Monturaqui Impact Crater Field Day 1

Planetary Spherules Project: Monturaqui Impact Crater Field Day 1(Tue-Fri Dec. 2-5)

We find ourselves here in San Pedro de Atacama after a busy few days in Antofagasta. On the 2nd of December we had a whole-scale student swap, dropping Kelli and Renee off at the airport and picking up Sarah Byram at the same time. Both Kelli and Renee made it back safely, and Sarah arrived after what must have been close to a full day of travelling looking bright and fresh. I gave her the option of napping (which I would have probably taken had it been me) but she was a trooper and decided to come out for the afternoon and run some errands with me. We had the next day in Antofagasta free as well, and on the Friday morning loaded up our mini-bus with all our field gear and belongings and drove across the Atacama Desert to head for San Pedro, the Andes, and our next area of interest, Monturaqui Impact Crater.

This was the second time I’ve made this trek from the coast to San Pedro this year, because I was also on the High Lakes Project expedition with Nathalie, Edmond and Carlos, which ended just a few weeks ago (, and we started that expedition with the same bus journey through the desert. This time our goal was not the summit of the lovely volcanoes which frame our view to the east, but a crater formed by the impact of a meteorite approximately one million years ago.

The two new members of our PSP team are Sarah, an undergraduate at the University of Iowa working with me on her senior honors thesis, and Carlos, a medical doctor on this part of the project as a ‘just in case’ precaution because we will be working in some remote areas. We arrived in San Pedro, a vibrant and historically rich town with wide streets and charming adobe buildings, after roughly a four-hour journey. Our first day in the field, Friday the 2nd, consisted of a stroll around the crater, which is about 400 meters in diameter, to get me re-acquainted with the geology and introduce Sarah to the details of her new field area.

Sarah with her first sample

After the obligatory 30 minutes of awe and admiration for the spectacular line of Andes volcanoes providing a backdrop and just plain coolness of being on the rim of a meteorite impact crater we managed to pull ourselves together and tear our eyes away from the view long enough to start our survey around the crater in a counter-clockwise fashion. We are in the southern hemisphere, after all, and if water goes down the drain counter-clockwise here, then it seems fitting that geologists ought to loop around a crater counter-clockwise as well. We got a little distracted about a third of the way around when we found ourselves in a dense field of ‘impactite’ – rock formed from the fusion of melted rock and melted meteorite. Monturaqui is special because the impactite here contains spherules of metal thought to be wee little blobs of melted meteorite. Sarah was delighted with her first sample (see photo) and it made a great start to this project to find such spectacular rocks right at the start. We’re planning a long-distance traverse to sample for metal and glass spherules in the distal ejecta blanket over the next two days, which will take us away from the crater itself but will let us stretch our legs on some hiking in this spectacular area.