by Ian Kluft
e-mail: ![i k (dash) b r c r a t e r -at- t h u n d e r [dot] s b a y {dot} o r g](brcrater-email.jpg){kind=small}
January 16, 2011
On this page...
Once again, I'll post an annual summary of where the research stands
with the suspected impact structure at the Black Rock Desert.
This project about researching the suspected impact crater started in early January 2007. I had thought for years that the Black Rock Range and other parts of the Black Rock Desert were "the strangest volcano I've ever seen." While some rocks had the right color to be lava, there were no signs of cinder cones, lava flows or other features I had come to expect from volcanoes while growing up in far-northern California, 120 miles to the west. Some apparent volcanic necks in odd places helped sustain the image of a volcano. And Black Rock Point itself looked to me like a plug dome volcano, until I got corrected that it isn't. There were conflicting stories about what it is, like sedimentary rock or a magma extrusion. Then it became a mystery. Eventually when I was introduced to the science of recognizing impact craters, things kept sounding familiar from sights at the Black Rock region.
The project had an awkward start, bringing up the idea while learning about the science of impact crater recognition. Some people wanted everything to be done like university research. Since I'm not funded like a university, that just wasn't feasible for me. There was really no way to get started but to open a discussion. I've been seeking just enough attention to find others who are also interested in helping with the research.
For anyone wanting to learn about the science of impact crater recognition, I highly recommend the e-book "Traces of Catastrophe" by Dr Bevan M French of the Smithsonian Institution, distributed online by the Lunar and Planetary Institute. I still often refer to it as a reference.
Initially, the arcs in the Kamma and Calico Mountains got my attention as a candidate for the rim, which led to an initial hypothesis that the crater would be a 30x40 mile ellipse. A non-circular outline was problematic - but I posted the observation anyway. The research has to be driven by its data, not expectations of it.
Stratofox member Bob Verish, a retired NASA/JPL planetary scientist and geologist, provided some good advice. While remaining politely skeptical as anyone should when considering a new idea, he suggested that if he was going to take an impact theory seriously, there needed to at least be breccia (jumbled and re-cemented rocks) at the site. Even as he mentioned it, we already had plenty of photos from previous trips to indicate there was literally mountains of it. So far so good. But it was only a start.
In 2008, in the article Breccia/fractured rock boundary at Upper High Dry, I summarized Bob's advice and our observations so far. We sought to better understand the structure of the rocks in the region. The search for breccia led us to notice a recurring observation of breccia overlying deeply fractured rocks. Under the impact theory, that fits with "target" rocks that got smashed, and the debris that landed on them. It turns out to be an observation which is standing the test of time as we continue to make more observations like it across the region.
In 2009, the 30x40 mile ellipse hypothesis just didn't seem to be holding water. Observations appearing consistent with an impact were being made outside it too. In my article "State of the Research - January 2009", I said that I was going to back off on claiming the 30x40 mile ellipse. It's difficult to put the pieces together where erosion has erased so much of it.
When I would zoom out a relief map to the scale of the state of Nevada, the Black Rock Desert has an apparent disturbance to the general pattern of the Great Basin mountain ranges. It resembles a circular area much wider than the area we were focusing on. It was just a few weeks later in January... Looking at that circular area again, I noticed there are more arc-shaped mountain ranges surrounding the entire Black Rock region. The arcs fit together into a circle 54 miles (87 km) in diameter. I posted an article "Updated candidate crater outline and diameter - January 2009".
A computer-fitted circle on the map puts the center at 40.90 N 118.94 W, on the Black Rock Desert playa (lakebed) at the Quinn River Sink. All the highest peaks surrounding the Black Rock Desert region are literally on the circle - including Granite Peak, Pahute Peak, King Lear Peak, Majuba Mountain and KBSK Mountain. The previously-theorized outline in the arc of the Kamma Mountains actually supports this better, fitting a circle concentric within the wider circle. Large impact craters often have concentric uplift rings. There's no ellipse any more. This made for a more likely sounding hypothesis.
I noticed that after I posted the map of the new outline of a KML-mapped circle matching arcs of the mountain ranges, a lot of the feedback has changed. People seem to have more patience with letting us perform the research now, rather than just dismissing the idea.
In 2009, we got help from another geologist, Rich Loring of Reno. He saw the article about this research in the December 2008 issue of Discover Magazine. Soon after he expressed interest in the research, I noticed the 87km circular outline. Rich provided a very helpful sanity check on this outline. He knew that county geological maps, only available on paper, are more detailed than the USGS maps we had been using online. Nevada's Washoe, Pershing and Humboldt Counties intersect at the Black Rock Desert - and each have separate geological maps. Without making any conclusions from it, he confirmed that the geology does change between the inside and outside along that entire circle. It isn't proof of an impact. But it's a detail we needed one way or the other to test the confidence in the new outline. And it passed that test.
Rich also joined us on a day hike to explore Pahsupp Mountain in May 2009,
where we found the first observation of breccia overlying fractured rocks
across the playa from the Black Rock Range.
That significantly widened the area with those observations.
Our geologist advisers Bob and Rich have kept in touch. Neither were able to schedule a trip in 2010. Rich was traveling on all the dates we considered trips. Bob was planning to come later in the season. But the weather turned wet early and closed the season on us before he got a chance. Oh well. Sometimes that happens.
Even I only got to Black Rock twice in 2010. One was for a rocket launch meet in June. The second was to photograph the Perseids Meteor Shower in August under the extremely dark skies at Black Rock.
This observation helped expand by miles the area where we've observed breccia overlying fractured and jointed rocks.
I've been doing this occasionally, usually when I have an airline frequent flyer trip as an excuse. In Aug 2007 I visited Sierra Madera Crater near Fort Stockton, Texas. In Sep 2008 I explored the Santa Fe impact structure near Santa Fe, New Mexico where well-formed shatter cones were recently discovered to be right at the side of a road in a canyon. In 2009 I didn't visit any.
In 2010, I visited 5 confirmed impact structures -
two in Tennessee and one each in Kentucky, Arizona and Utah.
For the most part, these can be considered preliminary exploration.
I encountered a lot of private lands that were not open for free roaming.
But in all cases, I got to see rock formations vastly different from the
surrounding countryside.
Info on Wells Creek Crater: local newspaper, Earth Impact Database, Wikipedia, Google Maps
The round-shaped Middlesboro Basin has always stood out as different in the otherwise impenetrable ridges of the Appalachian Mountains. The basin focused streams into the head of the Cumberland River. And it eroded the ridges to form Cumberland Gap, an important trail for Native Americans and early westward migration in US history. It's described in a Planetary Science Institute newsletter article: "Impact at Cumberland Gap: Where Natural and National History Collide" (PDF).
I explored the town of Middlesboro, which is located in the crater. The center of the Middlesboro Crater is at the golf course. The friendly people there are used to visitors asking about the crater. I easily found rocks with shatter cones right near the club house. However, as a good guest, it was proper to take only photos and otherwise leave their property alone.
As an aviation enthusiast, of course I stopped by the Middlesboro Airport. (It's also inside the crater.) I discovered that it was the site that the WWII P-38 fighter called "Glacier Girl" was restored to flying condition after being recovered from Greenland. I saw Glacier Girl fly in the air show at Oshkosh in July. What a pleasant surprise to find the place where it was restored! And the people were very friendly. It was a nice visit.
Info on Middlesboro Crater: local newspaper, Earth Impact Database, Impact Field Studies Group (PDF), Wikipedia, Google Maps
More info on Flynn Creek Crater: Earth Impact Database, Wikipedia, Google Maps
Craters really don't get much more dramatic than this one. The crater is so geologically young (about 50,000 years) that the forces of erosion haven't affected it much yet.
With its conspicuous view, it caught attention of geologists long ago. Though it had been argued for decades, it was the first scientifically proven as an impact crater in 1960 by Eugene Shoemaker. Overturned rock layers in the ejecta field and high-pressure shocked minerals, both of which had also been found in the nuclear test craters in Nevada, became the proof that a meteor explodes violently on impact due to the extreme speed that it comes from space. This was the place where he mapped the structure of the rocks and pioneered the science of impact crater recognition.
Info on Meteor Crater: Visitor Center, USGS Astrogeology, Earth Impact Database, Wikipedia, Google Maps
There is a trail to the bottom. But it takes a minimum of 7 hours round trip, which would leave little or no margin on the shortest days of the year. Also, there was an incoming snowstorm a day away. So this was just an initial exploration - for safety's sake, I stuck to the short overlook trail.
Even at the overlook, you've traversed several concentric rings to get there and are well inside the structure. The usually-horizontal layering of rocks in Canyonlands has clearly been upset in the immediate vicinity of Upheaval Dome. There the rock layers have uncharacteristic slopes and faulting to them.
Like many other impact sites, initially geologists wouldn't even consider the impact theory. So the theory for decades was that a salt dome bulged up and the top was eroded off to make the rings. But eventually shatter cones and shocked minerals were found there, proving the impact origin of the site. (That was evidence the rocks were briefly exposed to pressures vastly beyond what any volcano is capable of.) Eugene Shoemaker was involved in documenting that proof.
In spite of now decades-old scientific proof, the National Park Service has been slow to update its materials. It usually still lists the salt dome and impact theories as competing explanations, probably indicating they were afraid to ruffle someone's feathers. Though a more recent brochure describes it as definitively proven to be an impact, like it should.
Info on Upheaval Dome: National Park Service, Earth Impact Database, Wikipedia, Google Maps
That can't necessarily be applied directly to Black Rock. It isn't clear from existing eroded terrain whether there was a single central uplift. The Kamma Mountains provide evidence for an uplift ring, which could mean there was a depression in the center, where we would have expected to find shatter cones.
Taking 0.06 x 87km yields 5.22km diameter, or 2.61km radius. Now that we have an estimate of Black Rock's center point at 40.90 N 118.94 W, we can experiment with the radius and the coordinates to see what we get.
It turns out a 2.61km radius around Black Rock's center point is entirely on the playa. Or rather, any bedrock is buried under the playa there.
So it lends more analytical weight to my realization from last year that we're not making the progress I had hoped from looking primarily for shatter cones. Indeed, these numbers suggest limiting the search for shatter cones much closer to the center point, if any bedrock exposures can be found. In order to find proof, we'll most likely need to focus on collecting samples for an electron microscope. The less-than-textbook-quality conical structures we found in the Black Rock Range and at Pahsupp Mountain may be the best we'll find at those distances from the center.
But then again, that's just a guess. So with less emphasis than before, we'll still try looking for shatter cones closer to the estimated center point.
He describes one sample as looking like fractured intrusive, volcanic rock. He got it from a rock structure at the west side of the base of Black Rock Point, which looked at a distance like a volcanic neck. He says, "But it turned out not to be extrusive lava at all - it appears to be an intrusive rock that might be emplaced much deeper, and possibly underlying the 'fractured rock'." He noted it appears consistent with what to expect in the area of a central uplift. So he'll examine for evidence of shocked-quartz in thin-sections he made from the specimens from this outcrop.
We had hoped to return in 2010. For now, that sample is the best we have. It'll be the first to take to a lab. Now I get to find out how much this costs.
And of course, there will be more exploration trips to Black Rock.
We'll continue to have the research follow where the data leads. At some point if the electron microscope turns up results, it would then become time to write a paper. I expect it might be co-authored by at least Bob, Rich and me. And everyone who has helped will be thanked again. But at this point there is no guarantee if or when all of that might happen.
Since the Black Rock Desert is an inhospitable place, one shouldn't travel there alone. For safety purposes, we can often use help an extra 4x4 vehicle with a Ham Radio to get a vehicle un-stuck or in case we need to get help.