Post-glacial inflation-deflation cycles, tilting, and faulting in the Yellowstone Caldera based on Yellowstone Lake shorelines

Abstract

The Yellowstone caldera, like many other later Quaternary calderas of the world, exhibits dramatic unrest. Between 1923 and, the center of the Yellowstone caldera rose nearly one meter along an axis between its two resurgent domes Smith, 1979, Dzurisin andYamashita, 1987). From 1985From until 1995, it subsided at about two cm/yr (Dzurisin and others, 1990). More recent radar interferometry studies show renewed inflation of the northeastern resurgent dome between 1995 and 1996; this inflation migrated to the southwestern resurgent dome from 1996 to 1997 (Wicks and others, 1998).We extend this record back in time using dated geomorphic evidence of postglacial Yellowstone Lake shorelines around the northern shore, and Yellowstone River levels in the outlet area. We date these shorelines using carbon isotopic and archeological methods. Following Meyer and Locke (1986) and Locke and Meyer (1994), we identify the modern shoreline as S1 (1.9 ± 0.3 m above the lake gage datum), map paleoshoreline terraces S2 to S6, and infer that the prominent shorelines were cut during intracaldera uplift episodes that produced rising water levels. Doming along the caldera axis reduces the gradient of the Yellowstone River from Le Hardys Rapids to the Yellowstone Lake outlet and ultimately causes an increase in lake level. The 1923 doming is part of a longer uplift episode that has reduced the Yellowstone River gradient to a "pool" with a drop of only 0.25 m over most of this 5 km reach. We also present new evidence that doming has caused submergence of some Holocene lake and river levels.Shoreline S5 is about 14 m above datum and estimated to be ~12.6 ka, because it post-dates a large hydrothermal explosion deposit from the Mary Bay area (MB-II) that occurred ~13 ka. S4 formed about 8 m above datum ~10.7 ka as dated by archeology and 14 C, and was accompanied by offset on the Fishing Bridge fault. About 9.7 ka, the Yellowstone River eroded the "S-meander", followed by a ~5 m rise in lake level to S2. The lowest generally recognizable shoreline is S2. It is ~5 m above datum (3 m above S1) and is ~8 ka, as dated on both sides of the outlet. Yellowstone Lake and the river near Fishing Bridge were 5-6 m below their present level about 3-4 ka, as indicated by 14 C ages from submerged beach deposits, drowned valleys, and submerged Yellowstone River gravels. Thus, the lake in the outlet region has been below or near its present level for about half the time since a 1 km-thick icecap melted from the Yellowstone Lake basin about 16 ka.The amplitude of two rises in lake and river level can be estimated based on the altitude of LeHardys Rapids, indicators of former lake and river levels, and reconstruction of the river gradient from the outlet to Le Hardys Rapids. Both between ~9.5 ka and ~8.5 ka, and after ~3 ka, Le Hardys Rapids (LHR) was uplifted about 8 meters above the outlet, suggesting a cyclic deformation process. Older possible rises in lake level are suggested by locations where the ~10.7 ka S4 truncates older shorelines, an...

Duration, magnitude, and frequency of subaerial volcano deformation events: New results from Latin America using InSAR and a global synthesis

“…On the other hand, some areas have been continuously deforming for decades, and even millennia, without eruption [e.g., Newhall and Dzurisin , 1988]. Centuries long patterns of deformation alternating between uplift and subsidence at Campi Flegrei [ Cinque et al , 1985], Yellowstone [ Pierce et al , 2002], and possibly Long Valley [ Reid , 1992], have yielded net uplift of only 15–40 m. Uplift at Socorro has been continuous between at least 1912–2008, but proposed evidence for continuous uplift lasting 10,000 years or more is dubious [ Fialko et al , 2001; Finnegan and Pritchard , 2009].…”

Reproductive biology and pollination ecology of the rare Yellowstone Park endemicAbronia ammophila(Nyctaginaceae)

“…The lake basin is a large caldera that was formed approximately 640 000 years ago when the magma chamber of two separate domes collapsed. The lake is 352 km 2 in area, although it was originally 32 m higher than current levels (Pierce et al . 2002; US National Park Service 2004).…”

The role of magma chamber-fault interaction in caldera forming eruptions

“…The level of 2.5 MPa is shown by the dotted line as a minimum level providing dyke propagation for slow chamber infilling activity on the lake floor. The vertical offset of the fault has been detected in the area of the Yellowstone River outlet (Pierce et al 2002) measuring up to 6 m. Yellowstone Lake is still a zone of hydrothermal activity. The regional fault apparently does not cut through the entire chamber roof but terminates midway.…”

“…The largest pool is located in the northeast corner of the caldera under the Sour Creek dome. Its evolution since the last glaciation is recorded in the elevation variation of the Yellowstone Lake shoreline (Pierce et al 2002). Pulses of magma replenishment correspond to the peak levels of uplift at roughly every 1,500 years, followed by a general subsidence at an average rate of 0.5 cm/a in Holocene times (presumably from gradual solidification and degassing of the large volume of magma).…”