Kilauea, the most active volcano on Hawaii, has been in continual eruption since 1983.

It entered a new phase in early May when fractures along a rift on the eastern side of the volcano opened during a series of earthquakes – some of which became volcanic fissures from which lava was erupted.

These fissures allowed magma that had been ponded in a lava summit lake to drain onto the ground surface as lava flows lower down the mountain.

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This was close to a residential subdivision known as Leilani Estates, where a new volcanic cone has since developed.

Kilauea is buttressed on its north-west side by the enormous mass of Mauna Loa volcano, but its south-east slopes face the ocean and are unsupported.

The magma from beneath the volcano usually erupts from the summit of the volcano, and there was a spectacular lava lake there in March.

However two rift zones (areas where the volcano is splitting apart), extending east and south-west from the summit, can make it possible for lava to erupts from Kilauea’s flanks too.

The current activity is based along the east rift zone.

According to the US Geological Survey, 23 separate new fractures there became volcanic fissures from which lava was erupted.

By the end of May, ‘fissure 8’ (the eighth new fissure to have announced itself) had become dominant – with activity at the others ceasing or subsiding.

This was the source of the lava that by June 4 was flowing into the sea several miles away near the Vacationland resort, where it completely filled what had previously been Kapoho Bay.

By mid-June, the coagulated spatter around the persistently active part of fissure 8 had built a cone approaching 200ft high.

This is a prominent and substantial feature on the landscape, and one that is likely to endure for thousands of years unless it is obliterated by later more violent or voluminous volcanic activity.

The question naturally arises as to whether this new hill and source of all that lava is a volcano in its own right.

If you look on the internet you will typically find ‘volcano’ defined as something like ‘a landscape feature produced at a site where magma is erupted’.

Such a simplistic definition would qualify the ‘fissure 8’ cone as a volcano, but I think just about every professional volcanologist would reject this, on the grounds that it is merely a subsidiary vent belonging to Kilauea.

This is because it is fed by magma from the source that supplies Kilauea as a whole, and could equally well have erupted elsewhere on Kilauea.

The new cone at fissure 8 is not significantly more substantial than numerous older subsidiary cones elsewhere on Kilauea.

However, you would search in vain for a formally sanctioned definition of the term ‘volcano’ to quantify the degree of connectedness or mutual size relationships in a way that could settle this issue. …..more here