Mt. St. Helens: before the 1980 eruption eruption Bulge: plug that is pushed out by magma within the conduit.
Pyroclastic eruption Mt. St. Helens Landslide Release of pressure Lateral blast Pyroclastic flow- down with the pull of gravity Ash cloud-vertical Ash fall
Landslide Gravitational force “pulls” unstable material down slope Fills canyons and valleys with debris
Landslide, Mt. Shasta 300,000 years ago 20 times more material than the Mt. St. Helens landslide
Lateral Blast: extreme pyroclastic flow In the case of Mt. St. Helens, the landslide “uncorked” the vent. Gas and debris were released under tremendous force Burns and destroys anything in its path
Lateral Blast Large area completely devastated (23 X19 miles) Trees knocked down Vegetation burned off
Mt. Unzen, Japan Japan Geologists examined volcanoes all around the world. Mt. Unzen, Japan and Mt. Hood, Washington have the potential for lateral eruptions.
Pyroclastic flow: hot gas propels pyroclastic debris Gravitational force pulls hot gas and pyroclastic debris down slope from the initial vertical eruption. Montserrat, 1997
Pyroclastic FlowFlow Mt. Pinatubo, Philippines 1991 May reach 100 miles per hour Burns or suffocates anything in its path
Vertical Eruptions: Plinian If the initial eruption is vertical the force sends debris into the stratosphere
Global cooling: debris blocks sunlight
Mt. Pinatubo Major eruptions blocking Sun’s radiation Cooled global temperatures by.5-.6 degrees Centigrade
Volcanism 1815- Large eruption in the tropics; once thought to be Tambora in Indonesia –Global temperatures fell –Crops failed throughout Europe and famine spread –Mary Shelly told her house guests the story of Frankenstein and his creator died in the arctic because they were unable to go outside during their vacation
Ash fall Acts as an abrasive Clogs machinery, covers vegetation, irritates lungs and eyes Ash deposited associated with the eruption of the Long Valley Caldera Photomicrograph of ash from the Mt. Tehama eruption (Lassen Peak)
Iceland Located on the North Atlantic mid- oceanic ridge Hot spot What type of lava? Viscosity? Eruptive style?
Iceland's Eyjafjallajokull volcano Volcanic eruption under ice produces steam and other gases to propel pyroclastic debris into the atmosphere European air travel was interrupted for weeks
Mt. Yasur, May 30, 2010 Some flights rerouted or cancelled in Australia
Volume of Pyroclastic Debris Ash
Lahars Remobilized ash, rock and debris by water Water source needed: rain, snow melt
Mt. St. Helens
Mt. Rainier: lahars from the last 5600 years
Lahars: Mt. Pinatubo
Lava Flow Destroys everything in path People and animals can usually escape
Iceland: The Eldfell volcano on the island of Heimaey New land was created during the 1973 eruption.
Jokulhlaup One third of country is covered by active volcanoes About 13% covered by glaciers The lava melts the ice cap At one point the large volume of water pours rapidly to the adjacent area
Gas Emissions Sometimes gas release is concentrated and toxic to vegetation and people Horseshoe Lake near Mammoth, California
Carbon dioxide leaked out of Lake Nyos, Africa suffocating 1700 people and all animal life.
Understanding Volcanic Hazards Past history –How often –Types of hazards –Extent of hazards –Location of past events Ash deposits associated with the eruption of Santorini, Greece