首页 | 本学科首页   官方微博 | 高级检索  
     检索      


The magma budget of Volcan Arenal, Costa Rica from 1968 to 1980
Authors:G Wadge  
Abstract:The volume of magma emitted by Volcan Arenal from July 1968 to March 1980 has been calculated to be 304 × 106 m3 (dense rock equivalent). Most of this magma has been emplaced as block lava flows on the western flanks of the volcano following the initial explosive eruptions in 1968. From 1968 to 1973 the volumetric discharge rate of magma decreased from about 3-2 m3 s−1 to about 1 m3 s−1. During a break in activity in late 1973 the site of effusion moved from Crater A to Crater C about 400 m higher. Subsequent effusion was at a lower rate (0.3 m3 s−1) which remained constant for the next six years. Comparison of dry-tilt measurements during this latter period of steady-state effusion with numerical finite-element models of Arenal's elastic response to the evacuation of magma from an underlying reservoir favor a very shallow reservoir (< 2 km depth) to explain the data. However, the constraints imposed by the measured volumes of magma are not compatible with such a reservoir. Instead, it is argued that the steady downward tilting of the volcano's summit was caused by the loading of the western side of the volcano by about 19 × 106 m3 of lava. Surface loading by lava flows may be an important deformational effect at other volcanoes. A system of magma supply involving open conduits (pipes) for the uppermost one kilometer and transitory conduits (cracks) to a crustal reservoir is proposed. This crustal reservoir initially contained a compositionally graded magma which was evacuated from 1968 to 1973. The subsequent abrupt decrease in effusion rate is compatible with the increased magmatic head required to reach Crater C. The constancy of magma composition and effusion rate from 1974 to 1980 implies a homogeneous magma reservoir.
Keywords:
本文献已被 ScienceDirect 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号