Huge erratic boulders in Tonga deposited by a prehistoric tsunami

Abstract

Research Article| February 01, 2009 Huge erratic boulders in Tonga deposited by a prehistoric tsunami Cliff Frohlich; Cliff Frohlich * 1Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758-4445, USA *E-mail: cliff@ig.utexas.edu. Search for other works by this author on: GSW Google Scholar Matthew J. Hornbach; Matthew J. Hornbach 1Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758-4445, USA Search for other works by this author on: GSW Google Scholar Frederick W. Taylor; Frederick W. Taylor 1Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758-4445, USA Search for other works by this author on: GSW Google Scholar Chuan-Chou Shen; Chuan-Chou Shen 2Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan, Republic of China Search for other works by this author on: GSW Google Scholar 'Apai Moala; 'Apai Moala 3Geology Section, Ministry of Lands, Survey, and Natural Resources, Nuku'alofa, Tonga Search for other works by this author on: GSW Google Scholar Allan E. Morton; Allan E. Morton 4343 Harvard Avenue, Rexburg, Idaho 83440, USA Search for other works by this author on: GSW Google Scholar Jens Kruger Jens Kruger 5SOPAC, South Pacific Islands Applied Geoscience Commission, Nabua, Fiji Islands Search for other works by this author on: GSW Google Scholar Author and Article Information Cliff Frohlich * 1Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758-4445, USA Matthew J. Hornbach 1Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758-4445, USA Frederick W. Taylor 1Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758-4445, USA Chuan-Chou Shen 2Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan, Republic of China 'Apai Moala 3Geology Section, Ministry of Lands, Survey, and Natural Resources, Nuku'alofa, Tonga Allan E. Morton 4343 Harvard Avenue, Rexburg, Idaho 83440, USA Jens Kruger 5SOPAC, South Pacific Islands Applied Geoscience Commission, Nabua, Fiji Islands *E-mail: cliff@ig.utexas.edu. Publisher: Geological Society of America Received: 20 Jun 2008 Revision Received: 25 Sep 2008 Accepted: 06 Oct 2008 First Online: 12 Oct 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2009 Geological Society of America Geology (2009) 37 (2): 131–134. https://doi.org/10.1130/G25277A.1 Article history Received: 20 Jun 2008 Revision Received: 25 Sep 2008 Accepted: 06 Oct 2008 First Online: 12 Oct 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Cliff Frohlich, Matthew J. Hornbach, Frederick W. Taylor, Chuan-Chou Shen, 'Apai Moala, Allan E. Morton, Jens Kruger; Huge erratic boulders in Tonga deposited by a prehistoric tsunami. Geology 2009;; 37 (2): 131–134. doi: https://doi.org/10.1130/G25277A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Along some coastlines there are erratic boulders apparently emplaced by tsunamis or cyclonic storms; evaluating their origin and time of emplacement places constraints on the frequency, severity, and location of coastal hazards. Seven such large coral limestone boulders are present near Fahefa village on Tongatapu Island, southwest Pacific, apparently emplaced by a prehistoric tsunami. These boulders are 10–20 m above sea level and above any possible source, and all are 100–400 m from the present shoreline. Coral 230Th ages indicate that the limestone formed during the last interglacial sea-level highstand, ca. 120–130 ka. The largest boulder is ~20 times more massive than any reported boulders emplaced by historically documented storms and may be the largest known tsunami or storm erratic worldwide situated above its source. We performed computer simulations to assess whether tsunamis produced by earthquakes, undersea landslides, or volcanoes could emplace the boulders. The simulations indicate that either volcanic flank collapse along the Tofua arc ~30–40 km to the southwest or undersea landslides on the submarine slopes of Tongatapu could be responsible. Either could explain why these boulders are not widespread on Tongatapu, and instead occur in a localized group along the western coast. This study demonstrates that small (<1 km3) submarine slope failures sometimes generate locally large tsunamis. The Fahefa boulders are in a well-studied and well-populated area, yet were unknown to the scientific community until recently; this suggests that systematic searches elsewhere for erratic boulders and other tsunami deposits might provide new information for assessing the size and extent of prehistoric tsunamis. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.