LAVA FLOW GROWTH INFERRED FROM MORPHOMETRIC PARAMETERS - A CASE-STUDYOF CITLALTEPETL VOLCANO, MEXICO

Recent (Quaternary) lava fields, such as those of Citlaltepetl (Pico d e Orizaba) volcano in Mexico, are excellent places to obtain precise m easurements of how-held dimensions that can be used to estimate volume , eruption duration and effusion rates. The relationship between these parameters and the influence of some other interrelated features such as lava composition, superficial structures and lava type are importa nt tools that can help to infer conditions when the lavas were active and thus improve understanding of how how fields grow. The Holocene la vas of Citlaltepetl volcano are homogeneous in composition (dacites) a nd are generally blocky with well-developed levees. The eruption durat ion obtained for the Citlaltepetl lavas by a method proposed by C. Kil burn and R. Lopes presents a good correlation with the different lava types morphologically classified here. Results from that method compar e favourably with the inferred effusion rates estimated by an empirica l cooling method (Graetz). The lavas show different behaviour, mainly controlled by fluctuations in the effusion rate that promote changes f rom single- to multiple-flow style. The maximum distance achieved by a flow is directly proportional to the effusion rate in Citlaltepetl la vas, but it is always lower for multiple flows, independent of the Vol ume of erupted lava. Observations of Citlaltepetl lavas can be used to understand how lava flow growth occurs on other volcanoes.