Chronology of Kīlauea's summit eruption, 2008 - 2017
November 2007 to March 2008: Precursory signs
Kīlauea Volcano's summit was quiet for 25 years following the 1982 eruption, and Halema‘uma‘u, with an overlook on its crater rim, was a popular visitor destination in Hawai‘i Volcanoes National Park. Signs of new activity, however, gradually appeared in late 2007. In November and December of that year, sulfur dioxide emissions and seismic tremor began increasing above normal background levels. Gas emissions and tremor continued to increase during the first few months of 2008, and by early March these monitoring parameters were several times higher than normal.
Increasing gas emission rates in early 2008 produced high concentrations of sulfur dioxide around the Halema‘uma‘u parking lot. For this reason, the National Park closed the western portion of Crater Rim Drive to the public on February 20, 2008.
The first signs of change on the surface occurred on March 12, 2008, when a fumarolic area abruptly appeared on the south wall of Halema‘uma‘u, directly below the Halema‘uma‘u Overlook (closed to the public at that time). This fumarolic area, emitting a thick gas plume, enlarged over subsequent days and was incandescent (glowing) at night.
2008: Eruption starts, a new crater, and explosions
A small earthquake struck Kīlauea's summit at 2:58 am on the morning of March 19, 2008, coincident with collapse of the fumarolic area. A new, small crater formed from this collapse, which was also associated with an explosive eruption of blocks that fell around the Halema‘uma‘u Overlook. These dense, angular blocks were all "lithic", meaning that they came from old, solidified lava that formed the floor of Halema‘uma‘u. No fresh ("juvenile") lava was erupted in this initial, vent-opening explosion.
This new crater, now informally called the "Overlook crater", emitted a thick gas plume that obscured views inside. Over the following months, HVO geologists occasionally saw a deep red glow in the crater through the thick fume. Molten spatter was occasionally thrown from the vent, and was further evidence that lava was present deep in the new crater.
Following the March 19 explosion, several other explosions occurred during 2008, depositing lithic blocks as well as juvenile lava bombs around the Halema‘uma‘u Overlook, which remained closed to the public due to the ongoing hazard.
The first clear view of lava in the crater occurred on September 5, 2008, when a roiling, bubbling lava pond was seen deep in the crater during a helicopter overflight. But this view was fleeting, and the lava level soon dropped. Views of lava inside the Overlook crater by HVO geologists were infrequent during the rest of 2008. Although National Park visitors could not directly see the lava from public viewing areas, the new vent provided an impressive nighttime glow.
2009: Deep, fluctuating lava pond activity
Views inside the Overlook crater from the Halema‘uma‘u rim improved as continued collapses enlarged the Overlook crater, and thermal cameras provided clearer views through the thick fume. HVO geologists could see that the crater was very deep, and laser scanning revealed that the bottom was about 200 m (220 yards) below the floor of Halema‘uma‘u.
During periods of summit inflation, lava would rise and cover the floor of the Overlook crater, creating a short-lived lava pond. Subsequent deflation would cause the pond to drain, leaving small puffing vents on the floor of the Overlook crater. This cycle of rising and falling lava level occurred numerous times during 2009, producing many brief, small lava ponds.
The Overlook crater continued to enlarge as portions of the overhanging crater rim collapsed, consuming more of the floor of Halema‘uma‘u.
2010: The start of continuous lava lake activity
In early February 2010, a collapse of the floor the Overlook crater was followed by the appearance of a new lava pond at the bottom of the crater. Unlike the brief lava ponds of 2009, this lava pond persisted and enlarged throughout 2010, evolving into a sustained lava lake. The lake surface consisted of large crustal plates, with spattering commonly active at the margin. Lava remained deep in the Overlook crater, and views of the lake from the rim of Halema‘uma‘u were challenging.
The lake commonly experienced cycles of "gas pistoning", in which the lake surface would rise up to 20 meters (yards) as spattering diminished, followed by violent spattering and a rapid drop of the lava surface. This process has been explained as the cyclic accumulation and release of gas in the lake.
2011: Disruptions, draining, and recovery
Significant summit inflation in the opening months of 2011 accompanied a rapid rise in the lava lake. As the lake rose it widened as it filled the flared geometry of the Overlook crater. For the first time, there were clear views of the lake from Halema‘uma‘u. The lake reached about 60 meters (yards) below the floor of Halema‘uma‘u in early March, and these high lava levels were associated with heating and cracking of the Overlook crater walls. Loud popping and cracking sounds could be heard, and collapses of the Overlook crater walls increased. Several of the larger collapses triggered small explosions of spatter from the lake, providing clear evidence that the explosions in the Overlook crater are triggered by rockfalls.
Summit inflation and rising lava levels, as well as increasing numbers of small earthquakes in February and early March, were signs that Kīlauea's magmatic system was pressurizing. On March 5, 2011, an intrusion of magma along Kīlauea's East Rift Zone created new vents west of Pu‘u ‘Ō‘ō cone, site of Kīlauea's ongoing East Rift Zone eruption that began in 1983. This event depressurized the magmatic system, causing the summit lava lake to completely drain, dropping 140 meters (460 feet) and leaving the Overlook crater empty for over a week. Lava fountaining near Pu‘u ‘Ō‘ō continued for nearly five days, but ceased as the magma system recovered. Lava soon reappeared at the bottom of the Overlook crater and began rising again through the next few months.
By August the lake had returned to its previous high levels. This renewed cycle of pressurization triggered a new vent to open on Pu‘u ‘Ō‘ō on August 3, which again triggered a major drop in the summit lava lake. The lake soon recovered, dropping slightly when another new vent opened at Pu‘u ‘Ō‘ō on September 21, and remained at a relatively high level in the Overlook crater during the remainder of 2011.
2012: Gradually rising lava levels
The lake rose slowly during most of 2012, but the rise rate was far from steady. A common cycle called a "DI" (deflation-inflation) event, representing fluctuations in the pressure of Kīlauea's magmatic system, frequently affected the lake level. During the deflation phase of DI events, the lake would drop 10 meters (yards) or more, followed by the inflation phase a few days later when the lake would abruptly rise, often returning to its original level. These short-term ups and downs were superimposed on a longer-term increase in lake level through 2012.
An unusually abrupt rise in October 2012 brought lake to within 20 meters (yards) of the floor of Halema‘uma‘u, providing the clearest views of the lake thus far from Halema‘uma‘u. Albeit at a high level, the lake was still not visible from public viewing areas.
2013-2017: Continuous lava lake activity, brief overflows, rising levels
The lake remained relatively high in 2013, with lava normally about 30-60 meters (yards) below the floor of Halema‘uma‘u. Around 2013 the lake began a phase of prolonged and consistent behavior, with lava normally upwelling at the north end of the lake and slowly migrating south, where it sank at the lake margins. Spattering was common, most often at the margins with one consistent spatter source at the southeast corner of the lake. This behavior was especially clear in movies of thermal imagery.
The lake level continued to fluctuate with deflation-inflation cycles of the summit magma chamber. The lake surface consisted of large black crustal plates, separated by incandescent spreading zones. The size and shape of the crustal plates were constantly evolving as the plates slowly migrated from north to south and an average speed of 10-20 cm (4-8 in) per second. Occasional collapses of the Overlook crater walls triggered more explosions which deposited spatter around the Halema‘uma‘u Overlook.
In April, 2015, an abrupt increase in the rate of summit inflation drove the lake level higher still. By the end of the month, lava spilled out onto the floor of Halema‘uma‘u Crater in several episodes, covering about a quarter of the crater floor with fresh lava flows. This was not only the first time that lava spilled over the rim during the current eruption, but it was the first time that lava in the lake was directly visible from public viewing areas. By May 10, the lake level abruptly dropped as summit deflation occurred.
In early 2016, the lake began a phase of prolonged rise, and the lake was occasionally visible from Jaggar Overlook in the first half of the year. By late 2016 the lake was consistently close to the Overlook crater rim and was frequently visible. During the inflation phase of DI events, the lake would rise slightly, with spattering and the lake surface visible from Jaggar Overlook. Subsequent deflation resulted in a lake level drop taking it just out of view. This up and down sequence continued into 2017. Not surprisingly, Jaggar Museum has been a popular visitor destination in Hawai`i Volcanoes National Park, particularly at dusk.
Enlargement of the Overlook crater has continued, and by late 2016 the Overlook crater was roughly 250 m long and 190 m wide. The lake had similar dimensions, as it filled the majority of the crater. Only a handful of persistent lava lakes exist on Earth, and the lake in Halema‘uma‘u Crater is now one of the two largest (Nyiragongo Volcano, Democratic Republic of the Congo, has a lava lake on a similar scale). As of early 2017, as the summit eruption approaches its ten year anniversary, there are no signs of the eruption ramping up or slowing down. The past few years have had remarkably consistent lake activity, and this will likely continue for some time.