Lava fountain and ‘A‘ā during Pu‘u ‘Ō‘ō ep. 21

Beginning with episode 20 (June 7, 1984), fountain-fed ‘A‘ā flows spreading from Pu‘u ‘Ō‘ō became the norm, mainly because of a substantial increase in fountain heights. During the earlier episodes, fountain heights rarely exceeded 250 m (820 ft), but later episodes erupted fountains consistently higher than 300 m (985 ft), sometimes higher than 400 m (1,310 ft). ‘A‘ā flows were fed directly by fallback from the fountains, resulting in lava with a higher viscosity and yield strength, owing to the loss of heat and volatile components.