VOLCANIC ERUPTIONS

A bit about volcanoes… Volcanoes form when magma reaches the Earth's surface, causing eruptions of lava and ash. They occur at destructive (compressional) and constructive (tensional) plate boundaries. There are three different types of eruptions. .An important measure of eruptive strength is Volcanic Explosivity Index (VEI), a magnitudic scale ranging from 0 to 8 that often correlates to eruptive types.

• The main vent is the main outlet for the magma to escape. The crater is created after an eruption blows the top off the volcano. Secondary vents are smaller outlets through which magma escapes. The magma chamber is a collection of magma inside the Earth, below the volcano.

Mount St Helens 1980 (MEDC) Mount St Helens is on the plate boundary between the Juan de Fuca plate and North American plate. The 1980 eruption resulted when a huge section of the mountaintop was forced outward and fell away from the mountain. The pressure of magma from within the mountain had been increasing over the years and the rock eventually gave way. With the blocking rock removed, huge amounts of hot rock, ash, and gas exploded from the opening with incredible force. The primary effects include the death of 63 people mainly from poisonous gases, hot ash and gases destroyed forests and logging camps and (mudflows of ash and water) covered an extensive area surrounding the volcano.

Mount St Helens 1980 (MEDC) the secondary effects include Ash blocked rivers destroying popular fishing sites and causing flooding. This in turn destroyed crops and livestock, Flooding destroyed communications such as road and railway bridges, sediment carried downstream ruined barge transport on the Columbia River. The short term solutions carried out here include communications such as roads and bridges being repaired and people were rehoused. The long term solutions include soil fertility improved due to ash deposits, the volcano is now closely measured and tourism has increased boosting local economy.

Chances Peak, Montserrat, 1995-97 - an LEDC Montserrat is a small island in the Caribbean. There is a volcanic area located in the south of the island on Soufriere Hills called Chances Peak. Before 1995 it had been dormant for over 300 years. In 1995 the volcano began to give off warning signs of an eruption (small earthquakes and eruptions of dust and ash). The volcano erupted due to it lying on a destructive plate boundary Short term results include evacuation of the population, abandonment of the capital city, the British government gave money for redevelopment and the unemployment rose due to the down fall in the local tourist industry. Long term results include an exclusion zone set up in the volcanic region, a volcanic observatory was built to monitor the volcano, new roads and a new airport were built, services in the north of the island were expanded, the presence of the volcano resulted in a growth in tourism.

How do volcanic eruptions affect the climate How do volcanic eruptions affect the climate? Volcanoes can have both a cooling and warming effect on the planets climate When volcanoes erupt, they emit a mixture of gases and particles into the air. Some of them, such as ash and sulphur dioxide, have a cooling effect, because they (or the substances they cause) reflect sunlight away from the earth. Others, such as CO2, cause warming by adding to the the greenhouse effect.

How do volcanic eruptions affect people? Volcanoes affect people in many ways, some are good, some are not. Some of the bad ways are that houses, buildings, roads, and fields can get covered with ash. Some of the good ways that volcanoes affect people include producing spectacular scenery, and producing very rich soils for farming. If the ash fall is heavy it can make it impossible to breathe. Lava flows are almost always too slow to run over people, but they can run over houses, roads, and any other structures. Pyroclastic flows are mixtures of hot gas and ash, and they travel very quickly down the slopes of volcanoes. They are so hot and choking that if you are caught in one it will kill you.

How do volcanic eruptions affect the environment? Volcanic eruptions can be extremely damaging to the environment, particularly because of a number of toxic gases possibly present in pyroclastic material. It typically consists mainly of water vapour, but it also contains carbon dioxide and sulphur dioxide gas. Carbon dioxide emitted from volcanoes adds to the natural greenhouse effect. The main good effect that volcanoes have on the environment is to provide nutrients to the surrounding soil. Volcanic ash often contains minerals that are beneficial to plants, and if it is very fine ash it is able to break down quickly and get mixed into the soil.

Why do people live in Hazardous areas? Physical/ environmental - Good Climate, Fertile soil, natural resources for fishing, farming. Human/social - Family heritage, community, work, no choice due to money, lack of education to do other work, steps to be taken reducing being put at risk. Economic - work, from farming, tourism maybe, fishing, it is where property is owned

Webliography http://www.guardian.co.uk/environment/2011/feb/09/volcanoes-climate http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/volcanoes_rev6.sht ml http://volcano.oregonstate.edu/how-do-volcanoes-affect-people http://www.lenntech.com/volcanic-eruptions-environment.htm http://library.thinkquest.org/06aug/00886/index_files/Page307.htm http://ih-igcse- geography.wikispaces.com/3.7+Why+do+people+live+in+hazardous+areas %3F