The power of exponents never ceases to amaze me. Cecil says that roughly one trillion barrels of oil have been pumped from beneath the earth’s surface. A few minutes with a conversion tool (which tells me that a barrel is equivalent to about 7.35 cubic feet) and Microsoft Excel reveal that the total volume of oil extracted so far could be contained in a cube less than one mile on a side–5,143 feet, to be precise. If that’s hard to visualize, then imagine a chunk of Lake Michigan measuring about four miles square. That’s the volume of oil we’ve used.
Looking at it another way, a trillion barrels of oil spread over the Earth’s surface would create a film about three ten-thousandths of an inch thick. A human hair is about one-thousandth of an inch in diameter, for comparison.
I read an article in PopSci or PopMech recently. They said it’s not like sucking liquid out of a lake, it’s more like sucking liquid out of a sponge.
As the oil comes out, water in the surrounding rock and dirt comes in.
I think I read another article years back that said in some oil wells, they pump CO2 or something else in to replace oil when they take a lot out, but they didn’t mention this in the PopSci mag.
There is a Denver Post article about hydraulic fracturing used to obtain natural gas in Sublette County, Wyoming, where the groundwater supply is being contaminated. Of course, a 2004 EPA report found the process “safe.”
What about subsidence from coal-mining? How likely are areas above and around coal mines to face collapse?
Did you miss this in the column?
[QUOTE=Cecil Adams]
It’s the removal of solid stuff, though, that you really have to worry about. Some coal mines practice what’s called longwall mining, where the roof is allowed to cave in behind the miners as they dig out the coal in front of them. In principle the resulting subsidence is easier to predict and plan for, but still it often causes serious damage as nearby buildings, roads, train tracks, and pipelines sink four to six feet. (Mine owners are supposed to pay compensation.) That’s not the worst that can happen, though. The hamlet of Centralia, Pennsylvania, was rendered uninhabitable in the 1980s after a coal seam underneath it caught fire, opening up steaming hot sinkholes filled with toxic gases. The fire’s still going and could burn another 250 years.
Salt mines are a special case: they can slowly squeeze shut as the salt deforms beneath the weight of the rock above, or they can collapse when leaking groundwater dissolves the salt pillars holding up the roof. The Retsof Salt Mine in upstate New York is a prime example of the latter problem; its 1994 cave-in led to gaping sinkholes, a wrecked bridge, and utility damage.
[/QUOTE]
In what column? It’s not like there was a link to it!
Apologies for sounding brusque; since this thread was about the column, I assumed you were commenting on it. Here’s a link for you - I admit that the Archive Search on the Straight Dope page does not seem to call it up directly.
Welcome to the SDMB, granville.
A link to the column you’re commenting on is appreciated. I’ve added a link to your post.
No probs, Una. I’ve seen a video of that Lake Peigneur incident, and that looked pretty damned hairy! That must have been scary to have seen first-hand.