Lecture Notes: Understanding Maps and Contour Lines

Symbols and Features on Maps

• Maps use symbols to represent various features:
  • US Geological Survey Map:
    • Black squares/rectangles for buildings.
    • Blue lines for creeks.
    • Black circles for water tanks (Signal Hill).
• Function of Water Tanks:
  • Positioned on hills for gravity-fed water pressure.
  • Provides consistent pressure, even during power outages.

Types of Tanks on Maps

• Oil Tanks (Wilmington):
  • Tanks are spread apart to prevent fire spread.
  • Berms (dirt ridges) prevent oil leakage from contaminating the environment.

Understanding Map Colors

• World Map of Natural Vegetation:
  • Pink areas for deserts.
  • Yellow areas for tropical grasslands.
  • Black lines denote boundaries, but do not represent exact real-world separations.
• Real-world transitions are gradual and not clear-cut as depicted by black lines.

Population Density Maps

• World Map of Population Density:
  • Different colors represent population ranges (e.g., orange: 25-50 people/sq mile).
  • Lines indicate exact population numbers at boundaries (e.g., 25 people on a boundary line).
• ISO Lines:
  • Lines representing equal values (e.g., population, temperature).
  • Common types include isotherms (temperature) and isobars (pressure).

Contour Lines and Topographic Maps

• Contours:
  • Represent lines of equal elevation on maps.
  • Types of maps include topographic maps (e.g., US Geological Survey).
• Understanding Contours:
  • Visual example with a volcanic island:
    • Contours marked at increments (e.g., 0, 50, 100 feet)
    • Determine summit location and elevation using contour intervals.
    • Missing contour lines (e.g., 150) indicate elevation limits.
• Using Contours for Elevation:
  • Determine elevation at a point between contours (e.g., between 60 and 80 feet).
  • Estimate elevation based on evenly sloping assumptions.
  • Real elevation might vary due to terrain variations (e.g., cliffs).