Study of the mechanism of volcanic explosions and the resulting ballistics

The larger magnitude explosive eruptions of Volcán de Colima during 1999, 2003 and 2005 produced projectiles that landed at distances of up to 3 km from the volcano. The characteristics of the ballistics and their impact craters are being studied. Some interesting variations in the spatial distribution have been observed. Various theoretical studies have produced numerical models of the explosive process and the production of ballistics. However, there have been very few well documented studies of real data. In this study over 1000 impacts have been measured and recorded. The theoretical models will be compared with the data.

By calculating the bomb distribution of each event, it will be possible to estimate the total volume of material ejected and calculate the energy of the eruption. By examining the characteristics of individual ballistics, it has been noted that the distribution has varied for different events. A clearly non-symmetrical distribution, suggests a non-vertical orientation of the conduit.

Impacts project

These photos show some of the variety of impact craters that have been observed at Volcán de Colima. In the first photo (A) a crater measuring about 3 m in diameter was formed by this black ballistic. The colour and texture were characteristic of dome material which was blown out forming a crater by an explosion in August 2003. The dome formed during the 2001-2003 effusive eruption.

Some bombs have been observed to hit the ground bounce without fragmenting and then land several metres away. This is a reflection of firmer ground. Some bombs bounce changing their direction. This is due to them spinning through the air (B).

(C) Other craters are shallower compared with their size. (D) In some cases the bomb fragments with all the pieces remaining inside the crater. Here you can see a very good example.

Mario Lopéz Rosas: Study of the ballistics produced by the explosive events at Volcán de Colima during 1999 and 2003