Physical Geology - Test #2, 1999 - Deep time, & surface processes - Practice version


Matching (choose best fit, 2 points each)

   trilobite  A) waterfalls or rapids, migrate upstream as headward retreat, associated w harder layer
   Werner  B) unique deposit at end of Mesozoic w high Iridium content & mass extinction boundary
   Count Buffon  C) time period of recent major ice ages, from roughly 1.8 Ma to 10,000 ka
   half life  D) material deposited by river action in flood plains, the fill part of cut and fill.
   tree rings  E) material deposited by mass wasting processes, poorly sorted, nearby sources
   boundary clay  F) example of barrier island complex, undergoing transgressive retreat.
   alluvium  G) developed a schema of universal formations, given rock type formed in a distinct period
   knickpoint  H) site where surface drainage goes subsurface, connected with soluble bedrock.
   Gros Ventre  I) differs for different radioactive isotopes, constant under earthly conditions, imp.in dating
   colluvium  J) time since about 10,000 years ago and the demise of the last major ice advance.
    wavebase  K) used in dendrochronology, unique historical signature allows dating of wood
   Padre island  L) wide spread fossil type that characterizes part of the Paleozoic, especially the Cambrian
   Holocene  M) depth to which given size wave can disturb sediment, about = 1/2 wave length.
   Pleistocene  N) estimated earth ca. 100,000 years old on basis of cooling cannon balls and burnt fingers
   swallow hole  O) site in Wyoming of large historic rock slide, with inclined bedding as the slip plane.
     P) cavity in limestone produced by now extinct swallows which had 6' wing spans

Diagrammatic, short essay and fill in the blank questions. Read carefully and answer the best you can. Partial credit given.

1) Number the following Eras from 1 oldest to 5, the youngest in the space to the left. Connect with a line the era with the best geologic trait. (5 pts.)

 order  era  geologic trait
   Mesozoic  time of snowball earth
   Archean  time dinosaurs flourished
   Cenozoic  began with an explosion of life forms
   Paleozoic  time mammals flourished
   Proterozoic  time when meteor impacts much more common

Bonus: Write next to each era that approximate time it started. (1/2 point each)

2) Using the cross section diagram below do the following. List from 1 to 7, oldest to youngest, by relative age the given rocky types. (5 pts.)

3) Lord Kelvin estimated the age of the earth in the 1860s as no more than 15-20 million years on the basis of mathematical equations that could describe the conductive cooling of a sphere. List 4 parameters in those equations that determine the history of a cooling sphere. (3 pts.)

What was not known of in Lord Kelvin's time that makes this good science, but with a false premise, so that it underestimates the age of the earth. _____________________________________________________________

4) Roughly how old are the oldest known rocks on earth? (2 pts.) _______________

5) The ratio of a radioactive isotope X to its daughter product Y was measured to be 1 to 7 in a sampled mineral. If the half live is 26 million years how long has it been since the "clock was set", the system was closed and Y started accumulating in the mineral due to decay of X. _________________________

b) This assumes that the mineral had no isotope Y in it to start out with. For some minerals and isotopes this would not be the case. If there was some original daughter product Y, would the measured age be greater or less than the real age (circle the right answer)?

c) If the ratio of another radioactive isotope W and its daughter product Z was measured to be 1 to 1 in the same mineral as above and the half life for W was 300 Ma, is the closure temperature of istopes W and Z higher or lower than X and Y? This is a thought question. (4 pts.)

6) List one of the important assumptions behind radiometric dating. ______________________________

Different radiometric clocks reflect different closure and associated geologic events. For typical U-Pb systems the closure event is _____________________. For the K-Ar system it is _______________________. For Carbon-14 it is _____________________________. (4 pts.)

7) We talked about a host of -isms, and perspectives on earth history: for each one of the following phenomena or geologic events assign the most appropriate -ism that describes it. Two examples are given. (4 pts.)

 wave that pave Lanai  
 Milkanovich cycles  
 large impacts  
 Velikovsky hypothesis of Venus passby of earth  
 a cooling earth  gradualism
 large igneous province production  
 Cambrian faunal explosion  punctuated equilibrium

Write a few summary sentences characterizing the nature of geologic history as you understand it. This is a difficult thought question.

8)
Name the three types of load a river carries. Mark with an X the one characterized by the coarsest debris? Mark with a check the one that contributes to the saltiness of the oceans. (3 pts.)

a) _________________________________

b) _________________________________

c) _________________________________

9) Use the map diagram of a fluvial system below to answer the following. a) Which site likely represents a landform and deposits from a previous cut and fill cycle, i.e. a terrace (choose from letters A-G)? ____________. b) At which site would you likely find cross-bedded and well sorted sands in point bars? _______________ c) At which site would you likely find coarser conglomerates? ____________ d) At which site would mass wasting most likely be most prevalent at present? _____________, e) What process would be causing mass wasting at this site? ___________________________ __________________________ , f) At which site would you most likely find evidence of old mass wasting features? ________ , g) At which site will mass wasting be most likely to occur in the future? __________ h) At which site will the most organic rich sediments lilkely be accumulating? _________

10) List four critical factors that determine slope stability. (4 pts.)

a) ________________________________

b) ____________________________________

c) ________________________________

d) ____________________________________

11) Label the various forces as to their names and their role in deciding whether slip occurs. Mark with an X the force (vector, arrow) which commonly grows in the spring in areas of snowmelt? If significant tilting occurred due to intrusion of magma underneath, which force would remain unaffected? ____________________ (3pts.)

12) Consider the three end member types of deltas with different forces predominating in shaping the upper, near shore sediments. Match the delta type with the most likely character of the upper sediments. (3 pts.)

 River dominated delta  numerous storm deposits, and mainly sand (little mud)
 Tide dominated delta  local coal deposits, and unimodal (one dominant direction) paleocurrents
 Wave dominated delta  bimodal paleocurrents and lots of mud


Bonus: Name actual deltas that exemplify each type.

13) Describe longshore drift and its importance. (3 pts.)

 

14) On the black and white image below mark and describe with arrows and labels as many of the shoreline components and processes as possible. (3 pts.)

15) Use the graph below to answer the following. Note the time scale is broken up into four time segments (e.g. time AB, BC, CD,DE. (4 pts.) a) For what time segments do you expect glacial advance? _______ b) For what time segments would you expect a terminal moraine to form? _______ c) For what time segments do you expect glacial retreat? _______ d) If this was for all of Antarctica during which segment will sea level increase? ______

16) List 6 distinctive landforms or deposits that are telltale signs of past glaciation. (3 pts.)

a) ________________________________

b) ____________________________________

c) ________________________________

d) ____________________________________

e) ________________________________

f) _____________________________________


17) List 2 controlling factors for the position and geometry of cave passages in a karst terrane? (3 pts.)

a)____________________________________________

b) _________________________________________

18) A later phase in the history of a cave is infilling. What type of material fills the cave in with time? (4 pts.)

 

19) On the field trip we saw the three local rock units listed on the left. Make the best connection with the other three columns by drawing lines clearly connecting the terms in the four columns. (3 pts.)

 Dakota Fm.  glacial outwash  youngest in age  limestones
 Kansas City Group  marine sea  middle inage  x-bedded sandstones
 Pleistocene deposits  fluvial system  oldest  gravels and tills

20) Create a question that you think may provide some new insight into some of the geology that we have discussed in this second part of the course, but which was not asked in the above questions. You need not answer the question. Some of the more interesting questions will be reported back to the class. (up to 4 pts.)