A rare celestial event is set to take place later this month, continuing periodically on certain dates through 2025. While the event has long drawn eager visitors to a unique rock formation in southwest Colorado every 18.6 years, a series of temporary safety closures will make it impossible for the public to experience the event at the site this time around.

On July 15, the rising moon will be seen aligned between Chimney Rock and Companion Rock sandstone spires at the Pagosa Springs-area Chimney Rock National Monument. This occurs when a ‘major lunar standstill’ takes place, which is described on the Chimney Rock Interpretive Association website as when “the moon appears to pause for about three years, rising at the same point on the horizon” –  a departure from the way it rises at different points on the horizon during most years. According to an article from the New York Times, the moon will appear to rise at the same spot during these standstill events for two to three nights in a row, multiple times over the three-year period.

While not fully understood, it is believed that this celestial occurrence impacted the construction of the Chacoan-style Great House on top of Chimney Rock’s high mesa, which was built around 1076 AD and serves as an ideal viewing point for the major lunar standstill. Over the course of about five to 15 minutes on certain dates over a three-year period, the moon rises directly between the two rock formations as it climbs into the night sky.

While locals and tourists, alike, have trekked into the area to witness the event in the past, temporary closures to be put in place by the US Forest Service will make that impossible during this occurrence, which will happen during select dates from 2023 to 2025.

The closures stem from risks associated with entering the national monument at night, also impacted by the removal of a two-story fire tower that served as the only modern structure from which the event could be safely viewed. There are also concerns with the public being able to safely navigate the treacherous terrain under nightfall, with the strenuous upper mesa trail flanked by 1,000-foot cliff drops.

Discussion is taking place regarding how to share the event with the public despite the closures, which has included possible live-streaming options. A limited number of people will be permitted in the area for the sake of scientific research and videography.

The closures will include Chimney Rock Road and Chimney Picnic Parking Road, as well as Great House Trail.

Dates of the closure are as follows:

• July 15-16, 2023
• August 11-12, 2023
• September 6-9, 2023
• October 3-5, 2023
• October 31-November 1-2, 2023
• November 27-29, 2023
• December 25-26, 2023
• July 3-4, 2024
• July 30-31 and August 1, 2024
• August 26-29, 2024
• September 22-24, 2024
• October 20-21, 2024
• November 16-18, 2024
• December 13-15, 2024
• July 21-22, 2025
• August 16-18, 2025
• September 12-14, 2025
• October 10-11, 2025
• November 6-8, 2025
• December 4-5, 2025

Additional information of the significance of the major lunar standstill at Chimney Rock can be found here.

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