Contours-and-landforms

GRADE 9 MAPWORK: CONTOUR LINES

Definition and Purpose of Contour Lines

  • Contour Lines: Connect places of equal altitude.

  • Depict various landforms on a map, enabling the visualization of terrain.

  • Help in determining the characteristics of an area’s terrain by interpreting the lines.

Contour Interval

  • Contour Interval: The height difference between successive contour lines.

  • Standard interval on 1:50,000 Topographic maps is 20m.

  • Important for understanding elevation changes within the map area.

Types of Slopes

Gradual Slopes

  • Indicated by further apart contour lines.

  • A result of a more gradual slope without steep inclines.

Steep Slopes

  • Characterized by closer together contour lines.

  • Indicates a steep incline, often requiring careful navigation.

Uniform Slopes

  • Contour lines are evenly spaced, indicating a consistent gradient.

  • The slope remains the same throughout the interval.

Concave Slopes

  • Slopes are gradual at the base but become steep closer to the summit.

  • This shape can impact water drainage and vegetation growth.

Convex Slopes

  • Slopes are steep at the base and gradually flatten out towards the summit.

  • Typically result in a less abrupt transition to flatter ground.

Terraced Slopes

  • Resemble "steps" with alternate steep and gradual sections.

  • May occur naturally due to rock layers or can be created by farmers to facilitate agriculture by providing flat cultivation areas.

Landform Identification through Contour Lines

  • Arrangement of contour lines allows for the identification of various landforms.

  • Key principles include slope, shape, and altitude to recognize terrain features effectively.

Specific Landforms

Koppie or Hill

  • Defined as a low, free-standing hill.

  • Represented by concentric rings of contour lines in its simplest form.

Butte

  • A hill characterized by having steep sections before a relatively flat top.

  • Often found in arid regions where erosion has occurred.

Mesa

  • Known as a "tabletop" (in Spanish), an elongated butte.

  • Its length exceeds its height, often creating extensive plateau-like features.

Saddle

  • A low-lying area situated between two peaks.

  • Resembles a riding saddle, providing a transition between higher elevations.

Valley and Spur

Valley

  • A low-lying area formed by the erosion of flowing water.

  • Usually flanked by higher land known as spurs or interlocking spurs.

  • Identifiable by sharp "V-shaped" contours pointing towards higher ground with rivers or streams typically present.

Spur

  • Higher-lying ground adjacent to valleys.

  • Recognizable by rounded "U-shaped" contours pointing towards lower ground.

  • Spurs usually do not contain rivers, indicating their elevation relative to the surrounding landscape.