Environmental hazards

Supervolcanoes; their unpredictability and mystery make them into the worst environmental hazards our planet can face in one of their rare but catastrophic eruptions. Our lack of understanding regarding them is the cause for concern, but we cannot understand and predict eruptions, they’re unique according to the scale and other factors. We have some knowledge but due to the fact that no supervolcano has had a full-scale eruption in the past 2,000 years, we can only try to guess the extremity of eruptions through the studies of rocks and fossils from the time. A supervolcano is phenomenally large, around 50 to 100km in diameter on average and has a huge bubble of sticky magma beneath it, tens of kilometres across that is trapped under overlying rock and with gases such as sulphur dioxide, water vapour and carbon dioxide trapped in it.

They are formed near destructive plate boundaries where material from a plate that is descending rises back to the surface, this magma then rises up creating the large bubble of magma below the overlaying rock. They are also formed at continental hotspots, in either situation; the continental crust is being extended locally. This then makes weaknesses that allow the magma plumes to rise over very long periods of time and this process occurring over so much time (in some cases hundreds of thousands of years) is why the magma lakes have such an colossal mass. They erupt around every 50,000 to 100,000 years, in the eruption is over 1,000 cubic km of material that is blasted into the air, this causes unimaginable damage, short and long term.

On the VEI (Volcano Explosivity Index) a supervolcano is the top of the scale. The eruptions can begin in numerous ways: an earthquake could crack the rock above and release the magma, the pressure could push off the rock when it becomes too high or a significant drop in pressure could release the dissolved gases in the magma solution causing an explosive froth to blast out angrily. It is because of the sheer power of the explosions from these volcanoes that they are able to create such havoc with Earth as we know it. The features of Yellowstone National Park result from great explosive eruptions and profound collapse of the ground, enormously thick lava flows, uplift and extensive faulting, and the erosive power of flowing water and ice. The Yellowstone Supervolcano is the volcanic field which produced the past three supereruptions from the Yellowstone hotspot. The three super eruptions occurred 2.1 million, 1.3 million, and 640,000 years ago. The Island Park Caldera supereruption (2.1 million years ago), which produced the Huckleberry Ridge Tuff, was the largest. Mount St. Helens erupted on May 18, 1980, in the northwest corner of the United States; it killed 57 people and expelled one cubic kilometer of ash. The first Yellowstone supervolcanic eruption 2.1 million years ago was at least 25,000 times larger than the Mount St. Helens eruption.

The next supereruption, based upon size, formed the Yellowstone Caldera (640,000 years ago) and produced the Lava Creek Tuff. The Henry’s Fork Caldera (1.2 million years ago) produced the smaller Mesa Falls Tuff but is the only caldera from the Snake River Plain-Yellowstone hotspot that is clearly visible in the present day. The caldera is oval-shaped, in the state of Wyoming and is 55km by 72km, it lies over a hotspot. Because of movement in the Earth’s tectonic plates (they move slowly against, over and under one another) the North American plate moves to the southwest, this carries the landscape over the magma hot spot. The image below shows how it appears as if it were migrating eastward.

The supervolcano at Yellowstone has erupted around every 600,000 years; the last eruption was 640,000 years ago. Today, 20 million people live within 1,000 kilometers of the supervolcano; these are the people that will be most affected by ash fall if an eruption occurs. It can range from 1 to 5 meters, when the ash is very deep, it can collapse roofs and destroy buildings. Depending on the explosivity of the eruption, everything within 500km of the volcano could be completely destroyed with nothing left. From just one of the Supervolcanoes erupting, all people and animals worldwide will be affected severely. The primary effects will be: * People being killed and injured .

* Residential and commercial properties and towns destroyed. * Communications and transport interrupted.
But there are much more long term issues; these are the secondary effects: * Polluted water can cause disease and due to the shortages of clean water the disease may spread. * Social issues from losses in family and stress from trying to rebuild their lives. * Loss of income – Yellowstone is a magnificent tourist attraction. * Increased imports – Crops and plants will be buried in ash or destroyed entirely and the animals will be unable to graze on the land so products will have to be shipped somehow without the use of air as the ash will prevent them from flying. * Could possibly cause tsunamis that can travel up to 5,000km. Before the super eruption, large earthquakes would likely swarm the surrounding areas until the huge blast that would erase Yellowstone completely off the map.

There are some estimates that 87,000 people would die immediately. After the initial eruption, clouds of gas and rock would burn everything in its path with temperatures reaching to hundreds of degrees Celsius. A major issue is the ash. Ashfall would cover the western United States and also enter the jet stream with the potential to cripple air transportation and threaten the world’s food supply. It’s also a possibility that the cloud of ash could block out solar radiation due the fact Sulfur gas is usually in magma and released during eruptions (see ash deposits below).

The world would face a few years of mild climate change caused by the supereruptions’ ash cloud, which would wrap around the globe, casting Earth in shadow for several days and altering the chemical composition of the atmosphere for around a decade. Sulfur produces particles called aerosols, which can cool the climate by blocking sunlight. The sulfur may stay in the atmosphere with the ash, this could cause a ‘volcanic winter’ which could see temperatures drop from 5 to 10 degrees Celsius, there were some saying it could result in an ice age. The idea of this constant winter throughout the world is enough of a threat, where would we get enough supplies for 7 billion people when the conditions have changed globally? Thankfully, other scientists have other ideas. Stephen Self, director of the Volcano Dynamics Group at the Open University in the U.K said this statement about the Secondary effects: “Foreign governments may come to the aid and embark on a major ash cleanup operation, for the U.S but otherwise, inhospitable conditions would persist in the Midwestern U.S. for about a decade.

Records reveal that new vegetation starts to take hold about 10 years after supereruptions. It depends on how much rainfall the area receives, as rainfall is the main way you clear ash off the land. Also, the huge volume of magma means there would still be some sulfur injected into the atmosphere, but work has shown that you reach a sort of limit in the amount of aerosols you can produce with sulfur gas. It means that our earlier suggestions that there would be a severe temperature change is not right,” A research team analyzed some of the youngest volcanic rocks from the area, known as rhyolites, which are made of silica-rich minerals. The composition, shape and other features of crystals in these rocks could shed light on when and how they were formed, and thus on activity deep below the surface. Their findings are that the magma that gave rise to these rocks ascended rapidly from sources about 5 to 6 miles (8 to 10 km) below the surface.

The researchers say any volcanism at Yellowstone will probably resume at these sources. The problem with all Supervolcanoes is that they are hard to predict, there’s could be many more worldwide we have no knowledge of. Even using the knowledge of when the most explosive composite volcanoes are going to erupt, it’s useless as Yellowstone has been showing the signs for many years, which is why it’s so popular with tourists. The ground had been inflating for years as in the diagram to the left. Research could make predicting eruptions easier and governments have evacuation plans in place if the eruption is deemed as imminent; however, can we really stop the deaths? We cannot control physical features and natural processes of the earth, they created the place we live today by erupting and will evolve it in the future into something new when they burst. All we can do is try to take as many precautions as possible, and learn from evidence we have.