Chapter 1: The track of the Yellowstone hot spot: Volcanism, faulting, and uplift

Abstract

The track of the Yellowstone hot spot is represented by a systematic northeast-trending linear belt of silicic, caldera-forming volcanism that arrived at Yellowstone 2 Ma, was near American Falls, Idaho about 10 Ma, and started about 16 Ma near the Nevada-Oregon-Idaho border. From 16 to 10 Ma, particularly 16 to 14 Ma, volcanism was widely dispersed around the inferred hot-spot track in a region that now forms a moderately high volcanic plateau. From 10 to 2 Ma, silicic volcanism migrated N54°E toward Yellowstone at about 3 cm/year, leaving in its wake the topographic and structural depression of the eastern Snake River Plain (SRP). This <10-Ma hot-spot track has the same rate and direction as that predicted by motion of the North American plate over a thermal plume fixed in the mantle. The eastern SRP is a linear, mountainbounded, 90-km-wide trench almost entirely(?) floored by calderas that are thinly covered by basalt flows. The current hot-spot position at Yellowstone is spatially related to active faulting and uplift.Basin-and-range faults in the Yellowstone-SRP region are classified into six types based on both recency of offset and height of the associated bedrock escarpment. The distribution of these fault types permits definition of three adjoining belts of faults and a pattern of waxing, culminating, and waning fault activity. The central belt, Belt II, is the most active and is characterized by faults active since 15 ka on range fronts >700 m high. Belt II has two arms forming a V that joins at Yellowstone: One arm of Belt II trends south to the Wasatch front; the other arm trends west and includes the sites of the 1959 Hebgen Lake and 1983 Borah Peak earthquakes. Fault Belt I is farthest away from the SRP and contains relatively new and reactivated faults that have not produced new bedrock escarpments higher than 200 m during the present episode of faulting. Belt III is the innermost active belt near the SRP. It contains faults that have moved since 15 to 120 ka and that have been active long enough to produce range fronts more than 500 m high. A belt with inactive faults, belt IV, occurs only south of the SRP and contains range-front faults that experienced high rates of activity coincident with hot-spot volcanism in the late Tertiary on the adjacent SRP. Comparison of these belts of fault activity with historic seismic activity reveals similarities but differences in detail.That uplift migrated outward from the hot-spot track is suggested by (1) the Yellowstone crescent of high terrain that is about 0.5 km higher than the surrounding terrain, is about 350 km across at Yellowstone, wraps around Yellowstone like a bow wave, and has arms that extend 400 km southerly and westerly from its apex;(2) readily erodible rocks forming young, high mountains in parts of this crescent; (3) geodetic surveys and paleotopographic reconstructions that indicate young uplift near the axis of the Yellowstone crescent; (4) the fact that on the outer slope of this Pierce, K. L., and Morgan, L. A., 1992, The track of the Y...

Extensive soft-sediment deformation and peperite formation at the base of a rhyolite lava: Owyhee Mountains, SW Idaho, USA

“…1a). The thermal anomaly of the Yellowstone hotspot softened the lithosphere, triggering failure along planes with weak lithostatic strength and initiated rifting (Pierce and Morgan 1992;Wood and Clemens 2002;Bonnichsen et al 2004Bonnichsen et al , 2008. Rifting of the WSRP began at 12 Ma, correlating with the passage of the hotspot to the south and ceased at~7 Ma (Pierce and Morgan 1992;Wood and Clemens 2002;Bonnichsen et al 2004).…”

“…The thermal anomaly of the Yellowstone hotspot softened the lithosphere, triggering failure along planes with weak lithostatic strength and initiated rifting (Pierce and Morgan 1992;Wood and Clemens 2002;Bonnichsen et al 2004Bonnichsen et al , 2008. Rifting of the WSRP began at 12 Ma, correlating with the passage of the hotspot to the south and ceased at~7 Ma (Pierce and Morgan 1992;Wood and Clemens 2002;Bonnichsen et al 2004). The low topography of the WSRP was filled with Lake Idaho from its formation at 12 to 2 Ma (Wood and Clemens 2002;Branney et al 2008) (although it is unclear if the lake was consistently present during this time) (Bonnichsen et al 2004).…”

“…Associated with the initial rifting of the WSRP, between 11.7 and 11.0 Ma, localised rhyolite lavas, the BOwyhee Front volcanism^(the Jump Creek Rhyolite lava, the Reynolds Creek Rhyolite lava, the Cerro el Otoño Dome Field and the Wilson Creek Ignimbrite) were extruded from venting zones at the margins of the WSRP (Pierce and Morgan 1992;Perkins and Nash 2002;Bonnichsen et al 2004Bonnichsen et al , 2008Bonnichsen Walker and MacLeod (1991), Pierce and Morgan (1992), Cummings et al (2000) and Lewis et al (2012). Owyhee Mountains highlighted by box.…”

“…The WSRP is situated 100 km north of the Yellowstone hotspot trail (Pierce and Morgan 1992;Shervais and Hanan 2008) (Fig. 1a).…”

“…1a, b). The OIG is a Miocene-age, N-Strending, extensional graben situated in southwestern Idaho and southeastern Oregon at the most northerly extent of the Basin and Range Province (Pierce and Morgan 1992;Manley 1995;Cummings et al 2000;Wood and Clemens 2002) (Fig. 1a).…”