The first factor to be considered is the type of the magma. With acidic magma, the magma is very viscous and this can determine how powerful and explosive an eruption is. This is due to the high silica content and low temperature. The more silica in the magma, the thicker and stickier it is. This type of magma is dangerous because it has a tendency to plug the volcano, trapping gasses which build pressure and eventually erupting violently!
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.
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.
Because of this the lava is resistant to flow and often forms blockages in vents. Pressure builds up because of the lava blockages and trapped gases, therefore these eruptions are very violent and dangerous. These eruptions usually involve pyroclastics and ash, which are hazards both on a local and a global scale. An example of a volcano at a destructive plate boundary is Mt St Helens in Washington, USA. At constructive plate boundaries, the lava is generally basaltic and therefore has low viscosity, meaning that it flows easily and gases can escape easily.
Analyse the factors that cause differences in the hazards posed by volcanoes around the world (40 marks) Volcanic hazards pose a risk to people and their property in both primary and secondary form. A volcano is an opening in the Earth's crust which lava, ash and gases erupt. A volcanic eruption can cause many deaths, illnesses, destruction of infrastructure, crops and livestock, all which will affect the economy and GNP of a country. There are many factors involved which cause differences in the severity of the destruction caused by a volcano, such as, locations of settlements, monitoring, plate boundaries and the economic status of a country, however these are different for each volcano around the world. I will be discussing factors that cause differences in hazards posed by volcanoes.
Volcanic events occur due to the movement of plate tectonics- this can be at destructive, constructive or conservative boundaries. Hazards are created when these events have an impact on human life/ activity and come in the form of primary and secondary effects. Primary effects include pyroclastic flow, lava flow and volcanic gases. Volcanic gases are emitted from volcanoes almost constantly and include carbon dioxide, carbon monoxide and hydrogen sulphide. These gases increase around the time of an eruption.
Its relatively low temperature, high silica content and 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, acidic magma is more likely to produce
The shortcomings are derived through the process of converting and using fossil fuel, it releases the most prominent green house gases into our atmosphere. Mining for the coal results in mass destruction of massive areas of land, putting the habiting species, and the workers, lives at risk. This raises a dilemma of whether it is wise to use fossil fuel at all. The burning of fossil fuels also damages are planet extensively, for example-a huge problem in today’s day and age-Global warming. It has a terrible effect on our planet: For instance, in Antarctica and Arctic higher temperature leads to the meltdown of ice and rise in sea level-threatening places such as the Maldives of being completely submerged in water.
Most of the time the bigger rocks crumble into pieces before they hit the ground, which creates an explosion. Medium-sized meteors normally disintegrate in the atmosphere. Smaller rocks that hit the ground usually don't have much of an impact. The massive impact of an asteroid 65 million years ago caused huge destruction to Earth. As the asteroid got closer to Earth, it would have created a huge shock wave, heating everything miles around it.
* A reservoir of boiling magma some three kilometres wide formed within Vesuvius, trapped inside by a plug of old magma. Chemical reaction involving water and gases finally shattered the lava plug and Vesuvius roared back to life. * The eruption of AD 79 was very unusual, without lava or other characteristics normally associated with volcanoes. It was a Plinian eruption – the most dangerous and feared kind of all – involving super-heated gas, magma and ash that form a giant towering column that builds up into the sky. The magma cools and falls to the earth as pumice.