During 1-4 March, activity from Kīlauea's summit caldera and east rift zone was similar to activity during the previous several weeks. The level of the circulating lava-pool surface in the deep pit within Halemaʻumaʻu crater fluctuated and rose to at most 70 below the crater floor. Scattered surface flows were active on the pali and coastal plain, and lava covered large portions of Puʻu ʻŌʻō's crater floor. An unusually high number of earthquakes were located at Kīlauea; during 1-4 March a majority of the earthquakes were located at the upper east rift zone.

On 5 March at 1342 there was the onset of rapid deflation at Puʻu ʻŌʻō and increased tremor along Kīlauea's middle east rift zone, and at 1400 the summit began to deflate. Between 1416 and 1421 the floor of the Puʻu ʻŌʻō crater began to collapse and within 10 minutes incandescent ring fractures opened on the crater floor. As the floor continued to drop, lava appeared in the center and the NE spatter cone collapsed. The collapse of a large block along the E crater wall produced an ash plume. The floor continued to drop as fume obscured the camera view at 1626. The Aviation Color Code was raised to Red and the Volcano Alert Level was raised to Warning. A later report indicated that the crater floor dropped a minimum of 115 m.

Coincident with the Puʻu ʻŌʻō collapse, an earthquake swarm began along the east rift zone in the area of Maka'opuhi and Napau craters, WSW of Puʻu ʻŌʻō. A fissure, ultimately 2.3 km long, opened along the east rift zone between Napau Crater and Puʻu ʻŌʻō, erupting spatter up to 25 m high and lava that burned nearby vegetation. Lava on one side of the fissure flowed into a nearby deep parallel fissure and disappeared. Fissure activity had paused by 2155.

Kīlauea's summit continued to deflate and the lava lake level within the Halemaʻumaʻu crater vent dropped, facilitating rockfalls from the vent wall. On 6 March at 0703 the lake level to receded almost beyond the webcam view following a large collapse. Spattering from the fissure resumed and two more fissures opened that produced more gas than lava. Spatter was reaching heights of 40 m. The tiltmeter on the N flank of Puʻu ʻŌʻō recorded over 150 microradians of deflation beginning at 1400 on 5 March that markedly slowed by the morning of 6 March. Rockfalls exposed incandescent areas within Puʻu ʻŌʻō. Lava flows on the coastal plain and pali were less active. The average sulfur dioxide emission rate from all east rift zone sources was 10,000 tonnes/day on 6 March, 2011, the highest rate there since an eruptive surge in July 2008 produced an emission rate of 7,000 tonnes/day.

On 7 March the Aviation Color Code was lowered to Orange. Vigorous spattering from the W end of the fissure continued; spatter rose as high as 30 m. No active lava flows were observed on the pali or coastal plain. The lava lake surface in Halemaʻumaʻu crater was 200 m below the crater floor, based on visual estimates. Rockfalls in the crater produced dusty-brown plumes during 7-8 March. Low fountains and spattering from the fissure fed several lava flows that advanced S.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

INSIVUMEH reported that during 2-3 March explosions from Santa María's Santiaguito lava dome complex produced ash plumes that rose 800 m above Caliente dome and drifted SW. Avalanches traveled S, SE, and SW, and ashfall was reported in Monte Claro, Patzulín, La Florida, and El Faro on the S and SE flanks. Two pyroclastic flows were also detected. On 3 March an explosion produced an ash plume that rose 800 m above Caliente dome and drifted W and SW. Ashfall was reported in multiple areas downwind. The explosion was accompanied by a pyroclastic flow that traveled 2.5 km down Rio Nima I on the SE flank. A few explosions occurred during 3-4 March; ash plumes rose 900 m above Caliente dome. Ash fell in La Florida, El Faro, and Palajunoj (SW flank). Based on analyses of satellite imagery, the Washington VAAC reported that ash was detected on 6 March. The next day an ash plume drifted almost 20 km SW.

During 7-8 March the seismic network detected explosions, avalanches, and pyroclastic flows. At least eight pyroclastic flows descended the E flank and deposited material in Rio Nima II. Ash plumes rose 1 km and drifted S and SW causing ashfall in areas downwind.

Sources: Washington Volcanic Ash Advisory Center (VAAC), Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)

Based on information from JMA, the Tokyo VAAC reported that during 2-5 and 8 March explosions from Sakura-jima produced plumes that rose to altitudes of 1.2-1.8 km (4,000-6,000 ft) a.s.l. and drifted E, SE, and S. During 2-4 and 5 March, pilots reported that ash plumes rose to altitudes of 1.5-3 km (5,000-10,000 ft) a.s.l. Some plumes drifted N and SE.

Source: Tokyo Volcanic Ash Advisory Center (VAAC)

During 2-8 March, PHIVOLCS reported that up to four daily volcanic earthquakes at Bulusan were detected by the seismic network. Although cloud cover mostly prevented observations of the summit area, steam was observed rising from thermal vents during 2-4 and 7-8 March. Based on notices from the Manila airport (RPLL) and satellite image observations, the Tokyo VAAC reported that during 3-4 March ash was observed.

Sources: Tokyo Volcanic Ash Advisory Center (VAAC), Philippine Institute of Volcanology and Seismology (PHIVOLCS)

KVERT reported that moderate seismic activity was detected at Karymsky during 25 February-4 March. Seismic data indicated that possible ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. Satellite imagery showed a thermal anomaly over the volcano on 25 February and 2 March. The Aviation Color Code remained at Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

The Tokyo VAAC reported that an ash plume from Kirishima's Shinmoe-dake (Shinmoe peak) observed by a pilot on 3 March rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted NE. Based on reports from JMA, the Tokyo VAAC reported that plumes rose to altitudes of 1.5-3 km (5,000-10,000 ft) a.s.l. and drifted SE during 3-4 and 8 March.

Source: Tokyo Volcanic Ash Advisory Center (VAAC)

KVERT reported that during 25 February-4 March seismicity from Kizimen was high but variable, and many shallow volcanic earthquakes as well as volcanic tremor continued to be detected. Satellite images showed a bright thermal anomaly over the volcano daily. Ash plumes drifted 180 km N on 25 and 28 February, and 2 March. The Aviation Color Code remained at Orange.

Based on information from KEMSD and analyses of satellite imagery, the Tokyo VAAC reported that on 5 March eruptions produced plumes that rose to altitudes of 6.1-6.4 km (20,000-21,000 ft) a.s.l.

Sources: Tokyo Volcanic Ash Advisory Center (VAAC), Kamchatkan Volcanic Eruption Response Team (KVERT)

CVGHM reported that gas plumes rose from Merapi during 28 February-6 March. The highest plume which rose 100 m and drifted E was observed on 5 March from the Babadan post on the NW flank. The number of multi-phase (MP) earthquakes was slightly lower compared to the previous week. The Alert Level remained at 2 (on a scale of 1-4).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

CENAPRED reported that during 2-4 and 6 March steam-and-gas emissions from Popocatépetl occasionally contained small amounts of ash. The Washington VAAC noted that a gas-and-ash plume drifting 130 km SE at an altitude of 9.1 km (30,000 ft) a.s.l. on 3 March.

Sources: Centro Nacional de Prevencion de Desastres (CENAPRED), Washington Volcanic Ash Advisory Center (VAAC)

KVERT reported that moderate seismic activity was detected at Shiveluch during 25 February-4 March. Gas-and-steam activity was observed during 24-25 February; cloud cover prevented observations on the other days. A thermal anomaly over the lava dome was observed in satellite imagery during 25-26 February, and 2 March. Ash plumes drifted over 140 km N during 26-27 February. The Aviation Color Code remained at Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

MVO reported that during 25 February-4 March activity at the Soufrière Hills lava dome was at a low level. Clear views from a helicopter on 3 March revealed modest changes in the lava dome; continued degradation of the W face was evident and the E face showed undercutting with overhanging areas. Small areas of incandescence were visible on the N face of the dome during clear evenings. The Hazard Level remained at 3.

Source: Montserrat Volcano Observatory (MVO)

Based on information from JMA, the Tokyo VAAC reported an explosion from Suwanose-jima on 3 March. Details of a possible resulting plume were not reported.

Source: Tokyo Volcanic Ash Advisory Center (VAAC)