Monday, April 13, 2009

Do Earth fissures exhale water vapor?

Earth fractures open to the atmosphere "breathe" by convection on a daily basis, several orders of magnitude greater than unfractured ground.

A paper in Geophysical Research Letters notes that "Historically, these fractures have been studied merely as participants in aquifer recharge or aquifer contamination during periods of infiltration. In general, they are considered inactive when there is no precipitation." But new field measurements during no-flow periods find that the fractures are not inactive as thought.

This may have significant consequences for Earth fissures in Arizona and similar areas. It's been presumed that the fissures reach down to subsiding water tables and thus may serve as conduits to groundwater resources. Any concerns about this have been about contaminants getting into the groundwater. But this new paper suggests our fissures could be sending water vapor into the atmosphere; enough to exacerbate the water table drop and further subsidence? We need to know if this is happening along Earth fissures and if so, is it a significant factor. [right, Earth fissure in Willcox basin, AZ. My photo, 2006]

Ref: Weisbrod, N., M. I. Dragila, U. Nachshon, and M. Pillersdorf (2009), Falling through the cracks: The role of fractures in Earth-atmosphere gas exchange, Geophys. Res. Lett., 36, L02401, doi:10.1029/2008GL036096.

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