Sediment yield following severe volcanic disturbance—A two-decade perspective from Mount St. Helens

Abstract

Research Article| September 01, 2000 Sediment yield following severe volcanic disturbance—A two-decade perspective from Mount St. Helens J.J. Major; J.J. Major 1U.S. Geological Survey, Cascades Volcano Observatory, Vancouver, Washington 98661, USA Search for other works by this author on: GSW Google Scholar T.C. Pierson; T.C. Pierson 1U.S. Geological Survey, Cascades Volcano Observatory, Vancouver, Washington 98661, USA Search for other works by this author on: GSW Google Scholar R.L. Dinehart; R.L. Dinehart 2U.S. Geological Survey, University of California, Sacramento, California 95819, USA Search for other works by this author on: GSW Google Scholar J.E. Costa J.E. Costa 3U.S. Geological Survey, Portland, Oregon 97216, USA Search for other works by this author on: GSW Google Scholar Author and Article Information J.J. Major 1U.S. Geological Survey, Cascades Volcano Observatory, Vancouver, Washington 98661, USA T.C. Pierson 1U.S. Geological Survey, Cascades Volcano Observatory, Vancouver, Washington 98661, USA R.L. Dinehart 2U.S. Geological Survey, University of California, Sacramento, California 95819, USA J.E. Costa 3U.S. Geological Survey, Portland, Oregon 97216, USA Publisher: Geological Society of America Received: 09 Mar 2000 Revision Received: 16 Jun 2000 Accepted: 07 Jul 2000 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2000) 28 (9): 819–822. https://doi.org/10.1130/0091-7613(2000)28<819:SYFSVD>2.0.CO;2 Article history Received: 09 Mar 2000 Revision Received: 16 Jun 2000 Accepted: 07 Jul 2000 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation J.J. Major, T.C. Pierson, R.L. Dinehart, J.E. Costa; Sediment yield following severe volcanic disturbance—A two-decade perspective from Mount St. Helens. Geology 2000;; 28 (9): 819–822. doi: https://doi.org/10.1130/0091-7613(2000)28<819:SYFSVD>2.0.CO;2 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 Explosive volcanic eruptions perturb water and sediment fluxes in watersheds; consequently, posteruption sediment yields can exceed pre-eruption yields by several orders of magnitude. Annual suspended-sediment yields following the catastrophic 1980 Mount St. Helens eruption were as much as 500 times greater than typical background level, and they generally declined nonlinearly for more than a decade. Although sediment yields responded primarily to type and degree of disturbance, streamflow fluctuations significantly affected sediment-yield trends. Consecutive years (1995–1999) of above-average discharge reversed the nonlinear decline and rejuvenated yields to average values measured within a few years of the eruption. After 20 yr, the average annual suspended-sediment yield from the 1980 debris-avalanche deposit remains 100 times (104 Mg [megagrams]/km2) above typical background level (∼102 Mg/km2). Within five years of the eruption, annual yields from valleys coated by lahar deposits roughly plateaued, and average yields remain about 10 times (103 Mg/km2) above background level. Yield from a basin devastated solely by a blast pyroclastic current diminished to background level within five years. These data demonstrate long-term instability of eruption-generated detritus, and show that effective mitigation measures must remain functional for decades. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.