Name ________________

Soc. Sec. # ____________________

Geol. 111GSurvey of Geology

Lecture Exam 2

Multiple Choice (3 points each)

Circle the correct letter to complete the sentence.

1. Which of the following are true of weathering?

a) Weathering is the primarily way in which clay minerals are formed.

b) Weathering occurs in response to wind, water, temperature changes, plant growth, and chemical reactions.

c) Weathering occurs at low temperatures and pressures at the earth's surface.

d) All of the above.

2. The process of hydrolysis during chemical weathering involves:

a) removal of silica tetrahedra from the structure of a mineral

b) addition of H+ and OH- groups to the structure of a mineral

c) dissolution of the mineral followed by oxidation

d) removal of oxygen from the structure of a mineral

3. Which of the following minerals is the most stable when under attack by chemical weathering?

a) Amphibole

b) Olivine

c) Quartz

d) Pyroxene

4. Non-foliated metamorphic rocks are classified based on their:

a) mineral composition.

b) mineral rounding

c) mineral layering.

d) mineral grade.

5. At convergent plate boundaries (those that generate subduction zones) what type(s) of metamorphism would you expect to find:

a) cataclastic

b) contact

c) dynamothermal

d) all of the above

6. Detrital or clastic sedimentary rocks are classified based on:

a) size of crystals

b) composition of crystals

c) size of grains

d) temperature of formation

7. The protolith of a slate is a:

a) mudrock or shale.

b) basalt

c) granite

d) quartzite

8. The low grade metamorphic rock called greenschist generally contains what index mineral?

a) chlorite

b) K-feldspar (orthoclase)

c) quartz

d) silliminite

9. Foliated structure in metamorphic rocks is formed by:

a) recrystallization of minerals into equant crystals.

b) recrystallization of minerals into index minerals.

c) the reorientation and parallel alignment of tabular minerals producing lineation.

d) lithostatic pressure

10. Clastic or detrital sediments are deposited:

a) by chemical precipitation from sea water.

b) when turbulent water carries the particles in suspension.

c) when the transporting medium losses energy and can't carry the particles anymore.

d) by erosion

11. Chemical precipitates or non-detrital sedimentary rocks are classified primarily based on:

a) crystal color

b) crystal chemical composition

c) crystal size

d) crystal sorting

12. Compaction during lithification is primarily caused by:

a) increasing lithostatic pressure from burial

b) hydrolysis

c) increasing temperature during burial

d) foliation

13.Metamorphism is the process by which rocks undergo a change in mineralogy or texture or both:

a) during melting and magma generation

b) while in the solid state

c) during erosion and transport to a depositional center

d) during intense chemical weathering

14.Contact metamorphismoccurs:

a) adjacent to igneous intrusive bodies

b) during deep burial of sediments

c) at subduction zones due to very high pressure frictional forces

d) none of the above

15. Sedimentary rocks that you would expect to find in deep, quiet water environments from the source are:

a) shales

b) conglomerates

c) slates

d) breccias

16. Mechanical weathering of rocks can occur by:

a) pressure release when rocks that were generated deep in the crust are brought to the surface.

b) frost wedging caused by the expansion of water during freezing

c) the growth and expansion of root systems

d) all of the above

17. Weathering in sedimentary rocks is primarily the result of what two processes:

a) compaction and dissolution

b) bacterial breakdown of organic matter into sediments and oxidation

c) mechanical breakdown into grains and chemical reactions

d) erosion and transport of sediment

18. Temperatures high enough to metamorphose a rock are generated by:

a) deep burial of sediments

b) intrusion of hot molten magma

c) friction during plate subduction

d) all of the above

19. Preserved remains or traces of ancient life forms in sedimentary rocks are called:

a) oolites

b) pedalfers

c) fossils

d) mudcracks

20. The grade of metamorphic rocks depends on:

a) the temperature to which the rocks were heated

b) the composition of hot fluids that flow through the rocks

c) the type and amount of pressure to which the rocks are subjected

d) how well they do on this exam!

Matching (2 points each)

Match the rock type with the correct description.

21. ______ marble a) pebble to boulder size, angular clasts in a finer grained matrix

22. ______ slate b) medium grade metamorphism of a shale

23. ______ chlorite c) silica-rich, non-detrital sedimentary rock

24. ______ conglomerate d) pebble to boulder size, rounded clasts in a finer grained matrix

25. ______ chert e) high grade metamorphic index mineral

26. ______ breccia f) non-detrital sedimentary rock composed of  an evaporite mineral

27. ______ shale g) low grade metamorphic index mineral

28. ______ schist h) clastic rock composed of clay-sized material

29. ______ rock gypsum i) high grade metamorphism of a limestone

30. ______ silliminite j) low grade metamorphism of a shale

Fill in the blank (2 points each)

Fill in the blank using the choice of words listed below:

laminated	amphibole	erosion	beds
massive	pressure	temperature	eolian/wind
trace fossils	compound	non-detrital	contact aureole
halite (NaCl)	crystal form	high	cataclastic
rounding	gravity	basalt	foliations
erosion	body fossils	sandstone	medium
chlorite	density	oxidation	dissolution
hydrolysis	pyroxene	clastic/detrital	sorting
dissolution	low	lithosphere	quartz
marine	plagioclase	burial	cementation

31. The difference between a breccia and a conglomerate is the degree of clast __________________

32. Divergent plate boundaries are characterized by contact and __________________ metamorphism.

33. _____________ is a chemical weathering reaction where oxygen ions

are added to the mineral structure producing a new mineral.

34. Amphibolites are indicative of____________________ grade of metamorphism.

35.The zone of metamorphism surrounding a pluton in contact metamorphism

is called a ____________.

36.The type of chemical weathering where minerals are broken down into

their component ions is termed ______________.

Short Answer (4 points each)

37. What types of metamorphism would you expect in the Las Cruces area?

38. List the changes in texture (grain size, grain rounding, grain sorting) you

would expect to observe in clastic sedimentary rocks as you move farther

away from the source of sediment.

Proximal (close) to source Distal (far) from source

1) Grain size:

2) Rounding:

3) Sorting: