Introduction

Background on Volcanoes

Types of Volcanic Eruptions

Volcanic Hazards

The Role of a Meteorologist

Volcanoes and Climate

Volcanoes and Flooding

Forecasting Tools

Conclusion

References

Most scientists knows the difference between a geologist and a meteorologist; a geologist studies the earth, including the materials it is made of, its structure and the processes acting on the earth and a meteorologist studies the atmosphere. To the general public a scientist is a scientist. Meteorologists are often expected to answer questions about earthquakes, volcanoes, tsunamis and other aspects that do not necessarily fall under their area of expertise. The purpose of this project is to introduce the concept of volcanoes and explain the role a meteorologist may take during and after an eruption, specifically in the interest of public safety and providing information to the public.

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The outermost part of the earth is called the lithosphere, which is broken into several plates. These plates float on top of a denser surface called the asthenosphere (USGS, 2008a). There are three types of boundaries that have to do with the movement of plates; they are convergent, divergent and transform boundaries. Crust is destroyed and one plate dives under the other plate at a convergent boundary, whereas the plates pull apart and new crust is formed at a divergent boundary. A transform boundary is where the plates slide past each other with no crust created or destroyed. Out of these three boundaries, convergent and divergent plate boundaries are the most likely locations of volcanism (The COMET Program, 2011c).

Plate Boundaries (USGS, 1999).

Temperature and pressure are high and rocks are soft and partly melted within the asthenosphere, which results in a slow movement. Due to temperature instabilities, convection currents form and bring hot matter from deeper in the mantel to the surface. This process causes convection currents to diverge at the base of the lithosphere, which puts tension on the plate. The combination of heat flow and this tension cause the plate to break apart (USGS, 2008a).

At the divergent boundary, molten rock from below rises cools and solidifies when it makes contact with the cool ocean water; this forms new lithosphere. As new lithosphere is formed, the older lithosphere moves farther away, cooling and becoming less dense. Once the old lithosphere is less dense than the underlying asthenosphere, it sinks forming a subduction zone, which is a type of convergent plate boundary (USGS, 2008a).

While divergent and convergent boundaries are the most likely locations of volcanism, convergent boundaries have the most explosive volcanoes (The COMET Program, 2011c). At a convergent boundary, temperatures and pressures cause fluids to be released from the subducting plate. The fluids help melt the solid mantle above the plate and form magma, which rises to the surface. A lot of this magma cools and turns into plutonic rock below the surface, which can form the cores of great mountain ranges once erosion exposes them, however some of the magma can reach the surface and erupt from volcanic rocks. These eruptions and the accumulation of lava and ash form volcanic mountains (USGS, 2008a).

The most active volcanoes in the world fall within the “Ring of Fire”, which circles the Pacific Basin (The COMET Program, 2011c). The Cascade Range is one of the ranges in the United States that falls in the “Ring of Fire”. This range has 13 volcanoes in Washington, Oregon and northern California (The COMET Program, 2011c). There have been about two eruptions per century over the past 4,000 years within this range (The COMET Program, 2011c). While the number or eruptions are lower for the Cascade Range, “from Kamchatka Peninsula to southeast Alaska, there were 97 eruptions between 1970 and 2008” (The COMET Program, 2011c). An average of ten eruptions occurs each day, although most of the eruptions are small (The COMET Program, 2011c). Not all eruptions fall along a subduction zone or within the “Ring of Fire”; they are just more common in these regions.

Ring of Fire (USGS, 1999).

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Four common types of eruptions include Hawaiian, Stombolian, Vulcanian and Plinian eruptions, with Hawaiian eruptions the least explosive and Plinian eruptions the most explosive (The COMET Program, 2011c). In terms of ash clouds, Hawaiian eruptions rarely produce ash and Strombolian eruptions can produce ash, although it is short-lived and doesn’t make it far in the atmosphere (The COMET Program, 2011c). Vulcanian eruptions produce a cloud of “ash-laden gas explodes from the crater and rises high above the peaks” (The COMET Program, 2011c). Plinian eruptions are the most powerful with ash and volcanic gas reaching the stratosphere. The Plinian eruptions are also responsible for dangerous pyroclastic flows; they are the type of eruptions meteorologists should be the most concerned with (The COMET Program, 2011c).

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Some volcanic hazards include tephra, pyroclastic flows, lahars, lava flows and volcanic gases. Tephra are fragments of volcanic rock and lava that are blasted into the air, with the smallest particles being carried the farthest away by winds. Tephra can causes darkness during day, collapsing roofs, damage to machinery and vehicles, agricultural issues, slippery or blocked roads, power outages and issues with waste water systems (USGS, 2009). Pyroclastic flows are a combination of hot ash, pumice, rock and volcanic gases rushing down the volcano along the ground and can move faster than 100 kilometers per hour (USGS, 2010b). They can cause destruction to anything in their path, bury sites, burn forests, crops and buildings and melt snow and ice to form lahars (USGS, 2008b). A lahar is a mixture of rock debris and water and is also known as a mudflow. Lahars can be a result of the snow or ice melt from a pyroclastic flow, but can also be caused by intense rainfall (USGS, 2008c). Lava flows are the molten rock that end up on the surface after an eruption and can be moving or solidified. Lava flow causes a threat to everything in their path, much like a pyroclastic flow and can also lead to lahars (The COMET Program, 2011c).

Volcanic gases are found within magma and enter the atmosphere during an eruption. Gases can also make it into the atmosphere through soil, volcanic vents, fumaroles and hydrothermal systems (USGS, 2010a). Some gases found within a volcano include water vapor, carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrogen, carbon monoxide, hydrogen chloride, hydrogen fluoride and helium, with water vapor, carbon dioxide and sulfur dioxide being the most abundant (USGS, 2010a). Sulfur dioxide, carbon dioxide and hydrogen fluoride are the greatest hazard to people, animals, property and agriculture. Sulfur dioxide, hydrogen chloride and hydrogen fluoride can all result in acid rain, however sulfur dioxide has the largest impact on climatology, because it can also cause volcanic smog (vog), lead to global cooling and ozone depletion (USGS, 2010a).

Tephra, lahars and volcanic gases are the volcanic hazards that have the largest effect on the role of a meteorologist. The wind forecasts are important for understanding the fate of tephra transportation, whereas precipitation forecast, especially heavy rainfall forecasts, are important for understanding the likelihood of devastating lahars forming. The volcanic hazards that would most affect the role of a meteorologist include tephra, lahars and volcanic gases, with volcanic gases having the largest impact on the role of a meteorologist.

Lahar (USGS, 2008c).

Tephra (USGS, 2009).

Tephra (USGS, 2009).

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Volcanic eruptions have a huge impact on the aviation industry, maritime operations and society. To the aviation industry, damage can occur to aircraft, including a loss of power to the engines, damage to electrical systems and damage to windscreens and other leading edges, but can also affect the runways, taxiways, tarmac, terminal, hangars, communication systems, electrical facilities, ground transportation and maintenance of aircraft and vehicles at an airport (The COMET Program, 2011a). Additionally, the ash can lead to wet ash that will require longer breaking times, reduced visibility and many other problems. Aside from the safety hazards, there are also economic impacts. A study by Oxford Economics on the 2010 eruption of Iceland's Eyjafjallajokull found global loses during the first week following the eruption of about $2.6 billion (Oxford Economics, 2010). During and after a volcanic eruption, wind and rainfall forecasts become important to the aviation industry. Forecasting the fate of ash and how it will be transported by winds and precipitation not only affect the safety of flights, but also the operations at several airports.

Similar to the aviation industry, maritime operations are also greatly affected by volcanic eruptions. Volcanic ash reduce visibilities making navigation difficult, but the ash can also damage machinery and the engine on a vessel, along with presenting problems to communication systems, corrosion to metal, health problems to crew, passengers and cargo. Pumice floating on the surface of water also presents navigational issues and threats to the vessel (The COMET Program, 2011a). These threats are not only safety hazards, but also have great economic impacts. Meteorologists are often expected to issue volcanic ash fall advisories to warn the maritime community of potential hazards.

Impacts on society include air quality, health, agriculture, ground transportation, communications and water quality. A volcanic eruption can greatly reduce the air quality, leading to reduced visibility, volcanic smog and respiratory system problems, along with eye and skin irritation (The COMET Program, 2011a). Volcanic ash can threaten crops, livestock and new forest growth, cause ground transportation hazards due to low visibilities, slippery roads and mechanical issues, result in power outages and the breaking of power lines, damage structures by collapsing roofs due to the weight of heavy ash and affect radio communications (The COMET Program, 2011a). Volcanic ash can also effect water quality by changing its acidity and damaging filters at treatment plants, along with damaging waste water systems (The COMET Program, 2011a). A meteorologist’s forecast on precipitation and wind plays a role in planning the fate of ash transport during and after a volcanic eruption. An accurate forecast can aide in keeping the public safe from some of these health risks and allow the community/local government to properly plan to try and reduce the impacts from a volcanic eruption.

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The most important impact of volcanic ash to a meteorologist is on the climate. Sulfur has the largest impact on climate, specifically when it makes it into the stratosphere during a Plinian eruption. Once gaseous sulfur compounds make it into the stratosphere, they are above the troposphere where weather occurs. This prevents the compounds from precipitating out and they can remain in the stratosphere for years (The COMET Program, 2011a). When enough gaseous sulfur compounds make it into the stratosphere, they absorb and scatter parts of the solar radiation reaching the atmosphere. These gaseous sulfur compounds affect the energy balance and lead to climate change, or in this case global surface cooling and stratospheric warming (The COMET Program, 2011a). In the stratosphere, gaseous sulfur compounds are dispersed by eddies found within the westerlies. An eruption of this magnitude in the tropical region can have climatic impacts on both the northern and southern hemisphere due to stratospheric circulation (The COMET Program, 2011a).

The troposphere is the layer where all weather occurs. The stratosphere is the layer above the troposphere where the "good" ozone is found. This is also the layer where volcanic clouds go during a Plinian eruption. (National Weather Service, 2010).

To understand the effect of volcanic clouds, think about a typical cloudy day and night. On a cloudy day, clouds scatter solar radiation causing cooler temperatures, but at night, they emit long wave radiation to the surface keeping temperatures forming dropping too much. Similarly, a volcanic cloud will result in cooler days, but warmer nights (The COMET Program, 2011a). The eruption of Mt. Pinatubo in 1991 resulted in a global surface temperature change of 0.5 degrees Celsius during the first year following the eruption. There was also a two degrees Celsius warming to the lower stratosphere (The COMET Program, 2011a). Following the eruption of Mt. St. Helens in 1980, temperatures in eastern Washington State were eight degrees Celsius cooler during the day and eight degrees Celsius warmer at night (Mass and Robock, 1982).

Eruption of Mt. Pinatubo in 1991 (USGS, 2012).

Eruption of Mount St. Helens in 1980 (USGS, 2009).

Even though an eruption occurs at one location, it can still impact the climate for the rest of the globe. This is because of the atmospheric dynamic response. In simple terms, if the tropics experience stratospheric warming, the temperature gradient between the equator and poles is increased, which can cause a positive phase of the North Atlantic Oscillation (NAO), which can lead to winter warming in the northern hemisphere (The COMET Program, 2011a). Volcanic eruptions can both enhance and reduce the effect of El Nino and the Southern Oscillation.

With a volcanic cloud present, it has been mentioned there would be a decrease in shortwave radiation reaching the surface of Earth. This also affects the amount of precipitation received in tropical regions during the summer, due to less evaporation (The COMET Program, 2011a). Southeast Asia is the largest land mass near the tropics and may notice a huge reduction in precipitation after an eruption because the decreased land-water contrast will reduce their monsoon season (The COMET Program, 2011a). There is also less precipitation across the central Africa and central Southern American region, affecting the location of the Intertropical Convergence Zone (ITCZ) (The COMET Program, 2011a). A decrease in shortwave radiation can also lead to cooler sea-surface temperatures.

While a lot of research is still beginning conducted on the effects of volcanoes on hurricanes, it is understood that hurricanes originate from tropical thunderstorms and the preferred environmental conditions include moisture, warm water and low wind shear (The University of Rhode Island, 2011). The cooler sea-surface temperatures and reduction in summer precipitation (leading to fewer storms) could possibly mean volcanoes decrease the number of hurricanes (Klemetti, 2012).

The ozone layer is found in the stratosphere. Recall the stratosphere is the level of the atmosphere were the volcanic clouds would be present during a Plinian eruption. The presence of volcanic clouds and gases in the stratosphere also lead to the destruction of stratospheric ozone. Stratospheric ozone is the good ozone, which absorbs dangerous ultraviolet radiation from the sun (The COMET Program, 2011a).

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Volcanoes have an impact of climatology, especially global temperature change, but they also have short and long-term effects on flooding. As already mentioned, volcanic eruptions can lead to the melting of ice and snow, which results in lahars. The surge of water from melted snow and ice can lead to flash flooding and localized flooding. The transport of sediment during lahars can also reshape riverbeds and increase the risk of flooding long after the eruption during future events of heavy rainfall (The COMET Program, 2011a). The effect volcanoes have on short and long-term flooding is important to the meteorologists when issuing flash flood and flood watches, warning and advisories. It is well known in the weather community that flooding is currently the leading severe weather related killer.

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There are several tools available to assist a meteorologist during and after an eruption. Visible imagery, thermal infrared imagery, shortwave infrared imagery, false color imagery, spilt window imagery, principal component imagery, reflectance projects and sulfur dioxide products can be used to help identify the presence of ash. (The COMET Program, 2011b). Information from the Volcanic Ash Advisory Center (VAAC), satellite, radar, pilot reports and webcams can help a meteorologist determine the plume height, while upstream wind observations, forecast winds and the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model can be used to determine the plume drift (The COMET Program, 2011b).

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In the case of a volcanic eruption, while not a geologist, a meteorologist may be expected to answer questions about the impact of an eruption, so it is important to understand the fundamentals of plate tectonics, how volcanoes form and the types of volcanic eruptions and their impacts. A meteorologist also needs to understand the impacts of an eruption on the aviation industry, maritime operations, agriculture, society and climatology to provide an accurate forecast when dealing with impacts of volcanic ash and gases.

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Daily Mail Reported, 2010. Dramatic satellite pictures show Iceland volcano still erupting... but ash on the wane at last. Accessed April 16, 2012.

The COMET Program, 2011a. Volcanic Ash: Impacts to Aviation, Climate, Maritime Operations and Society. Accessed April 10, 2012.

The COMET Program, 2011b. Volcanic Ash: Observation Tools and Dispersion Models. Accessed April 10, 2012.

The COMET Program, 2011c. Volcanic Ash: Volcanism. Accessed April 10, 2012.

Klemetti, Erik, 2012. Volcanoes and Hurricanes: Mortal Enemies, Best Friends? Accessed April 10, 2012.

Mass, C. and Robock, A., 1982. Volcanic Gases and Their Effects. Accessed April 10, 2012.

National Weather Service, 2010. Standarized Temperature Profile. Accessed April 16, 2012.

Oxford Economics, 2010. The Economic Impacts of Air Travel Restrictions Due to Volcanic Ash. Accessed April 10, 2012.

The University of Rhode Island, 2011. Hurricanes: Science and Society. Accessed April 10, 2012.

USGS, 2012. Volcanic Gases adn Climate Change Overview. Accessed April 16, 2012.

USGS, 2010a. Volcanic Gases and Their Effects. Accessed April 10, 2012.

USGS, 2010b. VHP Photo Glossary: Pyroclastic Flow. Accessed April 10, 2012.

USGS, 2009. Volcanic Hazards: Tephra, including volcanic ash. Accessed April 10, 2012.

USGS, 2008a. Plate Tectonics in a Nutshell. Accessed April 10, 2012.

USGS, 2008b. Pyroclastic Flows and Their Effects. Accessed April 10, 2012.

USGS, 2008c. VHP Photo Glossary: Lahar. Accessed April 10, 2012.

USGS, 1999. Understanding plate motions. Accessed April 10, 2012.

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