Reading:
Consider the following questions regard to Figure 10.13A on page 206 of the workbook. Enter your answer to the answer sheet on the right.
Take a look of the geologic map of Ohio, what are the two rock units appeared twice at separated localities on the map? [answer in blanks 03 and 04]?
Find similarity among Figure 10.13A, Figure 10.7B and the Ohio map.
05. What is the geologic stucture on the western half of Ohio?
06. Toward which direction [north or south] does the fold on western Ohio plunge?
Examine the two map patterns and related structures on Figure 10.6. Notice the relationship between the sequence of rock age and the type of fold.
07. Examine the rock layer pattern on the Ohio map, particularly the eastern half of the State. Is the rock becoming older or younger toward the east?
If each of the stucture in Figure 10.6 is divided into the east half and the west half, Is the pattern on the eastern Ohio similar to that in the
Examine figure 10.13B. The small circular pattern is the geologic map of the Black Hills, Dakota.
12. The rock at the center of the Black Hill is younger or older than those on the outside? (read the map legend)
13. The structure of the Black Hill is a _____________. (hint: figure10.10)
14. Examine the geologic map of Michigan (figure 10.13C). It is a larger and an incomplete circular pattern similar to that of Black Hills. By examining the age distribution of the rock layers, we conclude that the structure of Michigan is a ___________________. (hint: figure 10.10 again)
15. Take a look of a map we temporarily call it the Appalachian Geologic Map, which is a geologic map over Ohio and neighboring States. It also shows an elongated bullseye. This maps covers a numbers of States. Ohio is located at the [NW, NE, SW, SE] corner of the map. (hint: compare the map pattern with the pattern of Ohio Geologic Map]
16. Compare the color code of the Appalachian map with that of the Ohio Geologic Map, we find out that the blue color at the center of the bullseye is ______________ in age (continue to #17)
17. and is the [youngest, oldest] rock unit of the bullseye.
18. According to the rock distribution, this Appalachian map has a structure of a _______________ (hint: figure 10.10)
The geologic map of Ohio is an example of map called "bed rock map". As we see, rock units on the map are all sedimentary rocks. All these sedimentary rock units laid upon a much thicker rock complex called the "basement rock". We can see the relationship between the basement rock and the sedimentary rock cover on the cross section of the Ohio geologic map. The cross section clearly illustrated that over the western Ohio, the structure is an anticline and on the eastern Ohio, the structure is a monocline which is deepened toward east into a structural basin.
There is another special map which use contour line to illustrate the surface of this basement rock. This type of map is called the Basement Contour Map, which is one example in a type of map called "Subsurface Structure Map". The basement contour map of Ohio can be viewed on a link in the Ohio Geologic Survey website. Click on the "PDF version" to bring up a bigger map on which you can read the contour line value. (you may use the magnifier of the PDF Reader to enlarge the map)
19. According to the basement contour map of Ohio, the igneous and metamorphic rock basement of Ohio is as shallow as __________ feet below the sealevel, and ...
20. ... as deep as _______________ feet below the sealevel near the center of the basin.
21. The elevation of Ohio at the west is about 600 ft. So the thickness of sedimentary rock at western Ohio is about _____________ ft.
22. The elevaiton of Ohio at the east is about 1100 ft. So the maximum thickness of sedimentary rock at eastern Ohio is about ___________________ ft.