APPLYING GOOGLE EARTH TO GEOLOGIC STUDIES: STRATIGRAPHY AND PETROLOGY OF A BASALT FIELD IN CENTRAL ARIZONA

Google Earth is a free internet visualization tool used over the past three years in educational, commercial, and recreational applications. Google Earth can also be utilized as a research tool in geologic field studies for sampling, for the identification of rock formations, and for determining extent of coverage. This method of using satellite imagery for geology has several advantages over traditional field practices and provides an efficient approach to acquiring field information.

Specifically, we used Google Earth to initiate a petrologic study of the Stewart Mountain Miocene basalt field in central Arizona, located ~50 km northeast of Phoenix and within the Goldfield-Superstition volcanic province. The petrologic objectives include how Stewart Mountain basalts relate petrologically to other Western US Miocene basalts, and in particular, to basaltic lavas in the southern Basin and Range volcanic province.

Prior to our field visit, Google Earth imagery prepared us to sample a ~3.5 km² area for what appeared in the images to be five lavas based on color variations, and on stratigraphy acquired from the images by 3-D manipulation to accentuate relief. The color variations and stratigraphy showed that mafic rock layers (the basaltic lavas) are interbedded with non-mafic layers. Uncertainty in the exact number of lavas was because of shadows, color variations due to vegetation and weathering, and possible presence of faults.

During ground-truthing, Google Earth enabled us to verify the stratigraphy and to expediently reach and sample the lavas at pre-selected locations. Additionally, Google Earth images carried in the field facilitated efficient traverses for reaching new areas of geologic interest. Particularly beneficial in this regard, the images readily show full aerial extent of each lava studied, thereby providing thorough coverage for potential sampling sites. Post-field work, Google Earth afforded organizational and presentational tools, such as precise marking of sample sites by 'thumbtacks' on the images. Finally, compared to traditional field methods, our application of Google Earth suggests that we reduced the time by half required to prepare for, carry out, and organize our field research where contrasting mafic and non-mafic rock formations occur.