![failed to open port volcano box failed to open port volcano box](https://fotos.subefotos.com/820954183c167d5cb288a54e2a1afd48o.jpg)
![failed to open port volcano box failed to open port volcano box](https://img.yumpu.com/3475791/1/184x260/hi-403-bluetooth-box-for-gps-receiver-user-manual-hkavionics.jpg)
The large cone in the left center is cone D, one of eight postcaldera cones. (bottom) Pre-2008 panoramic view of Okmok caldera, looking west from the East Rim. The red dot shows the location of the viewpoint for the photo, and the white letter D shows the location of cone D. The 1997 lava flow is visible as a light area extending NE from the SW part of the caldera. (top) Setting of Okmok volcano, with inset of eastern Umnak Island from a SAR image, modified from Mann et al. A new cone, not yet officially named, formed during the 2008 eruption and is located ∼2 km east of the geometric center of the caldera. The cones, labeled cones A through H, are located in a ring just inside the caldera walls. Several large basaltic cones have been built inside the caldera since the last caldera-forming eruption. The calderas are roughly concentric and of similar size, and these eruptions produced thick deposits of rhyodacite tephra. The present caldera results from two huge caldera-forming eruptions, ∼12,000 (Okmok I) and 2050 (Okmok II) years before present. The caldera is ∼10 km in diameter, with its floor ∼400 m above sea level and its rim ∼300 m higher. Okmok volcano ( = Okmok) is a large caldera that forms the eastern part of Umnak island in the eastern Aleutian arc ( Figure 1), which erupted beginning on 12 July 2008. The asynchronous transition from deflation to inflation, controlled by the distance of the site from the source, indicates that paired deep deflation and shallow inflation is required to explain the observations. Reinflation of the volcano commenced within at most 3 weeks after the end of ash emissions and was evident at a near-source site while a far-field site continued to deflate for an additional 4–5 weeks.
FAILED TO OPEN PORT VOLCANO BOX SERIES
During the eruption, the GPS time series indicate three distinct pulses of deflation rather than a single, smoothly decaying process, with the initial pulse being the largest. Although source depth estimates from a Mogi model can be biased due to elastic layering or heterogeneity, the GPS data require the 2008 eruptive source to be shallower than the preeruptive inflation source. Deflation during the eruption resulted from a decrease in pressure from a source estimated to be at 2.1 km below sea level using a Mogi model. Although GPS data for the precursory period are too sparse to derive a unique source model, the data show that either the center of pressurization shifted from its 1997–2005 location during the immediate precursory time interval or the shape of the pressure source changed from a sphere to something else. The 2008 eruption of Okmok volcano was preceded by 6–7 months of immediate precursory inflation, which followed ∼3 years of quiescence during which no significant magma was intruded at shallow depth.