Innumerable as the Starrs of Night,
Or Starrs of Morning,
Dew-drops, which the Sun
on every leaf and every flouer
Beauty is truth, truth beauty,
— that is all
Ye know on earth, and all
ye need to know.
E = M
Energy is eternal delight.
Impearls: "A Great Eye, lidless, (formerly) wreathed in flame..." - Chicxulub, the dinosaur-killer crater
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“A Great Eye, lidless, (formerly) wreathed in flame…” –
It's well accepted among scientists nowadays that the dinosaurs — along with three-quarters of all species on earth, land and sea — disappeared in the aftermath of the cataclysmic collision of a sizable asteroid or comet impacting the earth some 65 million years ago. Though the huge, multi-ringed, some 180 kilometers (112 miles) in diameter crater resulting from that cosmic trainwreck was found over a decade ago — buried at the northwestern tip of the Yucatan peninsula in Mexico, beneath up to a kilometer of sediments — it's apparently invisible as far as any visible effect on the surface topography of that part of the Yucatan (which basically is about as flat as a pancake) is concerned.
The deeply buried crater's seeming irrelevance to affairs on the surface is more apparent than real, however. The porous limestone (so-called “karst”) basement of the Yucatan is pierced by a plenitude of water-filled sinkholes, known locally as “cenotes”. These cenotes fall into patterns (easily visible on detailed road maps, for example) which, it turns out, congregate along the buried outer wall of the stupendous concentric-ringed prehistoric crater.
(Thus, one can swim in a pool lying atop the old dinosaur-killer crater rim. A fond remembrance: rather like the Pantheon in Rome, one might say, the underground cenote raised a vast dome vaulting through the rock ceiling into daylight for only a brief circle, through which sunlight poured to blaze in the otherwise dark, quiet pool, down the roof and along the sides of which stalactite and stalagmite columns marched….)
As A. R. Hildebrand and his colleagues (authors of the paper in Nature “Size and structure of the Chicxulub crater revealed by horizontal gravity gradients and cenotes” that is considered in this piece) describe it: 1
The authors also note that, “The edges of the crater (and associated gravity-gradient features) correspond to bends in the coastline, and interior gradient features sometimes correlate with rocky points along the coastline.”
Beyond those surficial physical consequences of the subterranean crater's presence, the team assembling this marvelous figure and accompanying article, in effect — “merely” by careful measurement of seemingly trivial changes in gravity — have stripped the veil off this vast interred sepulchre, revealing the blasted hole in all its ruined glory! Kudos to the group for putting together this dramatic portrait — which isn't an image at all in the sense of a photograph, but might as well be for the clarity of the scene it presents.
The authors interpret the spectacular visage of the ancient crater: 1
Hildebrand et al. acknowledge that, “the peripheral strong gradient features are truncated or diverted for the northern third of the crater.
Magnetic and seismic data confirm that a completely circular basin and impact structure is present, and some weak circular structure appears in the gravity data north of the truncation of the peripheral gradient features, but the cause of the truncation of Chicxulub's gravity expression remains to be understood.”
Here's the Abstract from A. R. Hildebrand and colleagues' Nature article: 1
1 A. R. Hildebrand, M. Pilkington, M. Connors, C. Ortiz-Aleman, and R. E. Chavez, “Size and structure of the Chicxulub crater revealed by horizontal gravity gradients and cenotes,” Nature, Vol. 376, Issue No. 6539 (dated 1995-08-03), pp. 415-417 [doi:10.1038/376415a0]. Requires pay-per-view for full text.
UPDATE: 2004-01-19 19:00 UT: Substantial rewording and material added from Hildebrand et al.
UPDATE: 2005-07-24 06:00 UT: Compression on crater image decreased.
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