Faye Moser MS Candidate in Earth Science University of North Carolina Charlotte fviscounccedu September 2016 GSA Dr Martha Cary Eppes Univ of N Carolina Charlotte Dr Brian Collins ID: 932734
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Slide1
Spatial and temporal variability in rock dome exfoliation & weathering
Faye MoserMS Candidate in Earth ScienceUniversity of North Carolina Charlottefvisco@uncc.eduSeptember 2016 [GSA]
Dr. Martha Cary Eppes
Univ. of N. Carolina Charlotte
Dr. Brian Collins
USGS, Menlo Park, California
Dr. Greg M. Stock
National Park Service, Yosemite National Park
Slide2Agenda
Background & Significance
Study site
Research Questions
Methodology
Data & Results
Stone Mountain, GA
Bald Rock Dome, CA
Half Dome, CA
Stone Mountain, NC
Diamond Rock and Paarl Rock
, South Africa
Corcovado Mountain
, Brazil
Slide3The formation of exfoliation joints is influenced by…
Overburden Removal?
Leith et al. [2014]
Surface Morphology?
Martel [2006, 2011]
From
Collins and Stock [2016]
From J. Merck lecture, University of Maryland 2010
From
Eppes et al. 2016
Climate?
Slide4https://www.youtube.com/user/dotysan
https://www.youtube.com/watch?v=MWhmoW1PzwU
Slide5https://www.youtube.com/user/dotysan
Slide6Study area: Twain Harte, CA
Slide7Preliminary recon results
Previous generations of exfoliation
Fresh exfoliation surface
1 m
Slide8Research questions
How is cracking changing through time and space?Short term evolution (10
-1
yr)Long term evolution (10
5
yr) Are similar exfoliation events occurring regionally?Domes
Slabs
Slide9Field Methods
Mapped 15 granodiorite domes and their associated slabsCracking – stratified random sampling scheme by slabSchmidt hammerAcoustic emission (AE) sensorsTemperature sensors
Subsurface crack meters
Extensometer
1050 m
Slide10Slab identification
1
3
2
Slide11Slab characteristics
Slide12Slab characteristics cont.
Frequency
Spall height (mm)
Slab 1
Slab 4
Slab 3
Slab 2
Slab exfoliation processes are consistent.
Slide13Exfoliation slab age proxies
0 = fresh crack 6 = most weathered
Slide14Slab age proxies cont.
MEAN: 200 mm
MEAN: 261 mm
MEAN: 270 mm
MEAN: 226 mm
Crack length (mm)
Slab weathering increases with age.
Frequency
Slab 1
Slab 4
Slab 3
Slab 2
Slide15Thermal influences
Slide16Summary points for “The Rock” Exfoliation
Exfoliation processes are consistent through TIME and SPACE, long-term (105).
Short term
(10
-1 yr) cracking is triggered by
thermal cycling.
Further questions
Reconcile observed short-term triggers with long-term exfoliation drivers
Curvature?
Unloading?
Slide17Thank you!
Acknowledgments:Co-authors Dr. Martha Cary Eppes, Dr. Brian Collins, Dr. Greg StockGSA Graduate Research Grant Fund (2015, 2016)GSA On to the Future Scholarship (2016)
Ephrum
Laubhann & Suzanne ChingTwain Harte Lake AssociationCondor Earth Technologies, Inc.Sugar Pine RV Park