Mexico - Colima volcano update 6 Feb 2002

from European Volcanological Society
Published on 06 Feb 2002
A lava dome has filled the crater of Volcán de Colima, México and provoked the first intermediate-size (up to 1 km of length) rock falls on the southern flank of the volcano that started at 17:21 (L.T) on February 4. The lava dome began to grow at the beginning of May, 2001 (BGVN, 26:05). The velocity of magma ascent sharply increased in October 2001, and by the end of January 2002, the total volume of the dome was estimated as 1,450,000 m3. The continuous process of inflation that was recorded by the deformation monitoring network and the numerous very small (magnitude less than 0) earthquakes that have been recorded during the last two weeks indicate a high probability of the formation of lava and pyroclastic flows that would threaten the residents of the nearest villages. Based on this information, discussed during the February 4 night meeting of the Scientific Advisory Committee of Colima University, the authorities of Colima State decided to evacuate the nearest village of La Yerbabuena, situated at a distance of 8 km from the crater. The evacuation of about 200 persons from took place on February 5. ( Universidad de Colima))
As of the 3rd of February, Universidad de Colima has reported that an aerial observation was attempted on 2 Feb at Colima but was thwarted by weather conditions. However, brief periods of incandescence from the new dome continue to be observed. The monitored parameters do not show significant changes in last the 24 hours. They continue being observed incandescence of short duration in the top. In the flights made on Feb. 2 by Members of the Advisory Scientific Committee, the state could not be appreciated in which is the dome due to the climatologic conditions. The colour code at Colima is currently at YELLOW. The recent activity of the volcano of Colima on is declared by the growth of a dome (it stains black) in the top, that has been visible from the city of Colima on for several days. Nevertheless this phenomenon gave beginning in the month of October of 2001 and has been monitored from its origin by the Advisory Scientific Committee for the Volcano of Colima on. The Advisory Scientific Committee has raised the possibility of occurrence of two scenes with base in the pursuit of the monitoring parameters, as well as in the observation of the type of eruptive activity during last the forty years: 1) first of them it is that in the course of days to weeks the dome collapse or spills by the South flank, generating a lava front accompanied by the well-known hot flows of ash and rock (pyroclastic flows), similars to observed in November and the December of 1998. Probably the reach of the initial flows will be similar to those of that year, that is to say, will reach smaller distances to the 5 kilometers. The movement of these flows will generate ash clouds that could hurry on the neighboring populations, depending on predominant winds. In this respect it will be necessary to take into account that the ash precipitation on the water bodies could cause its contamination reason why it is recommended to maintain places setting: sinks, drainages and wells. 2) the second scene is that this dome lets grow and that in an indetermine time they happen one or several explosions like those of February, May and July of 1999, destroying parts or the totality of the dome, whose reach of sent fragments (ballistic missiles) will not exceed a radius of 5 kilometers from the top. The possibility that does not discard both phenomenons appear permanent in the time. Information translate from spanish : University of Colima - Advisory scientfic Committe.