| The eruptive activity of Mt. St. Helens beginning in March, 1980, coupled with earthquake activity on Mt. Hood in early July, has generated increased interest in the fumaroles near the summit of Mt. Hood. These fumaroles are associated with Crater Rock, a hornblende dacite plug, extruded 200 to 300 years ago. A major eruption in about 1700 and lesser eruptions in 1805, 1859, and 1865 were centered near Crater Rock. It is likely that future eruptions will occur in this area. Changes in the surficial characteristics of the fumaroles or changes in the composition of the gas emitted by the fumaroles could precede an eruption by a sufficient length of time to help predict the eruption. -- Nehring, et.al., 1981 |
