Stratigraphy and geochronology of Holocene basaltic tephra deposits on the southeastern flank of Mauna Loa volcano, Island of Hawaiʻi, and implications for volcanic hazards

Abstract

Abstract

Abstract Tephra deposits are widespread across the Island of Hawaiʻi, many of which have been poorly studied. An understanding of the ages and sources of these tephras is important for assessing the frequency of explosive eruptions and thus the hazard potential from individual volcanoes on the island. This study presents new data from a 2-meter-thick section of tephra located midway up the southeastern flank of Mauna Loa volcano on the Island of Hawaiʻi. A total of 15 new radiocarbon dates constrain eruptive activity to between 6540 ± 40 cal BP (5493 BCE ) and 276 ± 21 cal BP (1635 CE ). The average recurrence interval for tephra deposition is estimated to be 240 years for the past ca. 9,000 years. Repose recurrence intervals vary from 15 to 882 years, indicating that the actual timing between tephra-producing explosive eruptions is more variable than the ca. 240-year average recurrence interval. The deposition and preservation of the section appears to be influenced by its location near tree line, its proximity to the trade wind inversion layer, and preservation by flanking flows. Most layers consist predominantly of fine ash with pedogenic or palagonitic alteration. Petrologic examination indicates that most of the tephra layers, although significantly altered, contain some fresh glass from which in situ geochemical data can be obtained. Thus, the outcrop provides an important type section that can be used for correlating tephra units between Kīlauea and Mauna Loa.