Craters, calderas, and hyaloclastites on young Pacific seamounts

Abstract

Craters, calderas, and bedded hyaloclastites are commonly associated with seamounts. New Sea MARC 1 side‐looking sonar data for the summit of MOK seamount located near the East Pacific Rise (EPR) at 10°N show that MOK has a large caldera consisting of three coalesced circular depressions. These data also reveal many features such as stepped crater walls, talus deposits, ring faults, intracaldera flows, small cones, lava tubes and channels, and other features. Results of an ALVIN submersible dive in the crater of seamount “F” near the EPR at 21°22′N, 108°37′W revealed the presence of bedded hyaloclastite deposits; bedded hyaloclastites were also recovered by dredging of six other volcanoes all with summit craters. The bedded hyaloclastites are thin blankets of several types of basalt glass shards in a matrix of bottom sediment, clay, and ferromanganese minerals. The glass shards are chemically homogeneous and similar to midocean ridge basalts and transitional basalt lavas typical of young seamounts. Hyaloclastite deposits are crudely inverse graded with tabular, platy shards parallel to bedding. The characteristics of bedded hyaloclastites on seamount suggest an origin by rapid eruption rate, explosive mixing of magma and seawater, followed by rapid transport and deposition, such as may occur during submarine lava fountaining.

Evolution of fluid–rock interaction in the Reykjanes geothermal system, Iceland: Evidence from Iceland Deep Drilling Project core RN-17B

“…Similar deep submarine deposits have been described for Pacific Ocean seamounts (Batiza et al, 1984), for the Mid-Atlantic Ridge (Schmincke et al, 1979), and for fossil seamounts in Hokkaido, Japan (Yamagishi, 1991). Batiza et al (1984) described crudely bedded hyaloclastite deposits accumulating in depressions present at the crests of seamounts.…”

“…Batiza et al (1984) described crudely bedded hyaloclastite deposits accumulating in depressions present at the crests of seamounts. Schmincke et al (1979) argued that the Mid-Atlantic Ridge hyaloclastite deposits formed by a combination of pillows slumping on the sides of pillow basalt mounds and seawater currents preferentially carrying glass shards, sand-sized crystalline fragments, and clasts with chilled margins from rapidly erupting basalt and depositing them nearby.…”

The Seismic Stratigraphy and Sedimentary History of the East Mariana and Pigafetta Basins of the Western Pacific

“…The growth of submarine volcanoes from abyssal depths through the critical depth (pressure) for the onset of explosive volcanism and/or hydromagmatic processes leads to the production of hyaloclastic material. For example, Batiza et al (1984) provide convincing evidence for lava fountaining even at depths >3000 m which created abundant hyaloclastite deposits on young seamounts near the East Pacific Rise and ash-size glass shards are presently being produced at active submarine volcanoes such as "Kick em Jenny" . Hyaloclastite grain-flow deposits recovered during DSDP Leg 47, interpreted to have formed subaqueously during the initial growth of one of the Canary Islands, have been redeposited at least 100 km into the surrounding basin (Schmincke and von Rad, 1979).…”

Deep submarine pyroclastic eruptions: theory and predicted landforms and deposits

“…Lonsdale and Batiza (1980) reported the presence of extensive £ows of volcaniclastics on the summits of four seamounts 8001 200 m above the £anks of the EPR interpreted to have formed in deep-water phreatomagmatic eruptions (see also Batiza et al, 1984). Smith and Batiza (1989) documented extensive volcaniclastic deposits at depths from 1240^2500 m on six additional seamounts near the EPR and located several vent areas (see also Maicher et al, 2000;Maicher and White, 2001).…”