Shattered Earth – Making Rock Flow

66 million years ago rock was shattered in the Earth’s crust of the Yucatan Peninsula. Nearly instantaneously, once immobile granite was flowing over distances of tens of kilometers at speeds in excess of a hundred kilometers per hour.  Shattered rock ejected from the crater was moving even faster, with speeds in excess of 20,000 kilometers per hour.  How, scientists wonder, was rock so suddenly transformed?

Clues of that process occur in the core recovered by our expedition.   To tease those clues from the core, two teams, on overlapping shifts, are describing each centimeter of the core.  Throughout that process, the geologists are looking for evidence of the damage caused by impact and trying to discern how that damage may have – at least for a moment 66 million years ago – completely changed the properties of rock.

Geologists Annemarie Pickersgil and Auriol Rae examining core

That damage was produced by the explosive blast of the impacting asteroid and its tremendous shock pressures. That shock radiated through the Earth’s crust causing anomalies in rock’s behavior.  The details of that damage and the resulting anomalies have – until now – been difficult to study.

In addition to the visual clues geologists are seeing in the core, others on the team are measuring physical properties, such as density, to further evaluate how the rock was changed in those brief few moments of impact.  While some of the rock properties were restored and, thus, the rock may appear to be the same today, tell-tale clues, like density, are revealing a different story.

Geophysicist Gail Christeson measuring density

By David Kring

Feature image: MMowat@ECORD_IODP (showing a core linescan and CT density image)

All other Images: DKring@ECORD_IODP




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