planning, and disaster management.
• Contour intervals help determine the height difference between contour lines.
• Various landforms such as hills, valleys, mountains, plains, and plateaus can be identified using contour maps.
• A potato model activity helps in understanding how contour maps represent 3D landforms in 2D form.

Conclusion

Contour maps are an essential tool in geography, helping people understand the Earth’s surface in a detailed manner. They are widely used in construction, military, farming, and environmental planning. Learning to read contour maps allows us to navigate landscapes effectively and make better use of land resources.