Examples of cliff failures along the shores of Mediterranean Sea and the role of bioerosion

Sinem Ugur; Ömer Aydan; Halil Kumsar

doi:10.68732/b7a72ca500a5e595

Paper contribution

Examples of cliff failures along the shores of Mediterranean Sea and the role of bioerosion

Sinem Ugur; Ömer Aydan; Halil Kumsar

DOI: https://doi.org/10.68732/b7a72ca500a5e595
Proceedings: EUROCK 2026
Pages: 297-302
Submitted: 28 January 2026
Accepted: 15 June 2026
Published: 12 August 2026

Summary

Abstract

It is known that some organisms can bore holes in rock formations consisting of such as limestone, sandstone, andesite and tuff. The authors investigated several sites along the Mediterranean Sea coasts and found many examples of rocks bored by organisms. The authors carried out some observations on bioerosion state and causes of rocks along sea-shores with cliffs in several locations of this region, particularly, Türkiye (Kuşadası Bay, Ekmeksiz Bay, Antalya, Ayvalık, Bodrum, Ören), Turkish Republic of Cyprus (from Magusa to Yeşilırmak), Croatia (Dubrovnik), Egypt (Alexandria) and Spain (Alicante). Rocks are various depending upon the geology of area surveyed. This study is concerned on the role of several organisms on the toe erosion along sea cliffs and their subsequent collapse. The erosion state and porous structure of some of rocks and their effect on their mechanical strength are assessed. Some available mechanical stability assessment methods are utilized to evaluate stability state of the stable and collapsed cliffs surveyed and their implications and findings are discussed. It is shown that the cliff stability can be assessed with the incorporation of the role of bioerosion.

Contributors

Authors

Sinem Ugur Fırat University, Turkiye ORCID 0000-0001-8367-0920
Ömer Aydan University of the Ryukyus, Okinawa, Japan ORCID 0000-0002-7304-6486
Halil Kumsar Pamukkale University, Geological Engineering, Denizli, Türkiye

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Full paper (PDF)Paper_33_Eurock_2026.pdf · 1.4 MB

Works cited

References

Alwany, A. Magdy, A., Ellen Thaler andMichael Stachowitsch (2009). Parrotfishbioerosion on Egyptian Red Seareefs. Journal of Experimental Marine Biologyand Ecology 371, 170–176.
Aydan, Ö. 2020. Rock Mechanics and Rock Engineering: Applications. Vol.2, CRC Press, Taylor and Francis Group, 379p, ISBN 978-0-367-42162-5.
Aydan, Ö. (2022). Some thoughts on slope stability issues in Mars, EUROCK2022, Helsinki, Finland, 8p.
Aydan, Ö. (2023). Some Rock Dynamics Issues in Mars. 49th Rock Mechanics Symposium of Japan, 36-41.
Aydan, Ö. and Kawamoto T. 1992. The stability of slopes and underground openings against flexural toppling and their stabilization, Rock Mechanics and Rock Engineering, Vol. 25, Issue 3, pp. 143-165, 1992.
Aydan, Ö., N. Tokashiki (2016). The evaluation of stability of overhanging Ryukyu limestone cliffs utilizing rock mass characteristics inferred from RMQR and intact rock, EUROCK2016, Ürgüp, 601-606.
Aydan, Ö., T. Kyoya, Y. Ichikawa, T. Kawamoto and Y. Shimizu (1989). A model study on failure modes and mechanisms of slopes in discontinuous rock mass. The 24th Annual meetings of Soil Mechanics and Foundation Eng. of Japan, Miyazaki, 415, 1089-1093.
Aydan, Ö., Ulusay, R. & Tokashiki, N. 2014. A new rockmass quality rating system:Rock Mass Quality Rating(RMQR) and its application to the estimation ofgeomechanicalcharacteristics of rock masses. Rock Mech RockEng 47: 1255–1276.
Aydan, Ö. Tokashiki, N., Ito, T. Shuri, Y. (2025). Multi-parameter response monitoring of a cliff at Miyagi Island of Okinawa Prefecture, Japan and the responses during earthquakes. EUROCK2025, Trondheim, ISBN 978-82-8208-079-8, 8p.
Horiuchi, K,. Ö. Aydan, N. Tokashiki, NZ Nasiry (2019). Some considerations on the causes of cliff failures of Ryukyu Limestone in Ryukyu Archipelago and the analysis of a recent cliff failure. Geotechnical Journal, Japan Society of Civil Engineers, Vol. 75, No. 2, 216-233.
Kázmér, Miklós and Danko Taboroši (2012). Bioerosion on the small scale –examples from the tropical and subtropicallittoral. Monostori Jubilee Volume, Hantkeniana 7, 37-94, Budapest.
Tokashiki, N. Aydan, Ö.2010. The stability assessment of overhanging Ryukyu limestone cliffs with an emphasis on the evaluation of tensile strength of Rock Mass. Journal of Geotechnical Engineering, JSCE, 66(2),397-406.
Tokashiki, N. and Aydan, Ö. 2011.A comparative study on the analytical and numerical stability assessment methods for rock cliffs in Ryukyu Islands. The 13thInternational Conf. of the International Association for Computer Methods and Advances in Geomechanics, Melbourne, 663-668.
Uğur, S. and Aydan, Ö. 2023. The mechanism of bioerosion and its effect on sea-cliffs (in Turkish). Yer Mühendisliği, No. 19, Year 11, June, 38-47.
Uğur, S. and Aydan, Ö. 2024. The possible role of the bioerosion on the stability of sea cliffs in Ryukyu Archipelago. EUROCK2024, Alicante, 716-721.

[1] Alwany, A. Magdy, A., Ellen Thaler andMichael Stachowitsch (2009). Parrotfishbioerosion on Egyptian Red Seareefs. Journal of Experimental Marine Biologyand Ecology 371, 170–176.

[2] Aydan, Ö. 2020. Rock Mechanics and Rock Engineering: Applications. Vol.2, CRC Press, Taylor and Francis Group, 379p, ISBN 978-0-367-42162-5.

[3] Aydan, Ö. (2022). Some thoughts on slope stability issues in Mars, EUROCK2022, Helsinki, Finland, 8p.

[4] Aydan, Ö. (2023). Some Rock Dynamics Issues in Mars. 49th Rock Mechanics Symposium of Japan, 36-41.

[5] Aydan, Ö. and Kawamoto T. 1992. The stability of slopes and underground openings against flexural toppling and their stabilization, Rock Mechanics and Rock Engineering, Vol. 25, Issue 3, pp. 143-165, 1992.

[6] Aydan, Ö., N. Tokashiki (2016). The evaluation of stability of overhanging Ryukyu limestone cliffs utilizing rock mass characteristics inferred from RMQR and intact rock, EUROCK2016, Ürgüp, 601-606.

[7] Aydan, Ö., T. Kyoya, Y. Ichikawa, T. Kawamoto and Y. Shimizu (1989). A model study on failure modes and mechanisms of slopes in discontinuous rock mass. The 24th Annual meetings of Soil Mechanics and Foundation Eng. of Japan, Miyazaki, 415, 1089-1093.

[8] Aydan, Ö., Ulusay, R. & Tokashiki, N. 2014. A new rockmass quality rating system:Rock Mass Quality Rating(RMQR) and its application to the estimation ofgeomechanicalcharacteristics of rock masses. Rock Mech RockEng 47: 1255–1276.

[9] Aydan, Ö. Tokashiki, N., Ito, T. Shuri, Y. (2025). Multi-parameter response monitoring of a cliff at Miyagi Island of Okinawa Prefecture, Japan and the responses during earthquakes. EUROCK2025, Trondheim, ISBN 978-82-8208-079-8, 8p.

[10] Horiuchi, K,. Ö. Aydan, N. Tokashiki, NZ Nasiry (2019). Some considerations on the causes of cliff failures of Ryukyu Limestone in Ryukyu Archipelago and the analysis of a recent cliff failure. Geotechnical Journal, Japan Society of Civil Engineers, Vol. 75, No. 2, 216-233.

[11] Kázmér, Miklós and Danko Taboroši (2012). Bioerosion on the small scale –examples from the tropical and subtropicallittoral. Monostori Jubilee Volume, Hantkeniana 7, 37-94, Budapest.

[12] Tokashiki, N. Aydan, Ö.2010. The stability assessment of overhanging Ryukyu limestone cliffs with an emphasis on the evaluation of tensile strength of Rock Mass. Journal of Geotechnical Engineering, JSCE, 66(2),397-406.

[13] Tokashiki, N. and Aydan, Ö. 2011.A comparative study on the analytical and numerical stability assessment methods for rock cliffs in Ryukyu Islands. The 13thInternational Conf. of the International Association for Computer Methods and Advances in Geomechanics, Melbourne, 663-668.

[14] Uğur, S. and Aydan, Ö. 2023. The mechanism of bioerosion and its effect on sea-cliffs (in Turkish). Yer Mühendisliği, No. 19, Year 11, June, 38-47.

[15] Uğur, S. and Aydan, Ö. 2024. The possible role of the bioerosion on the stability of sea cliffs in Ryukyu Archipelago. EUROCK2024, Alicante, 716-721.