The web is filled with a lot of nonsense dressed up to look like science. This blog is a good example: A Catastrophe of Comets
The owner that blog "Crater Hunter" circles up things that he thinks are impact craters on Google Earth images. Someone cited this blog in the comment section of one of my Watts Up With That posts. To which I replied:

That region of Mexico was over a subduction zone during the Tertiary. The region is rife with intrusive and extrusive Tertiary-aged igneous rocks and Cretaceous sedimentary rocks.
Crater Hunter seemed to be focused in a lineation that he claimed was part of "the pristine radial outwards flowing pyroclastic density current surrounding the mountain a couple of hundred miles away." As nearly as I could tell, he thought the NE-striking lineation in the image below was part of a recent radial pyroclastic flow...

A quick look at a geologic map of the region shows that the lineation is a ridge composed of NW-dipping Cretaceous-aged limestone & shale...

There are lots of volcanic and igneous outcrops in the area… All of them of Tertiary age and most rhyolitic… None of them are even remotely associated with impact-related geology.
The owner that blog "Crater Hunter" circles up things that he thinks are impact craters on Google Earth images. Someone cited this blog in the comment section of one of my Watts Up With That posts. To which I replied:
David Middleton says:
November 3, 2011 at 9:56 am
There is nothing mysterious about the “Chihuahuan Ignimbrites”… And the rhyolitic eruptions from which they were sourced occurred in the Mid-Tertiary…
November 3, 2011 at 9:56 am
beng says:
November 3, 2011 at 8:52 am
[...]
And there’s quite a bit of geologic evidence for an impact, too:
http://craterhunter.wordpress.com/no...ment/part-two/
That blog is 100% science fiction.November 3, 2011 at 8:52 am
[...]
And there’s quite a bit of geologic evidence for an impact, too:
http://craterhunter.wordpress.com/no...ment/part-two/
There is nothing mysterious about the “Chihuahuan Ignimbrites”… And the rhyolitic eruptions from which they were sourced occurred in the Mid-Tertiary…
Petrogenesis of voluminous mid-Tertiary ignimbrites of the Sierra Madre Occidental, Chihuahua, Mexico
Maryellen Cameron, William C. Bagby and Kenneth L. Cameron
Abstract
The mid-Tertiary ignimbrites of the Sierra Madre Occidental of western Mexico constitute the largest continuous rhyolitic province in the world. The rhyolites appear to represent part of a continental magmatic arc that was emplaced when an eastward-dipping subduction zone was located beneath western Mexico.
In the Batopilas region of the northern Sierra Madre Occidental the mid-Tertiary Upper Volcanic sequence is composed predominantly of rhyolitic ignimbrites, but volumetrically minor lava flows as mafic as basaltic andesite are also present.
[…]
LINK
Maryellen Cameron, William C. Bagby and Kenneth L. Cameron
Abstract
The mid-Tertiary ignimbrites of the Sierra Madre Occidental of western Mexico constitute the largest continuous rhyolitic province in the world. The rhyolites appear to represent part of a continental magmatic arc that was emplaced when an eastward-dipping subduction zone was located beneath western Mexico.
In the Batopilas region of the northern Sierra Madre Occidental the mid-Tertiary Upper Volcanic sequence is composed predominantly of rhyolitic ignimbrites, but volumetrically minor lava flows as mafic as basaltic andesite are also present.
[…]
LINK
Major ignimbrites and volcanic centers of the Copper Canyon area: A view into the core of Mexico’s Sierra Madre Occidental
Eric R. Swanson, Kirt A. Kempter, Fred W. McDowell and William C. McIntosh
Abstract
Reconnaissance mapping along Copper Canyon highway has established ignimbrite stratigraphic relationships over a relatively large area in the central part of the Sierra Madre Occidental volcanic field in western Chihuahua, Mexico. The oldest ignimbrites are found in the central part of the area, and they include units previously mapped from north of the study area, in and around the Tomóchic volcanic complex. Copper Canyon, at the southern end of the study area, exposes younger units, including the intracaldera tuff of the Copper Canyon caldera and five overlying ignimbrites. Well-exposed calderas are found near San Juanito, in the central part of the map area, and at Sierra Manzanita, to the far north. Stratigraphic evidence for yet another caldera in the northern part of the area is found in the Sierra El Comanche. The stratigraphic and limited available isotopic age data suggest that volcanism was particularly active ∼30 m.y. ago. This reconnaissance survey also documented lava-flow lithologies consistent with previous observations from Tomóchic that intermediate lavas have erupted throughout that area’s volcanic history and that basaltic andesite became particularly abundant as felsic volcanism waned.
[…]
LINK
Even if the mid-Tertiary ignimbrites of the Sierra Madre Occidental of western Mexico were caused by an extraterrestrial impact event, it would have happened ~30 million years prior to the extinction of the North American megafauna.
Eric R. Swanson, Kirt A. Kempter, Fred W. McDowell and William C. McIntosh
Abstract
Reconnaissance mapping along Copper Canyon highway has established ignimbrite stratigraphic relationships over a relatively large area in the central part of the Sierra Madre Occidental volcanic field in western Chihuahua, Mexico. The oldest ignimbrites are found in the central part of the area, and they include units previously mapped from north of the study area, in and around the Tomóchic volcanic complex. Copper Canyon, at the southern end of the study area, exposes younger units, including the intracaldera tuff of the Copper Canyon caldera and five overlying ignimbrites. Well-exposed calderas are found near San Juanito, in the central part of the map area, and at Sierra Manzanita, to the far north. Stratigraphic evidence for yet another caldera in the northern part of the area is found in the Sierra El Comanche. The stratigraphic and limited available isotopic age data suggest that volcanism was particularly active ∼30 m.y. ago. This reconnaissance survey also documented lava-flow lithologies consistent with previous observations from Tomóchic that intermediate lavas have erupted throughout that area’s volcanic history and that basaltic andesite became particularly abundant as felsic volcanism waned.
[…]
LINK

That region of Mexico was over a subduction zone during the Tertiary. The region is rife with intrusive and extrusive Tertiary-aged igneous rocks and Cretaceous sedimentary rocks.
Crater Hunter seemed to be focused in a lineation that he claimed was part of "the pristine radial outwards flowing pyroclastic density current surrounding the mountain a couple of hundred miles away." As nearly as I could tell, he thought the NE-striking lineation in the image below was part of a recent radial pyroclastic flow...

A quick look at a geologic map of the region shows that the lineation is a ridge composed of NW-dipping Cretaceous-aged limestone & shale...

There are lots of volcanic and igneous outcrops in the area… All of them of Tertiary age and most rhyolitic… None of them are even remotely associated with impact-related geology.
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