| 日時: | 2009 年 12月 8日 (火) 10:00 - 12:00 |
| 場所: |
神戸大学自然科学総合研究棟 3号館 606号室, |
| 講演者: | D. Baratoux (UMR 5562, CNRS, Observatoire Midi-Pyrénées) |
| タイトル: | Impact cratering and the formation of shatter cones - The enigma remains |
| abstract: | Shatter cones are one of the most accepted field evidence for an
impact crater. However, the exact mechanism of formation is still
debated and several contrasting ideas can be found in the literature.
The identification of shatter cones is not straightforward and I will
recall their main characteristics. Several points deserve a particular
attention when evaluating models of formation: (1) the shape, not
conical but curved, (2) the presence of surface striations, and (2)
the direction of apices. Recent ideas (Sagy et al., 2002, 20O4 and
Baratoux and Melosh, 2003, Wieland et al., 2006) will be presented.
While the enigma remains, it is now clear that shatter cones result
from tensile fractures during shock unloading just behind the passage
of the shock front and are controlled by rock heterogeneities.
Preliminary observations of shatter cones in basalt made during a
field campaign in August 2009 in Vargeao and Vista Allegre (Brazil)
will be presented at this occasion.
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