• journal_title：Geological Society of America Bulletin
• Contributor：DANIEL J. FORNARI ; DONALD W. PETERSON ; JOHN P. LOCKWOOD ; ALEXANDER MALAHOFF ; BRUCE C. HEEZEN
• Publisher：Geological Society of America
• Date：1979-
• Format：text/html
• Language：en
• Identifier：10.1130/0016-7606(1979)90<435:SEOTSR>2.0.CO;2
• journal_abbrev：Geological Society of America Bulletin
• issn：0016-7606
• volume：90
• issue：5
• firstpage：435

North-south–trending dikes exhibiting well-developed columnar jointing have been visually observed on a series of submersible dives to the submarine extension of the southwest rift zone of Mauna Loa Volcano, Hawaii. These dikes are exposed along a west-facing 1,900-m-high scarp that is the sea-floor expression of the southwest rift zone. They form prominent walls, 10 to 60 m high and 1 to 3 m thick at their crests, separated by sediment- and rubble-mantled benches. The talus at the base of each dike consists of faceted blocks of basalt broken from the face of the wall.

Major-element analyses of samples collected m>in situm> show the rocks to be of “normal” Mauna Loa tholeiite composition.