The world active volcanoes often coincide with a earth forming plates border. The mid ocean ridges produce a volcanic materials as constantly. There are a subduction zones and ocean pits like Japan, Philipin, Chilli, Italy among regions having an active volcano. As it as seen, these regions coincide with the world seismic zones, but the volcanic activity is not only seen at place of the transforming faults like North-Turkey or Sun-enderyas fault at America's California because, the melt material transition from the mantle to the surface is not made, thus there is not any active volcano. there are a very much lava mid ocean ridts at voleanos , but volcanos of under thrust zones often are an explosive and they have less lava.
There often are a human fatalities caused from volcanism at volcanic regions of continental margin or subduction regions.
At summary, we can say that subduction or underthrust regions are a dangerous for humans life due to seismicity and volcanism, however this rule doesn't completely apply to allover of regions.
Some of volcanos are occurred resulting from hot points at, like Hawai-Islands volcanos.
These regions (hot points) are not over the plates border, but what the volcanic eruptions occur in these regions. Canadian Tuzo Wilson and American Jason Morgan proposed a hot points theory. According to it, at some of earth regions , there are a hot points that it is made a mantle melt there, and the caused melt eject after rising. These eruptions are seen inside lithosphere plates, and the motive plate will be melted and hole at a different points resulting from the plates movement and being fix of hot points place.
For this reason, Hawaii-Islands have been resulted along with one line.
98% voclanos occur at regions that have a past volcanos. The volcanic occurrence has had and has a less fatalities than earthquake.
In general, The volcanism don't affect on people life at most of world regions extensively, and only it can be a dangerous at very active regions that we obtain a new volcanos report there every year.
The duration of one volcanic eruption can take from half of hour to years. But, at non- subduction regions, it is an average about 2 months.
When does the intensity of one eruption is more during that eruption? At explosive eruptions, early days have a maximum intensity, and even first hours have a maximum intensity. Of course, we can not conclude that with passing first hours of eruption, the danger has been eliminated.
But it is possible that a few days or even one month after a first eruption, the most intensity of eruptions occur, like Sant-HelenMountain eruption(1980) or Kerakatova (1882) that it's the most intensity of eruptions has been one month after first eruption.
Well, now Damavand with a last lavas with 38500 years old, do it erupt again? Be sure, no. But given the start of eruption is accompany with the earthquake, we can keep away from dangers of volcanism given it.
For finding information from the eruptions times of one volcano, it is useful using geochronology methods(determining of stones radiometry age), as we can find it's eruptions date given the lavas of one volcano and their radiometry age determination
Prediction of volcanic activities:
These predictions are very hard, and sometimes are false, and they are based on two principles, one principle is volcano geological knowledge and other one is the setting of one control station at volcano area.
Given the geological studies and age determination of one volcano, we can know it's activities type, number of eruptions, order and rule of eruptions and sleep time of volcano.
The setting of the control station at volcanos that it is possible their activity, is useful. In these stations, seismographs and soil movement test device are installed which they are named as tilt meter.
The penetration of magma from depth to the surface is caused to break stones under volcano, that these fractures cause the shakings. By continuing the fractures and rising the magma upward, the rised magma will eject finally.
Confrontation with a risk:
The best way of the confrontation against risk of eruptions and volcanoes activities, is a leave and discharge of region.
At dated on 13.Nov.1985, geologists reported from Colombia Nevadodel Roiez volcanism, but no one regarded it.
The authorities didn't order to discharge Armero, small Town.
As a result of the mud flood, Armero town was destroyed and were killed about 2000 persons.
The preparation of volcanos risk maps is a simple work due to observe the volcano devices on earth surface.
The eruption type is an important at determining an amount of risk. As we must know that whether the eruption is an explosive or mild, that this case will change the fate of work very much. Because the speed of Lava movement is 10-100m/h, while nuee ardent has 200 km/h speed.
In fact, the nuee ardent is a hot gases and solid particles of volcano that fall on the people around volcano. The amount of gas or solid particles can be very different.
Environment energy (Energy sources-Effects of energy sources development):
At a present, the grow at the energy consumption is a triple the population grow. The fossil fuels are cheapest of energy sources for humans, and form 95% world consumption fuel. The most important of energy sources that can use by humans are: solar energy that there is at our environment without any contamination and the solar energy equivalent to 6milion oil gallon reflects to Iran daily. In fact, the energies source caused from fossil fuels is the same solar energy, that the grow of plants and animals has been caused by it.
The atomic energy is caused from atoms core fission and it is able to back much energy to us that the production and the use of it needs to the advanced technology.
One atomic reactor and related PowerStation is established and usable at high cost, and the environmental features of the caused wastes will continue at least by 1500 years later resulting from making these wastes. The atomic wastes disposal is a problem that there is for reactors owner? And nuclear energy consumers, and it is not easily achievable the places of nuclear wastes disposal. As the disposal of these wastes is not acceptable by any country, unless the country of consumer accept it. Because soils or waters that the nuclear wastes are buried in them, will become a polluted and un usable for humans.
Among other energy sources, there are a fossil fuels. The use of these energy sources, on one way, is caused to consume an oxygen and, on other way, the environment pollution, and today, it threats the human life on the earth. These fuels are: oil, gas and coal that are used on different ratios at a different countries.
Another one of energy sources is a flowing water that can be used using dams. This energy source is usable more at bulk water regions of the world, and it will be usable after converting to the electric energy.
The wind energy, at some of the world points that are windy, is usable easily.
This energy source has a less value compared to other energy sources has a less value compared to other energy sources, and it is recoverable at a special regions.
Today, the use of the melt material energy has been considered at regions of the world that have an active volcanos. As at regions of Island, the hot water and thermal energy are used for heating the houses.
The use of volcanic zones energy is possible as there are a water storages also. Because this is a water that first it must be heated and then the existing energy will be usable.