Mauna Loa is the largest active volcano on Earth. It dominates the Island of Hawai ‘i, covering just over half the island.
During the past 3,000 years, Mauna Loa has erupted lava flows, on average, every 6 years. Since 1843, Mauna Loa has erupted 33 times, averaging one eruption every 5 years.
Scientists know each of the two Hawaiian volcanoes has its own plumbing —separate, shallow magma chambers. Such chambers are the source of Kilauea’s lava lake, which has now emptied. But 50 miles (80 kilometers) down, in a part of the Earth’s mantle layer called the asthenosphere, Mauna Loa and Kilauea are dynamically coupled, said Helge Gonnermann, a professor at Rice University in Houston, who is the lead author of the study showing the link.
The study suggests that Mauna Loa’s and Kilauea’s opposing pattern — when one is active, the other is quiet — occurs because eruptions at one volcano release pressure in the other.
The model helps explains some intriguing observations: When one volcano inflates, the other starts to bulge about six months later. At times, such as in 2005, both volcanoes inflate at the same, GPS data show
The model suggests Mauna Loa, which produced its most recent blast in 1984, had accumulated enough magma for another eruption, but its pressure was relieved by Kilauea’s heightened activity.
“The hypothesis coming out of this model is that if we hadn’t seen this increased activity at Kilauea, then we would not have seen this pressure relief,” Gonnermann said.
The decline in summit-derived flows and increase in rift zone activity was likely related to the formation of Moku‘āweoweo Caldera due to collapse of the summit—lava flows erupted within the caldera were trapped, unable to overflow the caldera rim.
The cause of the transition from summit-dominated lava flows to prolonged eruption of flows from the rift zones is not known. It was probably related to significant change in the volcano’s magma supply or reservoir plumbing system, the advent of explosive activity, and/or flank instability.
The submarine flanks of Mauna Loa and adjacent seafloor are mantled by several enormous landslide deposits that significantly altered the shape of the volcano.
Two of the youngest and largest landslides occurred from a source area on the west flank of the volcano that includes Kealakekua Bay—the ‘Ālika 1 and 2 landslides. The ‘Ālika 1 slide moved directly west about 80 km (50 mi) down the steep submarine slope and produced a broad hummocky deposit on the seafloor.
The younger ‘Ālika 2 slide also moved west for a short distance, then turned northwest because it was diverted by the ‘Ālika 1 deposit; the second landslide also traveled a distance of about 100 km (60 mi). The ‘Ālika 2 landslide may have produced a giant tsunami that swept Lāna‘i about 105,000 years ago. Upslope of Kealakekua Bay, a zone of unusually steep slopes is interpreted by geologists as buried faults, the head land of one or both landslides that subsequently were covered by lava flows.
Landslides have also occurred from the volcano’s southwestern flank. The South Kona landslide occurred after about 250,000 years ago, which corresponds to the approximate time when Mauna Loa emerged above sea level. Landslides and faulting helped shape the southern embayment of the coast and steep west-facing scarp of the submerged Southwest Rift Zone.
Nīnole Hills – old flows mark the site of abandoned rift zone
The Nīnole Hills are steep-sided and heavily vegetated flat-topped ridges located on the southeastern flank of Mauna Loa. Age dating, and chemical analysis of lava flows exposed in Nīnole Hills indicates they were erupted about 125,000 years ago from Mauna Loa.
In 2013, a detailed gravity survey of the area identified an elongate gravity high, which suggests a concentration of intrusive rocks associated with a rift zone. Geologists now interpret the Nīnole Hills as part of the volcano’s original southern rift zone, which was later abandoned as a new rift zone formed to the west.
The “hills” subsequently formed as erosion carved deep canyons and valleys into the old flows. Geologists infer that the large landslides from Mauna Loa’s western and southern flanks caused the rift to migrate westward to the present location of the Southwest Rift Zone.
Mauna Loa has an explosive history
Mauna Loa is not known to have produced an explosive eruption since 1843, but there is geologic evidence for some explosive activity in the past 1,000 to 300 years.
Geologists have identified at least 4 debris fans comprised of fragmented rock deposits on top of pāhoehoe lava flows that spread from the summit. The largest blocks found in these deposits are as large as 2.2 m (7.2 ft) in diameter and weigh more than 17,000 kg (38,000 lbs). The fine-grained fragments typical of explosive deposits are hard to find, and were probably removed by storms, rain and strong winds that frequently sweep across the summit. Geologists estimate that the 4 sites represent three separate explosive eruptions. This evidence suggests that future explosive eruptions in the summit area are possible.
Mauna Loa erupted most recently in March-April 1984. Following more than two years of increased seismicity and summit inflation, the eruption began at 1:30 a.m., HST, on March 25, when a fissure opened in Moku‘āweoweo, the volcano’s summit caldera.
By 4:00 a.m., the eruption had migrated into Mauna Loa’s upper Northeast Rift Zone, where active fissures eventually reached the 2,835-m (9,300-ft) elevation. Fast-moving ‘a‘ā flows advanced downslope, and, in a matter of days, lava was within 6 km (4 miles) of Hilo city limits. Fortunately, the eruption ended on April 15 before lava reached Hilo.
Saturday, July 7, 2018, 5:30 PM HST (Sunday, July 8, 2018, 03:30 UTC)
MAUNA LOA VOLCANO (VNUM #332020)
19°28’30” N 155°36’29” W, Summit Elevation 13681 ft (4170 m)
Current Volcano Alert Level: NORMAL
Current Aviation Color Code: GREEN
HVO seismic and deformation monitoring networks have been recording near-background levels of seismicity and ground motion at Mauna Loa Volcano for at least the last six months. These observations indicate that the volcano is no longer at an elevated level of activity. Accordingly, on June 21, HVO reduced the Mauna Loa alert level to NORMAL and the aviation color code to GREEN.
Background: Mauna Loa is the largest active volcano on Earth. Eruptions typically start at the summit and, within minutes to months of eruption onset, about half of the eruptions migrate into either the Northeast or Southwest Rift Zones. Since 1843, the volcano has erupted 33 times with intervals between eruptions ranging from months to decades. Mauna Loa last erupted 34 years ago, in 1984.
Mauna Loa eruptions tend to produce voluminous, fast-moving lava flows that can impact communities on the east and west sides of the Island of Hawai`i. Since the mid-19th century, the city of Hilo in east Hawai’i has been threatened by seven Mauna Loa lava flows. Mauna Loa lava flows have reached the south and west coasts of the island eight times: 1859, 1868, 1887, 1926, 1919, and three times in 1950.
From 2014 through much of 2017, HVO seismic stations recorded variable, but overall elevated rates of shallow, small-magnitude earthquakes beneath Mauna Loa’s summit, upper Southwest Rift Zone, and west flank. During that same time period, HVO measured ground deformation consistent with input of magma into the volcano’s shallow magma storage system.
July 8, 2018 Lava Threatens Ahalanui
The current Leilani Estates eruption of Kilauea Volcano is now threatening Ahalanui Beach Park (Hot Pond) and Kua O Ka La Charter School nearby. Pele has crossed the 1955 lava flow between the ocean and Highway 137 and this morning was about 3-400 yards from the hot pond/school. Reports from Paradise Helicopters’ pilot Sean Regehr say the flow is now within 200 yards.
Apparently, a blockage of the tube system in Kapoho caused the diversion and overflows from the lava channel near Kapoho Crater that have consumed most of the homes and buildings to the north and are now approaching the Ahalanui area. Numerous tongues of lava were threatening the are this morning. The enormous ocean entry across Kapoho Bay and the former Vacationland subdivision now has a two-mile-long flow front, with many plumes emanating from the lava pouring into the Pacific Ocean there.
The source of the eruption upslope is, of course Fissure 8. The output remains constant, although maybe a bit subdued this morning… but Pele continues to generate ten cubic meters of lava per second from this vent… somewhere in the neighborhood of 9 million cubic meters of lava every day. It sends 2-thousand-degree fluid lava downslope in rivers… to the ocean entry some eight miles below.
Earlier this month, hundreds of homes were destroyed in Kapoho Beach lots and Vacationland to the south.
The current Leilani Estates eruption of Kilauea Volcano is still threatening Ahalanui Beach Park (Hot Pond) and Kua O Ka La Charter School nearby… but as of this morning was about 150 yards away from each.
Pele crossed the 1955 lava flow between the ocean and Highway 137 and this morning, in spite of an abundance of lava behind the flow front, had slowed considerably by 6:00 am today.
Apparently, another overflow has sent lava in the direction of Cinderland and Railroad Ave… Philip Ong reports no mandatory evacuation has been ordered, but the lava is flowing northeast near Bryson’s cinders in Kapoho. If substantial, this activity could possibly rob lava from the flow headed toward the hot pond.
The enormous ocean entry across Kapoho Bay and the former Vacationland subdivision now has a two-mile-long flow front, with many plumes emanating from the lava pouring into the Pacific Ocean there