Petrologic monitoring of 1981 and 1982 eruptive products from Mount St. Helens
Science
By: K. V. Cashman and J. E. Taggart
Links
- The Publications Warehouse does not have links to digital versions of this publication at this time
- Download citation as: RIS | Dublin Core
Abstract
New material from the dacite lava dome of Mount St. Helens, collected soon after the start of each successive extrusion, is subjected to rapid chemical and petrologic analysis. The crystallinity of the dacite lava produced in 1981 and 1982 is 38 to 42 percent, about 10 percent higher than for products of the explosive 1980 eruptions. This increase in crystallinity accompanies a decrease in the ratio of hornblende to hornblende plus orthopyroxene, which suggests that the volatile-rich, crystal-poor material explosively erupted in 1980 came from the top of a zoned magma chamber and that a lower, volatile-poor and crystal-rich region is now being tapped. The major-element chemistry of the dacite lava has remained essentially constant (62 to 63 percent silica) since August 1980, ending a trend of decreasing silica seen in the products of the explosive eruptions of May through August 1980.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Petrologic monitoring of 1981 and 1982 eruptive products from Mount St. Helens |
| Series title | Science |
| Volume | 221 |
| Issue | 4618 |
| Year Published | 1983 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Science |
| First page | 1385 |
| Last page | 1387 |
| Google Analytic Metrics | Metrics page |