Cerro Pachón

A Special Place

The Andes mountain range, where you'll find Cerro Pachón (the mountain Rubin Observatory sits on) is the longest above-water mountain range in the world and the second-highest only after the Himalayas in Asia. The Andes are also highly volcanic! However, the stretch where Cerro Pachón is located doesn’t have any volcanoes at all. Geologists believe that’s because the Pacific tectonic plate slides under the South American plate there at an angle that is too shallow to cause volcanoes. Regardless, the lack of volcanoes means Cerro Pachón and the surrounding mountains are great places for observing the night sky with their high peaks and dry air.

But the lack of volcanoes doesn’t mean a lack of earthquakes. Cerro Pachón feels small earthquakes pretty regularly, and that’s one of the reasons Rubin’s telescope is directly mounted to a huge concrete pier embedded in the stable foundational bedrock of the mountain. As added protection from vibrations (from earthquakes, or even wind) the pier is a completely separate structure from the rest of the observatory building. In fact, inside the observatory you can actually see the gap between the massive concrete pier and the rest of the building!

Cerro Pachón is also home to many different plant and animal species that have adapted to survive in the high, dry desert climate. Cacti, shrubs, and wildflowers frequent the landscape. Sometimes foxes roam the hillsides or Andean condors swoop overhead, and viscachas (adorable rodents that look like a squirrel-rabbit hybrid) regularly join our scientists for sunset shows. Because it has a desert climate, Cerro Pachón also hosts familiar desert species like lizards, snakes, spiders, scorpions, and a whole bunch of insects.