Aswolken

Aswolken, or ash clouds, are clouds of fine volcanic ash suspended in the atmosphere following explosive volcanic activity. They consist of tephra particles, typically silica-rich glassy shards and pumice fragments, ranging from microscopic to millimeter sizes, often accompanied by volcanic gases such as water vapor and sulfur dioxide. The cloud can form a vertical eruption plume and, depending on eruption energy and atmospheric conditions, rise to several tens of kilometers above the vent.

Once formed, ash clouds are transported by atmospheric winds, becoming dispersed over large areas and sometimes encircling the globe during major eruptions. The dispersion is influenced by wind patterns, atmospheric stability, and particle size, making ash clouds unpredictable in their spread and duration. Observable indicators include satellite imagery, seismic signals, and ground-based observations, complemented by numerical dispersion models.

Hazards associated with aswolken are substantial. Ash is highly abrasive and can cause engine failure or shutdown in aircraft, damage to sensors and cooling systems, and reduced visibility for pilots. Ground deposition can contaminate water supplies, abrade machinery, disrupt agriculture, and pose respiratory health risks to people and animals. Sulfur gases released with ash can form aerosols and contribute to acid rain and short-term climate effects.

Monitoring and response involve Volcanic Ash Advisory Centers and meteorological agencies that issue advisories, NOTAMs, and aviation restrictions. Satellite sensors, radar, and lidar support plume tracking, while dispersion models inform risk assessment and mitigation for affected regions. Notable examples include the ash clouds from the 2010 Eyjafjallajökull eruption in Iceland and the 1991 Pinatubo activity.