In this video segment, Jenda Johnson shows how to use candles of varying heights to demonstrate the hazard of volcanic gases. Jenda makes CO2 gas using baking soda and vinegar then gradually fills a bowl containing candles of different heights with the gas. The candles are progressively extinguished from shortest to tallest as the level of CO2 gas in the bowl rises.
This PowerPoint presentation covers the basics of Cascade volcanoes and volcanic hazards. The presentation was developed by Beth Pratt-Sitaula and Jenda Johnson with assistance from Denise Thompson. Before veiwing this PowerPoint presentation, viewers are encouraged to review the PDF Introduction to Pacific Northwest Plate Tectonics, Earthquakes, and Volcanoes under the Cascadia Earthquakes and Tsunamis topic.
Some volcanic craters form by the violent expulsion of magma (liquid rock) when it reaches Earth’s surface where liquid rock is referred to as “lava”. However, many volcanic craters form by collapse of the rock near the summit of the volcano. When magma pushes up through Earth’s crust, it must displace the surrounding and overlying rocks as it works its way toward the surface. When magma enters a shallow reservoir beneath a volcano, the ground above that magma chamber can “inflate,” pushing the ground upward and outward away from the center of the volcano. When an eruption occurs, magma is removed from the shallow reservoir beneath a volcano and the volcano can “deflate” with the ground sinking downwards and inward toward the center of the volcano. This inflation-deflation process can fracture and weaken the ground surrounding and above the magma chamber. The fractured rocks can sink to form a round or elliptical depression of the ground called a “caldera”. The formation of a caldera can be a catastrophic process that accompanies a violent eruption (e.g. geologically-recent eruptions of Yellowstone in Wyoming or Long Valley in eastern California) or a relatively gentle volcanic eruption (e.g. eruptions of basaltic lavas from Hawaiian volcanoes). This flour box demonstration takes learners through the stepwise process of “predicting” what you might see before and after a caldera collapse.
This 5-page PDF provides a brief introduction to the primary methods of monitoring volcanoes. Approaches to monitoring ground deformation on and around volcanoes are described along with methods for monitoring earthquake activity beneath a volcano and monitoring volcanic gas emissions.
The shape of the ground surface on or around a volcano sometimes precedes volcanic eruptions. Monitoring the shape of volcanoes has become an important component of volcano monitoring programs. This animation explains the principles of GPS and tiltmeter monitoring of volcanoes. The animation was developed by the Mt St Helens Institute, US Geological Survey Johnston Ridge Observatory, IRIS, and EarthScope.
This animation was developed by the Educational Multimedia Visualization Center of the Department of Earth Science, University of California at Santa Barbara, under the direction of Professor Tanya Atwater. The animation shows how subduction of an oceanic plate beneath a continental plate can produce an accretionary wedge of oceanic sediment and “lights the lava lamp” by generating magma in the asthenospheric mantle above the subducting plate.
Earthquakes of small magnitude and shallow depth often occur beneath volcanoes that are approaching eruption. These earthquakes are caused by heating of rocks beneath the volcano as magma works its way up into shallow chambers beneath the volcano and by pressure changes within the rising magma. This animation explains the principles of seismic monitoring of volcanoes. The animation was developed by the Mt St Helens Institute, US Geological Survey Johnston Ridge Observatory, IRIS, and EarthScope.
This animation shows the three-dimensional views of the Cascadia subduction zone. The Juan de Fuca Plate is created at the Juan de Fuca Ridge, then subducts beneath the Pacific Northwest portion of the North American Plate. The location of earthquakes, generation of magma, upward migration of magma, and eruption of Cascade volcanoes are illustrated.
Virtual Field Environment of field locations explored during TOTLE summer workshops. Effective use of this teaching resource requires DSL internet connection or faster internet connection. Your browser needs to have Adobe Flash Player installed.
This PDF provides a brief (12 page) introduction to regional plate tectonics, earthquakes, and volcanoes of the Pacific Northwest. The focus is mainly on the subduction zone (coast to Cascade Mountains) because that is where most of the earthquakes and volcanoes occur, and where tsunamis can be generated. This information was gathered and repurposed by Jenda Johnson and Bob Butler from the Pacific Northwest Seismograph Network (www.pnsn.org/), the U.S. Geological Survey (www.usgs.gov), and from two books: Orphan Tsunami of 1700, by Brian Awtater and others, and At Risk: Earthquakes and Tsunamis on the West Coast by John Clague and others.