New National Monument – Chimney Rock

    This past week President Obama designated Chimney Rock, a rock formation in southern Colorado, as a national monument.
    Chimney Rock is a sandstone formation consisting of two side-by-side pillars or towers that are coincidentally arranged such that at certain times the rising Moon is framed by the two towers. These certain times occur for a 2-3 year period centered on an 18.61 year cycle that is called the ‘Major Lunar Standstill‘. The Moon, like the Sun, rises and sets at different positions along the horizon throughout the year. For the Moon this repetitive cycle culminates with the Moon rising at its furthest north position which places it between the two Chimney Rock towers for a couple of days each month. The most recent cycle of lunar standstills ended in 2007 meaning that the next cycle of lunar standstills will not be until 2022.

Interestingly there are other chimney rocks:
Chimney Rock Park, North Carolina
Chimney Rock National Historic Site, Nebraska