Here are the highlights of Mount St. Helens activity over the last 2000 years:
Goat Rocks Eruptive Period
Approximately 1800 A.D.
This eruptive period lasted for 100-150 years. Known events include ash explosions in 1842, which was followed by the extrusion of the Goat Rocks dome. Contemporary accounts indicate activity several times during the 1840s and 1850s, but are non-specific and even contradictory. The last significant activity before 1980 was "dense smoke and fire" in 1857, although minor, unconfirmed eruptions were reported in 1898, 1903, and 1921
Kalama Eruptive Period
1479 to 1482 A.D.
This eruptive period included two major ejections of ash, as well as lava flows and dome building.
Sugar Bowl Eruptive Period
Approximately 800 A.D.
Mount St. Helens was reshaped by a combination of dome building, a lateral blast, and pyroclastic flows during this period of volcanic activity.
Castle Creek Eruptive Period
200 B.C. to 300 A.D.
Major activity during this era included ejextions of ash, pyroclastic flows, and lava flows.
Data Source: USGS/Cascades Volcano Observatory: Mount St. Helens Eruptive History
>> Details of 1980 Mount St. Helens Activity
>> Recent Mount St. Helens Activity
