Activity 1 Getting oriented – An introduction to the Tucson Basin and map reading
Map reading is an important skill when studying your environment. In this activity you’ll
identify features of the Santa Cruz River Basin, familiarize yourself with spatial
coordinates, read contour lines and practice calculating distances.
Materials
The Basics
Distance
Ruler
Tucson and Nogales USGS topographic 1:250,000 maps
The map scale identifies what the map distances (on the paper) represent
in real life (on the ground). The map’s scale bar is located at the bottom
of the map.
Elevation
The brown squiggly lines on the map are contour lines and the number
associated with each line describe the elevation of each point on the map.
The contour interval is the difference in elevation between adjacent
contour lines. The contour interval is listed below the distance scale at
the bottom of the map. In many notable places (especially mountain tops
and landmarks) the elevation is also listed in black numbers.
Location
The numbers that surround all four sides of the map describe the northsouth and east-west position on the map. These numbers are called
UTM coordinates and allow you precisely describe a location.
Get oriented
1. The contour interval for this map is ___________ feet.
There are 2.5 contour lines between downtown Tucson and Marana. What is the
elevation difference between the two cities?
(Another way to answer this question is to find the elevations listed for each location
and then determine the difference by subtraction.)
2. Find the map scale and determine the number of miles in 1 inch:
1 inch = __________________ miles
This information can be used to calculate distances. If the distance between San
Xavier and Davis Monthan Airforce base is 2.5 inches on the map, then in real life
the distance is [2.5 inches x (# miles in an inch)] miles.
3. Now you’re ready to find the coordinates and the elevations of the following
locations – you’ll need both the Tucson and Nogales maps:
Location
UTM
Latitude (N-S)
UTM
Longitude (E-W)
Elevation (feet)
Marana
Downtown Tucson
Nogales
Mt. Lemmon
Santa Catalina Mountains
Wasson Peak
Tucson Mountains
Mt. Wrightson
Santa Rita Mountains
Santa Cruz River at the
Intersection of I-10 and I-19
Santa Cruz River at
Green Valley
Desert View High School
4. Of these locations which is the highest? Which is the lowest?
5. Marana, Tucson, Green Valley and Nogales are all located near the Santa Cruz
River. From their elevations, determine which direction the Santa Cruz flows.
List the cities and their elevations in the order that they receive water from the
Santa Cruz (first to last). Hint: remember that water only flows downhill.
6. What are the three main mountain ranges that surround Tucson?
7. If it rains on Wasson Peak, what is the minimum distance that the water might
travel on the surface before it reaches the Santa Cruz River?
8. If you drop an orange in the Santa Cruz River in Nogales during a flood (when
there’s actually water in the Santa Cruz), what distance (in miles) will that orange
need to travel before it reaches the junction of I-10 and I-19 near the Santa
Cruz?