Geol 4110
Class 6 - Reading Topographic and Geologic Maps
2/29/08
Lecture: Powerpoint on topographic and geologic maps
In-class Exercise: Reading the Topographic Map of the Duluth Quadrangle (8 pts)
1) Describe the TRS location of UMD T____, R_____, Sec______, _____ 1/4 (0.5 pts)
2) Go outside and determine the UTM coordinates of your location with a GPS. (0.5 pts)
____________N ____________E, is this consistent with the map?_________
3) 11,000 years ago, the shoreline of Glacial Lake Duluth stood at 1150' above sea level.
Determine from the elevation of these features whether the following locations were under
(U) or above (A) lake level. (1.5 pts)
UMD_____
St. Scholastica ______ Washburn School (T50N, R14W, Sec11)_______
Hartley Pond (T50N, R14W, Sec 2 SW)_____ Central H.S. (T50N, R14W, Sec 21)______
East H.S. (T50N, R14W, Sec 13)______ Radio Towers (T50N, R14W, Sec 28)_______
4) Determine the elevations (within 10’) and TRS of the following intersections. (1.5 pts)
Mesaba Ave & Hwy 194* Elev._______; T____N, R_____W, Sec ____, ____1/4 of____1/4
(*Central Entrance)
17th Ave E & 4th St
Elev._______; T____N, R_____W, Sec ____, ____1/4 of____1/4
London Rd & Regent St.
Elev._______; T____N, R_____W, Sec ____, ____1/4 of____1/4
5) What is the highest elevation of Skyline Parkway along Hawk Ridge (T50N, R13W, Sec 6
and T51N, R13W, Sec 32)?_____________ (0.5 pts)
6) What is the elevation drop of Chester Creek between Kenwood Ave and Superior St.
__________ft. (0.5 pts)
7) If you were standing at the NE corner of Kenwood School (T50N, R14W, Sec. 10) and you
wanted to hike a straight line to the Hartley Pond Dam (T50N, R14W, Sec. 2 SW) (2 pts)
a) what bearing (or compass azimuth) would you take? - _________
b) how far would you have to walk (in meters)? __________
c) what extremes in elevation would you experience? Highest ________ Lowest ________
d) what time of year would you prefer to make the trek and why? ____________________
_________________________________________________________________________
8) What cultural feature lies at UTM coordinates 5189500N/567700E? ____________________
(0.5 pts)
9) On a piece of graph paper, draw a topographic profile along the T50-51N township line from
the SW corner of Sec. 35 to the SE corner of Sec. 31. For your vertical scale, assume 1
square = 100 feet. (2 pts)
What is the vertical exaggeration of your profile?___________ (0.5 pts)
Homework Exercise: Reading the Geologic Map of the Little Marais quadrangle (8 pts)
Access a .pdf file of this map from the class website or use a paper copy handed out in class.
1) Determine the basic igneous rock type (basalt, gabbro, granite, or rhyolite) that composes
each of these units (1.5 pts):
brg - ____________________
brd - _______________________
blg - ____________________
blo - _______________________
nmb - _____________________
npr - _______________________
2) What is the oldest geologic unit in the Schroeder Lutsen sequence? ____________ (0.5 pt)
3) The Beaver River Diabase and the Blesner Lake Diorite are complex intrusions that display
similar progressions of mafic rock types. Enter the map unit abbreviations for the Blesner
Lake units that are similar in rock type to the Beaver River diabase units below (1.5 pt).
Beaver River Diabase Units
Blesner Lake Diorite Units
brd
______
brg
______
brc
______
brf
______
4) Which of these two intrusions is older? _____________________________; What field
observations do you think led to the interpretation that these intrusive rocks belong to two
different intrusive events (hint: what geological principle defining relative geologic time was
used?) ____________________________________________________________________
______________________________________________________________________(1 pts)
5) Foliation in intrusive rocks is a fabric related to the planar alignment of elongate crystals in
the rock. What general direction is the foliation tilted (dipping) in unit blf in Section 29
(T58N, R6W)?________________________; What is the general tilt direction of foliation in
unit brc in the west half of Section 21 (T58N, R6W)?________________________ (1 pts)
6) Report on the clastic rock attributes of the Little Marais conglomerate (1 pt)
Sorting: _________________________
Compositional Maturity: __________________________
Angularity:______________________________
Bedding: ______________________________
7) How many lava flow contacts are exposed along the shore from the west edge of the map to
the nf unit? __________; Are the lava flows near the map edge older or younger than the
flows near the nf unit?______________ (1 pts)
8) Assuming the north-trending fault in the northwest corner of the map experienced mostly
strike-slip motion, is the displacement right-lateral or left-lateral? (circle one, 0.5 pts)