Tracing Highs and Lows in San Francisco

Purpose

The purpose of this activity is to use a topographic map to identify differences between landforms. 

Objective

Students will be able to identify hills and valleys as well as determine relative steepness.

Time Needed

45 minutes

CA State Science Standards (9-12):

State Investigation and Experimentation Standards:

1.h. "Read and interpret topographic and geologic maps."

1.m. "Investigate a science-based societal issue,"e.g..."land and water use decisions in California."

 

Background Information

Published topographic maps show three important things: Direction, Distance and Elevation. A north arrow indicates direction.  Usually north is at the top of the map.  A scale bar and numerical scale conversion indicate distance.  A ruler can be used to measure the distance between two points on the map and then the map distance can be converted to actual distance using the scale bar and/or numerical conversion.  The numerical conversion tells you how many inches of actual distance one inch of map distance is equal to.  For example, the numerical scale 1:24000 means that every one inch measured on the map represents 24,000 inches of actual distance. Contour lines are used to show vertical elevation.  Each contour line represents a line of equal elevation on earthÕs surface.  Sea level is the zero elevation contour line.  Contour line basics: Contour lines do not cross but may converge at locations that are steeply sloped.  The farther apart the contour lines are spaced, the more gently sloped the represented surface is (gradient).  The elevation difference between two adjacent contour lines is called the contour interval.  Concentric contours represent hills. Contour lines take a V-shape pointing upstream or uphill where they cross rivers or the lowest point in a valley. 

              

Useful conversions:

12 inches = 1 foot          1 inch = 2.54 centimeters           1 kilometer = 100 meters

5,280 feet = 1 mile         1 meter = 100 centimeters

Conversion example:

(3 in map distance) * (    24000 in actual distance     ) * (     1 ft actual distance   ) * (1 mile actual distance) =  1.14

                              (        1 in map distance          )        ( 12 in actual distance   )    (5280 ft actual distance)       miles

Note: * indicates multiplication and

_________  indicates division

Key Terms:

Elevation                           Relief

Contour interval                Topography (Hill, Ridge, Valley)

Contour line                      Scale

Gradient (slope)                conversion

Materials Needed

North and South SF 7.5' topographic quadrangles

Simplified topographic map

Tracing paper for each student

Blank white paper and pencils

Rulers

 

Activity:

  1. Identify the scale bar, north arrow, and contour interval on your map.
  1. Use the USGS topographic map to find a place that you know to be a hill.  Use the simplified map to note the pattern of contour lines at this location. (small closed circles) These are topographic highs.
 


  1. Now locate other places with similar contour line patterns.
  1. Find a place on the map that you know to be a valley or basin.  Use the simplified map to note the pattern of contour lines at this location.  (V-shaped lines) These are topographic lows.
 


  1. Now locate other places with a similar contour pattern. 
  1. Find your school, note whether it is in a high or low location.
  1. Identify a place on the map where the contour lines are close together, then identify a place where contour lines are far apart. 
 


  1. Plan two hikes, approximately the same distance, one that is gentle and one that is steep. 

(Remember: contour lines that are close together represent steep slopes and those that are farther apart represent gentle slopes)

 


  1. Trace these two hikes onto the tracing paper.  Be sure to note the starting elevation and the elevation at the end of each hike. 
  1. Use your ruler and map scale to determine the distance of each hike.
  1. Calculate the slope of each hike using the following formula:

Slope = |Ending Elevation – Starting Elevation|

Distance of Hike

  1. Check to make sure that the slope for your steep hike is greater than the slope for your gentle hike.

Questions:

  1. Write down the scale of the map and contour interval of the map.
  2. Describe the contour lines at your topographic high or hill
  3. Describe the contour lines at your topographic low or valley
  4. Write down the approximate elevation of your school. Is it on a topographic High or low?
  5. What type of feature is near the contour lines that are close together, and what type of feature do you see where the contour lines are far apart?
  6. Write down the starting and ending elevation of your gentle hike.
  7. Write down the distance of you gentle hike
  8. Write down the starting and ending elevation of your steep hike.
  9. Write down the distance of you steep hike
  10. Write down your calculated slope, showing your work.
  11. Discuss your slope calculation results.  What do the differences in slope mean?