Mt St Helens is by far the most active volcano in the Pacific Northwest.
Its latest eruption was in 2004, which was followed by a period of dome
building which halted in early 2008.
The Mountain seems to have gotten its start just before the last ice age
ended, some 10,000 years ago. The volcano was particularly
restless in the mid-19th century, when it was intermittently active for
at least a 26-year span from 1831 to 1857. Some scientists suspect that
Mount St. Helens also was active sporadically during the three decades
before 1831, including a major explosive eruption in 1800. Some of
the more recent major eruptions still show their scars on the forests
surrounding the still-growing mountain.
Although minor steam explosions may have occurred in 1898, 1903, and 1921,
the mountain gave little or no evidence of being a volcanic hazard for
more than a century after 1857. Consequently, the majority of
20th-century residents and visitors thought of Mount St. Helens not as a
menace, but as a serene, beautiful mountain playground teeming with
wildlife and available for leisure activities throughout the year. At
the base of the volcano's northern flank, Spirit Lake, with its clear,
refreshing water and wooded shores, was especially popular as a
recreational area for hiking, camping, fishing, swimming and boating.
The tranquility of the Mount St. Helens region was shattered in the
spring of 1980, however, when the volcano stirred from its long repose,
shook, swelled, and exploded back to life.
