Volcanic ash clouds can be visible for thousands of kilometers because the ash particles suspended in the atmosphere can be transported over long distances by the winds, reflecting and scattering sunlight.
During a major eruption, ash clouds can reach impressive heights, averaging between 10 and 20 km in altitude. The most violent volcanoes even eject ash up to 30 km or higher, directly impacting the stratosphere. At this altitude, particles remain suspended for longer, escaping the turbulent atmospheric layers below. As a result, they spread over thousands of kilometers, sometimes even in just a few days. A striking example: the eruption of Pinatubo in 1991 propelled ash over 35 km high, enhancing visibility across several countries.
Volcanic ash clouds are easily carried over very long distances by the powerful winds that blow in the upper layers of the atmosphere. At these altitudes, jet streams, which are true aerial highways, push volcanic particles at high speeds over thousands of kilometers. Moreover, the direction taken by these ashes directly depends on these winds, which explains why regions located far from the volcano can see volcanic plumes arrive. These fast and consistent winds facilitate the horizontal dispersion of fine particles, thus allowing an ash cloud to spread over a large part of the globe in just a few days.
Volcanic particles are mainly composed of tiny fragments of rock, volcanic glass, and sometimes even crystals. Very fine, they can remain suspended in the air for a long time. Their small sizes, typically less than a few micrometers, greatly facilitate their transport over vast distances. These tiny particles effectively reflect sunlight, making them well-visible even far from their place of origin. When sunlight strikes these particles, they scatter or absorb light very efficiently, enhancing a kind of grayish veil or haze that can sometimes appear orange, visible thousands of kilometers away. Finally, their large quantity and uniform dispersion in the atmosphere significantly increase their visibility at very long distances.
Weather phenomena play a crucial role in perceiving ash clouds from long distances. For example, a clear and open sky particularly facilitates direct observation from the ground. Similarly, during sunrise or sunset, the specific angle of the rays allows for optimal reflection on volcanic particles, making ash clouds even more apparent and visible with their often reddish or orange hue. Weather systems such as anticyclones can also encourage the slow and extensive dispersion of clouds over very long distances, further increasing their visibility. In contrast, rain, snow, or high humidity can limit visibility at a distance by bringing these volcanic particles to the ground or obscuring them.
Modern weather satellites can detect and track volcanic ash clouds in nearly real-time, which greatly aids civil aviation by reducing the risk for international flights.
An aircraft encountering a volcanic cloud can suffer significant damage, as the particles can melt in the hot engines and then quickly solidify as they cool, potentially leading to a critical engine failure.
The spectacular colors observed during sunsets after a volcanic eruption come from volcanic particles dispersed in the upper atmosphere, which scatter the light spectrum and create vivid shades of orange, red, or pink.
Very fine volcanic ash can be transported by atmospheric currents over 20,000 kilometers, circling the Earth several times before settling back to the ground.
The very fine particles of volcanic ash dispersed in the upper atmosphere filter and scatter sunlight in a unique way, enhancing the red and orange hues during sunrises and sunsets.
In the event of ash fallout, it is recommended to stay indoors, securely close all openings (doors, windows), avoid using air conditioning if it brings in outside air, and protect the respiratory system when going outside (wearing a mask is advised).
Thanks to weather models and satellite measurements, it is possible to obtain relatively accurate estimates of the trajectory of an ash cloud. However, as atmospheric conditions change rapidly, these forecasts can evolve and are constantly updated.
Volcanic ash clouds can remain visible for several days, or even weeks. Their duration mainly depends on the altitude at which the ash is injected, the atmospheric conditions, and the size of the emitted volcanic particles.
Yes, volcanic ash particles can severely damage aircraft engines, obstruct sensors, and even lead to the complete shutdown of engines in flight. That is why aviation authorities often change flight routes during major volcanic eruptions.
No one has answered this quiz yet, be the first!' :-)
Question 1/5
