Cascade volcanism hazards and eruption risks in western North America

¶ … Cascade Volcanism, Volcanoes, and What to Do When They Erupt

Volcanoes can be a scary thing, especially for those inexperienced in handling such a rare and potentially devastating occurrence. However, there are many things to learn from volcanoes that provide a little relief for those days when fear and worry kick in. But first, it is important to understand what cascade volcanism is as Mt. Grumble is in the Cascade chain (Olsen, 2008). The Cascade chain or Cascade Volcanoes are a series of volcanoes in western North America within a volcanic arc. They extend from southwestern British Columbia to Washington and Oregon and then Northern California, covering 1,100 km.

The formation of the Cascade Volcanoes came to be because of the Gorda Plate and Juan de Fuca, Explorer subduction under the North American Plate (Olsen, 2008). Such downward and sideways movement creates changes to the earth\'s crust that can lead to the production of volcanoes. The constant movement allows for continuous formation and collection of magma into diapirs. The magma then slowly rises via the mantle wedge, feeding the various volcanic arcs.

The Cascade Range houses major cities like Vancouver, Portland, and Seattle with populations of a total of more than ten million people (Olsen, 2008). Researchers categorize the Cascade volcanoes as some of the most perilous because of their eruptive history and increased likelihood for future eruptions. Additionally, the volcanoes exist as part of the Pacific Ring of Fire with several past eruptions recorded. The two most recent in history were 1914 to 1920\'s Lassen Peak and 1980\'s Mt. St. Helens eruption. Is that scary? No worries, these eruptions even, Mt. St. Helens only led to a small number of deaths and most were from asphyxiation.

Mt. Grumble is part of the Cascade chain and is a composite volcano. Composite volcanoes exist as steep-sided volcanoes made up of numerous layers of volcanic rocks (Sigurdsson, 2015). These rocks typically range from ash and rock debris to high-viscosity lava. St. Helens with its major and historic eruption is a composite volcano.

Many volcanoes exist as composite volcanoes with some having snowy peaks. Mt. Grumble has a snowy peak that can cause a potential hazard known as lahars. Lahars falls into the category of debris where mixtures of water and particles of varying sizes from enormous boulders to clay-size particles. They form due to hot pyroclastic flows/surges flowing over ice and snow. They can also happen when these surges enter watershed systems (Blong, 2013). Examples of dangerous lahars are Indonesian volcanoes that have led to the destruction of numerous lives and villages due to the eventual creation of floods and hyperconcentrated streamflow.

Other potential dangers that come from volcanic eruptions are pyroclastic density currents. These hazards are gravity-driven, ground-hugging, and fast moving mixtures of hot gases and rock fragments (Blong, 2013). Although dangerous and they have the potential of killing many people, they are typically confined to valleys. Depending on the size of the eruption, cities or town located a fair distance away like Bloomdale may not experience such effects.

Another potential hazard that many do not think of are volcanic gases. Magma contains dissolved gases that when released in the atmosphere creates a surge of carbon monoxide, carbon dioxide, chlorine, fluorine and other gases into the atmosphere through vents transforming into acid aerosols. Some of these compounds like fluorine and chlorine to poisonous acids when they react with water, causing damage to skin, respiratory systems, and eyes. Large eruptions can cause effects to the regional and even global climate. Although people tend to only think of magma and debris causing problems, volcanic gases can be just as deadly and can lead to asphyxiation-related fatalities.

Fear not, there are ways to protect from these hazards. Most importantly many volcanic eruptions are small and many living near a volcano can evade most danger by simply being a few kilometers away from the site. When they are predicted to hit, it will come with advanced warning, more than enough time for residents to evacuate their homes. This is because predictability of volcanic eruptions can be more accurate than earthquake detection. The tell-tale signs of a volcano range from escaping gas, tiny earthquakes, and alterations in the volcano\'s shape. (Blong, 2013) Some buildings and homes have been built with volcanoes in mind, able to withstand the weight of falling ash.

Things like survival kits containing first aid, water, a flashlight, a radio, batteries, food, and dust masks can help anyone escaping a volcano zone be prepared for any potential problems (Blong, 2013). Again, many volcanoes are easy to predict and come with advanced warnings for people to escape from the danger zones. This means volcanoes are not as dangerous if people make sure to evacuate and take the necessary precautions in a timely manner.