Browsing by Author "Bryan, Wilfred B."
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- Fractionation, partial melting, and mixing in normal basalts from 22~25˚ N, mid-atlantic ridgePublication . Bryan, Wilfred B.Much of the recent work on ocean ridge basalts has been directed toward supposedly «abnormal» sections of spreading ridges associated with inferred «mantle plumes». Such samples are especially well represented in the successful deep drilling accomplished by DSDP leg 37 (Aumento, Melson, et al., 1977) and in the data set from FAMOUS (White and Bryan, 1977; Langmuir et al., 1977; Bryan, 1979). The Mid-Atlantic Ridge near 22° N has been the source of many of the basalt samples on which our concepts of «normal» sea floor are based. As a result of a series of cruises associated with study of a «normal» oceanic crustal section in and near the Kane Fracture Zone at 24° N, about 150 new glass and whole rock major element analyses and trace element analyses of selected samples have been completed, representing dredge stations between 22° and 25° N. The data are discussed in detail by Bryan et al., 1981. These dredge data are supplemented by extensive published data for DSDP sites 395 and 396 located nearby (Melson, Rabinowitz et al., 1978; Dmitriev, Heirtzler et al., 1978). In both quantity and compositional diversity, these samples approach those from leg 37 and FAMOUS. However, some important differences do exist, both in absolute element abundances and in the nature of inter-element co-variances of both major and trace element data.
- Mt. St. Helens, Washington : initial eruptive events and morphologic changesPublication . Bryan, Wilfred B.After a week of increasing seismic activity, on March 27, 1980, Mt. St. Helens erupted ash and steam to a height of some 2000 m above the new summit crater. This eruption broke a 125-year period of dormancy for this volcano, which had become a popular scenic attraction and center d outdoor recreational activity in the south western corner of the state of Washington. The U.S. Geological Survey hastily called in experts from Denver, Menlo Park, and the Hawaiian volcano observatory, and geologists and volcanologists converged on the mountain from all over the world. Toward the middle d April the frequency of eruptions declined, and local newspapers and television stations confidently reported that the eruptions were over, and that scientists were packing up and leaving. However, the U.S. Geological Survey continued to monitor a bulge on the north flank of the volcano, which grew outward at up to 2 m per day. Small phreatic eruptions took place again from May 7 to May 14, while growth of the bulge continued at a nearly constant rate. On the morning of May 18, a major eruption destroyed the summit and north flank of the mountain. In intensity and volume of material involved, this eruption appears to be equivalent to the 79 a.d. eruption of Vesuvius that destroyed Pompeii. Although the remote location of Mt. St. Helens prevented major loss d life, about 60 people are known dead or remain unaccounted for as a result of this eruption. This note summarizes observations d eruptive activity and morphologic changes in the volcano up to the eruption of May 18. Reference data include both aerial and ground based still photography and sketches, and 16 mm mode film taken from a U.S. Geological Survey observation camp about 15 km northwest d the mountain. Additional background data and details of eruptions and compositions of eruptive products through, August 1980, are given by Hoblitt et al., 1980.