Not karst, part 2

For the same two-and-a-half years I've also (incorrectly) called this other-worldly stuff, found at Jobos, Middles and other beaches, "karst." Like the beachrock in a previous post, this is also not karst. Actually, in some ways it's more interesting than karst.

This is eolianite. It is in fact an ancient sand dune, created by the wind (probably) in the last million years, and then turned to stone (the proper term is "lithified"). Wind-borne sand and pounding waves have eroded it to the wickedly sharp but relatively brittle formations we climb on today. (For more information see the Wikipedia article.) It turns out there is a lot of eolianite along PR's north coast. Check out this page to learn more.

There is karst on the island, lots of it. The two most famous examples at the Camuy Caves and the radio telescope observatory in Arecibo, which was built where it is because of a giant natural sinkhole.

Thanks again to our friend Kathy Hall for sharing some of this information and getting me started looking for more.

Other links:
Arecibo Observatory - http://www.naic.edu/

Karst - http://geography.about.com/od/physicalgeography/a/karst.htm
http://geomaps.wr.usgs.gov/parks/cave/karst.html

Geography of Puerto Rico - http://en.wikipedia.org/wiki/Geography_of_Puerto_Rico
http://geology.uprm.edu/Morelock/wcpr7.htm#
http://geology.uprm.edu/Morelock/beachsys.htm