Gases pose the greatest hazard close to the vent where concentrations are greatest. Away from the vent the gases quickly diffuse into the air. Long term exposure to volcanic fumes may aggravate existing respiratory problems. It may also cause headaches and fatigue in healthy people. The gases also limit visibility, when they become trapped by atmospheric conditions.
The greatest beneficial 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. Countries where lots of people live in close proximity to volcanoes to reap the benefits of this rich soil include Indonesia, The Philippines, Japan, Italy and Mexico.
Another, less relevant benefit might be the fact that volcanic slopes are often rather inaccessible, especially if they are steep. Thus they can provide refuges for rare plants and animals from the ravages of humans and livestock.
Earth’s source of water can be attributed to volcanic gases. The process of adding to the water and atmosphere is very slow, but it has been going on for the past 4.5 billion years. Volcanoes helped cool off the earth removing heat from its interior. Volcanic emissions have produced the atmosphere and the water of the oceans. Volcanoes make islands and add to the continents. Our Earth has gained its shape and beauty from its volcanoes. Volcanic deposits are also used as building materials. Basalt and diabase are used for crushed stone, concrete, aggregate roofing granules and railroad ballasts. High-density basalt is used in the concrete shields of nuclear reactors.
Pumice and volcanic ash are used as abrasives, mostly in hand soaps and household cleaners. The finest grades are used to finish silverware, polish metal parts before electroplating, and for woodworking. In ancient Rome lime and volcanic ash were mixed to make cement. In modern times pumice and volcanic ash have been used to make cement for major construction projects (dams) in California and Oklahoma. The materials, which are deposited by volcanoes, have a variety of uses and these can be blamed for the high population around volcanoes. Volcanic materials ultimately break down to form some of the most fertile soils on Earth. People use volcanic products as construction materials, as abrasive and cleaning agents, and as raw materials for many chemical and industrial uses. The internal heat associated with some young volcanic systems has been harnessed to produce geothermal energy. The benefits of living in close proximity to all these resources must outweigh the possibility of death and destruction should an eruption occur.
Volcanoes in Japan are highly explosive. One of the Earth’s largest explosive eruptions was produced 6,300 years ago by Kikai, Japan. No other volcanic region can boast 41 eruptions of such great magnitude. Most of the volcanoes in this region are a result of subduction of westward moving sima under the Asian plate. The volcanoes around Japan are largely basaltic and far more explosive than oceanic hotspot volcanoes like those found in Hawaii. A lot of these volcanoes is under water and is known as submarine volcanoes.
Perhaps Japans most famous eruptions were that of Unzen which occurred in 1792. About a month after lava had ceased flowing from the crater a huge landslide swept through the city of Shimabara and down into the sea generating a tsunami. More than 15,000 people were killed by these awesome after effects of the eruption.
200 years later, in 1991, the Unzen volcano once again began spewing ash. A lava dome appeared at its summit, this dome repeatedly collapsed producing destructive ash flows, which reached a speed of 200 kilometres per hour.
A century ago Bandai volcano collapsed. After a week of seismic activity a large earthquake ensued. A series of violent explosion were heard coming from the stricken volcano.
There are more than 75 active volcanoes in Japan yet the Island is one of the most densely populated in the world. Due to the highly explosive nature of the volcanoes in Japan it is an extremely hazardous place top live. However, do to its explosive nature the land is rich in volcanic deposits, including basalt. As the island is so tightly packed with volcanoes the whole area is rich for farming and quarrying. Making the perfect foundations for a healthy and successful nation. This easy living experienced by the Japanese people gave them time to do other things, as food and resources were abundant. It can be argued that it is because of this that Japan has managed to grow up to become one of the most technologically advanced peoples in the world. Their continual success interrupted ever so often by the eruption of one of the many volcanoes.
Mexico is also plagued with volcanoes. One farmer witnessed the birth of a volcano when he found an 88-foot crack in his cornfield, which had opened up during the night. It grew to 1,353 feet. After nine years of erupting it went dormant. The farmer lost his cornfield and 4,500 people lost their homes.
One of Mexico’s most active volcanoes is Popocatepetl. It became active just before Christmas in 1994 after lying dormant for fifty years. A series of earthquakes were felt this signalled the start of an eruption. A grey ash cloud hung over the volcano summit. 19 villages were evacuated to the east of Popocatepetl when the wind started to blow the ash cloud in their direction.
Since the Spanish arrived at Popocateptl in 1519 the volcano has erupted 15 times. The eruptions have usually been quite mild, consisting of rising ash columns. However, should something more threatening is expelled from the volcano there are 20 million people living in the vicinity.
One of Mexico’s most famous eruptions was that of El Chichon in 1982. Previously the small volcano had not been deemed much of a threat, non-volcanic mountains surround it and nothing more sinister than a few small plumes of smoke had ever been reported. The eruption itself was small but it was the first eruption to have tit atmospheric effects studied. In comparison with an eruption as large as tat of Mount St. Helens, this small eruption was much more significant. Measurements of the atmosphere showed that the atmosphere was 140 times denser than after the Mount St. Helens eruption. El Chichon produced some climate effects. The temperature of the stratosphere increased by 4 degrees C.
An increasing number of people are living near volcanoes in Mexico. As the country develops and the population increases so does the demand for land. As building space becomes sparser people have begun to move closer to the volcanoes. This is not the only reason; they want to take advantage of the rich soil and abundant resources, but also, as a higher class moves in, to look at the scenery. Mount Rainer, near Mexico City, is considered to be the most dangerous volcano in America, although it is dormant now, its previous eruptions have been violent ones. The main reason it is so feared is the massive number of people living near it.
Both of these volcanic regions, Mexico and Japan have the potential to turn into disaster areas. There are a few factors, which draw people to the shadow of an active volcano. Lack of space anywhere else is a big factor which applies to both countries and which is becoming increasingly apparent. Many have found though, that living in this fruitful environment has benefited them greatly. The reasons to live in the volcano wake are the same for both countries but the consequences for those people are different from each country. Japan can easily bounce back form a devastating eruption because of its advanced, acompomplished status. It has the money and the resources to recover sufficiently in a short space of time without a damning effect on the economy. However, Mexico is just trying to achieve this status, it is still developing. A devastating eruption would mean that many were left homeless with nowhere to go, little aid and little comfort as its country is lacking the money and resources to provide those things.
Mexico’s population had little choice about where they could place their homes whereas the Japanese made living in these dangerous environments benefit them. For developing countries the effects can be devastating, less so for those countries who can afford to battle such a catastrophe.