HydroGEOPHYSICS’ Dr. Nigel Crook, & Dr. Dale Rucker use Waterborne Electrical Resistivity to explore the subbottom sediments and other geological features of Mono Lake in California to answer questions related to recent-past volcanic and tectonic events.
Nigel and Dale’s work at Mono Lake was recently published in The Journal of Environmental and Engineering Geophysics and also featured in the new Science Channel TV show Secrets of the Underground (episode #4). In the show Scientist Rob Nelson investigates strange underground locations around the world, using the latest technology and research to shed new light on subsurface secrets.
Mono Lake is located on the eastern side of the Sierra Nevada Mountains in California. The lake, contains a significant amount of dissolved solids due to being a terminal lake with no outlet. Dissolved salts in the runoff thus remain in the lake and raise the water’s pH levels and salt concentration creating a hypersaline aquatic system and high alkalinity (pH=10 or equivalent to 4 milligrams of NaOH per liter of water). Because of the high salt concentration no fish are native to the lake. The shallow saline lake, formed at least 760,000 years ago in an endorheic basin.
The survey was conducted to determine if the method could be used to define subbottom sediments and other geological features to answer questions related to recent-past volcanic and tectonic events. The survey used a 15-meter dipole-dipole array towed at approximately 2 mph behind a small flat bottomed boat. The survey was limited in scope to collecting approximately 6,000 m of data
within the western cove, where substantial core sampling has taken place. Comparison of the methods indicates the towed array can
obtain good quality data despite the lake’s conductivity being in excess of 84,000 uS/cm. The resistivity models reconstructed geological material upwards of 400 ohm-m to depths of 35 m, which likely represent hard rock below the lake.
This work showed that data quality from a waterborne resistivity survey was sufﬁcient to produce coherent models that could be attributed to geological features described by existing maps. Conductive layers beneath the water column were interpreted as sediments that have accumulated since the late Holocene. Deeper resistive bodies could be related to older intrusive igneous rocks. It was conclude that the method could be used to map most of the shallow areas of the lake, where the water column is less than 20 m. The deepest areas of the lake, south of Paoha Island, would require streamer resistivity cables with an electrode spacing of at least 60 m.
The Show Secrets of the Underground
Sprawling subterranean worlds live right below our feet; bizarre phenomena and histories long thought lost lie waiting to be uncovered.
Emmy Award-winning explorer and ecologist Rob Nelson goes digging to unearth these fascinating archeological and architectural enigmas. Sparing no expense, and using ground penetrating radar and the latest in cutting-edge 3D imaging, Nelson travels America seeking out the dark beauty of its underworld.
The thrilling season opener sees the adventurer exploring the legendary network of intricate tunnels at Alcatraz, following in the footsteps of the countless convicts who burrowed within their cramped confines, desperately seeking a route out of the seemingly inescapable prison.
The series will zigzag across the country, as our host ventures out in search of the likes of Al Capone’s Prohibition pathways; the so-called ‘American Stonehenge’; and Pennsylvania’s fabled mass grave. Join the adventure – no headlamp required.