Volcanoes - eZine on the subjects volcanoes and volcanology
Volcanoes are openings in the earth's crust from which lava and gases escape. Volcanic eruptions are an important part of the genesis and of our planet's ecosystem. Volcanism dominates the lives of millions people and created wide parts of the appearance of the earth.
Volcano videographer, Marc Szeglat, reports from the world of volcanoes and volcanic activity. Here you will find general information about volcanoes and volcanology. In the blog you can read latest news about eruptions, photo galleries and videos of volcanic eruptions.
September 25, 2017 Gunung Agung At Gunung Agung on Bali the seismic is elevated and the volcano is ready for an eruption. Volcanologists of the PVMGB register a lot of shallow earthquake in 1-2 km deep. More than 17.000 Villagers were evacuated. The International Airport is ready to close if volcanic ash is a threat to air traffic.
September 24, 2017 Manaro Voui
Eruption on Ambae/Vanuatu is in progress. Around the crater of Manaro Voui volcano an evacuation zone was established. 8,000 residents left their home.
Top 10 Volcanoes
Etna is the biggest volcano in Europe and one of Italy's most active volcanoes. This volcano reaches a high of 3454 m. Etna is a complex shield volcano that can erupt in very different ways. In recent years, the volcano produced a number of phases with paroxysmal eruptions. A new crater cone was formed by these paroxysm.
Erta Alé is a flat shield volcano in the Ethiopian desert Danakil. At its summit there is a caldera. In this a crater has formed in which a lava lake boils. The Lava lake is active since more than 40 years.
Kilauea is located on Big Island Hawaii. This shield volcano is one of the most active volcanoes in the USA. As a hot-spot volcano in the middle of an oceanic plate it produces very thin lava. Time after time, spectacular lava lakes form in the craters in the craters Halema'uma'u and Pu'u 'O'o. Lava flows often run into the sea.
Merapi is located in the direct vicinity of the Indonesian major city Yogyakarta. This volcano is a high-risk volcano. Merapi often erupts explosively, or forms domes and dangerous pyroclastic flows.
Nyiragongo is one of the shield volcanoes, which are normally relatively harmless. A lava lake boils in its crater. But this lake occasionally leaks out through faults in the volcano's flanks. The lava then flows into the Congolese city of Goma and causes major destruction.
Ol Doinyo Lengai
Ol Doinyo Lengai is known among the Massai in Tanzania as the "Mountain of God". The volcano is a rarity for vulcanologists because it produces the coldest lava in the world. The carbonate-based lava looks like mud and is approx. 550 degrees hot.
Piton de la Fournaise
Piton de la Fournaise is located on the island of La Réunion in the Indian Ocean. The volcano has many similarities with the Kilauea. Most eruptions are wonderful natural spectacles, but occasionally villages are destroyed.
Soufrière Hills in the Caribbean is a dangerous dome volcano. In 1995 pyroclastic flows destroyed the capital of the island of Montserrat. Plymouth now looks like a ghost-town.
Vesuvius achieved tragic fame when its pyroclastic flows destroyed the Roman cities of Pompeii, Herculaneum and Stabiae in the year 79 AD. Several million people now live in the area around it. Another disastrous eruption is likely.
Yellowstone has the potential for a super volcano eruption that could change the global climate and lead to an extinction of species. Its cataclysms take place at intervals of approx. 640,000 years. A new eruption is statistically due. The Yellowstone caldera currently houses a unique natural landscape with numerous geysers and hot springs.
FAQ about volcanoes and volcanism
What is a volcano?
A volcano is an opening in the earth's crust. Molten rock and gases that rise from the earth's mantle escape. The molten rock solidifies and accumulates in the form of lava around the opening. The result is an elevation, or a conical shaped mountain referred to as a volcano.
What takes place during a volcanic eruption?
During the ascent of magma to the surface, the principle of hydrostatic pressure relief takes place. Magma is less dense than the surrounding rock and it begins to rise like an air bubble in water. During ascent the external pressure on magma decreases and it is decompressed. Gases that till this point had been dissolved in the magma escape like the opening of a champagne bottle. Once at the surface, lava is expelled into the air by excess gas pressure and the volcano erupts.
Where does the lava come from?
Lava which is still underground and contains much gas is referred to as magma. This is primarily generated by the partial melting of silicate rocks in the earth's mantle. Magma can also form due to the melting of subducted earth crust which occurs along the plate boundaries.
How hot is lava?
Depending on the composition of the lava and the depth and the speed at which the magma rises, the temperature of lava can vary between approximately 500 ° C and 1250 ° C.
How fast can lava flow?
This is dependent on the composition of the lava, its temperature and the concentration of crystals it contains. In general, the more silicon dioxide contained in lava, the colder lava is and the more crystals and bubbles lava contains, the slower the lava. It can become so tough that it no longer flows, and become lodged in the crater (doming) like a brittle cork. At the other extreme are low-viscosity, hot lava flows (pahoehoe lava on Hawaii) that can reach speeds of 100 km / h on steep slopes.
Where are most volcanoes located?
Most volcanoes form along the continental margins and along the plate boundaries around the Pacific Ocean. This region is therefore referred to as the "Ring of Fire". Many volcanoes extend along divergent plate boundaries such as the mid-ocean ridges. Volcanoes also occur along continental fault zones such as the East African Rift Valley. There are also "hot spot" volcanoes such as Hawaii and Yellowstone which are formed by mantle plumes that rise from the core-mantle boundary.
Pyroclastic flows are the main hazard during ash rich eruptions and pelean eruptions on dome volcanoes. If a lava dome, or a huge ash cloud collapse may result in an avalanche of volcanic ashes, blocks and gases. These avalanches can reach speeds up to 400 km / h and be hot over 800 degrees Celsius. Pyroclastic flows can travel long distances and flow over water.
How likely is the eruption of a supervolcano such as Yellowstone?
In the media, the term "supervolcano" is often used and associated with an imminent eruption of the Yellowstone volcano. It is true that a volcanic eruption in the Yellowstone Caldera is statistically overdue and that magma is moving in the caldera underground which leads to the swelling of the caldera floor and the emergence of new hot springs. However, local volcanologists agree that a volcanic eruption is not imminent.
The highest volcano on mainland is Nevado Ojos del Salado in Chile. This volcano is 6885 m high. Its last big eruption took place 1000 years ago. Today the volcano is in a stadium of fumarolic activity.
The highest volcano on world is Mount Mauna Loa on Hawaii. The volcano rises 4139 m above the pacific ocean but from its base on the ground of the sea Mauna Loa measures more than 9000 m. Mauna Loa is the highest Mountain on earth. Another volcano on Hawaii is Kilauea. This is the most active volcano in the USA and for more than 30 years in almost permanent eruption.
The loudest sound on earth in historical time was produced by the volcano Krakatau. In 1883 Krakatau exploded in a huge eruption. Pyroclastic flows and tsunamis were generated and more than 36.000 people lost their live in this disaster. The explosion bang was heard in a distance of 4700 km
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