 Little Ring Mountain at the northern end of the field contains at least 70 % brown volcanic glass with isolated phenocrysts of plagioclase. Vesicular textures are up to 5 %, suggesting that the lava erupted subaerially. Probable xenocrysts of quartz have been identified at the volcano. At least one xenolith fragment has been found in loose rubble at the volcano and included several quartz xenocrysts and polycrystalline quartz xenoliths in a glassy matrix with trachytic plagioclase.
