REPORT:
Deposits of Pre-1980 Pyroclastic Flows and Lahars from Mount St. Helens Volcano, Washington

Table of Contents

• Abstract
• Introduction
  • Topographic and geologic setting of the volcano
  • Hot dry flows of particulate material and associated ash clouds
    • Pyroclastic flows
    • Pyroclastic surges
    • Ash clouds
  • Lahars
  • Tephra
  • Methods used to date deposits
  • Summary of the eruptive history of Mount St. Helens
• Deposits of pre-Mount St. Helens glaciations
• Ape Canyon eruptive stage
  • Deposits
  • Nature and age of volcanism
• Cougar eruptive stage
  • Deposits
    • South and southwest of the volcano
    • West side of the volcano
    • Southeast side of the volcano
  • Nature and age of volcanism
• Glacial deposits of Fraser age
• Swift Creek eruptive stage
  • Deposits
    • South side of volcano
    • West side of volcano
    • East side of volcano
    • Southeast side of volcano
  • Nature and age of volcanism
• Spirit Lake eruptive stage
  • Smith Creek eruptive period
    • Deposits
      • East side of volcano
      • North side of volcano
    • Nature and age of volcanism
  • Pine Creek eruptive period
    • Deposits
      • Pine Creek valley
      • Valleys of Colspring Creek, Kalama River, and South Fork Toutle River
      • Vanneys of North Fork Toutle River and Castle Creek
    • Nature and age of volcanism
  • Castle Creek eruptive period
    • Deposits
      • Pyroclastic-flow deposits and lava flows in and near the Castle Creek valley
      • Lava flows on the north and northeast sides of the volcano
      • Pyroclastic-surge deposit in Ape Canyon
      • Dome on the east side of the volcano
      • Lahars and lava flows on the southeast side of the volcano
      • Deposits in the Kalama River valley
      • Lava flows on the south and southwest sides of the volcano
    • Nature and age of volcanism
  • Sugar Bowl eruptive period
    • Fragmental deposits associated with the Sugar Bowl dome
      • Air-fall tephra
        • Ballistic fragments
        • Wind-transported tephra
      • Pyroclastic-flow deposits
      • Lahars
    • Origin of the Sugar Bowl fragmental deposits
    • East dome
  • Kalama eruptive period
    • Deposits of early Kalama age
    • Deposits of middle Kalama age
    • Deposits of late Kalama age
    • Nature and age of volcanism
  • Glacial deposits of Holocene age
  • Goat Rocks eruptive period
    • Deposits
      • Tephra layer T
      • "Floating island" lava flow
      • Tephra erupted in 1842
      • Goat Rocks dome
    • Nature and age of volcanism
• The future
• References
• Appendix A