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Submarine mass-wasting and volcanism on the flanks of Ulleungdo Island and Anyongbok Seamount in the East Sea of Korea

Deniz Cukur1, David M. Buchs2, In-Kwon Um1, Gee-Soo Kong1, Jong-Hwa Chun1, Senay Horozal3, Seong-Pil Kim1

  • Affiliations:  1 Marine Geology and Energy Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, Republic of Korea; 2School of Earth and Environmental Sciences, Cardiff University, UK ; 3Department of Geoscience, University of Malta, Malta

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 76

  • Programme No: 6.2.12

  • Theme 6 > Session 2

Abstract

Mass-wasting and submarine volcanic events on the lower flanks of seamounts and islands are important for understanding submarine geohazards associated with the evolution of large intra-oceanic volcanoes. These events were studied in the East Sea of Korea using new piston cores from the foot of Anyongbok Seamount and Ulleungdo Island. At the Anyongbok Seamount, numerous ca. 1 to 20 cm-thick pumiceous lapilli to breccia layers were found interbedded with background pelagic sediments. New petrographic and geochemical analyses of volcanic glass in these layers and other tephra in the region support their formation by local, subaqueous volcanic eruptions (<500 meters below sea level), with no or limited post-depositional reworking. In contrast, a ca. 2.65 m-thick, normally graded layer of pumiceous breccia to lapilli was cored at the foot of Ulleungdo Island. Mud clasts and compositional heterogeneity of the pumices towards the base of the deposit indicate reworking by gravity flow along the island's slope. This is consistent with chirp seismic profiles that show transparent seismic facies and locally hummocky topography - features diagnostics of Mass Transport Deposits (MTDs). Volcanic glass composition in the MTD and other tephra layers in the East Sea and Japan suggest that the pumiceous MTD at Ulleungdo Island correlate to U-Ym (or SKP-I) Plinian eruption at ~40 ka. This indicates that large subaerial eruptions can produce submarine MTDs associated with regional tephra fallout and/or pumice rafts. This is the first evidence for volcanogenic deep-sea MTDs and explosive volcanism at an island and seamount in the East Sea.