Abstract Title: Causes and Consequences of the Voluminous Late-Cenozoic 
Volcanism of the Northern Great Basin

Abstract Author(s): Carlson, Richard, Department of Terrestrial Magnetism, 
Carnegie Institution of Washington, 5241 Broad Branch Rd, NW., Washington, DC, 
20015  

Abstract: Beginning at approximately 17 Ma, a line of volcanic vents developed 
along the Washington/Oregon - Idaho borders extending from central Washington 
to central Nevada. When corrected for Basin and Range extension, this series of 
eruptive centers follows a north-south line paralleling, but slightly west of, 
the "0.706" line. The southern boundary of predominantly basaltic volcanism 
coincides with the Orevada rift, which also marks the northern boundary of 
exposed pre-Cenozoic basement in this area. Following this initial volcanic 
flair up, central-eastern Oregon has remained the most volcanically active area 
within the Great Basin. Though some have connected this volcanism with the 
Yellowstone plume, another explanation is that the 1000km long N-S line of 
basaltic volcanism reflects back-arc volcanism instigated by the arrival of hot 
mantle that infilled the mantle area vacated by the retreating subducting 
Juan-de-Fuca plate. The area of extensive volcanism in the northern Great Basin 
is large enough that it would be difficult to cover with sufficient resolution 
with a "typical" PASSCAL scale experiment, but is well within the range covered 
by one USArray transportable deployment. Imaging targets are many: (1) What 
does the 0.706 line look like with depth? (2) Can imaging of the temperature 
structure of the mantle beneath this area, including detection of the downgoing 
slab, resolve whether the magmatism on the Plateau is plume-derived or related 
to edge flow around the slab? (3) Are the observed geographically-correlated 
changes in basalt composition associated with changes in crust and/or 
lithosphere thickness? (4) What is the current extension rate in this area? (5) 
What is the character of the Moho across the Oregon Plateau - how much crustal 
modification has occurred because of the extensive volcanism?