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The

Impact Crater, France

Rochechouart church. Image: Roger Suthren

The Rochechouart impact crater, west of Limoges in central France (maps), was created around 214 million years ago, during the late Triassic Period, by a large extraterrestrial body striking the Earth. In this now gentle landscape of woods and fields, evidence of the impact may be seen in disused and working quarries, and also in the distinctive stone used in many mediaeval buildings. The castle at Rochechouart, important in the wars between England and France in Richard the Lionheart's time, is built of impact breccia. Churches in nearby villages are built of glassy melt rocks produced by the impact (map of the breccias). The granitic rocks of the basement were extensively fragmented by the impact, and shatter cones have been found.

It is now thought that the Rochechouart structure is just one of a chain of at least five impact craters formed when a fragmented comet hit the Earth. The images below show some of the features of the impact structure, and the fragmented and melted rocks produced by the impact.

If you visit Rochechouart, there is an excellent museum, Espace Metéorite Paul Pellas, at 16, rue Jean Parvy, the main street of the old town.

The chateau at Rochechouart owes its defensive position to a resistant outcrop of meteorite impact breccia. The chateau is itself built of the impact breccia. So are most of the buildings in this fortified mediaeval town. Before modern transport, builders used whatever suitable materials were locally available. The base of the crater (approximately indicated by the red dashed line), with impact breccia lying on top of shattered basement rock, lies under grass in the steep slope below the chateau. (information from Marchat, 1996).

Rochechouart church is also built of impact breccia

Whilst it is easy to work, the breccia used for frames and carvings has not proved very resistant to weathering over the centuries.

During rebuilding of the castle (15th century?), this problem was solved by using local granite for structural and ornamental components, such as these columns and arches.

The Rochechouart breccia consists largely of shattered fragments of the local igneous and metamorphic basement rocks. The fragments are seen clearly here in the walls of the chateau.

Here is a sawn slice of the Rochechouart breccia. The holes represent soft fragments destroyed by weathering.

Links

• Association Pierre de Lune, Maison de la Météorite - 16 rue Jean Parvy 87600 ROCHECHOUART, France.
• La Météorite de Rochechouart (Académie de Limoges University)
• Other impact structures in Europe (Geological Survey, Canada)

Local information

• Office du Tourisme du Pays de la Météorite, Rue Victor Hugo, 87600 ROCHECHOUART. Tel/Fax 05.55.03.72.73

References

• MARCHAT, C. 1996. Les structures d'impacts météoritiques. Un exemple en France: Rochechouart - Chassenon. Editions de l'Association Pierre de Lune, Rochechouart. 43 pp.

Last Modified:

Last updated 22 January, 2009 at 22:17