1. UNIT 4: MAPPING THE EARTH

2. After Unit 4 you should be able to:
Accurately write coordinates
Use a map containing latitude and longitude
Determine latitude using the altitude of Polaris
Determine differences in time zones
Successfully use all maps from the ESRT containing latitude and longitude
Interpret major topographical features such as hills, river valleys, and depressions
Accurately draw contour lines
Determine the direction a stream is flowing
Determine the contour interval on a map
Determine the gradient of a feature such as a hill or a stream
Correctly draw a profile of a topographical feature
Determine the steepest side of a topographical feature such as a hill or lake
Determine the maximum altitude of a mountain or hill

3. Unit 4 vocabulary you should be able to use and understand:
Coordinates
Latitude
Longitude
Equator
Parallels
Meridians
Altitude
Polaris
Little Dipper
Prime Meridian
Tropic of Cancer
Tropic of Capricorn
International Date Line
Time zones
Topographic map
Field
Contour line
Elevation
Depression
Contour interval
Index contour line
Gradient
Steep
Distance
Profile

4. The creation and interpretation of maps are very important skills and are critical aspects of a student’s understanding in Earth Science. The standard systems of latitude and longitude and topography will be covered in this unit.

5. How do we describe our position on Earth?
We use the internationally accepted system of latitude and longitude
A set of specific coordinates can describe any location on Earth’s surface with a high degree of precision

6. Being Specific Using Coordinates
Lines of latitude and longitude are broken into degrees
Modern GPS units use decimal degrees such as ( oN , oW)
On printed maps however, each degree of latitude or longitude is broken into 60 minutes (‘), and each minute is broken into 60 seconds (“). We will use this system.
At the Equator, a whole degree of latitude or longitude is about 70 miles high or wide.

7. Reading Coordinates
Coordinates are read (latitude, longitude)
Latitudinal readings will be North or South
Longitudinal readings will be East or West
For example:
43o13’56” N , 77o34’19” W would read:
43 degrees 13 minutes 56 seconds North, 77 degrees 34 minutes 19 seconds West

8. Latitude
Lines of latitude run laterally, or from side to side, on the Earth
Lines of latitude are sometimes referred to as parallels
Lines of latitude describe the degrees North (Northern Hemisphere) or South (Southern Hemisphere) of the Equator

9. Lines of Latitude
The Equator is 0o up to 90o North (North Pole) and 90o South (South Pole)
The direct rays of the Sun strike only in the tropics (between 23.5 oN and 23.5 oS)
Tropic of Cancer 23.5 oN  June 21st
Tropic of Capricorn 23.5 oS  December 21st

10. How were lines of latitude developed?
Lines of latitude are equal to the angle from the center of the Earth up and down (North and South)

11. Latitude and the North Star (Polaris)
The altitude, or angle above the horizon of Polaris is equal to the observer’s latitude
This is true only in the Northern Hemisphere because that is where Polaris is visible

12. Locating Polaris
Polaris can be found in the Northern sky
Polaris is part of the Little Dipper constellation

13. Longitude
Lines of longitude run vertically on the Earth and converge at the North and South Poles
Lines of longitude are often called meridians

14. Lines of Longitude
Lines of longitude are constructed based on the angle to the left or right of the Prime Meridian (0o) from the center of the Earth
The lines measure up to 180o in either direction (East or West)
At roughly 180o is the International Date Line, a location where a new day begins and an old day ends

15. Time Zones
Each hour, 15o of longitude is rotated eastward
This is a basis for our worldwide time zones, each about 15o wide
The day is older in the East and younger in the West

20. While latitude and longitude allow the pinpointing of a location on Earth, topographic maps allow surficial features to be expressed on a map, primarily elevation.

21. What is a topographic map?
A topographic map mainly shows changes in elevation (height above or below sea level) and bodies of water
Topographic maps offer a 1-dimensional view of a 3-dimensional landscape
Some advanced maps show additional features such as roads, buildings and many other items. These are typically identified in a key.
The map on this page shows the 7.5 minute x 15 minute (1/8o latitude x 1/40 longitude) quadrangle featuring Upper Saranac Lake in the Adirondack Mountains. Note the scale and key on the right side of the map.
Maps like this are important to search and rescue teams as well as hikers.

22. Fields
A field is an area where measurements are taken
Measurements can be taken for a number of different variables but elevation is the measurement represented by contour lines on a topographic map.
Again referring to the Upper Saranac Lake Map, you can see that the field (measureable area) is defined by lines of latitude and longitude. This is standard for topographic maps.

23. Drawing Contour Lines
Draw contour lines that connect elevation of equal value in the field
Lines are equal to an elevation which has units such as feet or meters

24. Depressions
Occasionally depressions must be represented on a map
The contour line is drawn as usual and then inside of the line hatch marks are drawn to show a decrease in elevation

25. Contour Lines Rules
All points on the line are of equal value
So any point on the 500 ft. contour line will be equal to 500 ft. in elevation
For this reason, contour lines will never cross
Unless there is a vertical or overhanging cliff

26. Contour Lines Rules Continued
When drawing contour lines, they should be smooth
Contour lines should run off of a map if they need to, they are a part of a loop even if you only see part of it

27. Contour lines follow the same rules as any isoline
If true, go through
Tip: Highlight elevation that you know that value will go through before drawing the line

28. Draw the 50 and 100 foot contour lines
What is the value of the ocean shoreline?

29. Stream Flow
When you see V’s in a stream channel, the bend in the V points uphill
Therefore, the stream flows opposite (or out of) the V
Draw the 500, 520, 540, 560, 580, and 600 ft. contour lines, then determine stream flow using arrows.

30. What is a contour interval?
A contour interval is how much the elevation changes in between contour lines
Steps can be taken to determine what the interval is

31. Steps to determining contour intervals:
Determine the difference in value between 2 close index contours (lines that are labeled)
____________________________

32. Steps to determining contour intervals
Determine the number of lines from one index contour line to the next
____________________________ 5 4 3 2 1

33. 580
560
540
520
Steps to determining contour intervals
Divide
Answer: ___________________________

34. Trends in Contour Lines
We can expect a steeper gradient (slope) where the lines are closer together
This indicates a more rapid change in elevation. Consider the lines on the topographic map from Chimney Bluffs field trip. The first hill we climbed was quite steep, as were the bluffs themselves, both represented by very close contour lines in your note packet.

35. Additional Trends
Where lines close as a loop, a depression, lake or mountaintop can be found. To determine which of these you are looking at, examine the contour lines around the closed loop. Are they higher or lower?
If the lines decrease in value, you have a hill or mountaintop. If they increase you have a depression or lake. Again, looking at the Chimney Bluffs formation, we see closed loops at the summit of the drumlin.

37. What is the gradient on a topographic map?
Gradient = change in field value / distance
The gradient between two points describes the change in elevation over a distance
Another word for gradient is slope. Consider that the equation for gradient is very similar to that of slope in a mathematics course (rise/run).

38. Steps:
Determine the change in elevation between the two points (include units)
Determine the distance between the two points (include units)
Divide and include both sets of units.
Determine the gradient between points X and Y on the map in your notes.

39. Determining Possible Elevations
Remember that each contour line is equal to a value, so any point in between contour lines must be between those two numbers
Mountaintops cannot exceed the next possible contour line elevation if that line does not exist.
What are possible elevations of point A in the map in your notes?

40. What is a profile?
A profile is the side image of a topographic feature

41. How do you create a profile?
Use a strip of paper to create tick marks on the contour lines (label elevation for each)
Use the tick marks to plot the points appropriately and connect with a smooth, arching line

42. Create a profile of Mount St. Helens

43. Create a profile of Lake Ontario