A small earthquake registering 2.9 on the Richter scale struck near White Island overnight.

Geonet reports the quake hit at 7.01pm 10km south of White Island and registered a depth of 5km.

Activity at White Island. Photo: Tracy Hardy.

The earthquake comes after Geonet scientists downgraded the volcano's alert level to one and reduced its aviation colour code to yellow.

Geonet says observations in the last week have shown that a small ash cone has been built in the 'hot lake” crater, which is the current focus of activity. The ash cone is surrounded by a small moat of water.

'It is likely in the short term, activity will alternate between dry and wet eruptions. When drier conditions prevail, like last week, some volcanic ash may be produced. If there is an increase in water near the vent then phreatic (steam-driven) eruptions may occur,” reports Geonet.

'The crater containing the lava dome remains unchanged.”

Seismic tremor levels are currently low, which is thought to partly reflect the lack of water involvement in the current activity.

A gas flight on February 26 measured around 600 tonnes per day of SO₂ (sulphur dioxide), and 1,950 tonnes per day of CO₂ (carbon dioxide), similar to other measurements made since the start of 2013.

White Island remains in a heightened state of unrest and the long term outcome of the unrest remains unclear.

GeoNet says it could lead to explosive eruptions and larger ash emissions, like in August 2012, or decline to background activity.

'In the short term it is expected that activity will be variable, largely reflecting the influence of water on the style of activity.”