A volcano is a surface landform resulting from the extrusion of magma from underground as lava, ash, rocks, and gasses are erupted in various proportions. A hazard is something that poses a threat to life, the environment or property. Volcanoes can compromise all these things through the many hazards volcanoes presents. These include lahars, flash flooding, landslides, pyroclastic flows, ash clouds and many others. Each year, around 60 major volcanoes erupt globally.
Thicker, more viscous magma has a greater potential for explosive eruptions and therefore represent the greatest potential hazards. The thickest type of magma is known as Acid Magma. Its relatively low temperature (600C-1000C), high silica content and low proportion of dissolved gases causes its toothpaste-like consistency that leads to blockages and powerful eruptions. This can mean that the eruptions caused by thick magma can be less frequent and more difficult to predict, meaning that when an eruption does occur, it is usually with little or no warning, which can lead to catastrophic consequences as any nearby settlement will be relatively unprepared for the effects of a violent volcanic eruption. Furthermore, acid magma is more likely to produce clouds of smoke and ash due to the explosive nature of the eruption it causes, than thinner, basic lava.
If an eruption were to occur, a number of life-changing things would happen. Lava flow would burn everything in its path. Ash falls will cause suffocation; killing many. Along with the death of a good amount of people, the ash would block the sun causing us to experience massive climate changes, but not just for us; The whole world would experience it as well. Science is showing that the potential for an eruption of some of the earth’s biggest and deadliest volcanoes is very real and imminent.
When the eruption did occur it was seen as explosive as it produced large volumes of acidic lava, ash, pyroclastic flows and steam. However, volcanoes at constructive plate margins or hot spots are generally seen as less explosive. They produce continuous, yet gentle, eruptions of lava, such as the formation of the
These types of lava are very viscous due to its high silica content. This is because the lava rises from the subduction zone through continental lithosphere which has a low density and is filled with air spaces containing gases which become incorporated into the lava. This very viscous lava often blocks off vents of volcanoes and when the pressure building up in the vent is eventually released, the top of the volcano can be blown off leaving a huge crater, such as in the 2002 eruption of Mount Etna in Sicily. When the two plates involved are oceanic, explosions tend to be less violent than this as the melted lithosphere which forms the lava is denser and so contains fewer gases. At constructive boundaries where plates are moving apart from one another, basaltic lava is erupted between the gaps.
Just like the characteristic of a rock, climate also plays a role in the rate in which a rock will break down. With that being said, rocks that are exposed to a wet/ moist climate are more susceptible to chemical weathering. Thus, the rocks in this type of climate will decompose at an accelerated rate. On the other hand, dry climates are more vulnerable to mechanical weathering, which has a slower weathering rate. All in all, areas with warm temperatures will have faster chemical reactions, so, weathering in the tropics is rapid.
Explain why coastal California is considered a disaster hotspot? (15marks) A disaster hotspot is a country or area that is vulnerable/ disaster prone due the hazards that are; Geophysical, hydro- meteorological. A human factor that increases the risk is vulnerability which includes- population density, wealth and GDP (gross domestic products) which affects the impact of the natural hazard. California is considered a disaster hotspot as all of these factors contribute to an increased danger to human life, meaning it is susceptible to the following natural hazards: earthquake, tsunamis, volcanoes, droughts, wildfires, fog and smog, hurricanes and landslides. One hazard can often trigger others (e.g.
To what extent can preparedness and planning mitigate the effects of volcanic hazards? (40 Marks) A volcanic hazard is any threat to life and infrastructure due to volcanic activity and related situations such as a landslide near the volcano. There are many different types of volcanic hazard and each can have different impacts on the economy, society and environment in a region. It is extremely important that disaster reduction measures, such as early warning systems and land use planning, are implemented to try to reduce these impacts. There are three main stages to consider when managing a volcano: before the eruption, during its critical period and evacuation.
Gases dissolved in magma provide the motive force of volcanic eruptions, sulphurous volcanic gas and visible steam are usually the first things noticed on an active volcano as well as others that escape unseen for example through hot fumaroles, active vents, and porous ground surfaces. The limitations of taking these samples are remote location of these sites, intense and often hazardous fumes, frequent bad weather, and the potential for sudden eruptions can make regular sampling sometimes impossible and dangerous. Measuring gases remotely is possible but requires ideal weather and the availability of suitable aircraft or a network of roads around a
These include creating an exclusion zone around the volcano, being ready and able to evacuate residents and having an emergency supply of basic provisions, such as food. A study of the previous eruption history of a volcano is important in prediction, along with an understanding of the type of activity produced. At present, research is being conducted to see if it is possible to predict the time of an eruption accurately using the shock waves that are produced as magma