by Ian Kluft
January 22, 2009, updated January 31, 2009
I mentioned in the "State of the Research - January 2009" article that the old idea of the 30x40 mile ellipse was due for an update. After 2 years of researching this, including going back to look at maps, there has seemed to be more outside the 30x40 ellipse. Continuing to examine the maps for a better way to describe it, I found what appears to be a circle that follows a succession of terrain features all the way around. So this immediately jumps ahead as a much better candidate estimate than the ellipse.
Surprisingly, it actually increases the diameter to 54 miles or 87 km. That would probably be a maximum diameter which includes the terrace collapses. So that would be larger than the rim but surrounding it. An earlier version of this estimate was a concentric ring within this one which also fits a succession of terrain features at 51 miles or 82 km diameter, which would probably be closer to the original crater size.
The center of that circle also establishes a new estimate for the center of the suspected crater. It's a point on the Black Rock Playa very close to the Quinn River about 3 miles upstream (ENE) from it's mouth at the Quinn River Sink.
Center point: 40.90 north latitude, 118.94 west longitude
Diameter: approximately 54 miles or 87 km
The updated estimate of the center helps us to direct our efforts in the search for shatter cones or shock features. The estimate would be to look for them nearest to the center.
The map shown here helps to point out the sparse landmarks where the circle fits. This also potentially helps to describe some of the features in the area. Mountain ranges which are straight lines within the circle can be interpreted as post-cratering fault activity. These tend to be indicators that make the suspected crater appear very old.
My previous estimate of the 30x40 followed some eyeball lines:
The observation that the arc of the Kamma Mountains looks concentric within this larger circle is encouraging too. Large impact craters over 25km usually have concentric rings, according to "Traces of Catastrophe".
In 2007, a number of us looked at maps and mentioned various possible
circular features to examine. I checked with Scot Wilcoxon, Heather Stern
and Bob Verish to make sure that I'm not re-posting a previous suggestion
without giving its originator credit.
But having talked to everyone, it appears none of us were looking on this
big of a scale.
|Explore it on Google Maps...|
View Larger Map
|Mountain ranges which have arcs that fit the circle||Mountain ranges which cross the ring change appearance and elevation at that point|
The KML file of the ring used as an overlay in the Google Map can also be used in Google Earth.
The first estimate of the circle was a 51 mile / 82 km circle centered at 40.90, -118.94.
I noticed some more features following the ring outside the 82 km diameter. (Such as all the highest peaks in the region and contours of the Granite Range and Hog Ranch Mountains.) After asking around, the decision was to include the features out to the wider 54 mile / 87 km diameter, even though this may now include terrace collapse areas outside the actual rim. For now it's more important to point out the visible parts of the structure. The center point was moved about 1 km east to 40.90, -118.92 for what appeared to be a better fit, at least by eyeballing it.
A new section "Verifying the 87km ring for yourself" was added.
The diagram and text got additions several times. Most importantly, the mountain range names and info were added to both to help everyone find their way around.
Since I'm still making changes, I added the Revision History section.
A new section "Further Reading" was added.
I moved the estimated center point back to 40.90, -118.94 (1 km west). The diameter remains 87km.
The "what to look for" image was updated with one that's hopefully less busy looking and easier to read.
An observation about the arc of Crutcher Canyon and Squaw Valley as a possible outlying terrace collapse area was added to the section "Verifying the 87km ring for yourself".
A legend was added to the "Verifying the 87km ring for yourself" image. Some of the arcs were thin and some were thick. All of them are thick now. That keeps from having confusion with the thin lines used for labeling.
I swapped the images so that the "Verifying the 87km ring for yourself" image is at the top and the Google Map is below it.
The revision history was reformatted.