1. 1 Maps in Environmental Geology Lecture by Dr. Ken Galli, Boston College EESC116301 Environmental Issues and Resources July 14, 2016 Please do not distribute beyond the EESC116301Class.

2. Definitions To learn

3. 26X 8X Digital “photo” of coastal area Topographic map of same area Contour Interval is 20 feet. Sea level is 0 feet. Topographic profiles (cross-sections) along line A-A’ shown with Vertical Exaggeration of 26 times and 8 times. Vertical Exaggeration is the ratio of the vertical scale to the horizontal scale used for the topographic profile. steep nearly flat

5. 0m Datum: Plane representing sea level – all elevations are measured above this reference plane – 0 elevation. Imagine that sea-level was raised in 100m increments – what would be the appearance of the shoreline? Also imagine your path – walking around the island at 100m elevation. What would a topographic map look like if you projected this island with contours painted onto a flat surface? Galli’s Island

6. Rules of Contouring and Making Topographic Maps Contours are widely spaced on gentle slopes Contours are closely spaced on steep slopes North is always at the top of the map Map Scale: determines how much detail is shown on map: 1cm = 1000m (1km) less detailed 1cm = 10m more detailed. Graphic Scale is best, remains true if reduced/enlarged other aspects of maps will be illustrated in our first map exercise. Most of USA is available as U.S. Geological Survey Quadrangle Maps.

7. Topographic Profile Sometimes it is useful to see a “side view” of topography — to see this view a profile must be constructed. Example: Construct a profile along line A-A’ on Galli’s Island. Lay profile (graph) paper along line of profile. Project the elevation of contour where it intersects line of profile. Sketch smooth profile through points. Vertical Exaggeration = Horizontal Scale / Vert. Scale if H.Sc is 1cm=1km; V.Sc is 1cm=0.1km, then V.E. = 10X. Line of Profile Profile (XS) Map

9. Fault: fracture with movement shown on cross-sections as: Fault shown on maps as: D = Down U = Up or

10. Lithological contact Sand below Gravel above

11. Strike and Dip: establishing the attitude of planar surfaces on a map. Strike and Dip—used to illustrate the orientation of planar surfaces on a geologic map. Strike—orientation (compass direction) of layers of rock Actually, orientation of a line generated by intersection of 2 planes—imaginary horizontal plane and the bed, joint, or fault surface. Beds strike N-S and dip (are inclined) to the east at 45°

14. The Nobel-prize-winning physicist, Enrico Fermi, came up with this simple and intuitive way to deduce the circumference of the earth. 1. How many time zones do you pass through when you fly from New York to Los Angeles? Answer, 3 2. How many miles is it, about, over that same distance? Answer, about 3000. 3. How many miles per time zone, on average? Answer, about 1000 4. How many time zones must there be around the world? Answer, 24 because there are 24 hours in a day 5. How many miles around the world? Answer, 24 time zones x 1000 miles per time zone = 24000 miles Yes, it is about 24000 miles around the world. [40,075 km] So how do I get the diameter of the Earth 1. the formula for a circle is 2 pi r, right? where r is the radius and pi is about 3 2. so 24000 mi = 2 x 3 x r = 6 x r 3. therefore 24000 mi / 6 = r = 4000 mi 4. the diameter of the earth is 2 x r = 8000 mi, where the diameter is 2 times the radius 5. 1 mi = 1.6 km so 8000 mi x 1.6 km/mi = 12800 km (the correct answer is ~12742 km) So you can always figure out the dimensions from your basic knowledge of traveling!