Eruptions at Boring Lava Field occur in a concentrated manner, often in clusters of three to six vents, as at Bobs Mountain and Portland Hills. These types of vents typically produced similar types of magma in relatively short periods of time, and they also frequently show alignment. Vents in the field have generally produced basalt and basaltic andesite, with some andesitic eruptions, including those that produced the large Larch Mountain shield volcano.