In today’s Academic Minute, Dr. Bayani Cardenas of the University of Texas at Austin reveals what’s going on beneath the surface of a hot spring.
Bayani Cardenas is an associate professor and the William T. Stokes Centennial Teaching Fellow at the University of Texas at Austin. His research group uses a variety of approaches including traditional hydrologic and water quality monitoring, geophysical surveys, remote-sensing, and mathematical modeling to better understand the flow and transport dynamics of natural hydrologic systems. He holds a Ph.D. from the New Mexico Institute of Mining and Technology.
Dr. Bayani Cardenas – Hot Springs
Hot springs are ubiquitous features whose underground architecture is mostly unknown but are typically thought to originate from kilometers deep. In many environments, these springs are unique ecosystems hosting novel organisms. We documented a type of hot springs at the banks of a volcanic lake. The spring forms when relatively cool lake water that is at 35C seeps through the permeable lake sediment, pushes it downwards and shore-wards, mixes it with deeper and much warmer groundwater that is at 70C at velocities of hundreds of meters per day, then returns the water to the lake via the hot spring. This type of circulation is postulated to be what is underneath submarine black smokers near mid-oceanic ridges; we discovered their terrestrial cousin.
The groundwater flow velocities we measured are probably a record; in aquifers in the US Midwest, groundwater flows at rates of tens of centimeters per day. We also found that the groundwater mixing zone is flushed in a few hours and turns over the lake's volume of 45 million cubic meters in a few days. This very pronounced movement of heat and water is enough to affect the temperature of the lake; volcanic lakes are sometimes thought to be the main gateway for heat to escape from volcanoes that may keep them cooler than they might be in the absence of these lakes. The subsurface environment underneath the springs we discovered might also harbor organisms unknown to science since the environment is unique. The type of spring we studied is likely present but perhaps unrecognized at many areas. More work needs to be done to understand these unique underground environments.