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Ge121a: Advanced Field Geology: Formation of the channeled scablands,
eastern Washington Instructor:
Michael Lamb TA:
Joel Scheingross Goal: In this
course we will employ geomorphic mapping of fluvial terraces, topographic surveying,
sediment size measurements, rock-fracture measurements, and paleo-hydraulic and sediment transport calculations to
investigate the formation of the channeled scablands of eastern Washington
state. The channeled scablands were cut by what were likely the largest
floods known in Earth history, however, the timing and mechanics of erosion
are not well understood. This landscape is also an often-used analog for
similar features on Mars. The
class will focus on 3 to 4 key locations in the channeled scablands where
huge valleys were cut into basaltic rock by block plucking and waterfall
erosion. In addition to visiting iconic sites in this landscape, our
measurements and mapping will focus on addressing the following research
questions: 1) Were the channeled scablands cut progressively over multiple
flood events that spanned significant time, or were they carved nearly
instantaneously? 2) What are the active erosion processes during megaflood erosion? 3) What was the discharge of the
flood(s)? Trip Itinerary
Post trip activities: We will meet
once per week fall quarter (10/18 to 12/6) to work through the analysis of
data collected in the field. Tentative meeting time is Friday 3-5 pm, 267
Arms. Deliverables: 1) Field notebooks.
2) Geomorphic maps. 3) Digitized data (Excel) from channel and sediment-size
surveys. 4) Data analysis results (to be completed as a group after the
trip). DUE DECEMBER 6th Driving Route Map
Google
Earth File of Mapping
Areas (Subject to change. Please look at landscapes before the trip) Required
Readings (Please read before trip and bring your own copies on trip.): Baker,
The
Channeled Scabland: A Retrospective, Annual Reviews of Earth and
Planetary Science (Good overview) Baker,
The Spokane Flood Controversy and the
Martian Outflow Channels, 1978, Science (Historical context and Mars
analog) Benito and OConnor, 2003, Number
and size of last-glacial Missoula floods in the Columbia valley between Pasco
Basin, WA, and Portland, OR. (Number of floods and slackwater
deposits) McDonald et
al., 2012, Glacial
outburst floods and loess sedimentation documented during Oxygen Isotope
Stage 4 on the Columbia Plateau, Washington State (Evidence for older
floods) OConnor and Baker,
1992, Magnitudes
and implications of peak discharges from glacial Lake Missoula (paleo-hydraulics of the floods) Lamb,
M.P. and Fonstad, M.A., 2010, Rapid formation of a modern bedrock canyon by a
single flood event. Nature Geoscience, DOI: 10.1038/NGEO894. [PDF]
(erosion mechanics plucking) Breckenridge,
Field
Guide (Chapters 6: Dry Falls) Recommended
Readings: Breckenridge,
Field
Guide (other chapters, especially 5 and 7) Bjornstad, Field Guide (nice pictures) Lamb,
M.P. and Dietrich, W.E., 2009, The persistence of waterfalls in fractured
rock. Geological Society of America Bulletin, doi:
10.1130/B26842.1. [PDF]
(erosion mechanics waterfalls) Carling, 2009, Channel-scale erosional
bedforms in bedrock and in loose granular material:
character, processes and implications (erosion mechanics) Logistics: Camping will be in established campgrounds, but
there is a possibility water may be turned off if temperatures are cold. Expect
highs in the 50s F and lows ~40 F but potentially below freezing at night.
Bring warm clothes and warm sleeping bags. Please check weather.
The GPS Division will provide group camp
gear (stoves, lanterns, tables, chairs, water jugs, ice chests, pots &
pans, dishes). We also will bring measurement gear (hand levels, measuring
tapes, pebble count tapes, stadia rods, shovel, field books, maps, gps, laptops, colored pencils). We will shop for food
together on Day 2. The Division will only partially cover your food costs
($10/day), so please bring cash to pool for excess food costs. Students are responsible for their own field equipment. Please also bring your personal copies of the
required readings. You may choose to bring your own laptop for calculations. |
