This map shows the elevation of the water table by means of
contours on it (dashed lines). The elevation of the land surface
is shown by topographic contours (solid lines).
2. Which direction is the groundwater flowing?These questions should give you an idea of the kind of thinking I am after, and the way the questions may be structured. Answers to the questions, along with the reasoning, are given at the bottom of this page. I suggest that you try to take this exam without looking at the answers -- then check and see how you've done. When you miss a question, use my explanations to help figure out where you went wrong. Please note that these questions are on the hard side.
1. You are looking for some property where you can drill a well and get a good, reliable water supply. Which materials below would probably provide the poorest supply. Circle choices as you go, then choose answer. 1. very highly jointed and fractured volcanic rock 2. outwash gravels from a continental glacier 3. lake sediments 4. fine-grained, compact glacial till 5. greywacke sandstone
a. 1 and 2 b. 3 and 4 c. 2 and 5 d. 1 and 4 e. all of them would provide poor supplies
Questions 2 and 3 refer to the map below
a. NW to SE b. SW to NE c. NE to SW d. SE to NW e. you cannot tell from such a map
3. If you were drilling a well at point B, about how many feet down would you have to drill before you hit water?
a. 500 feet b. 230 feet c. 730 feet d. 270 feet e. you cannot tell from this sort of map
4. A rock with high porosity and high permeability would
a. provide little storage but transmit water easily b. provide much storage but transmit water poorly c. provide little storage and transmit water poorly d. provide much storage and transmit water easily e. the question is impossible: rocks of high porosity always have low permeability
Questions 5 through 9 refer to the geologic map below5. Which bed is the oldest?
a. pCm b. Dm c. Pl d. Tsh e. there is no way to tell from this map
6. Which bed is the youngest?
a. pCm b. Dm c. Pl d. Tsh e. there is no way to tell from this map
7. Are there any unconformities evident on the map?
a. yes, between pCm and Dm only b. yes, between pCm and Dm, and between Tsh and all the rocks it is in contact with c. yes, between Dm and Mss only d. no, all the beds are conformable e. there is no way to determine the answer from this map
8. What sort of geologic structure do the Paleozoic beds form?
a. a monocline b. a syncline plunging SW c. a syncline plunging NE d. an anticline plunging NE e. an anticline plunging SW
9. Some speculators are forming the Silver River Oil Exploration Company. Their land is shown on your geologic map. You wonder if you should buy in. After looking at the map and applying your geologic expertise, you decide:
a. There are likely source and reservoir rocks, and a good trap. b. Although there are possible source and reservoir rocks, there is no trap. c. There is no trap, and there are no possible source or reservoir rocks. d. There is a likely source rock and a trap, but no reservoir rocks e. There is no way to decide from the map
Look at questions 10-14 in the sample 1st midterm
15. Where would you most expect to find large normal faults?
a. mostly in the central areas of continents
b. in places where lithospheric plates are sliding by one other
c. in areas of strong crustal extension or stretching such as
on mid-oceanic ridges or in uparched continental areas
d. in areas of crustal shortening such as fold-mountain belts
and subduction zones
e. mostly in volcanic arcs
16. Ores of heavy metals (such as copper, lead, zinc, gold, silver,etc.)
are most commonly found
a. in sandstones and silts deposited in shallow marine (shelf) environments b. in shales deposited in swamps c. in association with hot springs and igneous or metamorphic rocks d. in stream gravels e. in association with strike-slip faults
17. In the block diagram below
a. the strike of the bed is E-W and the dip is N b. the strike of the bed is E-W and the dip is S c. the strike of the bed is N-S and the dip is E d. the strike of the bed is N-S and the dip is W e. the strike of the bed is N and the dip is S
18. You find a layer of coal exposed in a roadcut. Which one of the following rocks
would be most likely to be lying above it (on top of it)?
a. shale b. greywacke c. mica schist d. coarse angular conglomerate e. basalt
19. Which rock should produce the least clay on thorough chemical
weathering in a cool temperate climate?
a. granite b. quartz sandstone c. greenstone d. feldspar&endash;rich gabbro e. they would all produce about the same amount
20. A soil formed by thorough chemical weathering of gabbro
(mineral content: pyroxene, plagioclase) in the tropics
would consist mostly of
a. silica b. quartz and clay c. pyroxene and clay d. iron oxides and alumina e. olivine and pyroxene grains
21. If the same gabbro were weathered in a very arid area,
the upper part of the soil would probably consist mostly of
a. plagioclase and pyroxene grains, along with a little clay and iron oxide b. calcium carbonate and alumina c. quartz and clay d. nearly pure silica e. humus
22. In a humid temperate forested area, which of the rocks below would probably
weather the fastest?
a. silica-cemented quartz sandstone b. granite c. basalt d. limestone e. clay
23. Match the each of the dune types listed with the conditions appropriate
for its formation.
____unidirectional wind, ample sand supply A. barchan
____unidirectional wind, limited sand supply B. parabolic dune
____bidirectional strong winds, limited sand supply C. star dune
____winds from many directions D. transverse dune
____partially vegetated or downwind of blowout E. longitudinal (linear) dune
The correct matching order is:
a. DAECB b. EBACD c. EBCDA d. ACEBD e. CDBAE
Answers (with reasoning):
1. b (Lake sediments and fine-grained compact glacial till will both be
clay-rich and thus have very low permeabilities. To get a good
supply you need materials with high permeabilities.)
2. b (Draw lines at right angles to the water-table contours; flow will
be along these lines from high water table elevation to low wt elevation)
3. d (the ground surface elevation at B is approx. 500 ft, while the
wt contours show that its elevation is about 230 ft. The depth
to water is thus 500-230 = 270 ft.)
4. d (porosity measures the storage capacity of a material; the higher the
porosity, the more water can be stored. Permeability measures the
ease with which water can move through the material; the higher the
permeability, the more easily the water can be transmitted through it.)
5. a
6. d (To answer questions 5 and 6, you simply have to know the order of the periods
in the geologic time scale from oldest to youngest. You can look this scale
up in your text or lab manual. Precambrian rocks are the oldest ones in our
time scale; the Tertiary period is the youngest period but one, ending about
2 my ago.)
7. b (If you know the time scale, you can see that the rocks representing the
older Paleozoic rocks, i.e.those of the Cambrian, Ordovician, and Silurian
periods are missing; while all the rocks of the Mesozoic i.e., the Triassic,
Jurassic, and Cretaceous periods are absent. The Tertiary shale sits with
angular unconformity on the younger Paleozoic rocks.)
8. e (The overall pattern of the Paleozoic beds indicates an eroded plunging fold.
The youngest Paleozoic rocks -- i.e., the Permian limestone -- are in the
center of the fold, proving that it's a syncline [downfold]. A syncline
opens out in the direction of plunge. The fold patter here clearly opens
to the SW.)
9. b (The Devonian marine sediments are a possible source rock, and the
Mississippian sandstones are a possible reservoir rock. However there is
no trap: a syncline won't trap the oil, and there is also no caprock in the
Silver River area.)
10-14 (Plate tectonics questions. See sample midterm 1.)
15. c (Normal faults cause extension of the crust, hence are found especially in
areas of crustal stretching.)
16. c (Ores of heavy metals are typically associated with hot or once-hot rocks.
They are formed especially by hydrothermal alteration, contact metamorphism,
and sometimes magmatic segregation.)
17. d (The direction of dip is the direction the bed slopes-- i.e., the downslope
direction of the bedding surface. The strike is at right angles to the dip
direction. Refer to text and lab manual.)
18. a (Coals are laid down in swampy environments; clays (shale) and river or beach
sands are the most likely other sediments to be deposited in these areas.)
19. b (In a cool temperate climate, the water tends to be acidic. Quartz is stable
in acidic water and hence will weather very slowly. It will produce little
or no clay. All the other rocks contain aluminum or iron-bearing minerals [such
as feldspar and pyroxene] which are attacked by acidic water and weathered to clay.)
20. d (The minerals in the gabbro are high in aluminum and iron. In the tropics the
water tends to be neutral; this causes the silica to be leached, while the
iron and aluminum oxides and hydroxides formed by weathering are stable and
remain in the soil, forming laterites or bauxite.)
21. a (In a desert, the dryness means that chemical weathering will be slow and
physical breakdown -- perhaps granular disintegration due to expansion of
biotite grains-- will predominate.)
22. d (In the cool forested temperate climate, water would tend to be acidic.
Limestone dissolves readily in acidic water, hence will weather [by solution]
the fastest.
23. a (No reasoning here -- just knowing the conditions under which each dune type
forms.)