High-Resolution Ground-Based Magnetic Survey of a Buried Volcano: Anomaly B, Amargosa Desert, NV

Abstract

Aeromagnetic surveys over the Amargosa Desert, Nevada, have revealed the presence of several magnetic anomalies that have been interpreted to be caused by buried volcanoes; many of these anomalies have been confirmed by drilling. We present data collected from a high-resolution, ground-based magnetic survey over Anomaly B, the largest of these anomalies, that reveal details about a buried crater and its associated lava flow, not observed in the aeromagnetic surveys. These details provide insight into the nature of the eruption and volume of this buried volcano. Results from non-linear inversion demarcate a crater with a diameter of approximately 700 m and a base approximately 150 m below the ground surface. Coupled with well log data, the inversion results suggest a total volume for the Anomaly B crater area and associated lava flows of approximately 1.0 ± 0.4 km 3 , based on an estimated lava flow field area of 24 km 2 and a lava thickness of 42 ± 15 m. A workflow is presented for processing such large ground-based magnetic data sets with attendant GPS data, filtering these data and constructing maps and models using the provided PERL scripts.

How to use kernel density estimation as a diagnostic and forecasting tool for distributed volcanic vents

“…In some areas, bias develops because volcanic vents tend to be buried by subsequent eruptions (Wetmore et al, 2009). In other areas, volcanic vents are buried by sedimentation (George et al, 2015). The sensitivity of the analysis to these types of potential bias in the set of volcanic vent locations is important to consider and assess.…”

Near-surface geophysical mapping of an Upper Cretaceous submarine volcanic vent in Austin, Texas, USA

“…Geophysical methods, mostly gravity and magnetics, have been used across the world to better understand the internal structure of volcanic centers and the nature of the volcanic products (López Loera et al, 2008;Mrlina et al, 2009;Skácelová et al, 2010;Blaikie et al, 2012;Blaikie et al, 2014;George et al, 2015;Marshall et al, 2015). Points gathered from these papers, pertinent to this study, are: (1) magnetic anomalies generally are associated with near-vent facies and the structure of the upper parts of conduits in distributed volcanic fields; (2) magnetic anomalies associated with these structures are commonly on the order of 1000s nT; (3) use of geophysical surveys and applications of potential-field modeling are particularly important when vents are covered by sedimentation or obscured by erosion (e.g., Mrlina et al, 2009;Skácelová et al, 2010;George et al, 2015) and to determine the sizes of crater areas, especially where these are obscured by surface geology or cultural features (e.g., McLean and Betts, 2003;Blaikie et al, 2014;Marshall et al, 2015).…”

A new approach to probabilistic lava flow hazard assessments, applied to the Idaho National Laboratory, eastern Snake River Plain, Idaho, USA

“…Eruptive centers on the ESRP are generally well exposed, but variable subsidence and sedimentation obscure the most recent volcanism in some areas. Spatial density estimations that include buried eruptive centers in depocenters aids in removing some of the bias introduced by these processes (George et al, 2015). Like other volcanic fields, the geometries of eruptive centers on the ESRP vary from single vents to fissures and shields, creating a challenge for transforming map data of volcanic vents into a record of volcanic events.…”