In the footsteps of Apollo astronauts, literally!
No, really! I’ve walked in the same places that the Apollo astronauts honed their geology skills here on Earth. Actually, many a geologist has trained in locations that were used for Apollo training for the precise reason that they are great places to learn geology. Apollo training locations include a fair number of volcanoes, a few impact craters, and other barren rocky landscapes. The point of training, after all, was to prepare them to describe the rocky and otherworldly surface of the moon, and the moon is covered in lava and lots of big impact craters.
|Volcanic moon rock at the Chabot Space Center in Oakland California. Image courtesy of Wikimedia Commons.|
I encourage geologists and outdoor enthusiasts alike to check out this list of training locations and see how many places you have been that was used to prepare the Apollo astronauts for the moon. I was pleased to note how many places I have visited. In fact, many of the training locations included not just volcanoes, but maar volcanoes! Most of these craters are in the western United States including Zuni Salt Lake (1965, 1967) and Kilbourne Hole in NM (1969-71), Lunar Crater Volcanic Field in Nevada (1972), Ubehebe crater in Death Valley California (1971), and the San Francisco Volcanic Field in AZ (1964,1969). They also visited one of my favorite strato volcanoes in Alaska, Katmai (1965-66). Which erupted in 1912 to form the Valley of 10,000 smokes.
|Alison at the Nova Rupta lava dome that formed after the 1912 Katmai eruption in Alaska. I believe I am petting the lava dome in this photo. Pretty lava dome.|
There was one location; however, that was not a surprise: Iceland. In many ways Iceland is the ultimate geology training ground. The landscape has classic examples of tectonic, volcanic, hydrologic, and glacially modified landscapes, and they are accessible. So of course the astronauts went there.
|This geologist really loves rocks. Especially rocks in Iceland.|
There was another reason I wasn’t surprised. There is a gully at Askja volcano, Iceland, where I did my PhD research, named Nautagil, or astronaut gully, to commemorate their visit in 1965. It is one of the few locations at Askja that bears a sign identifying its title, and occurs fairly close to one of the few ‘roads’ around the volcano. This summer was the 50thanniversary of the first Apollo training mission to Iceland. Two of the astronauts who trained there Cunningham (1965) and Schmidt (1967) went back for a visit this summer.
Photographs and stories from the astronaut training missions indicate that the astronauts traveled around a fair bit in Askja caldera and among the younger lava flows and historic 1875 pumice deposit. They also visited Viti, which translates to hell, it is a maar volcano inside the caldera that contains tepid water frequented by tourists for a quick bath. The astronauts in training actually helped refine the reconstructed eruption sequence that involved Viti by simply observing that the maar’s deposits were on top of the main deposits from the 1875 eruption.
|Apollo astronauts at Askja volcano. Standing on the edge of Nautagil. NASA image.|
My favorite spot that the astronauts visited was in Nautagil itself. In fact they took a photo of one of the groups in front of a feature called the Rosa. The Rosa can be found in the in the photographs of many visitors at Askja, myself included! If you just put Nautagil into a search engine you will quickly see an image of the Rosa. It is a fascinating circular structure in the middle of a dike (intrusion of magma that cuts through the surrounding rock). The dike itself stands tall in the landscape as the surrounding rock has been eroded away, and the Rosa is a symmetrical window through the dike. The Icelandic word Rosa means rose in English, which tells me I’m not the only one to find this feature beautiful.
|Apollo astronaut geology training at Askja volcano, Iceland at the Rosa feature in Nautagil. NASA image.|
|An image of the Rosa without geologists climbing all over it. Note the radial cracks along the margins. The back of the hole is host rock.|
What interested me most is no one had tried to come up with a formal explanation of its origins, though surely lots of visitors have pondered how it got there. Any previous theories weren’t recorded anywhere we could find. As the Rosa is close to a feature I was studying during my PhD, it seemed likely that the Rosa was related. I was studying a series of complicated dikes recording the interaction of rising magma with ice-cemented sediments and water. We called them Coherent Margined Volcaniclastic Dikes (CMVDs). I will forever kick myself for not coming up with a more catchy name, but as a grad student I wanted to make sure I wasn’t breaking some code of serious geology or accidentally confusing my audience. So it got a very descriptive name.
Anyway, the dike that hosts the Rosa is one of dikes that has textures that indicate that it interacted with wet/frozen sediment. These textures occur about 100 m (~300 ft) further west in the same dike, and we estimated all of these features were formed fairly close to the surface. At the time this dike formed, Askja volcano was erupting under ice, so there was lots of water around. What we suspect formed the Rosa was trapped water, either water that was present in the sediment itself, or a block of ice that fell into a fissure between batches of magma. This water was heated up by the magma, and expanded, as water vapor does, to form the circular feature. The water may have been in the form of ice, ice cemented sediment, or liquid water. For more detailed discussion you can see my paper on it here. It is less likely that the water entered the dike from the margins / sides because of the intact nature of the glassy margins, and the preservation of a very thin texture called peperite. This micro-peperite further supported our model of frozen sediments by the dike. When dikes interact with wet sediments these peperite texture typically are centimeters to meters wide. In this case the dike only melted a few millimeters of the icy host, and meaning that there was less water available at the sides than would be available from above.
|Model showing the steps of CMVD formation with some conjecture about the formation of the Rosa at the bottom. A-1) Chill margins form along a rising basaltic dike. The ice-cemented host and overlying ice fracture. The gas driven pulses of magma depressurize near the host/ice/meltwater interface. A-2) Dike drainage creates space, allowing downward flooding of the water into the dike fracture. A-3) Meltwater and magma interact non-explosively, forming a slurry. A-4) Later pulses interact with the slurry; mingling continues. B) Motion of magmatic gas, steam and clasts develop near-vertical flow banding. A final pulse is chilled against the interior, resulting in radial cooling cracks. Evidence of the preceding steps may be preserved in the CMVD (labels). C) Formation of a very thin peperite between chill margin and ice-cemented host. D) Formation of the Rosa may have involved an iceblock, a block of ice-cemented host sediment, or wet sediment. Adapted from Graettinger et al. (2012) JVGR vol 217 doi:10.1016/j.jvolgeores.2011.12.008|
Investigating these interesting deposits was a great way to test my creative thinking during my PhD. Askja was certainly an inspiring place to work, and it the knowledge that many other explorers, geologists and outdoor lovers have spent time learning about the Earth (and the moon) there added to the ambiance. But there are always more questions to answer! One of my goals is to experimentally recreate some of these near surface magma water interactions at our large scale facility at the University at Buffalo. So hopefully in a few years I can write a new post that improves my hypothesis about the Rosa!