Abstract

Rather conspicuous trenches found on the south Atlantic island Tristan da Cunha, at the time of the investigation of the volcanic eruption of 1961, represent former courses of lava streams. They are as much as 20 feet wide and 25 feet deep and are flanked by levees built up by overflow followed by solidification. Variations are described, for some have walls that taper in at the bottom or flare at the top, and some do not have the levees. It is pointed out that the channels have not formed by collapse of a lava tunnel with resulting lava moraines or scoriaceous block walls on either side. Thus a clear distinction is made between lava levees, a constructional feature built up by overflowing solidifying lava, and lava moraines.

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