1. Geologic Maps and Cross Sections

2. Definition: A map which shows the distribution, nature and the age relationships of rock units and the occurrence of structural features.

3. Geological Maps and cross-sections
Outcrop pattern
Topography and attitude of the geological structures control the shape of the outcrop.
Outcrop pattern = attitude of beds + topography
Horizontal beds will follow the contour lines.
A vertical bed will appear as straight line on the map irrespective of the topography.
All dipping beds will cut across the contour lines and have zig-zag appearance on the map.

4. The Rule of Vs
One of the most important generalities is the "Rule of Vs", which states that where dipping surfaces are incised by stream valleys or canyons, their map view will make a "V" in the direction of dip.
If the surfaces dip vertically, then they do not make a "V"; if they are horizontal, then they will follow the contours: the "V" will point uphill.
The only exception to this rule comes when the dip of the bed is less than the gradient of the valley. Then, similar to horizontal surfaces, the surface will make a "V" that points upstream.

5. Oblique View. Beds dip progressively less as you go to the left
Oblique View. Beds dip progressively less as you go to the left. Block on right shows vertical beds.
Looking straight downwards (Map View). The vertical bed shows no "V", the two dipping beds show "Vs" in the direction of dip, the horizontal bed shows horizontal stripes on either side of the valley. Note that the "V" becomes increasingly pronounced as the dip decreases.

6. The rule of Vs, also shows other effects of variable topography on the outcrop pattern.
Where the terrain is steep, and so at a high angle to the dipping bed, the outcrop width is relatively narrow.
However, where the terrain is gentle, and so nearly parallel to the dipping bed, the outcrop width is much wider.

7. A B C D E
A:  The formation is horizontal, therefore the formation contacts, i.e., the lines on the map where the top and bottom surfaces of the formation intersect the topography, are parallel to the contour lines.
B:  The formation is vertical, therefore the formation contacts transect the map as straight lines.
C:  The V points up the valley, therefore the formation dips up-stream direction. The formation dips steeply, much more steeply than the stream gradient, so the “V” pattern is shallow or blunt.
D:  The V points up the valley, therefore the formation dips up-stream direction. The formation dips gently, much more gently than the stream gradient, so the “V” pattern is exaggerated. 
E:  The V points down the valley at an angle which is steeper than the stream gradient. The formation dips moderately towards down-stream direction.

14. Geological Map
Cross-section

17. 6 7 8 9 9 8 7 6 6 7 8 8 7 B A

18. 1000
1000 .
500
500 6 7 8 9

19. 1000
1000 .
500
500 6 7 8 9

20. 1000
1000 .
500
500 6 7 8 9

21. 1000
1000 .
500
500

22. 1000
1000
500
500 A B

24. 1000
1000
500
500 A B

25. 1000
1000 .
500
500 A B

26. 1000
1000
500
500 A B

27. Stratigraphic succession
Lithology
Thickness (feet)
100 +
partly eroded
Basalt
100
Rhyolite
100
Sandstone
200
Conglomerate
450 +
base not seen
Granite

28. Stratigraphic succession
Date:
Cross-section
Stratigraphic succession
Scale