Much of the political world is focused on Pennsylvania this week as the April 22 primary election approaches. But once the primary election is over, the candidates will pack up and leave and the state will slip off the political radar.

But another group of people, specifically geologists and natural gas drillers, have been focusing on Pennsylvania in recent years — and their attention is likely to continue for years, if not decades.

The geologic interest in Pennsylvania has to do with a potentially vast reservoir of natural gas that lies some 7,000 feet below the surface. A few exploratory wells in recent years have offered tantalizing hints at the potential of what is called the Marcellus Shale formation. Estimates vary widely, from a 2002 U.S. Geologic Survey of 1.9 trillion cubic feet to more recent estimate by researchers at Penn State University and Fredonia State University in New York of 168 trillion cubic feet.

For reference, the United States consumed 23 trillion cubic feet of natural gas in 2007. About 85 percent of U.S. natural gas consumption is supplied by domestic sources.

About half of the homes in the U.S. use natural gas and it is used to produce about 20 percent of the nation's electricity.

For decades, scientists have known that a huge pool of natural gas is trapped in the deep shale formation that stretches diagonally across Pennsylvania and extends into West Virginia and New York. But it was believed too difficult or expensive to explore and extract.

The technical difficulties of extracting natural gas from shale formations at depths of 7,000 to 9,000 feet are formidable, but higher energy costs and advancements in drilling technologies now make the gas in Marcellus Shale accessible and attractive.

Successful drilling in 2002 into a similar shale formation in North Texas has raised expectations that Pennsylvania could yield similar—some would say spectacular—results.

In recent weeks, articles have appeared in the WallStreet Journal, USAToday and the New York Times describing the increased land leasing and drilling plans associated with the Marcellus Shale.

Gas producers warn that it's too early to judge the potential of the Marcellus Shale formation in Pennsylvania, which runs through the north-central and southwestern parts of the state. But the newspaper articles paint a picture of a natural gas gold rush.

The Wall Street Journal article referred to surge in interest in the Marcellus, saying, "The result is a land rush unmatched anywhere else in North America as companies try to snap up drilling acreage." The New York Times article described land-leasing deals and said it was "a frenzy unlike any seen in decades unfolding here in rural Pennsylvania....Companies are risking big money on a bet that this area could produce billions of dollars worth of natural gas."

With rising energy prices, relatively clean-burning natural gas is increasingly attractive. And rising prices for natural gas help justify the risks related to the costly and difficult horizontal drilling technologies necessary to extract gas from the Marcellus Shale. Additionally, the proximity of the Marcellus gas reserves to the highly populated East Coast market makes the Marcellus Shale even more attractive.

Because the natural gas in the shale is trapped more than a mile below the surface and because of the specialized skills required to drill straight down 6,000 feet and then drill horizontally into the shale formation, large drilling companies from Texas and Oklahoma with such experience are moving into Pennsylvania. And while not many wells have been drilled into the Marcellus Shale, the prospects are tantalizing enough that the out-of-state gas producers are working to acquire drilling rights from farmers and larger landowners across the state.

While it still is too early to tell the ultimate impact of the gas trapped in the Marcellus Shale, it's exciting to see renewed interest in Pennsylvania for energy, about 150 years after oil was discovered at Titusville.