PHS 120
TOPOGRAPHIC MAP
BASICS
THE SUNNYSLOPE
QUADRANGLE, ARIZONA
Created By Stan Celestian – Instructor
copyright 2005
Introduction:
Topographic Maps are important tools of the Earth scientist. Many features are
shown on the map by the use of CONTOUR lines. A contour line is a line that
connects points of equal elevation. The starting point (0 foot contour line) is
sea level. On the topographic map these lines are shown as brown lines (*)
When this symbol (*) appears in the text it is your cue to press the enter key to advance to the next image.)
Created By Stan Celestian - Instructor
Introduction:
Contour Lines:
In general, note how the contour
lines are sub – parallel, they never
cross or touch and they never split.
Notice also that every 5th line is a
heavier line. These are called
index contour lines and they are
emphasized on the map to make
the counting of contour lines easier.
For example the index contour
directly above the 2000 line is
2100. (*)
How can you tell? You have to find
out what the contour interval is.
This bit of important information is
located at the bottom center of the
map. (*)
Introduction:
Contour Lines:
Below this it also states: Dotted lines represent 10-foot
contours. (Below that it states that the data for the contour lines was bases on
information obtained in 1929.)(*)
Here is an image of the bottom of the map. There is a lot of information located
here, but for now take a look at the area below the graphical scales. (*)
Below the scales it says the contour interval is 20 feet. (*)
Introduction:
Contour Lines:
So, you can see that the difference in elevation from one
normal contour line to the next is 20 feet. The dotted
contour line is found only in the flat area of the map. (*)
Introduction:
Contour Lines:
Back to Squaw Peak – Now that you understand that the
normal contour lines are separated 20 feet from the lines
above it and below it, it makes sense that every 5th line is
100 feet difference in elevation. To make it easier to count
these lines the 5th line is darkened. These are the INDEX
COUNTOUR lines. (*)
Check out the position of the 1700
foot line. (*)
What is the elevation of the little
unnamed hill just above it on the
right side of this illustration? (*)
Introduction:
What is the elevation of the little unnamed hill just above it?
Remember the purple line is the 1700 foot line. (*)
Contour Lines:
Going up to the summit (blue dot) of the
hill, the next INDEX CONTOUR line is
the 1800 foot line (red line). (*)
Finally, there is one more index contour
line closer to the summit. This is the
1900
.
foot contour line (black) (*)
Summit
BUT, we are not yet quite to the summit.
There are 3 normal contour lines. The
next contour line would be the 1920, the
next is the 1940 and the one closest to the
summit is the 1960. (*)
So, the summit of this hill is a little over
1960 feet. But it is below 1980 – otherwise
there would be another contour line. (*)
Introduction:
Contour Lines:
While your looking at Squaw Peak, notice that the brown
contour lines have different spacing. Where the contour lines
are close together, there is a steeper slope. Where the
contour lines are farther apart, the slope is more gentle. (*)
Introduction:
Contour Lines:
One last thing about contour lines is that they “V” upstream
when they cross a river drainage. Check out one of the
many unnamed streams on the map below. Blue represents
water features on topographic maps, and the line and three
dot pattern of the streams on this map indicate an intermittent
stream – sometimes it flows and sometimes it doesn’t. (*)
Next, notice how the
contour lines form a “V” and
that the “V” points towards
the top of Squaw Peak
(higher elevation), The rule
of thumb is that the “V’s”
point upstream,(*)
There are even other
drainages that are not
marked by streams but
simply by the pattern of the
“V”s. (*)
In this illustration of North Mountain Park (top central area of map) all the stream
drainages will be highlighted in purple. It includes the blue stream lines as well as the
unmarked drainage. Before you advance to the next image see if you can visualize
where this additional drainage would be on just the west side of the mountain. (*)
What was done was to draw a line
that connects the tips of the “V”s. As
you can see, this is a good example
of dendritic (branching) drainage. (*)
Let’s take another look at the information
at the bottom of the map. (*)
This is the name of the map and when it was created.
Photorevised means that the map was reevaluated in 1982 and that changes to the
1965 map were indicated in purple. Obviously, the map needs to be revised again. (*)
Let’s take a look at the scale next. (*)
Let’s take another look at the information
at the bottom of the map. (*)
This is the location of the Sunnyslope Quadrangle with
respect to the rest of the state of Arizona.
This simply means that an inch on the map is equivalent to 24000 inches on the surface
topmap
scaleis isequivalent
called thetofractional
scale:
of the Earth. OR 1mm The
on the
24000 mm
on the Earth’s surface. (*)
Scale 1: 24000. (*)
One unit of ANYTHING on the map is equal to 24000 of
those things on the Earth Surface. (*)
Let’s take another look at the information
at the bottom of the map. (*)
This is the area of the two scales. (*)
This is the graphical scale. The one you will be using in
the lab is the mile scale (the top of the three scales). Note
that the total length of the scale is 2 miles. (*)
Let’s take another look at the information
The left side of the scale is
into of
1/10’s
and the
at divided
the bottom
the map.
(*) right side is one mile. It is
very important to note the zero in the middle. It could make a huge difference in
your measurements and thus the accuracy of your answers. (*)
Some Basic Information about Topographic Maps
COLORS:
BLACK – Artificial features like buildings, dams, trails, railroad lines
BLUE – Water bodies or glaciers
BROWN – Contour lines
GREEN – Vegetation
RED – Some main roads, fences, public land system revisions
PINK – Urban areas
PURPLE - Revisions
(*)
LAKE WALES, FLORIDA QUADRANGLE (7.5 MINUTE SERIES)
Groundwater, like surface streams,
flows from areas of higher elevation
to lower elevation. The water flows
through the pore spaces of porous
and permeable rocks.
In which direction does the
groundwater flow in this area.
A hint is to look at the elevations of
the lakes. (*)
Like the Mammoth Cave area,
the Lake Wales area of Florida
is dominated by the solution of
limestone by groundwater.
Here, most of the depressions
are full of water. (*)
LAKE WALES, FLORIDA QUADRANGLE (7.5 MINUTE SERIES)
The lakes are roughly the
elevation of the water table. The
water will flow to the lake that
has the lowest elevation. (*)
Lake Wales is fairly
low, but what about
the others? (*)
LAKE WALES, FLORIDA QUADRANGLE (7.5 MINUTE SERIES)
Lake Serena is obviously at a level
of 116 feet, but what about the
lake to its south? (*)
The contour interval here is 5 feet.
So every index contour would be
25 feet. (*)
Starting with this 175 and counting down to the lake you can
see the elevation of the lake is just under 125 feet.
It is higher than Lake Serena and water flows underground
from this lake to Lake Serena. (*)
LAKE WALES, FLORIDA QUADRANGLE (7.5 MINUTE SERIES)
In a similar way, you should be
able to figure out the
approximate elevation of the
other lakes. (*)
~ 119’
~ 119’
~ 124’
~ 119’
~ 119’
~ 124’
~ 124’
LAKE WALES, FLORIDA QUADRANGLE (7.5 MINUTE SERIES)
So, based on the elevation of the
water table (lake levels) the
general movement of ground
water is towards Lake Wales.
the end