- Published: 27 February 2009
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Brad Simpson, age 11, of Charlotte, No. Carolina, for his question:
How can a mole breathe underground?
Last week we surveyed the groundwater and saw how vital it is to life on the surface. The ground also contains enormous quantities of air and other gases. Some of these are vital to the burrowing moles and also to multitudes of mini creatures that build and rebuild the soil. All living things depend on the plant world, the plants need soil, the soil needs both water and air to stay in good condition. But even ecologists tend to forget the importance of the ground air.
We are told that the atmosphere rests on the surface and its layers extend up for hundreds of miles. This over simplified picture ignores all the air that exists in caves and crevices, between the crumbs of sand and soil and in the pores of deeply buried rocks. For a long time, we have polluted and abused our soils. To rebuild them we must take a new look at this layer of ground air in the atmosphere's basement.
It is the nature of gases to mingle together and to permeate every available space. At sea level the weight of the lofty atmosphere exerts about 14 1/2 pounds of pressure per square inch. This helps to push the gaseous air into the soil and through deeper porous rocks. In the dirt there are plenty of air filled pockets to supply teeming hordes of large and small creatures that live underground.
When you poke a hole in the ground, it fills with air much faster than you can dig. Some seeps from surrounding soil, more presses down from above. A worm's tunnel fills with air as he digs his way through the dirt. The same thing happens when moles and badgers, aardvarks and other burrowers tunnel through the ground. Most of them also dig underground dens and bedrooms for themselves. These also fill with air.
Upstairs, the atmosphere circulates in weathery turmoil. The air underground circulates more slowly from space to space. Some gets mixed with volcanic fumes and non breathable gases from decomposing organic material. Pockets of stale or poisonous air often get trapped in mines and caves. But as a rule, these problems do not bother the moles and other burrowers.
Their tunnels have numerous exits that act as two way air vents. The under¬ ground air, stale with carbon dioxide, seeps outside and merges with the atmosphere.
Fresh air from above seeps down inside, bringing oxygen to the moles and to all the other underground populations.
It would be nice to know as much about the ground air as we know about the groundwater. But scientists tend to neglect this fascinating realm of subsurface ecology. They give us estimated figures on the groundwater. But though Andy searched diligently, he was unable to learn how much useable air is estimated to be underground. We need to know lots more about it in order to help the earth to restore her polluted and impoverished soils.