Farmers prefer to settle near volcanoes because the soil is very fertile due to the lava and volcanic ash deposits. When the volcano erupts, people leave the place for some time, and return to the risk zone after the eruption because the safer places are already inhabited. Moreover, for many people the area around the volcano is home, which they do not want to leave.
Because volcanoes are highly erratic, it becomes very difficult to predict volcanic eruptions. But there are ways of saving lives. Early tremors and earthquakes are often signs of a volcanic eruption—gases are emitted and the volcano expands by a few centimetres to a metre. The volcanologists carefully observe these signs. In 1991, before the eruption of the Pinatubo in Philippines, these signs were interpreted correctly and over 10,000 people were moved to safer places.
We can call a volcano dangerous only when it causes damage to human life. For instance, if a volcano erupts on the almost uninhabited East-Asian peninsula of Kamchatka, it is hardly reported in the news. But, if a volcano starts spewing hot gases and ash in a densely populated area, many lives are at risk. Explosive volcanic eruptions discharge huge quantities of dust and ash, often burying neighbouring areas. Thin, dark magma can flow at a fast speed of up to 1oo km/h making it impossible to escape. Volcanic eruptions can also have far-reaching consequences. When the Indonesian volcano Krakatau erupted in 1883, the volcanic ash reached up to a height of 8o km, which for some time darkened the sky worldwide.
Since the material coming out of the Earth’s core is different in different areas, the resultant changes are also different. If the magma is very hot, more than 1000°C, it is dark, thin and mostly flows quietly. The sides of such volcanoes have gradual slopes. Colder, and hence more viscous, magma often erupts in explosions. The volcanic cone is steeper. Because of the heat in the Earth’s core, geysers (water fountains), solfataras (discharge of hot sulfuric gases), and hot water sources are found near the volcano. These are often used for heating in places such as Iceland.
Volcanoes are natural phenomenon that occurs everywhere, but some places are more prone than the others. The molten rock and gas in the mantle called magma pushes its way upwards and pours to the surface through cracks in the crust. This is a volcano. There are different types of volcanoes; some are explosive others are not, and all erupt as spectacularly as we see on the television. Some eruptions take place unexpectedly, but others can be predicted, which is very important for the people living near a volcano.
Mountains are formed in two ways. When the tectonic plates move, they collide against each other. When the heavy oceanic part of the plate collides with the continental part, it submerges below it. The Andes, for instance, were formed in this way. The other way is when two continents collide with each other; the plates bend at the point of contact and fold up steeply. The Himalayas or the Alps were formed in this way around 35 million years ago and are counted among the ‘young’ mountains of the world. Old mountains, such as Black Forest or the Harz mountains, are lower ranges because peaks have been worn down by rain, ice, and wind over time.
[custom_search_and_filter]