Get our newsletter!
: "One of the most eye-catching guides to the world’s volcanoes ever published.
: Our professional team of volcanologists and photographers offers unique travel opportunities: volcano expeditions, photo tours, and relaxed walking & study tours.
The Volcano Adventure Guide
: Excellent information and background for anyone wishing to visit active volcanoes safely and enjoyably. The book presents guidelines to visiting 42 different volcanoes around the world.
: spaces available / : guaranteed / : few spaces left / : booked out
Maintaining the volcano and earthquake news sections on this website, the free Volcano Webcams tool
and interactive map widget
is a free-time, both time- and server cost intensive effort.
If you find the information useful and would like to support us, and help keep it alive and improve it, please consider making a small donation
. Thank you!
Illustrated Volcano Glossary
Volcanology: volcanic ash
Ash plume from an explosive eruption at Etna volcano (Italy)
Snow and ash from Hekla volcano's eruption in 2000
Ash emission from Etna' s NE crater (in 1999)
Ash deposits from numerous, turbulent pyroclastic flows during the Minoan eruption of Santorini volcano, Greece.
Volcanic ash is the term for all fine-grained volcanic products (smaller than 2 mm), normally magma or older rock fragmented during explosive eruptions.
Volcanic ash has nothing to do with fire, but is a mere definition of grain-size. Ash can range in size from sandy to extremely fine; any fragment ejected by a volcano less than 2 mm in diameter is called ash. It may consists of freshly ejected lava (usually turned into a glass shard because of rapid cooling), older fragmented rock, or small crystals.
Ash is produced by explosive activity when expanding gas fragments other material (uprising lava, surrounding rock). The more explosive an eruption, the more ash is usually produced. Hot ash can easily mix with air and erupted gasses and then form an eruption column. If the eruption column is buoyant it will rise to tens of km into the atmosphere during violent eruptions. These ash clouds can then be carried hundreds and thousands of km by wind, even circle the entire hemisphere for a few years before the finest particles are washed out. Ash-loaded eruption columns can also become too dense to rise vertically; instead, they will then collapse to form (usually hot) avalanches, so-called pyroclastic flows.
It is very common to observe that ash particles stick together to form small aggregates, so-called accretionary lapilli, enabling the ash to deposit because of the dramatically increased fall velocity of the aggregate.
Volcanic ash is a serious hazard to life and property; it can cause breathing problems, heavy ash loads on buildings cause the roofs to collapse. Ash plumes in the atmosphere threaten air traffic seriously, because ash even in small concentrations can disable jet engines.
More on VolcanoDiscovery:
Types of tours
: We offer a broad variety of tours to volcanic areas: volcano expeditions and specials, discovery tours with hiking, photography, nature and culture, pilot tours and private custom tours.
List and interactive map of recent earthquakes world-wide.
Photos from Greece
: We have traveled and studied extensively in Greece, in particular on its active volcanic areas such as Santorini, Nisyros, Milos, Methana.
Do you know which is the biggest volcano in the world?