On 9 May the intermittent eruption of lava in Leilani Estates in the lower East Rift Zone (ERZ) of Kilauea continued.
In the northeast part of the area, fissure 15 extended across Poihiki Road, generating a pahoehoe flow about 20 m (66 ft) long.
In the summit caldera, steady lowering of the Overlook Crater lava lake within Halema`uma`u crater raised the potential for steam-driven explosions if the lava column dropped to the groundwater level and allowed water into the conduit.
On 10 and 11 May, little new extrusive activity was noted from the ERZ fissures, though there were continued earthquakes, ground deformation, and considerable gas discharge.
Tiltmeters recorded ongoing deflation and the Overlook crater lava level continued to drop.
Fissure 16 opened at 0645 on 12 May near the end of Hinalo Road.
It produced a lava flow that traveled about 230 m before stalling around 1430.
An area that had been actively steaming developed into fissure 17, reported at 1800 just east of fissure 16, and was actively spattering and degassing.
At the summit, rockfalls from the steep walls into Overlook crater generated intermittent small steam-and-ash clouds throughout the day.
Lava eruptions continued on 13 May along the lower ERZ.
Aerial observations showed that a new outbreak in the early morning about 900 m NE of the end of Hinalo Street and 900 m S of Highway 132 was several hundred yards long and ejected spatter along with a slow-moving lava flow.
By late in the day this activity from fissure 17 was dominated by lava fountaining, explosions that sent spatter bombs to 100 m into the air, and several advancing lava flow lobes moving generally NE; as of 1900 one lobe was 2 m thick and advancing roughly parallel to Highway 132.
Steady, vigorous plumes of steam and occasionally minor amounts of ash rose from the Overlook vent and drifted downwind to the SW.
Later in the day, ash clouds rose up to 650 m (2,000 ft) above the vent.
Several strong earthquakes shook the Hawaiian Volcano Observatory and the surrounding area overnight.
Activity on the morning of 14 May in the lower ERZ was dominated by lava fountaining, explosions of spatter more than 30 m (100 ft) into the air, and an advancing flow from fissure 17 at the NE end of the fissure system.
As of 0630, the fissure 17 flow had traveled about 1.6 km roughly ESE parallel to the rift zone.
Fissure 18 was weakly active.
A 19th fissure spotted around 0800 just NE of Pohoiki Road and N of Hinalo Street produced a sluggish lava flow.
Volcanic gas emissions remained elevated throughout the area downwind of the vents.
Deflationary tilt at the summit continued and seismicity remained elevated.
On the morning of 15 May activity remained concentrated at fissure 17.
The lava flow had advanced about 380 m since 1430 on 14 May.
At 0645 the flow was nearly 2.5 km long.
However, the advance of the flow had slowed significantly since that afternoon.
Also in the morning a new fissure (20) located near fissure 18 produced two small pads of lava.
Ash emission from the Overlook crater increased compared to previous days.
Although varying in intensity, at times the plume contained enough ash to be gray in color.
Variable pulses sent the cloud to an estimated 1-1.3 km (3-4,000 ft) above the ground.
The ash cloud drifted generally W and SW from the summit and ash fell in the Ka'u Desert.
On 15 May the Aviation Color Code was raised from Orange to Red and the Volcano Alert Level remained at Warning.
Sources: Hawaii County Civil Defense Agency ,Hawaii Emergency Management Agency ,US Geological Survey Hawaiian Volcano Observatory (HVO)