Class 11 Geography Contour Mapping Notes: Contour mapping is like drawing lines on a map to show different heights of the land. These lines, called contours, help us see how steep or flat the land is. They’re drawn in brown color and are spaced apart based on how high or low the land is. If the lines are close together, it means the land is steep. If they’re far apart, it means the land is gentle. Contour maps help us understand the shape of hills, valleys, and other land features. They’re important for understanding geography and the world around us. 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.
Contour Mapping| Class 11 Geography
Table of Content
Contour Mapping With Contour Lines
A contour line, also known as an isoline or isopleth, is a curved line on a map that connects points with the same value. These lines represent constant values of a function with two variables. In cartography, contour lines are commonly referred to simply as “contours.” They depict points of equal elevation above a reference level, often the sea level. Contour lines are essential components of contour maps, such as topographic maps, which show features like valleys, hills, and slope steepness. In the following sections, we will delve deeper into the topic of Contour Mapping.
What is Contour Mapping?
A contour map illustrates the shape of the land surface through contour lines, with the spacing between these lines indicating the slope of the terrain. Essentially, contour mapping involves creating lines on a map based on equal values of a particular property derived from data points. While contour mapping is a type of topography mapping, it is important to note the distinction between the two.
Topographic maps provide detailed representations of natural and man-made features, whereas contour maps focus specifically on changes in elevation using contour lines. Each contour line on a map connects points with the same height. However, it is important to note that the method of contouring may vary between investigators, leading to differences in the resulting maps when interpolating between data points.
Contour Mapping According to the Crustal Thickness
Contour map of the Earth’s crustal thickness globally reveals a bimodal division in thickness. In ocean basins, the crust is relatively thin, measuring around 6 to 7 kilometers (excluding the water depth of 4 to 5 kilometers). Conversely, the continents boast an average crustal thickness of 39.7 kilometers. Along the ocean-continent margin, the crust typically measures around 30 kilometers thick, gradually increasing to 40 to 45 kilometers towards the continental interior.
However, regions with crust thicker than 50 kilometers are limited, including the Tibetan Plateau in western China and the Andes in western South America. It is important to note that the contour map only depicts large-scale crustal features, omitting locally thick crust regions. The crustal thickness doesn’t consistently correlate with age; for instance, the crust in western Australia, despite being older, is at least 10 kilometers thinner than that in central Australia. These areas with thicker crust often coincide with young and active mountain belts, characterized by high topography and susceptibility to rapid erosion.
What is a Contour?
Contours are imaginary lines connecting points of the same value, seen on maps depicting elevation or temperature. These lines represent uniform heights or values across a landscape. Contour maps display various contours, such as elevation contours, which indicate changes in height. The contour interval refers to the difference in height between each contour line, often measured in meters. By analyzing contour lines, we can determine the steepness of slopes.
Closer contour lines indicate steeper slopes, while widely spaced lines suggest gentler slopes. These patterns help identify different landforms like valleys, mountains, or hills, and their characteristics, such as flat valley floors or streams. Contour maps aid in identifying features like cone-shaped hills or hilltops.
Uses of Contour Mapping
Contours provide valuable information for understanding the terrain. They assist in various applications such as selecting suitable sites, determining drainage basin catchment areas, and assessing intervisibility between different locations. Some key uses of contours include:
- Understanding Ground Characteristics: Contours help in analyzing the nature of the ground, aiding in decision-making processes related to construction or land use.
- Route Identification: Contour maps provide essential data for identifying routes, helping planners and travelers navigate through different terrains effectively.
- Assessing Intervisibility: In situations where direct visibility between two points is not easily observable, contour maps enable the assessment of intervisibility, aiding in planning and communication between stations or observation points.
To Determine Catchment Area or Drainage Area
The contour map is instrumental in accurately delineating the catchment area of a river. The watershed line prominently demarcates the drainage basin, traversing through ridges and saddles of the terrain, ultimately encircling the river. This line is consistently perpendicular to the contour lines, facilitating precise identification of the catchment area. To measure the area enclosed between the watershed line and the river outlet, a planimeter is employed.
Conclusion
Contour mapping helps us understand the shape and features of the land. It uses contour lines to show things like elevation and slope. These maps are useful for planning where to build things, finding the best routes, and studying water flow.
By using contour maps, we can make better decisions about how to use and manage land. As technology improves, contour mapping keeps getting better, helping us learn more about the world around us.
Related Links
- Notes Chapter 1: Geography as a Discipline
- Importance of Sustainable Development
- CBSE Class 10 Geography Notes Chapter 3 : Water Resources
- What is the Difference between Temperate and Tropical Regions?
FAQs on Contour Mapping
What is contour mapping?
Contour mapping is a method used to represent the shape and elevation of the land surface on a two-dimensional map using contour lines.
What are contour lines?
Contour lines are imaginary lines that connect points of the same elevation on a map. They help visualize the shape and steepness of the terrain.
How are contour lines drawn?
Contour lines are drawn at regular intervals based on elevation data. The spacing between contour lines represents the slope of the land surface, with closer lines indicating steeper slopes and wider spacing indicating gentler slopes.
What information can be derived from contour maps?
Contour maps provide valuable information about the topography of an area, including the presence of hills, valleys, ridges, and depressions. They also help in determining the elevation and slope of the land surface.
How are contour maps used in various fields?
Contour maps are widely used in fields such as geography, geology, civil engineering, urban planning, and environmental science. They help in site selection, route planning, flood modeling, land development, and natural resource management.