Boulasse (Fosse)
A 21-metre-deep collapse forming a funnel about 70 metres in diameter, with no speleological interest as it stands.
EspeleoWorld
Boulasse (Fosse)
A 21-metre-deep collapse forming a funnel about 70 metres in diameter, with no speleological interest as it stands.
Vermenton
Depth: 21 m
Updated record
https://espeleoworld.com/en/c/boulasse-fosse-vermenton
Information can change. Always verify coordinates, access, weather, and cave conditions before setting out.
A 21-metre-deep collapse forming a funnel about 70 metres in diameter, with no speleological interest as it stands.
Description
Morphology
The drop of this collapse is significant, with a depth of 21 metres, forming a funnel about 70 metres in diameter. At each thaw, mechanical erosion carries many stones down to the bottom of the depression. No apparent fissure allows, in the current state of the collapse, any prospect of a dig likely to succeed in reaching the underground network. Its visit therefore offers hardly any speleological interest.
Hydrology
According to Mazoit (1954), the pit would be located on the underground course of the Serein. Microgravimetry measurements carried out in the late 1970s and early 1980s (Chabert Cl.) would also have shown the existence of underground galleries 8 metres in diameter at more than 50 metres depth and about twenty metres from the collapse. Unfortunately, this information has been lost.
Other details
Geology: Upper Oxfordian.
Source: Spéléo Club de Chablis (SCC) website > “Fosse Boulasse ou Trou de la Fourboulas (89441 - Vermenton)” -- https://www.scchablis.com/Site/Speleo/Invent/89/89441/fosse_boulasse.php
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Contains information from Grottocenter (Wikicaves), grottocenter.org, made available under the Open Database License (ODbL 1.0, https://opendatacommons.org/licenses/odbl/1-0/), modified. · https://grottocenter.org/ui/entrances/35248 · The derived data is available on request under the ODbL: [email protected] · data as of 2026 · Source: Grottocenter (Association Wikicaves), worldwide collaborative cave database (grottocenter.org), modified. CC BY-SA 3.0, https://creativecommons.org/licenses/by-sa/3.0/ Grottocenter (Wikicaves) · Text by BTH (Description générale), BTH (Géologie) · adapted by Espeleoworld (normalized, translated); the adaptation is licensed CC BY-SA 3.0, https://creativecommons.org/licenses/by-sa/3.0/ · https://grottocenter.org/ui/entrances/35248 · data as of 2026