Movement and emplacement of lava flows at Volcán de Colima, México: November 1998–February 1999

• Published in: Journal of volcanology and geothermal research 2002-09, Vol.117 (1), p.155-167
• Main Authors: Navarro-Ochoa, Carlos, Gavilanes-Ruı́z, Juan Carlos, Cortés-Cortés, Abel
• Format: Article
• Language: English
• Subjects: andesite; block-lava flow; Colima Volcano; crater explosion; lava dome; pyroclastic flows
• ISSN: 0377-0273; 1872-6097
• DOI: 10.1016/S0377-0273(02)00242-1

The first lava eruption of Volcán de Colima since 1991 was anticipated beginning in mid-1997 when seismic activity began to exceed background levels. On 20 November 1998, growth of a new andesitic lava dome began inside a crater produced by an explosion through the summit dome in July 1994. The 1998 block-lava dome grew rapidly at a rate of 4.4 m 3/s, attaining a volume of 3.8×10 5 m 3 in 24 h. About mid-day on 21 November the lava dome began to collapse, generating a series of block-and-ash flows that descended the SSW flank at speeds of 80–90 km/h, at intervals of 3–5 min. These pyroclastic flows were mostly deposited in the three branches of Barranca El Cordobán, reaching a maximum distance of 4.8 km from the summit at an altitude of 2040 m. The largest pyroclastic flows were emplaced on 25–26 November and their deposits had an estimated volume of 7.3×10 5 m 3. An andesitic block-lava flow (59 wt% SiO 2) then followed down the three branches of Barranca El Cordobán, reaching a maximum distance of 3.8 km in the central branch. The lava fronts of the western and central branches almost touched at 2300 m elevation. The eastern lava flow reached 2.8 km at 2560 m elevation. The total volume of the three lava flows is estimated as 39×10 6 m 3, assuming an average thickness of 20 m. The advance rate of the lava fronts in the early hours reached 36 m/h on steep slopes (up to 40°). These diminished to 0.2–1.0 m/h on flatter slopes (∼14°) in early February, as the activity waned. The viscosity of the block-lava flows, estimated from field observations, was extremely high: 10 9–10 10 Pa-s, ∼6 orders of magnitude greater than viscosities estimated for fluid basaltic magmas. The lava flows ceased movement in early February 1999, and the style of eruptive activity entered a more explosive phase, with a series of dome explosions that have continued into February 2001.