Structure of Lō‘ihi Seamount, Hawai‘i and Lava Flow Morphology From High-Resolution Mapping

David A Clague,Jennifer B Paduan,David W Caress,Craig L Moyer,Dana R Yoerger,Brian T Glazer

doi:10.3389/feart.2019.00058

Abstract

High-resolution bathymetric data were collected using AUV Sentry at the summit and at two hydrothermal vent fields on the deep south rift of L¯o‘ihi Seamount. The summit map records a nested series of caldera and pit crater collapse events, uplift of one resurgent block, and eruptions that formed at least five low lava shields that shaped the summit. The earliest and largest caldera, formed ~5900 years ago, bounds almost the entire summit plateau. The resurgent block was uplifted slightly more than 100 m and has a tilted surface with a dip of about 6.5° towards the SE. The resurgent block was then modified by collapse of a pit crater centered in the block that formed West Pit. The shallowest point on L¯o‘ihi’s summit is 986 m deep and is located on the northwest edge of the resurgent block. Several collapse events culminated in formation of East Pit, and the final collapse formed Pele’s Pit in 1996. The nine mapped collapse and resurgent structures indicate the presence of a shallow crustal magma chamber, ranging from depths of ~1 km to perhaps 2.5 km below the summit, and demonstrate that shallow sub-caldera magma reservoirs exist during the late pre-shield stage. On the deep south rift zone are young medium- to high-flux lava flows that likely erupted in 1996 and drained the shallow crustal magma chamber to trigger the collapse that formed Pele’s Pit. These low hummocky and channelized flows had molten cores and now host the FeMO hydrothermal field. The Shinkai Deep hydrothermal site is located among steep-sided hummocky flows that formed during low-flux eruptions. The Shinkai Ridge is most likely a coherent landslide block that originated on the east flank of L¯o‘ihi.

Highlights

The timing of development of shallow sub-caldera magma chambers and their overlying calderas remains uncertain in basaltic volcanoes
Lo‘ihi has been the focus of intense study with numerous oceanographic expeditions and Pisces IV and V, ALVIN, MIR, and Shinkai 6000 submersible and Kaiko and Jason remotely operated vehicle (ROV) dives that have collected samples and made visual and video observations
The new high-resolution summit bathymetry at Lo‘ihi Seamount shows a nested series of eight caldera and pit crater collapses events, uplift of one resurgent block, and eruptions that formed at least five low lava shields

Summary

Introduction

The timing of development of shallow sub-caldera magma chambers and their overlying calderas remains uncertain in basaltic volcanoes. Emery (1955) named Lo‘ihi and presented the first of several bathymetric charts showing the north-south elongate shape of the volcano and suggested that Lo‘ihi and nearby Papa‘u (Figure 2) might mark the locations of young submarine volcanoes related to the Hawai‘ian volcanic chain. It was not, until the Hawai‘ian Volcano Observatory’s seismic network detected earthquake swarms in 1971–1972 and 1975 located beneath the volcano (Klein, 1982; Bryan and Cooper, 1995) that Lo‘ihi was recognized as an active submarine volcano and the youngest in the Hawai‘ian-Emperor chain. In 1996, an intense seismic swarm (Caplan-Auerbach and Duennebier, 2001a,b) accompanied the formation of a new pit crater named Pele’s Pit (Lo‘ihi Science Team, 1997) and initiation of sulfide/sulfate deposition inside it (Davis and Clague, 1998; Davis et al, 2003), and again invigorated scientific work at Lo‘ihi. The formation of the summit pit crater in 1996 has renewed importance as summit collapse has recently occurred at Kılauea Volcano

Results

Discussion

Conclusion