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)?
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)
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.