Geology 56606660 Applied Geophysics 27 Apr 2018 Last
- Slides: 13
Geology 5660/6660 Applied Geophysics 27 Apr 2018 Last Time: Roots of Cordilleran Elevation (for fun) • Buoyancy under Cordilleran uplift combines crustal (strain, magmatic addition, hydration-related), thermal (rifting), and asthenospheric (convection = Yellowstone? , hydration? ) • High elevation in the northern Basin & Range has an asthenospheric source (shown by removing elevation due to surface processes, crustal thickness/buoyancy, lithospheric thermal mass) • Early estimates looked similar to modeling of plume swell sheared by an extending, variable thickness lithosphere; latest estimates are also high in SBR and Rio Grande rift • Colorado Plateau is some combination of crustal thickening (melts at edges + hydration) & regional asthenospheric support from outside the CP © A. R. Lowry 2018
Cordilleran elevations… Bahadori et al. Geosphere 2018 Out this week! Integration of western U. S. strain history shows Paleogene crustal thickness & elevations would be similar to Andean orogeny. . . (But neglects crustal thickening by magmatic addition and density changes by hydration). . .
Schmandt et al. , EPSL 2012 Out just last week! v. S tomography using “core waves” shows that the Yellowstone lowvelocity anomaly continues all the way to the core-mantle boundary. . . Nelson & Grand Nat. Geosci. 2018
Hot? Wet? Higher H 2 O Property Higher Temp. Cold? Dry? Slow Seismic Velocity Fast High Electrical Conductivity Low Mass Density ! Flow Strength ! These are important for the dynamics… Partial Melt !
“Dry” mantle peridotite “Hydrous” mantle serpentinite
Kanda et al. , in prep, 2018
Schmandt & Humphreys EPSL 2010
v. P v. S v. P/v. S Schmandt & Humphreys EPSL 2010
Pn (refracted Moho phase) tomography Buehler & Shearer, J. Geophys. Res. (2017) Moho temperature (from Pn & mineral physics) Schutt et al. , Geology (2017)
Meqbel et al. EPSL 2014
Meqbel et al. EPSL 2014
Crossey et al. EPSL 2016
Kennedy & van Soest (Science 2007): ~ Minimum Ra appears related to strain rate; high outlier values are associated with magmatism… Implications for mechanism of transfer?
