The volcano ancient Romans called the god of fire and blacksmithing. In honor of him, a small island was named in the Tyrrne Sea, the top of which was erupted in the fire and clouds of black smoke. Subsequently, all the firebreathing mountains began to be called in honor of this God.
The exact number of volcanoes is unknown. It also depends on the definition of a “volcano”: for example, there are “volcanic fields”, which make up hundreds of individual eruption centers, which are all associated with the same magmatic camera, and what can be considered or not considered the only “volcano”. There are probably millions of volcanoes that have been active throughout the life of the Earth. Over the past 10,000 years, according to the Smithsonian Institute of Volcanology, there are about 1,500 volcanoes, which, as you know, were active, and even more underwater volcanoes are unknown. There are about 600 existing craters, including 50-70 erupted annually. The rest are called extinct.
Volcanoes, as a rule, have a conical shape with a gentle sole. Are formed by the formation of faults or displacement of the earth’s crust. When part of the earth’s upper mantle or lower bark melts, magma is formed. The volcano is essentially a hole or a ventilation hole through which this magma and dissolved gases that it contains come out. Although there are several factors that cause volcanic eruption, three prevail:
Let’s briefly dwell on the description of these processes.
When the stone is melted inside the earth, its mass remains unchanged. Increasing volume creates an alloy, the density of which is lower than the environmental density. Then, by virtue of its buoyancy, this lighter magma rises to the surface. If the density of the magma between the zone of its generation and the surface is less than the density of others and overlying rocks, the magma reaches the surface and erupts.
Magma of the socalled Andesit and Riolithic compositions also contain dissolved volatile substances, such as water, sulfur dioxide and carbon dioxide. The experiments showed that the amount of dissolved gas in magma (its solubility) at atmospheric pressure is zero, but increases with an increase in pressure.
In Andesitic Magma, saturated with water, six kilometers from the surface, about 5 % of its weight dissolves in water. When this lava moves to the surface, the solubility of water in it decreases, and therefore the excess moisture is separated in the form of bubbles. As it approaches the surface, more and more fluid is released, thereby increasing the ratio of gas magmas in the channel. Когда объем пузырьков достигает около 75 процентов, лава распадается на пирокласты (частично расплавленные и твердые фрагменты) и взрывается.
The third process that causes volcanic eruptions is the appearance of a new magma in the hearth, which is already filled with lava of the same or other composition. This mixture makes part of the lava in the cell move up the channel and erupt on the surface.
Although volcanologists know these three processes well, they cannot yet predict the eruption of the volcano. But they have achieved significant progress in forecasting. It involves the probable nature and time of eruption in the controlled crater. The nature of the exit of the lava is based on the analysis of prehistoric and historical behavior of the volcano under consideration and its products. For example, a volcano, violently erupting ash and volcanic mudflows (or lahara), will probably do the same in the future.
Determination of the eruption time
The determination of the eruption time in the controlled volcano depends on the measurement of a number of parameters, including, but, not limited to them:
An excellent example of successful forecasting occurred in 1991. Volcanologists from the US geological service precisely predicted on June 15 the eruption of the Pinatubo volcano in the Philippines, which allowed to evacuate the Clark air base in a timely manner and save a thousand lives.