forming shallow dikes. Thus, the Kilauea volcano’s magma supply is estimated to
be 0.18 km
3 /year (Cayol et al. 2000).
Other sub-aerial volcanoes forming the island of Sao Miguel (in the Azores)
have a smaller production rate than Hawaii (0.02–0.03 km
3 per 100 years, Moore
1991) so it probably took longer to form an island in this area. During 1977, the
Karla volcano in Iceland was monitored at the same time as an earthquake while
the volcano deflated and magma poured along the flanks forming rift zones. It was
calculated that the tremor hypocenters migrated at a rate of 0.5 m/s along the rift
zone (Rutherford and Gardner 2000).
One of the tallest volcanoes in the world is located on Big Island of Hawaii.
This now inactive volcano is called Mauna-Kea and is about 8000 m high from its
base on the sea floor. It is taller than mount Mt. Everest in the Himalayas and its
summit culminates at 4100 m above sea level. Because of its privileged location
standing above the clouds, Mauna-Kea has become the site of an international
astrophysical observatory. Seven nations have built observatories on top of this
volcano. On the flank of the volcano at an altitude of 2000 m, there is a relay-zone
rest station for the staff to get accustomed to the high altitude while they spend the
night before going up to work in the observatories on the top.
Historical Eruptions
Even if there are fewer active volcanoes on emerged landmasses than under water,
they are the most spectacular because of their direct impact on human society and
our economy. During the past 500 years, volcanic eruptions have been responsible
for more than 200,000 deaths. It is of primordial interest for human beings to have
knowledge of the sea floor environment in order to better understand the physical
processes involved in producing natural hazards. For example monitoring deep
trenches in subduction zones and recording tectonic activity in active major faults
that can trigger earthquakes, such as the earthquake causing the tsunami of
Fukushima in March, 2011, might help to inform people before other natural
catastrophes occur. These tectonic stress-induced activities may be interrelated and
could affect structures that are thousands of kilometers away from each other.
Society expects Earth scientists to provide adequate and accurate warnings for
natural hazards. In order to estimate the risks of eruptions and/or earthquake
hazards, it is important for geologists to have a good knowledge about the history,
the composition and the structure of the area at risk. There are national and
international associations, which are involved in surveying and monitoring natural
hazards, but this is not yet operational everywhere in World. The lack or absence
of a continuous monitoring system in naturally high-risk areas could be disastrous
to humans. Blong (1984) estimated that on an average about 640 people per year
died from natural hazards in the twentieth century. Unfortunately, it is only after a
major disaster that government findings are made available for studying natural
hazards. For example, we now know that the Pacific ocean is one of the best
Growth of a Volcano
135
be 0.18 km
3 /year (Cayol et al. 2000).
Other sub-aerial volcanoes forming the island of Sao Miguel (in the Azores)
have a smaller production rate than Hawaii (0.02–0.03 km
3 per 100 years, Moore
1991) so it probably took longer to form an island in this area. During 1977, the
Karla volcano in Iceland was monitored at the same time as an earthquake while
the volcano deflated and magma poured along the flanks forming rift zones. It was
calculated that the tremor hypocenters migrated at a rate of 0.5 m/s along the rift
zone (Rutherford and Gardner 2000).
One of the tallest volcanoes in the world is located on Big Island of Hawaii.
This now inactive volcano is called Mauna-Kea and is about 8000 m high from its
base on the sea floor. It is taller than mount Mt. Everest in the Himalayas and its
summit culminates at 4100 m above sea level. Because of its privileged location
standing above the clouds, Mauna-Kea has become the site of an international
astrophysical observatory. Seven nations have built observatories on top of this
volcano. On the flank of the volcano at an altitude of 2000 m, there is a relay-zone
rest station for the staff to get accustomed to the high altitude while they spend the
night before going up to work in the observatories on the top.
Historical Eruptions
Even if there are fewer active volcanoes on emerged landmasses than under water,
they are the most spectacular because of their direct impact on human society and
our economy. During the past 500 years, volcanic eruptions have been responsible
for more than 200,000 deaths. It is of primordial interest for human beings to have
knowledge of the sea floor environment in order to better understand the physical
processes involved in producing natural hazards. For example monitoring deep
trenches in subduction zones and recording tectonic activity in active major faults
that can trigger earthquakes, such as the earthquake causing the tsunami of
Fukushima in March, 2011, might help to inform people before other natural
catastrophes occur. These tectonic stress-induced activities may be interrelated and
could affect structures that are thousands of kilometers away from each other.
Society expects Earth scientists to provide adequate and accurate warnings for
natural hazards. In order to estimate the risks of eruptions and/or earthquake
hazards, it is important for geologists to have a good knowledge about the history,
the composition and the structure of the area at risk. There are national and
international associations, which are involved in surveying and monitoring natural
hazards, but this is not yet operational everywhere in World. The lack or absence
of a continuous monitoring system in naturally high-risk areas could be disastrous
to humans. Blong (1984) estimated that on an average about 640 people per year
died from natural hazards in the twentieth century. Unfortunately, it is only after a
major disaster that government findings are made available for studying natural
hazards. For example, we now know that the Pacific ocean is one of the best
Growth of a Volcano
135