The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages, and a few new episodes were posted. Now, the blog/podcast is on a weekly schedule with diverse topics, and the Facebook Page showcases photos on Mineral Monday and Fossil Friday. Thanks for your interest!

Thursday, April 24, 2014

April 24. The Silurian-Devonian aquifer

Yesterday we talked about the porosity, or open space, you need to make an oil reservoir. It’s the same concept as you have for an aquifer, a subsurface reservoir for water. Across most of Iowa and parts of Wisconsin and Michigan, the Silurian and some Devonian rocks in the subsurface form an important groundwater aquifer. They are mostly porous carbonates – dolomites and limestones.

Some of the water wells in the Silurian aquifer in Iowa have yielded more than a million gallons per day for 40 years, but flows are pretty variable and a few hundred thousand gallons per day per well is probably more common. In the 1980s in Iowa, especially northeastern Iowa, two-thirds of the water from this aquifer was used for domestic and commercial water supplies, and about a quarter went to agricultural use including irrigation. The total was about 130 million gallons a day in 1985.

—Richard I. Gibson

USGS report

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