Strombolian

The size of Strombolian eruptions can vary but are often characterised by intermittent explosions, which occur due to the presence of gas in the magma chamber within the volcano.

That seismic activity is “an indicator of the intensity of the strombolian explosive activity,” the institute said late on Tuesday.

Strombolian is an adjective describing volcanic eruptions with violent explosions ejecting incandescent dust.

Authorities say Anak Krakatau is still active, and is in fact becoming increasingly active with what are known as Strombolian eruptions - short lived, explosive blasts of lava - being emitted.

Hawaiian and Strombolian eruptions emit gentle lava flow and moderate eruptions, respectively.