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!

Tuesday, June 24, 2014

June 24. Cave passages

We talked about Mammoth Cave the other day, but here’s a little more about its development. Cave passages tend to be linear, in part because moving water preferentially dissolves limestones along lines of weakness, such as linear joints or fractures and along bedding planes.  

Sometimes in places where joints and fractures are regularly spaced and relatively rectilinear, forming rectangles in map view, a cave system might approximate that pattern too. But water isn’t usually strictly limited to the joints, and collapsing caves can create new patterns as well. The map above of Mammoth Cave was compiled in 1897. There’s a certain degree of regularity, and several directions such as northeast-southwest that seem to predominate, but there’s actually quite a wide variety in the development of the cave passages dissolved in Mississippian limestones. Regular patterns do happen, but natural systems tend to be complex enough that regularity is usually the exception rather than the rule.

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Today’s birthday is David Dale Owen, born June 24, 1807, near New Lanark, Scotland. He was the son of Robert Owen, a reformer who established a social experiment at New Harmony, Indiana, in 1825. It was an attempt to establish a utopian society. It was an economic failure but New Harmony became a cultural and educational center, noted for scientific research. David Dale became a prominent geologist, doing some of the first work in the Midwestern United States. He was the State Geologist of Indiana, Kentucky, and Arkansas at various times between 1837 and his death in 1860.
—Richard I. Gibson

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