CAVES
'(<a href="http://www.j-archive.com/media/2008-11-25_DJ_04.jpg" target="_blank">Jon of the Clue Crew reports from Carlsbad Caverns National Park in New Mexico.</a>) Carlsbad Caverns is rich in columns; a column forms when <a href="http://www.j-archive.com/media/2008-11-25_DJ_04a.jpg" target="_blank">these</a> two calcite structures grow together, one from the top & one from the bottom'
stalagmites and stalactites