1. Cascade Volcanoes
There are 13 potentially active volcanoes in the Cascade Range of the northwest-ern United States

2. Mt. St. Helens – prior to the 1980 eruption

3. Mt. St. Helens after the 1980 eruption

4. Precursory stages of the Mt St Helens eruption

5. A seismically-induced landslide reduced lateral and vertical confinement, triggering the May 18, 1980 eruption of Mt. St Helens

6. Cross sections thru Mt St Helens showing deep rotational slide blocks which slid off the peak

7. Atmospheric impacts of the May 18, 1980 Mt St Helens eruption

8. The Mt St Helens eruption shot volcanic ash to an altitude of 60,000 feet, into the stratosphere

9. Relative distribution of blown down trees and lahar debris flows in the Toutle River Valley on the north side of Mt St Helens

10. The St Helens blast flattened Douglas fir trees over an area of 400 square kilometers

11. Lahars, debris flows, and debris chocking of rivers caused by the Mt
Lahars, debris flows, and debris chocking of rivers caused by the Mt. St. Helens eruption

12. Profiles of volcanic landforms

13. Volcanoes Nuée ardente – A deadly pyroclastic flow
Fiery pyroclastic flow made of hot gases infused with ash and other debris
Also known as glowing avalanches
Move down the slopes of a volcano at speeds up to 200 km per hour
Lahar – volcanic mudflow
Mixture of volcanic debris and water
Move down stream valleys and volcanic slopes, often with destructive results

14. A nueé ardente on Mt. St. Helens after the May 1980 eruption

15. Viscous lava flow passing through the village of Goma in the Congo during the eruption of Mt. Nyiragongo in January 2002

16. Other volcanic landforms
Fissure eruptions and lava plateaus
Fluid basaltic lava extruded from crustal fractures called fissures
Example = Columbia River Plateau
Lava domes
Bulbous mass of congealed lava
Associated with explosive eruptions of gas-rich magma

17. Columbia River Plateau

18. Lava dome at Mt. St. Helens

19. A lava dome