Our warming planet

Earth's Cracks May Contribute to Global Warming
Michael Reilly, Discovery News


Feb. 19, 2009 -- Whether devastating faults, dank caves or mud cracks on a drying desert plain, 1. Earth's surface is riddled with fractures. Now a new study had found that the cracks exhale large quantities of gas, perhaps enough to affect global warming.
Noam Weisbrod of Ben Gurion University of the Negev and a team of researchers monitored a crack about 2 meters long (6.5 feet) and 1 meter (3.3 feet) deep for two years in the Negev Desert is Israel. Each night, they watched as warm air in the crack drew water vapor out of the surrounding rock, and lifted it into the cold evening air.
If air in the crack is just 7 degrees warmer than the ambient temperature, it is buoyant enough to rise out of any crack in the ground bigger than 1 centimeter (0.4 inch) across, bringing with it any gases that leak out of the surrounding soil or rock.
But the team was surprised to find that the crack they studied gave off water vapor up to 200 times faster than areas without fractures.

Sometimes we go for walks at night, and you put your face over the mouth of a cave and you can feel a warm wind coming out," Weisbrod said. "Usually it's a nice hot wind in the cold air."
1. Like carbon dioxide, water vapor is a greenhouse gas that plays a crucial role in the way Earth's atmosphere traps heat from the sun. Though the team only measured water vapor, Weisbrod said it's likely that cracks also regularly emit elevated amounts of CO2 and nitrogen oxides.
This doesn't only happen in extremely dry areas, he added. The Negev is arid, but roughly equivalent in dryness to the area around Los Angeles, Calif., the American southwest, and many regions around the world. Fractures are common in soils and rocks in wet regions as well, Dan Yakir of the Weizman Institute of Science said.
Taken as a whole, emissions from fractures in the uppermost meter of the planet's crust may make a significant contribution to greenhouse gases in the atmosphere. But Weisbrod stressed it's too early to make such a conclusion; the team only studied one crack in detail out of millions.
"This has the potential to be important globally," Yakir said. "The biosphere soaks up 30 percent of the carbon, and soil respiration is a very large part of that. If cracks remove CO2 from soils much faster than usual, it's important. But this study is only a first step."