Volcanic Eruption and Wildfires

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    Volcanic

    Eruptions

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    How are Volcanoes Formed?Volcanoes are formed in various sizes and shapes. Cone-shaped volcanoes

    are the most common ones. Some volcanoes are only a long crack in the earth's

    crust. Volcanoes that resemble high mountains are the ones that are formed due to

    many volcanic eruptions.

    According to the theory of plate tectonics, the crust of the earth has many

    rigid plates that are floating. It is the pressure created by the currents caused by the

    heat energy from the earth's core that causes the movement of these plates. When

    the pressure becomes intense, the plates either move towards each other or away

    from each other horizontally.

    When two plates collide, one of the plates goes beneath the other, causing a

    friction in the earth's crust. The pressure caused by the friction will cause the

    underlying rocks to melt and make the magma rise. The hot, orange-red lava is

    thrown out of the mountaintop. Volcanoes of this type are considered threats to

    living beings. Their eruptions are violent and cause destruction to all living things in

    their proximity.

    A gap is formed when two layers of plates move away from each other. The

    hot lava rises through this gap. Volcanoes of this type occur on the ocean bed and

    is not visible. However, if a volcano erupts violently from an ocean, it rises above the

    ocean to create an island. Some volcanoes are formed in hotspot areas. The

    hotspots are the center-points of the earth plates. These plates are connected to

    the hot mantle of the earth. In brief, volcanoes are formed when the hot lava(magma) shoots out of the earth's crust. The lava becomes hard on cooling down to

    form a volcanic mountain.

    Causes of Volcanic Eruption

    The buoyancy and pressure of the gas within the earth's crust cause a

    volcano to erupt. Magma is formed when the upper mantle of the earth melts. A

    volcano erupts when the magma (the hot liquid) rises upwards by the pressure ofgas that is dissolved in it. This is one of the three predominant theories.

    According to the second theory, magma contains dissolved substances such

    as water, sulfur dioxide and carbon dioxide. The solubility of the gases is high as the

    pressure increases. The solubility of water decreases as the magma moves closer to

    the earth's surface and eventually separates from the magma.When the ratio of the

    gases becomes more in magma it causes the magma to disintegrate into

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    pyroclasts, a combination of partially molten and solid fragments, and the volcano

    erupts explosively.

    The third theory says that a volcano erupts when new magma is injected into

    a chamber that is already brimming with magma of similar or different compositions.

    The eruption occurs when the magma moves upwards due to the additional push

    exerted by the injection of new magma.

    Positive and negative effects of an eruption

    Positive Negative

    The dramatic scenery created by volcanic

    eruptions attracts tourists. This brings income to

    an area.

    Many lives can be lost as a result of a

    volcanic eruption.

    The lava and ash deposited during an

    eruption breaks down to provide valuable

    nutrients for the soil. This creates very fertile soilwhich is good for agriculture

    If the ash and mud from a volcanic

    eruption mix with rain water or melting

    snow, fast moving mudflows are created.These flows are calledlahars.

    The high level of heat and activity inside the

    Earth, close to a volcano, can provide

    opportunities for generating geothermal

    energy.

    Lava flows and lahars can destroy

    settlements and clear areas of woodland

    or agriculture.

    Human and natural landscapes can be

    destroyed and changed forever.

    Mount Pinatubo is part of a chain of composite volcanoes along the Luzon arc onthe west coast of the island (area map). The arc of volcanoes is due to the

    subduction of the Manila trench to the west. The volcano experienced major

    eruptions approximately 500, 3000, and 5500 years ago. The events of the 1991

    Mount Pinatubo eruption began in July 1990, when a magnitude 7.8 earthquake

    occurred 100 kilometers (62 miles) northeast of the Pinatubo region, determined to

    be a result of the reawakening of Mount Pinatubo. In mid-March 1991, villagers

    around Mount Pinatubo began feeling earthquakes and vulcanologists began to

    study the mountain. (Approximately 30,000 people lived on the flanks of the volcano

    prior to the disaster.) On April 2, small explosions from vents dusted local villages with

    ash. The first evacuations of 5,000 people were ordered later that month.

    Earthquakes and explosions continued. On June 5, a Level 3 alert was issued for two

    weeks due to the possibility of a major eruption. The extrusion of a lava dome on

    June 7 led to the issuance of a Level 5 alert on June 9, indicating an eruption in

    progress. An evacuation area 20 kilometers (12.4 miles) away from the volcano was

    established and 25,000 people were evacuated.

    http://geography.about.com/od/globalproblemsandissues/a/pinatubo.htm

    http://geography.about.com/od/globalproblemsandissues/a/pinatubo.htmhttp://geography.about.com/od/globalproblemsandissues/a/pinatubo.htmhttp://geography.about.com/od/globalproblemsandissues/a/pinatubo.htm
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    Wildfires

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    Description:A is any uncontrolledfirein combustible vegetation that occurs in the

    countryside or awildernessarea. Other names such as , ,

    , , , , , , and may be

    used to describe the same phenomenon depending on the type ofvegetationbeing

    burned. A wildfire differs from other fires by its extensive size, the speed at which

    it can spread out from its original source, its potential to change direction

    unexpectedly, and its ability to jump gaps such as roads, rivers andfire breaks.

    Wildfires are characterized in terms of the cause of ignition, their physical

    properties such as speed ofpropagation, the combustible material present, and the

    effect of weather on the fire.

    Wildfires occur on every continent exceptAntarctica. Wildfires are a common

    occurence inAustraliaespecially during the long hot summers usually experienced in

    the southern regions such aVictoria, Australia. Due toAustralia'shot and dry

    climate, wildfires (commonly refered to asbushfiresin Australia) pose a great risk

    to life and infrastrucure during all times of the year, though mostly throughout the

    hotter months of summer and spring.. In the United States, there are typically

    between 60,000 and 80,000 wildfires that occur each year, burning 3 million to

    10 million acres of land depending on the year. Fossil records and human history

    contain accounts of wildfires, as wildfires can occur in periodic intervals Wildfires can

    cause extensive damage, both to property and human life, but they also have various

    beneficial effects on wilderness areas. Some plant species depend on the effects offire for growth and reproduction, although large wildfires may also have negative

    ecological effects.

    Strategies of wildfire prevention, detection, and suppression have varied over

    the years, and international wildfire management experts encourage further

    development of technology and research. One of the more controversial techniques

    iscontrolled burning: permitting or even igniting smaller fires to minimize the

    http://en.wikipedia.org/wiki/Firehttp://en.wikipedia.org/wiki/Wildernesshttp://en.wikipedia.org/wiki/Bushfirehttp://en.wikipedia.org/wiki/Bushfirehttp://en.wikipedia.org/wiki/Peat#Fireshttp://en.wikipedia.org/wiki/Vegetationhttp://en.wikipedia.org/wiki/Fire_breakhttp://en.wiktionary.org/wiki/propagationhttp://en.wikipedia.org/wiki/Antarcticahttp://en.wikipedia.org/wiki/Australiahttp://en.wikipedia.org/wiki/Victoria,_Australiahttp://en.wikipedia.org/wiki/Australia%27shttp://en.wikipedia.org/wiki/Bushfireshttp://en.wikipedia.org/wiki/Controlled_burnhttp://en.wikipedia.org/wiki/Controlled_burnhttp://en.wikipedia.org/wiki/Controlled_burnhttp://en.wikipedia.org/wiki/Bushfireshttp://en.wikipedia.org/wiki/Australia%27shttp://en.wikipedia.org/wiki/Victoria,_Australiahttp://en.wikipedia.org/wiki/Australiahttp://en.wikipedia.org/wiki/Antarcticahttp://en.wiktionary.org/wiki/propagationhttp://en.wikipedia.org/wiki/Fire_breakhttp://en.wikipedia.org/wiki/Vegetationhttp://en.wikipedia.org/wiki/Peat#Fireshttp://en.wikipedia.org/wiki/Bushfirehttp://en.wikipedia.org/wiki/Wildernesshttp://en.wikipedia.org/wiki/Fire
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    amount of flammable material available for a potential wildfire. While some wildfires

    burn in remote forested regions, they can cause extensive destruction of homes and

    other property located in thewildland-urban interface: a zone of transition between

    developed areas and undeveloped wilderness.

    Wildfires are mainly caused due to climate change and human activities. Some of the

    common causes of wildfires are:

    Wildfires caused due to lightning occur at a frequency of three tofive per year. Since lightning is usually associated with rain, such wildfires do

    not spread over large areas.

    Majority of the cases of wildfires occur due to humancarelessness, especially while handling firewor