They were on board the CSIRO research vessel Investigator, during an IMAS voyage to the Kerguelen Plateau.
Big Ben, which includes the 2,745 m tall Mawson Peak, the highest mountain on Australian territory north of Antarctica, is known to have erupted at least three other times since 2000.
But the remoteness of Heard Island and the neighbouring McDonald Islands, also an active volcano, means eruptions are rarely glimpsed by people and usually only recognised from sparse satellite images.
Heard Island is located in the southern Indian Ocean, approximately 1,550 kilometers (963 miles) north of Antarctica. The island is a visible part of the Kerguelen Plateau, a submerged feature on the seafloor. Credit wikimedia