The volcanoes in Iceland emit ash clouds because they contain a large amount of silica, a component that, when it erupts, forms fine and light volcanic ash.
Iceland is located right on the border between two major tectonic plates: the North American plate and the Eurasian plate. These plates slowly drift apart each year by about 2 cm, which is relatively fast on a geological scale. As a result, this releases magma from the Earth's mantle, a hot and viscous layer beneath the plates. Additionally, the island is situated directly above a hotspot, a kind of column of very hot rocks rising from the depths of the Earth. This unique combination (plate boundary + hotspot) makes Icelandic volcanic activity particularly frequent and spectacular.
Icelandic volcanoes are mainly known for their subglacial and explosive eruptions. The direct interaction between very hot magma and ice causes instant vaporization of water: as a result, a powerful explosion fragments the rock into tiny particles. This sends enormous amounts of fine, lightweight ash into the atmosphere. A unique feature of Icelandic volcanoes is the alternation between effusive phases (fluid lava flows) and explosive phases, which makes their eruptions highly unpredictable. Moreover, their famous volcanic fissures, which are very numerous, function somewhat like aligned chimneys simultaneously spewing lava and fragments of rock over kilometers. It is this mixture of magma, water, ice, and aligned fissures that makes Icelandic volcanoes specialists in producing large clouds of ash.
The clouds of volcanic ash simply come from the brutal fragmentation of magma when a volcano erupts. Basically, when the pressure accumulated inside the volcano becomes enormous, the gas-charged magma rises quickly to the surface. At that precise moment, there is a kind of violent "devitrification" where the magma breaks into many tiny particles, thus forming volcanic ash. The more viscous and gas-rich the magma is, the more it explosively erupts, releasing these tiny fragments into the air. Then, these fine particles remain suspended and create what is called the ash cloud. The wind does the rest of the work by transporting them sometimes very far away.
When water from glaciers comes into contact with magma, it doesn't mix well. This causes a brutal cooling of the magma, resulting in hyper-violent explosions: this is called a phreatomagmatic eruption. All this agitation literally shatters the lava into tiny quickly cooled pieces, thus creating tons of volcanic ash. And since Iceland has quite a few giant glaciers right above its volcanoes, it’s really the perfect recipe for producing a lot of that famous ash. The local climate, with its high humidity and strong winds, also plays a role: it weakens the volcanic materials already in suspension and facilitates their dispersion far and wide.
Icelandic ash clouds can seriously disrupt air traffic. In 2010, the eruption of the volcano Eyjafjallajökull led to the cancellation of thousands of flights and stranded millions of passengers. These tiny ash particles, when they reach aircraft engines, melt and form a very dangerous layer of glass. When winds are strong, the ash can travel very quickly and very far—up to several hundred or thousands of kilometers in just a few days, even affecting very distant regions. On the ground, the ash covers crops and pastures, directly impacting agriculture, livestock, and drinking water. Residents sometimes have to wear masks to avoid respiratory issues caused by inhaling these irritating volcanic dust particles.
In Icelandic, the word 'jökulhlaup' refers to a sudden and spectacular flood caused by the rapid melting of a glacier due to the heat from a volcanic eruption.
Iceland has about 130 active or dormant volcanoes, making it one of the countries with the highest volcanic density in the world.
Icelandic volcanoes produce particularly fine and abrasive ash that can damage aircraft engines, which is why even a small amount of these particles can lead to airspace shutdowns.
The name 'Eyjafjallajökull' literally means in Icelandic 'the glacier of the island mountains,' and its complex pronunciation challenged journalists worldwide during the 2010 eruption.
The volcanoes of Iceland primarily result from the island's unique position straddling two divergent tectonic plates (the North American Plate and the Eurasian Plate), combined with the presence of a hotspot. This combination leads to eruptions that are both explosive and very rich in volcanic ash.
In general, volcanic ash clouds from Iceland can persist in the atmosphere for a few days to several weeks, depending on the strength of the eruption and the weather conditions.
It is advisable to wear a suitable respiratory mask, to limit outdoor activities, to protect the eyes with safety glasses, and to close windows and doors in order to minimize respiratory and eye irritation related to fine particles.
Volcanic ash clouds can lead to the cancellation of numerous flights, disrupt international air traffic, and cause severe damage to aircraft engines due to their abrasive composition.
Although it is impossible to predict exactly when an eruption will occur, scientists monitor precursor signs such as seismic activity, ground deformation, and magma movement to anticipate volcanic risks in Iceland.
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