NEAR VENT PROCESSES AT CERRO NEGRO VOLCANO: A GROUND PENETRATING RADAR INVESTIGATION

Cinder cones are often assumed to grow via Strombolian activity as described by McGetchin et al (1974). Data with which to evaluate this and other models has historically been collected via eyewitness accounts, photography of eruptions, and mapping of exposed deposits. However, the dangerous nature of eruptions often prohibits near vent observations and accessible deposits are rare. Therefore, in order to gain a better understanding of near vent processes which may be used in volcanic modeling and hazard assessment, new data collection techniques must be implemented. Ground penetrating radar (GPR) imaging of tephra can reveal details of deposits at depths of approximately 2-20+ meters. Data collected in the fall of 2007 is here used to investigate the near vent processes of Cerro Negro, an active basaltic cinder cone in Nicaragua. Each of three GPR profiles begins at the crater rim and continues down the cone to the tephra blanket. One transect follows the prevailing wind direction (SW) while the other two head off at angles to the first: one to the NW and one to the SSW. The data display evidence of cone steepening over time, patterns of ballistic and tephra dispersal, and faults within the cone, among other features.