67
crop with special profit on such soils. The eruption of Mount St. Helens and the regeneration of
life after the explosion were studied in detail
(Lovett 2000; Lindsey 2010). Scientists found
that life is able to reappear on bare, newly formed
volcanic rocks faster than expected. Legumes
that were able to take the nitrogen of the air
appeared ten years after the eruption. Soil production was helped by the organic matter of the
many died living beings in the loose volcanic
sediments. These enabled the appearance of
insects and higher herbivorous animals as well.
Eruptions of volcanoes causing great damage
in a given place in human scale are rare; therefore, direct threat is hardly felt in the society.
Table 3.1 shows that volcanoes characterised by
small eruptions (VEI 3>) over the Holocene were
activated frequently while volcanoes activating
with greater energy are getting less frequent.
Based on the above, the demand of the society
for science to develop increasingly reliable methods to predict major explosions can be considered
justified. In the case of Mount St. Helens, it was
mentioned that scientists working there could
forecast the time of eruption relatively accurately.
Based on Harangi (2015) the scientific bases
of forecast and the devices required for it are
overviewed in the following.
1. The first task is tracing the ascending flow of
magma and determine its velocity.
2. Signs of explosive eruptions include the formation of ruptures of various sizes on the surface of the volcano and the occurrence of
small earthquakes. These have to be monitored and the latter have to be measured using
seismographs.
3. As explosion approaches the surface will be
deformed increasingly. This can be followed
initially by devices then even with the naked
eye—with the help of one-or-two reference
points. The latter is only possible right before
the explosion, i.e. generally too late.
4. As explosion advances the temperature of surface rocks and that of the soil increases. The
temperature could be measured using soil
thermometers. It is important to note that
measurements shall be performed at numerous points.
5. As magma arrives near the surface pressure
will be lower making it effervesce and gases
will escape of it. Gases will move to the surface along ruptures. The intensity of gas
escape can be measured and even the composition of released gases can be analysed; however, special devices are required for it.
In most volcanoes all measurements and observations cannot be performed continuously. Satellite
measurements can cover the largest areas.
Measuring changes in the shape of the surface is
possible using the method of Synthetic Aperture
Radar Interferometry (InSAR). The device is
able to determine surface height changes from
the radar image with 0.1 mm/year accuracy. The
disadvantage of the method is that the satellite
can take 1–2 images of a certain area in a year.
Global positioning system (GPS) is also capable of three-dimensional positioning. Spatial
positioning only gives accurate results if measurements are made simultaneously in numerous
points.
InSAR and GPS measurements can be applied
together and even the volume of the ascending
magma can be estimated on the basis of the
results. In case large amount of gas is also produced and the relief is distorted and uplifted due
to the tension force of the gas as well the estimation of the volume of the magma is more difficult.
Accumulation of gases under the surface is
extremely dangerous because explosions can
erupt enormous quantity of hot gas and volcanic
ash and debris with huge speed destroying living
beings and buildings.
Finally, regarding volcanism, it has to be mentioned that magma generation and ascent is
almost continuous along plate margins forming
mid-oceanic ridges. Conditions at these places
enabled the development of peculiar marine life
that obtains essential energy by chemosynthesis
due to the lack of sunlight. Gases, primarily
hydrogen sulphide and minerals, released into the
ocean have a fundamental role in maintaining the
source of energy of this hidden ecosystem. This
deep sea volcanism, however, has no direct
effects on the life of the society. A significant
potential threat, however, has to be mentioned.
Large amount of methane hydrate (clathrate) in
3.2 Effects of Material Flows in the Mantle and the Lithosphere on the Society
crop with special profit on such soils. The eruption of Mount St. Helens and the regeneration of
life after the explosion were studied in detail
(Lovett 2000; Lindsey 2010). Scientists found
that life is able to reappear on bare, newly formed
volcanic rocks faster than expected. Legumes
that were able to take the nitrogen of the air
appeared ten years after the eruption. Soil production was helped by the organic matter of the
many died living beings in the loose volcanic
sediments. These enabled the appearance of
insects and higher herbivorous animals as well.
Eruptions of volcanoes causing great damage
in a given place in human scale are rare; therefore, direct threat is hardly felt in the society.
Table 3.1 shows that volcanoes characterised by
small eruptions (VEI 3>) over the Holocene were
activated frequently while volcanoes activating
with greater energy are getting less frequent.
Based on the above, the demand of the society
for science to develop increasingly reliable methods to predict major explosions can be considered
justified. In the case of Mount St. Helens, it was
mentioned that scientists working there could
forecast the time of eruption relatively accurately.
Based on Harangi (2015) the scientific bases
of forecast and the devices required for it are
overviewed in the following.
1. The first task is tracing the ascending flow of
magma and determine its velocity.
2. Signs of explosive eruptions include the formation of ruptures of various sizes on the surface of the volcano and the occurrence of
small earthquakes. These have to be monitored and the latter have to be measured using
seismographs.
3. As explosion approaches the surface will be
deformed increasingly. This can be followed
initially by devices then even with the naked
eye—with the help of one-or-two reference
points. The latter is only possible right before
the explosion, i.e. generally too late.
4. As explosion advances the temperature of surface rocks and that of the soil increases. The
temperature could be measured using soil
thermometers. It is important to note that
measurements shall be performed at numerous points.
5. As magma arrives near the surface pressure
will be lower making it effervesce and gases
will escape of it. Gases will move to the surface along ruptures. The intensity of gas
escape can be measured and even the composition of released gases can be analysed; however, special devices are required for it.
In most volcanoes all measurements and observations cannot be performed continuously. Satellite
measurements can cover the largest areas.
Measuring changes in the shape of the surface is
possible using the method of Synthetic Aperture
Radar Interferometry (InSAR). The device is
able to determine surface height changes from
the radar image with 0.1 mm/year accuracy. The
disadvantage of the method is that the satellite
can take 1–2 images of a certain area in a year.
Global positioning system (GPS) is also capable of three-dimensional positioning. Spatial
positioning only gives accurate results if measurements are made simultaneously in numerous
points.
InSAR and GPS measurements can be applied
together and even the volume of the ascending
magma can be estimated on the basis of the
results. In case large amount of gas is also produced and the relief is distorted and uplifted due
to the tension force of the gas as well the estimation of the volume of the magma is more difficult.
Accumulation of gases under the surface is
extremely dangerous because explosions can
erupt enormous quantity of hot gas and volcanic
ash and debris with huge speed destroying living
beings and buildings.
Finally, regarding volcanism, it has to be mentioned that magma generation and ascent is
almost continuous along plate margins forming
mid-oceanic ridges. Conditions at these places
enabled the development of peculiar marine life
that obtains essential energy by chemosynthesis
due to the lack of sunlight. Gases, primarily
hydrogen sulphide and minerals, released into the
ocean have a fundamental role in maintaining the
source of energy of this hidden ecosystem. This
deep sea volcanism, however, has no direct
effects on the life of the society. A significant
potential threat, however, has to be mentioned.
Large amount of methane hydrate (clathrate) in
3.2 Effects of Material Flows in the Mantle and the Lithosphere on the Society