When Will Mauna Loa Erupt Again
Information is preliminary and subject to change. All times are local (unless otherwise noted)
July 1975 (CSLP 48-75)
Lava fountains in the summit caldera and along ii rift zones
Card 2212 (07 July 1975) Lava fountains in the height caldera and along two rift zones
Mauna Loa volcano began erupting at 2344 hours HST, v July 1975 (0944 GMT 6 July). Past 0200 July 6th a line of fountains extended the length of the meridian caldera in a N30°Eastward direction through the cones of 1940 and 1949. Fresh lava covered virtually of the caldera floor, and overflowed from both South Pit and North Pit. Fountains extended for almost ii km beyond the caldera margin into the southwest rift zone, and new flows traveled as much every bit 3 km down the flanks of the volcano both southward and westward and partly filled the pit craters Lua Honhonu and Lua Hou. Fountains too extended into the northeast rift zone and ultimately reached 3 km beyond the margin of Northward Pit.
Caldera activity stopped between 0400 and 0500, soutwest rift zone activeness stopped well-nigh 0600, and activity full-bodied in the northeast rift zone along two en echelon fissures 1 km long at an summit of nearly 3,780 k. Major flows from these fountains traveled 5 km ENE forth the rift zone and 6 km NNE downwards the N flank. Activeness connected through the morning, declined in the afternoon, and all fountains ended by early on evening.
Frequent earthquakes centered along the northeast rift zone and harmonic tremor are continuing every bit of 0300 on seven July.
Data Contacts: Robert Tilling and Donald Due west. Peterson, Hawaiian Volcano Observatory, USGS.
November 1976 (NSEB 01:xiv) 
Cite this Study
Increased seismicity during 20-24 November
A substantial increment in the number of earthquakes beneath Mauna Loa was recorded twenty-24 November (table one). On the morning of 25 November, merely ane convulsion was recorded (beneath the NE rift). The USGS predicts a major eruption of Mauna Loa inside the side by side 18 months.
Table 1. Earthquakes recorded at Mauna Loa during xx-24 November 1976.
| Date | Outcome Totals |
| twenty Nov 1976 | 350 |
| 21 November 1976 | 200-300 |
| 22 Nov 1976 | 200-300 |
| 23 Nov 1976 | more than 300 |
| 24 Nov 1976 | less than 100 |
Information Contacts: UPI
January 1978 (SEAN 03:01) Cite this Report
New fumarolic activity and increased inflation rate
The July 1975 eruption of Mauna Loa has been described by Lockwood and others (1976). Soon after this eruption, Mauna Loa began to inflate, and, chiefly on the basis of the celebrated patterns of activeness, the USGS predicted that a second eruption, followed soon thereafter by a larger eruption from the NE rift, was likely to occur earlier July 1978. During the beginning half of 1977, withal, local seismicity and inflation rates declined considerably, and in July 1977 the USGS issued a press release withdrawing the "before July 1978" date for the predicted eruption. Seismicity below the acme region has remained depression, but measurements fabricated in Dec 1977 indicate that the inflation rate for June-December 1977 had increased to that recorded during 1976. Furthermore, dumbo smoke clouds have been emitted from the 1975 eruptive fissures since Oct 1977. The USGS has installed gas monitoring devices on one of these fumaroles and is continuing to monitor the volcano closely.
Reference. Lockwood, J., Koyanagi, R., Tilling, R., Holcomb, R., and Peterson, D., 1976, Mauna Loa threatening: Geotimes, v. 21, no. half-dozen, p. 12-15.
Data Contacts: Chiliad. Eaton, HVO, Hawaii.
May 1983 (SEAN 08:05) Cite this Report
Seismicity and peak caldera deformation increase
"Mauna Loa concluding erupted in July 1975. That eruption was preceded by an increase in both shallow and intermediate-depth earthquakes, and past extension of survey lines across the caldera (figure ane, left). Since 1980, and especially since early 1983, the number of shallow earthquakes beneath Mauna Loa has been increasing again. Intermediate-depth earthquakes have connected at a higher rate during the flow from 1978 to present than during 1971-73, simply accept not shown the same pattern of increase as they did in 1974 (figure i, right). Figure 1 likewise shows a recent increment in the rate of extension of survey lines across the summit caldera.
 | Figure one. Plot of cumulative number of local earthquakes at shallow (0-5 km) and intermediate (five-13 km) depths, and extension (in mm) on two survey lines across the elevation caldera, for 1970-75 (left), and 1978-83 (right). |
"The recent rate of strain from apparent intrusion of magma beneath the summit region shows an increasing tendency from both seismic and ground surface deformation data. The present strength of the pinnacle region is not known, and so no precise forecast of the next eruption can exist made. However, the present seismic and deformation data indicate a significantly increased probability of eruption of Mauna Loa during 1983 or 1984."
Data Contacts: R. Decker, R. Koyanagi, and J. Dvorak, HVO, Hawaii.
March 1984 (SEAN 09:03) Cite this Report
Fissure eruption produces voluminous lava flows from NE rift vents; So2-rich tropospheric plume reduces visibilities 7,000 km abroad
The following (except for the plume information) is from HVO. Times noted below are preliminary and subject to slight revision after later analysis. "A long-expected flank eruption of Mauna Loa began on 25 March, and had ended by 14 April.
Background. "When superlative seismic activity increased sharply in Apr 1974, Mauna Loa had non erupted since June 1950. Measurement of EDM lines across the meridian caldera (Mokuaweoweo) in the summer of 1974 revealed significant extensions, monitoring capabilities were increased, and a forecast of renewed activity was issued (Koyanagi and others, 1975). The superlative eruption of 5-6 July, 1975 lasted for less than 20 hours, and simply about 30 x 10half dozen m3 of lava were erupted. The eruption was identical to numerous other Mauna Loa summit eruptions that had been followed within 3 years by large flank eruptions. Given the historic record and standing inflation, a forecast was made for renewed eruptive action sometime earlier the summer of 1978 (Lockwood and others, 1976). The 1976 forecast was rescinded in 1977 just slow aggrandizement continued and some other forecast (based on an increase in the rate of geodetic modify and seismic activity) was issued in 1983. This called attention to the increased probability of a Mauna Loa eruption within the adjacent two years' (Decker and others, 1983), merely see SEAN 08:05 in which the forecast was more specific: 'a significantly increased probability of eruption of Mauna Loa during 1983 or 1984.'
Premonitory activeness. "The 25 March outbreak gave almost no brusk-term instrumental warning. Seismic activity had been increasing gradually through March (figure 2), but was relatively low immediately preceding the outbreak; simply 29 microearthquakes were recorded beneath the summit caldera during the preceding 24 hours (in contrast to 700 microearthquakes/solar day in September 1983).
 | Figure 2. Number of earthquakes per twenty-four hours at Mauna Loa, 1 Jan-5 April. The start of the eruption is indicated by an arrow. |
"Several people saw likely fume clouds from the pinnacle caldera and a camper at the summit noted small-scale explosions from the 1975 eruptive fissures on 23 March. One hiker had reported seeing 'glowing cracks' virtually the 1940 cone on xviii March, but no anomalous activity was detected on a thermal probe in the 1975 fumaroles. Oxidation state and temperatures of fumarolic gases remained substantially unchanged prior to the last satellite manual about midnight on 24 March.
Eruption narrative. "At 2255 on 24 March, a pocket-sized convulsion swarm began directly beneath the meridian. Weak harmonic tremor with an amplitude of virtually 1 mm was recorded at the elevation station (WIL, figure 3) at 2330. The number of small summit earthquakes increased at 2350. Tremor aamplitude recorded at the summit increased to near v mm at 0015 on 25 March, remained high at 0051, and was recorded on all Mauna Loa and Kīlauea summit area stations.
 | Figure 3. Sketch maps of the NE rift zone and summit of Mauna Loa, showing positions of 1984 lava flows (stippled) equally of 5 April. Eruption fissures are indicated by hachured lines. The border of the suburbs of Hilo is shown by a dotted line on the NE rift zone map. The areas covered are shown by the index map (inset). |
"At 0055 a magnitude 4.0 earthquake beneath the summit awoke geologists (from the University of Massachusetts) camped at Pu'u Ula'ula on the NE Rift Zone. At 0056, the telescope at the summit of Mauna Kea (42 km NNW of Mauna Loa) began high-amplitude oscillation, preventing astronomical observations for the adjacent few hours. Between 0051 and 0210, eleven earthquakes with magnitudes betwixt 2.0 and 4.i were recorded beneath the elevation. At 0100 borehole tiltmeters recorded the onset of rapid summit inflation.
"A armed forces satellite detected a strong infrared signal from the elevation at 0125. Glow was sighted in the SW portion (1940 cone expanse) of the summit caldera by an observer on the height of Mauna Kea at 0129, by the geologists at Pu'u Ula'ula at 0130, and from Kīlauea at 0140. At 0146, fountain reflection on smoke clouds observed from HVO suggested that fountaining extended across much of SW Mokuaweoweo and was migrating downwards the SW Rift Zone.
"At 0232 the tops of fountains within Mokuaweoweo were seen from Pu`u Ula`ula, suggesting a summit greater than 100 chiliad. At approximately 0340, fountaining ceased on the SW Rift Zone. At 0357, 30-m-high fountains migrated out of Mokuaweoweo, downwardly the upper NE Rift Zone. Lava flowed downrift and onto the SE flank.
"At approximately 0600, fountaining in the caldera gradually ended. At 0632, a new vent opened about 700 m E of Pohaku Hanalei and 8 minutes later another en echelon fissure began to erupt nigh 600 k downrift. Lava appearance was preceded by iii minutes of copious white steam emission from the crack. For the next 2.5 hours, activity waned.
"At 0905, profuse steaming appeared on a fracture at well-nigh 3,510 g altitude, and at 0910 fountaining fifteen-xl m high began at 3,410 m and migrated downrift. At 0930, fountains in a higher place Pohaku Hanalei died down as lava production increased to approximately i-2 x ten6 m3/60 minutes forth a two km-long curtain of fire between most 3,400 and iii,470 m. The loci of most vigorous fountaining alternated along the 2-km fountain length. Much of the production from these vents was consumed by an open crevice parallel to and S of the chief fissure upslope, although an aa flow did move 5 km SE, S of an 1880 menstruation. During activity of these vents, episodic turbulent emissions of crimson and brown `dust' from the eruptive fissures sent clouds to about 500 m height. At 1030, steaming was noted along a 1-km-long crack organization extending from about three,260-3,170 m, but there was no further downrift migration of eruptive vents for several hours. At virtually 1550, ground nifty extended below iii,000 m, and at 1641 eruptive vents opened at about 2,800 m and migrated both up- and downrift. At 1830 an eruptive vent extended nearly 1.7 km from about 2,770-two,930 k elevation. Fountains to 50 thou height fed fast-moving flows to the E and NE. Activity waned at the 3,400-m vents.
"By 0640 the side by side twenty-four hours, all lava production had ceased above 3000 1000. Fountains (to 30 grand summit) were localized along a 500-k segment of the fissure that had opened the previous afternoon. The fastest moving catamenia cut the electric line to the NOAA Mauna Loa Observatory before long earlier dawn. At 0845, the E flows were spread out over a wide area to a higher place i,900 m elevation, but their advance slowed during the day. Four principal eruptive vents then developed along this scissure system. Two vents fed the NE flow (1), while the other two fed the S (two-4) flows. Flow ane steadily advanced downslope 27-28 March (effigy iv), between the 1852 and 1942 lava flows. Approximately eighty% of the lava production fed menstruation i. Flows 2-four ceased significant accelerate by 28 March. The terminus of menses 1 stopped significant advance by early 29 March, while production at the vents remained essentially abiding. This suggested that a new branch flow had adult upslope. Bad weather prevented confirmation of the new co-operative until 30 March. This new flow (1A) moved rapidly downslope, N of flow 1.
 | Figure four. Rates of motion of flows ane, 1A, and 1B in kilometers per day. Pocket-size circles represnet observations of menstruation positions. Courtesy of J.P. Lockwood. |
"Phase 17 of Kīlauea's E Rift Zone eruption began that morn but had no apparent effect on Mauna Loa activity. As well Kīlauea tilt showed no deflection at the fourth dimension of the Mauna Loa outbreak on 25 March.
"Flow 1A slowed on 31 March as the feeding channel became sluggish, and the flow thickened and widened upstream. At 1215 on 5 April, the flow was moving very slowly (18 one thousand/60 minutes) slightly below 900 g top. A major overflow at nearly 2,000 chiliad shut off most of its lava supply and created a fast-moving menstruum (lB), which advanced 3 km NE to well-nigh 1,800 thousand elevation by 1700.
Deformation. "Much of the NE rift zone geodetic monitoring network was measured shortly before the 25 March outbreak, and EDM, tilt, and gravity stations were re-measured several times during the eruption. Although continuously recording tiltmeters at the summit showed sharp aggrandizement (dike emplacement) immediately preceding the outbreak, major subsidence of the summit region accompanied eruptive activity along the NE rift. The center of subsidence, near the Due south edge of the tiptop caldera (effigy 5), was coincident with the centre of uplift identified from repeated geodetic surveys between 1977 and 1983. The corporeality of superlative deflation recorded by tilt and horizontal distance measurements exceeded the amount of gradual aggrandizement of the volcano since the July 1975 summit eruption, suggesting substantial injection of magma into the summit area prior to this eruption, and possibly prior to the kickoff EDM line across the summit caldera in 1964. Maximum vertical top change, inferred from repeated gravity measurements, is 500 mm.
 | Figure 5. Tilt changes near the top of Mauna Loa, July 1983-thirty March 1984. |
"Big extensions occurred across the heart NE rift zone during dike emplacement on 25 March, only EDM monitor lines across this zone showed no significant change after the initial dilation. The rate of tiptop subsidence initially followed an exponential decay, similar to subsidence episodes in the summit region of Kīlauea. Since 30 March, tilt and horizontal distance measurements have indicated a steady rate of deflation (figures vi and vii), although measurements on 6 April suggest decreasing deflation rates.
 | Figure half dozen. Plot of meridian tilt vs. time, 25 March-3 April 1984. |
 | Figure 7. Change in horizontal distance across the summit of Mauna Loa vs. fourth dimension, 25 March-3 April 1984. |
Dike propagation. "All dikes were emplaced inside the commencement 15 hours of the eruption. The eruptive scissure (surface expression of dikes) extended discontinuously along a 25-km zone from 3,890 yard on the SW rift zone to nearly two,770 g on the NE rift zone. Footing nifty along most of this zone demonstrates the continuity of the dike at shallow levels. Lateral propagation rates vary from >2,500 m/hour down the SW rift zone to about 1,200 g/hour in lower parts of the NE rift zone (figure eight).
 | Figure viii. Charge per unit of propagation of eruption fissures, shown every bit distance from the 1940 cone (in the SW part of the summit caldera) vs. hours after the start of the eruption. |
Petrography, lava temperatures, and gas measurements. "Hand specimens of the 1984 basalt are very fine-grained with widely scattered (<1%) phenocrysts of olivine <3 mm in diameter and sparse microphenocrysts of plagioclase and clinopyroxene. Most olivines are anhedral, resorbed, commonly kinked, and surprisingly forsteritic (Fo88-xc). Plagioclase and clinopyroxene are barely resolvable in the groundmass. Maximum temperatures adamant repeatedly by thermocouple and radiometer ranged from 1,137 to ane,141°C and had non inverse equally of 5 April.
"Eruptive gases have been extensively sampled and analyzed. Observed C/Southward ratios are much lower than expected in primitive Hawaiian tholeiite, suggesting extensive degassing in a shallow (<4 km deep) magma reservoir.
Geoelectric studies. "Ane cocky-potential (SP) profile, showtime measured in July 1983, exists across the NE Rift Zone about 1 km W of the master erupting vents. The first complete reoccupation of the SP line three days afterwards the eruption's start showed an amplitude increase slightly > l00 mV centered over a zone about 300 m wide beyond the i.5 km-long crack zone Northward of Pu'u Ula'ula. VLF measurements prove that the dike is located nearly in the center of the cracked zone, directly beneath the pre-existing SP maximum, at a very approximate depth of 150 m.
Areal extent and volume of lava. "As of 5 April, 25-30 km2 of area was covered. The lava is generally pahoehoe near the vents, but is mostly aa more 2 km from the vents. The volume was estimated to exist about 150 x 106 mthree by 5 April."
Eruption plume. The eruption produced a big gas plume that was carried thousands of kilometers to the W. The feather from the summit caldera action was clearly visible from HVO. An airline pilot approaching Honolulu at dawn 25 March reported that the summit of the feather was between x.seven and 11 km altitude and was globe-trotting SW. Observers at Honolulu drome belfry (300 km NW of Mauna Loa) reported that the meridian of a tall cumulus-similar cloud became visible Due south of the airport just before dawn.
In that location was no testify that the plumage reached the stratosphere; the tropopause on 25 March was at nearly 18 km altitude. The plume was carried W by trade winds. By 30 March, a haze layer was detected at Wake and Johnston Islands (iii,900 km W and i,400 km WSW of Mauna Loa; table two). Haze reached Kwajalein (4,000 km WSW of Mauna Loa) the next day and had reached Guam (6,300 km WSW of Mauna Loa) past 2 April.
Table ii. Visibilities at airports on several islands affected past the plume from Mauna Loa (distances are from Mauna Loa). All times are Hawaiian Standard Time. Notation that all except Johnston Island are beyond the International Date Line from Hawaii. Data courtesy of NOAA.
| Isle | Distance | Visibility | Date and Time (1984) |
| Johnston | 1,400 km WSW | half-dozen km | 2200 on two April - 0200 on iii April |
| Wake | 3,900 km West | ane.half dozen km | 1200 on 2 April - 1700 on two Apr |
| Ponape | five,000 km WSW | 3.ii km | 1000 on 2 Apr - 1400 on ii April |
So2 emitted by Mauna Loa was detected by the TOMS instrument on the Nimbus 7 polar orbiting satellite, which passed over Hawaii daily at about local apex (figure 9). Although the TOMS instrument was designed to measure ozone, it is also sensitive to SOii. An algorithm has been developed to isolate Then2 values and calculate its approximate concentration inside pixels (picture elements) roughly l km in diameter. Preliminary estimates of the total SOii in the Mauna Loa plumage, using TOMS data, were roughly 130,000 metric tons on 26 March and 190,000 metric tons on 27 March.
 | Figure 9. Preliminary So2 information from the TOMS musical instrument on the Nimbus-seven satellite. All values less than 10 milliatmosphere-cm (100 ppm-meters) have been supressed. Each number or alphabetic character represents the boilerplate SOii value within an area 50 km across. 1 = 11-xv matm-cm = 101-150 ppm-thousand, 2 = sixteen-twenty matm-cm = 151-200s ppm-chiliad, etc; 9 is followed by A, B, C, etc. Courtesy of Arlin Krueger. |
References. Decker, R.W., Koyanagi, R.Y., Dvorak, J.J., Lockwood, J.P. Okamura, A.T. Yamashita, G.K., and Tanigawa, W.R., 1983, Seismicity and surface deformation of Mauna Loa volcano, Hawaii: EOS, v. 64, no. 37, p. 545-547.
Koyanagi, R.Y., Endo, Eastward.T., and Ebisu, J.S., 1975, Reawakening of Mauna Loa volcano, Hawaii; a preliminary evaluation of seismic evidence: Geophys. Res. Letters, v. ii, no. ix, p. 405-408.
Information Contacts: J. Lockwood and HVO staff, Hawaii; M. Rhodes, Univ. of Massachusetts; M. Garcia, Univ. of Hawaii; T. Casadevall, CVO, Vancouver, WA; A. Krueger, NASA/GSFC; Thousand. Matson, NOAA/NESDIS.
April 1984 (SEAN 09:04) Cite this Report
Major NE Rift Zone eruption ends; total eruption volume
"The NE Rift Zone eruption, which began on 25 March, concluded early the forenoon of xv Apr. Lava output and fountain vigor steadily decreased during the last week of the eruption. As flow channels became blocked (by sluggish aa and aqueduct collapse breccias) progressively farther upslope, flows terminated higher on Mauna Loa's NE flank. Many short overflows of pasty aa, up to 15 yard thick, moved less than a few hundred meters from these points of channel blockage. By x Apr, no lava flowed below 2,400 chiliad. The full area covered by new lavas increased very piffling after 5 April, as multiple flows mostly piled on top of older flows. Total book for this eruption was estimated at 180-250 x x6 g3."
Information Contacts: J. Lockwood and T. Wright, HVO, Hawaii.
Oct 1987 (SEAN 12:10) Cite this Report
Steady post-1984 reinflation eruption but seismicity low
"Mauna Loa'south latest eruption was in March-Apr 1984 on the Northeast rift zone. The eruption was associated with a large collapse (figure 10) and seismicity that peaked during and following the eruption (figure xi). Since 1984 the volcano has begun to reinflate, as shown by outward tilt and horizontal extension of Mauna Loa's summit area.
 | Effigy ten. EDM data along iii lines across Mauna Loa'southward tiptop caldera, Jan 1983-4 Nov 1987. HVO 93 is on the NW rim of the caldera, and the three lines cantankerous the caldera in ESE, SE, and Due south directions, respectively, to the SE rim. Courtesy of HVO. |
 | Figure 11. Daily number of recorded short-period (top) and long-period (middle) summit microearthquakes, and NE rift events (bottom) at Mauna Loa, Jan 1984-four Nov 1987. Courtesy of HVO. |
Seismicity. "Post-obit the increment and peak in seismicity of the last eruption in Mar-Apr 1984, the number of shallow microearthquakes had slowly decreased (figure 11). Most of the post-eruption events were attributed to the gradual structural adjustments from the major deflation at the top (resulting from the voluminous magma withdrawal) and the main eruptive vent near Pu'u Ulaula on the Northeast rift zone. The post-eruption blueprint of decreasing seismicity is indicated past the daily number of top microearthquakes and Northeast rift events.
"There has been no significant seismic activeness beneath the summit and rift zones of Mauna Loa since the 1984 eruption, and the present level of shallow seismicity is relatively low. There has been some increase in intermediate-depth events beneath the volcano noticed over the past year. About of the events are very small, recorded but on a few summit and rift stations, and essentially < 0.5 in magnitude.
Basis deformation. "Deformation studies show that Mauna Loa reinflation has been steady; at this writing the pinnacle has recovered over ane/three of the corporeality of subsidence that took identify during the eruption, as measured by both dry out tilt and cross-caldera EDM (figure 10).
"A forecast of the side by side Mauna Loa eruption will depend on two things: an increment in shallow earthquakes and tilt recovery. The final two eruptions showed a precursory period of 1 twelvemonth (July 1975 eruption) and 4 years (March 1984 eruption) respectively from the time of increased seismicity to the onset of eruption. In that location is no absolute level of tilt recovery at which we can specify that Mauna Loa volition erupt. However, we would consider roughly ninety% recovery from the 1984 deflation would point a state of readiness to erupt. On the ground of the data shown here we would not expect a Mauna Loa eruption for at least five years. We will update this estimate every bit we continue to monitor tilt and seismicity . . . ."
Information Contacts: T. Wright, R. Koyanagi, and A. Okamura, HVO.
February 1989 (SEAN xiv:02) Cite this Report
50% of 1984 deflation recovered; no shallow seismicity
By 17 November 1988, when Mauna Loa'south superlative tilt network was relevelled, the pinnacle region had recovered ~50% of the deflation associated with the 1984 eruption (figures 12 and 13). Intermediate-depth microearthquakes take occurred at a moderate rate in the acme region. Still, the abundant shallow seismicity that originated beneath the peak crater during the twelvemonth earlier the 1975 eruption and for 4 years before the 1984 eruption has not been observed. The absenteeism of such precursory shallow seismicity suggests to HVO geophysicists that the side by side eruption . . . is several years abroad.
 | Figure 12. Changes in N-S and Eastward-W components of tilt at Mauna Loa, measured by station NEW MOK 2 on the NW rim of the caldera, 1 June 1983-17 November 1988. |
 | Figure thirteen. Dry tilt changes near the peak of Mauna Loa from 23-27 April 1984 to 8-17 Nov 1988. Courtesy of T. Wright. |
Data Contacts: T. Wright, HVO.
July 1991 (BGVN 16:07) Cite this Study
Peak earthquake swarm
Surface deformation measurements indicate gradual reinflation of Mauna Loa's meridian since its 1984 eruption. Earthquake counts have fluctuated, but accept apparently increased since belatedly 1990.
Two bursts of intermediate-depth volcanic tremor, starting time at about 1200 on thirteen July, preceded a swarm of long-period earthquakes that continued for ~14 hours. Activity peaked between 2300 on 13 July and 0100 the next morning. As the long-period events gradually declined, shallow microearthquake action increased, and continued for about 6 hours. All of the events were too small-scale for precise location.
The 13 July activity began ~two hours earlier an convulsion swarm under the summit of Kīlauea. Seismicity at Mauna Loa has apparently returned to average background levels since mid-July.
Data Contacts: P. Okubo, HVO.
September 2002 (BGVN 27:09) Cite this Written report
Following ix years of irksome deflation, quicker aggrandizement since mid-May 2002
Mauna Loa is the southern-most volcano on the island of Hawaii. Post-obit the last eruption of Mauna Loa, during March-Apr 1984 (SEAN 09:03), there have been several periods of inflation and deflation at the volcano's summit caldera, Moku`aweoweo. As of September 2002, Mauna Loa has remained non-eruptive (figure 14) for 18.v years. The design of deformation at Moku`aweoweo abruptly changed in mid-May 2002 from deflation to inflation, lasting until at least September 2002. An annal of deformation and seismic data from Mauna Loa dating back to the 1970s provides an example of the volcano's pre-eruptive and precursory behavior.
 | Figure 14. Oblique shaded-relief map (N at top) showing the location of the city of Hilo and the v volcanoes that congenital the island of Hawaii. The young growing submarine volcano Lōʻihi is non shown. When including the submarine portions of Hawaii attributed to Mauna Loa, information technology ranks as Globe'due south largest agile volcano, encompassing 51 percent of the island'southward expanse and comprising a volume over ~ 65,000 km3. Courtesy HVO. |
After the last Bulletin report near Mauna Loa in July 1991(BGVN sixteen:07) the volcano'southward summit continued to gradually inflate as it had since the 1984 eruption. This trend reversed in 1993-1994 when distances across the caldera shortened by equally much every bit 7 cm, and leveling surveys in 1996 and 2000 measured more than 7 cm of subsidence SE of the caldera.
Start on 24 April 2002 at 0645 a notable cluster of deep earthquakes (darkest circles in figure 15) occurred in a 52-hour period. The earthquakes concluded on 26 April at 1045. Many of the epicenters plotted within or close to the caldera's SW margin. The earthquakes ranged in depth from 26 to 43 km and in magnitude from 1.ane to ane.seven. Several shallow earthquakes preceded this cluster; the largest, a magnitude 2.v event on 21 April at 1931, was located ~3 km below the SW rift zone. After the cluster, several deep long-period events were recorded beneath the SW rift zone. At that time data from the continuous tiltmeter, dilatometer, and near continuous global positioning system (GPS) stations failed to advise meaning deformation of Moku`aweoweo caldera, upper-rift zones, or outer flanks.
 | Figure 15. Plot showing the magnitudes, locations, and depths of earthquakes registered at Mauna Loa during 7 April- 26 September 2002. Following the swarm of deep earthquakes during 24-26 April (nighttime circles), seismicity was somewhat elevated. |
Aggrandizement. HVO maintains several continuously recording GPS stations installed in 1999 (figure 16). Beginning in late April or early May 2002, deformation information began to show signs of renewed action.
 | Figure 16. Map showing the several GPS stations HVO maintains on Mauna Loa as of September 2002. HVO plans to install several additional stations (white dots), on indefinite loan from Stanford University. Courtesy HVO. |
Figure 17 shows the change in distance betwixt MOKP and MLSP GPS stations, located on opposite sides of Moku`aweoweo. The increased distance between the two stations was interpreted to represent inflation of the acme magma reservoir, centered ~5 km below the caldera. The small amount of extension marks a noticeable alter from the blueprint of deflation during the preceding 9 years. GPS measurements besides revealed that the top area had inflated about two cm, consistent with swelling.
 | Figure 17. Graph showing the change in altitude between GPS stations MOKP and MLSP, located on opposite sides of Moku'aweoweo caldera, equally seen during 4 October 2000-30 September 2002. Altitude across Moku'aweoweo began to increase by v-6 cm/year starting in belatedly April-May 2002. Courtesy HVO. |
The switch from boring deflation to more rapid inflation occurred around 12 May. GPS data indicated lengthening at a rate of 5-6 cm per year. Therefore, equally of 26 September the caldera had widened about 2 cm since 12 May. Measurements at GPS stations farther out on the flanks showed that swelling occurred at more than than the acme, in particular, the upper part of the SE flank was moving outward.
In gild to exam the precision of the GPS measurements, HVO compared the GPS information against dry-tilt method information at the summit, an contained means to mensurate ground deformation using land-surveying instruments, deployed at regularly visited stations. These confirmed the GPS results, though with less precision.
Electronic-tiltmeter data obtained at the Moku'aweoweo tiltmeter were also analyzed for changes in tilt direction. No meaning volcanic tilt was recorded that deviated from the diurnal signal respective to daily temperature fluctuations, or an annual signal respective to seasonal temperature changes.
During the inflationary period, seismicity at Mauna Loa was at a somewhat elevated level following the 24-26 April earthquake cluster. Merely, information technology remained far lower than it was the months prior to the 1975 and 1984 eruptions.
May-September 2002 unrest in comparison to activity since 1974. For Mauna Loa these information sets are available: electric distance meter (EDM) measurements since nigh 1975, GPS observations since 1999, dry out-tilt observations since 1975, and seismicity since 1974. The adequacy to find unrest at Mauna Loa has increased in the by few years with the installation of many new, continuously recording electronic tiltmeters, GPS receivers, and strainmeters (effigy xviii).
 | Figure 18. Map showing locations of continuously recording instruments for measuring deformation and seismicity at Mauna Loa equally of September 2002. This map omits many additional benchmarks used in various deformation surveys. Courtesy HVO. |
Figure 19 shows the distance measured across Moku`aweoweo caldera between MOKP and MSLP benchmarks by EDM during 1975 to September 2002, and past GPS beginning in 1999. Abrupt extensions associated with the 1975 and 1984 eruptions were caused by the ascension of magma from the pinnacle reservoir to the surface. During the 1984 eruption, the height area subsided rapidly as lava erupted. When the eruption stopped, the acme reservoir over again began to inflate in response to the influx of magma, as indicated by the increasing altitude between the 2 benchmarks until about1993. Inflation did not occur again until early May 2002 when the slow contraction across the summit changed abruptly to extension. This extension rate is the highest since immediately after the 1984 eruption.
 | Figure nineteen. The change in distances across Moku`aweoweo caldera at Mauna Loa, between MOKP and MSLP benchmarks (see map inset) as measured past electronic distance meter since about 1975 to September 2002 and by GPS receivers since 1999. Note the abrupt change from wrinkle to extension in May 2002. Courtesy HVO. |
GPS measurements have only been made at Mauna Loa since 1999, but in that relatively short time an sharp alter in ground movement has been recorded (figure 20). Measurements made during January 1999-May 2002 show pocket-sized velocities of footing displacement towards the SW. In contrast, during May-September 2002 the management of ground motion changed from a adequately uniform, southeastward move to a predominately radial pattern. In addition, the charge per unit of ground movement increased past 5 to ten times.
 | Figure 20. Velocities of ground deportation measured past GPS stations on Mauna Loa during 1999 to 12 May 2002 (low-cal lines) and 12 May to 21 September 2002 (black lines). The arrows represent the speed and direction of movement. The tips of the arrows representing the actual motion bespeak prevarication somewhere within the uncertainty ellipses. Courtesy HVO. |
Ground tilt away from the caldera occurs when magma accumulates beneath the surface. Although electronic measurements provide much more precise readings, the dry out-tilt method remains in use at HVO after 35 years for several reasons. First, the measurements can be fabricated well-nigh anywhere at whatsoever time. Second, they are non field of study to long-term musical instrument drift. Lastly, they provide an independent corroboration of measurements made by more than sophisticated mod instruments. Dry-tilt measurements revealed the following: inflation between the 1975 and 1984 eruptions (figure 21a), inflation after the 1984 eruption, continuing until 1993 (effigy 21b), and deflation from 1993 through March (probably May) 2002 (figure 21c). After March (probably May), the tilt returned to an inflationary pattern (figure 21d). The most recent pattern of inflation is based on simply ii sets of measurements, and the tilt varies, with some smaller arrows pointing inward, then it is much less sure than the past patterns. Yet, the radial blueprint strongly suggests that aggrandizement is occurring.
 | Effigy 21. Rates of ground tilt measured in the summit region of Mauna Loa during 1975 to September 2002. Arrows point in the management of downward tilt charge per unit of the basis surface; arrow lengths show the amount of tilt in microradians (note scale confined). A) inflation during 1975-1984, between the last two eruptions at Mauna Loa; b) inflation after the 1984 eruption to 1993; c) deflation during 1993 to March (probably May) 2002; and d) a full general return to aggrandizement until at least September 2002. Courtesy HVO. |
HVO's telemetered seismographic network recorded pregnant changes in seismicity before the Mauna Loa eruptions in 1975 and 1984 (effigy 22). The short-term forecasts of these eruptions were based in large office on precursory activity. Both eruptions were preceded by an increase in earthquakes at intermediate depths NE of Moku`aweoweo, and then by an increase in shallower earthquakes below Mauna Loa'southward summit. From the 1984 eruption until belatedly Apr 2002, approximately xxx earthquakes were located per yr below Mauna Loa'south summit and upper flanks. Rates of seismicity moderately increased beginning in late April 2002, specially at depths greater than xv km (effigy 22d). As of 29 September 2002, 100 earthquakes were recorded in 2002 beneath the summit and upper flanks of the volcano, 83 of which occurred later on mid-April. This rate is markedly college than those of previous years, but it is nevertheless well beneath the rates seen prior to the last two eruptions. Earlier an eruption becomes imminent, HVO scientists wait that rates of shallow seismicity will elevate to levels much college than those observed in late September 2002.
 | Figure 22. Monthly earthquakes (bars, scales at left) and cumulative numbers of located earthquakes (curves, scales at right), separated into iii depth ranges, inside or beneath Mauna Loa between 1974 and 29 September 2002. The earthquakes shown occurred beneath Mauna Loa's summit and upper flanks and had magnitudes greater than one.0. Role "a" shows all earthquakes; "b", shallow earthquakes (0 to 5 km deep); "c", intermediate earthquakes (5 to 15 km deep); and "d", deep earthquakes (greater than xv km deep). Courtesy HVO. |
References. Moore J G, Clague D A, Holcomb R T, Lipman P W, Normark W R, Torresan M E, 1989. Prodigous submarine landslides on the Hawaiian Ridge. J Geophys Res, 94: 17,465-17,484; Lockwood J P, Lipman P Due west, 1987. Holocene eruptive history of Mauna Loa volcano. U S Geol Surv Prof Pap, 1350: 509-535.
Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, Howdy 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/).
September 2004 (BGVN 29:09) Cite this Report
Deep, long-menstruation earthquake swarm and contraction in July and Baronial 2004
After a swarm of deep earthquakes centered merely S of Mauna Loa'due south summit caldera in belatedly Apr 2002, seismicity remained barely elevated until July 2004. In other words, seismicity during belatedly April 2002-July 2004 stood far lower than it did in the months prior to the 1975 and 1984 eruptions.
Starting in July 2004, a swarm of pocket-size (M < 3), deep (> 40 km), more often than not long-period (LP) earthquakes occurred just Due south of the caldera and adjacent areas. Neither the depth nor the magnitude of the earthquakes inverse significantly. Through 13 October 2004 more than than 730 related earthquakes occurred beneath the summit caldera and the adjacent part of the SW rift zone.
The location and magnitude of earthquakes making up the recent swarm (seismicity from 24 April-15 Oct 2004, a vi-month interval) are shown in figure 23. Such a concentration of deep LP earthquakes from this office of Mauna Loa was unprecedented in the mod earthquake record dating dorsum to the 1960s. In contrast, more typical seismicity over a 6-month menstruation at Mauna Loa is shown in a figure in a previous issue (BGVN 27:09). By comparison to the interval 24 April-fifteen October 2004, earthquakes in a typical 6 month interval are relatively thin.
 | Effigy 23. Seismicity for Mauna Loa for the 6-month period 24 April-15 October 2004. Courtesy of the U.S. Geological Survey, Hawaiian Volcano Observatory. |
Aggrandizement continued at the meridian through the outset of the earthquake swarm. In tardily Baronial 2004, all the same, distances beyond the summit caldera began to contract significantly, apparently caused by the center of inflation shifting slightly to the S, rather than by deflation. This was the first contraction since inflation started in late April or early on May 2002. Toward the end of September, the contraction ended and the line once once more began to lengthen. During 2004, the inflation had been at a fairly steady to slightly increasing rate until the contraction in late August. When present, the lengthening, uplift, and tilting were taken to betoken swelling of the magma reservoir inside the volcano.
Data Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, Usa (URL: https://volcanoes.usgs.gov/observatories/hvo/).
May 2012 (BGVN 37:05) Cite this Report
2004-2010 deformation trends; intrusive bodies modeled
Mauna Loa has remained non-eruptive since April 1984. Nosotros previously reported on an April-October 2004, deep, long-period (LP) earthquake swarm and associated brief period of wrinkle (BGVN 29:09). After that and through 2010, deformation continued at variable rates and with brief pauses. During 2004-2010, HVO reported footling variation in gas emissions at Mauna Loa.
The material in this report is drawn from monitoring data collected by the USGS Hawaiian Volcano Observatory (HVO) and, in particular, Interferometric Synthetic Aperture Radar (InSAR) information provided by HVO'southward Mike Poland. A subsection below discusses the employ of deformation data as a basis for modeling inferred magma bodies in the subsurface at Mauna Loa (Amelung and others, 2007).
Slowed edifice inflation. Increased rates of aggrandizement following the April-October 2004 deep LP earthquake swarm continued through 2007, when HVO reported that GPS and InSAR-based inflation rates had slowed substantially. Comparison of radar interferograms roofing two intervals (xi October 2003-19 Nov 2005 and 24 March 2007-17 April 2010) highlights the slowed deformation rates during the latter interval (figure 24). To ameliorate understand the technique used to notice the slowed rate of deformation at Mauna Loa, see the next department.
 | Figure 24. Radar interferograms of Mauna Loa covering the time intervals of (a) eleven October 2003-19 Nov 2005 and (b) 24 March 2007-17 April 2010. These interferograms highlight the slowing of inflation during the latter interval. The large number of color bands ('fringes') in (a) indicates an increased charge per unit of inflation compared to the fewer number of fringes in (b). As depicted in the scale bar (bottom centre), concentric and cyclical sets of fringes bespeak a ground move of 2.83 cm towards the satellite's line-of-sight during the time interval shown in each image. The images were produced from information acquired by the European Infinite Agency's Ecology Satellite (ENVISAT), with an incidence angle of 25° from the ground, looking Westward to E. Courtesy of Michael Poland, USGS-HVO. |
InSAR technique to monitor deformation. A technique has emerged that enables scientists to create an image of where and how much displacement occurred over a ground or glacial (ice) surface (e.grand., Rosen and others, 2000). The technique'due south spatial coverage is variable from hundreds of square meters to hundreds of square kilometers. Measurements of the component of deformation forth the musical instrument's line-of-sight typically take centimeter-scale precision. While the precision may be less than some other deformation techniques (i.e., GPS monitoring or tilt measurements), the broad coverage can pinpoint particularly interesting patterns and assist define areas for collateral studies, including farther modeling of the causes of deformation (see next section).
The image, which is called a radar interferogram, compares 2 divide 'snapshots' acquired at distinct points in fourth dimension. The snapshots are radar images of the topography of the basis surface in the expanse of interest (figure 25) caused past an instrument mounted on an airplane or satellite. The images are generated past transmitting radar waves to the globe'southward surface; the radar waves and so reverberate (backscatter) and are measured upon their return to the musical instrument. To make one interferogram, two such images taken at different times are compared. Variations in the stage of the coherent radar bespeak in the two snapshots disclose areas where displacement occurred forth the instrument's line-of-sight (example radar waves A-E, figure 25). In some cases scientists collect and procedure plenty data to enable them to brand a time series of interferograms, for example, almanac interferograms that enable yearly comparisons of the ground surface over a decade of fourth dimension.
 | Effigy 25. A cartoon representation of the basic principles of radar interferometry. Every bit the satellite makes its first laissez passer over a ground surface ('Initial ground surface'), it collects radar waves reflected off of the ground surface (solid wave, 'laissez passer i'). During a subsequent orbit (often months to years afterwards), when the satellite again passes over the same ground surface, another collection is made from very well-nigh the aforementioned orbital location (dashed wave, 'laissez passer 2'). If the ground surface deformed during the time between data collections (due east.thou., 'Subsided ground surface'), then the nerveless radar waves of the second pass will exist out of stage compared to those collected during the first pass (example waves A-E, at right). The phase departure of the waves is and so converted into the component of ground move along the line-of-sight of the satellite (either towards or away from the satellite), and is represented by a color as part of a full color cycle. Since the technique is based on the stage difference of multiple waves, the accuracy is constrained by detectable fractions of the radar wave'southward wavelength. In figure 24, C-band radar (wavelength = 5.half dozen cm) was used. Image non drawn to scale. Paradigm created by GVP staff. |
On the interferograms, interference patterns appear as full color cycles, or 'fringes', indicating how far out of phase the radar waves are when they return to the satellite (figure 25); one fringe indicates a line-of-sight basis offset equivalent to ane one-half of the radar waves' wavelength. An increased number of fringes at a specific area within an image thus indicates increased deformation during the time between images, allowing estimation of deformation rates over the time menstruum analyzed. Our give-and-take of this technique has omitted various assumptions, sources of error, and corrections used to procedure and interpret the data.
Magma sleeping room and dike modeling. Amelung and others (2007) assessed measured ground deformation at Mauna Loa from InSAR data. They modeled the size, location, and geometry of inferred intrusive bodies beneath Mauna Loa that led to the observed surface deformation. Their modeling suggested a spherical magma bedchamber of 1.1 km radius, centered under the SE caldera margin at 4.7 km depth below the summit (0.v km below body of water level), and a vertical dike with most of its inflation occurring along an 8-km-long zone at depths of 4-8 km (Figure 26). The dike'due south direction of opening was normal to its inferred planar orientation. An HVO model, fit to ground-based GPS measurements, agrees with the model of Amelung and others (2007).
 | Figure 26. (a) Vertical and (b) East components of footing-velocity measured at Mauna Loa during 2002-2005, determined from RADARSAT-1 InSAR data, and (c) the resultant model of the subsurface along a vertical cross-section oriented NE-SW. The satellite looked towards the E ('look direction') and had an incidence angle of ~45° from the basis. The white lines indicate the NE and SW rift zones (NERZ and SWRZ, respectively) that co-operative off of the caldera. The black line and circumvolve in (a) and (b) betoken the map location of the modeled dike and magma sleeping accommodation, respectively, besides shown in cantankerous-department view in (c). The location and span of Mauna Loa'southward peak caldera is indicated at the top of (c). The modeled spherical magma chamber and dike beneath the summit are shown in (c), indicating modeled opening rates of the dike (shown by the colored squares, with calibration at bottom right). The dike opening rates are based on a uniform excess-magma pressure model of 1.viii Mpa/year, and are modeled to fit the measured footing-velocities shown in (a) and (b). Modified from Amelung and others (2007). |
References. Amelung, F., Yun, S.H., Walter, T.R., Segall, P., and Kim, S.W. (2007) Stress Control of Deep Rift Intrusion at Mauna Loa Volcano, Hawaii. Science, 316 (5827), pg. 1026-1030 (DOI: 10.1126/scientific discipline.1140035).
Rosen, P.A., Hensley, Southward., Joughin, I.R., Li, F.K., Madsen, Southward.N., Rodriguez, E., and Goldstein, R.M. (2000) Synthetic aperture radar interferometry, Proc. IEEE, 88, 333- 382.
Information Contacts: Michael Poland, Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); Christelle Wauthier, Section of Terrestrial Magnetism, Carnegie Institute of Washington, Washington, DC.
Source: https://volcano.si.edu/volcano.cfm?vn=332020
0 Response to "When Will Mauna Loa Erupt Again"
ارسال یک نظر