The strong Strombolian activity that accompanied the 18 May eruptive phase had stopped by 28 May. Observations on 20 May revealed the end of lava emissions, intense Strombolian activity from the active vents of Crater 1 (E crater), and degassing from Crater 3 (W crater). Two cones were built by Strombolian activity inside Crater 1. The smaller one, only a few meters high, is located near the E rim. The second, located in the W part of Crater 1, was about 10 m high. Strombolian activity was continuous in the small E cone, with ejection of bombs to a few meters, but was discontinuous and stronger in the W cone. Frequent explosions sent incandescent juvenile scoriae to 100 m above the crater rim; they fell up to tens of meters away from the rim. Significant ejections occurred at intervals of about 8-10 minutes. The funnel-shaped bottom of Crater 3 was obstructed by material, resulting in strong bursts of gas at intervals of 20-30 minutes that formed a column up to 100 m high. The column consisted of brown, non-juvenile dust and blocks that fell back into the crater.

The intensity of Strombolian activity at Crater 1 was lower on 27 May than during the previous visit, with fewer explosions and a decreased volume of ejected material. However, gas explosions at Crater 3 were continuing with the same frequency and intensity. No sounds indicative of Strombolian activity were heard during about one hour of observation 28 May. Only weak degassing was observed from the vents in Crater 1. The degassing was interrupted at intervals of 15-20 minutes by noisy gas explosions that formed a plume up to 100 m high composed of brown, non-juvenile dust and a few scoria blocks. At Crater 3, activity was similar to previous visits, with gas explosions and brown dust emissions at intervals of 20-30 minutes.

Geological Summary. Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the "Lighthouse of the Mediterranean" in the NE Aeolian Islands. This volcano has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent scarp that formed about 5,000 years ago due to a series of slope failures which extends to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Information Contacts: S. Calvari, IIV.