December 2013 LIP of the Month

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Magma supply and storage at Hawaiian volcanoes

Michael Poland

U.S. Geological Survey – Hawaiian Volcano Observatory

mpoland@usgs.gov

Extracted and modified from Poland et al. (in press) and Poland (in press)

Although not a Large Igneous Province (LIP) according to current definitions, Hawai’i has always been considered part of the LIP-related family of intraplate magmatism (e.g., Coffin and Eldholm, 1994; Bryan and Ernst, 2008; Ernst 2014). According to the traditional model for mantle plumes, classic LIPs, such as the Columbia River Flood Basalts, Deccan Traps, and Ontong Java Plateau, represent the eruption of plume heads, and age-progressive hot spot trails such as Hawai’i represent activity associated with a plume stem or tail (Morgan, 1972, 1981; Richards et al., 1989).  Also, given the detailed, continuous, and multidisciplinary study of magmatism in Hawai‘i over more than a century, lessons can be learned for how the magmatism of classic LIPs occurs and progresses.  For example, it is possible to track magma flux over time in Hawai‘i, which provides an indication of the processes that influence magma transport between the mantle and the surface.  Hawaiian volcanoes likewise may be analogs for volcanic structures that grow during LIP emplacement—especially large shield volcanoes with complex magmatic plumbing systems and eruptive histories.

Magma Supply

The Hawaiian-Emperor chain of seamounts and islands extends over 6,000 km across the Pacific Ocean (Figure 1), tracing a record of volcanic activity over the past ~80 m.y. with the age of volcanism progressively younger to the southeast (Clague and Dalrymple, 1987; Tilling and Dvorak, 1993).  Volcanism is attributed to a mantle melting anomaly, termed a “hot spot” (Wilson, 1963).  The origin of the hotspot is a subject of debate (e.g., Foulger et al., 2005), with some authors favoring a shallow (<150 km) depth of melting beneath Hawai‘i (Foulger, 2007; Anderson, 2011). The presence of a deep-seated mantle plume (Morgan, 1971), however, is strongly suggested by primitive geochemical signatures, including elevated helium isotopic ratios in erupted lavas (e.g., Kurz et al., 1983), and geophysical indications, especially from seismic imaging (e.g., Wolfe et al., 2009, 2011), of high-temperature upwelling from the lower mantle. 


Figure 1. Bathymetric map showing the Hawaiian and Emperor Seamount chains and Hawaiian Islands in the northwest Pacific Ocean basin. Inset shows relief map of the Island of Hawai‘i, with the five volcanoes that make up the island outlined. Arrow indicates plate motion velocity in millimeters per year (Gripp and Gordon, 2002).

Regardless of its origin, the Hawaiian hot spot is the most productive on Earth based on buoyancy fluxes (e.g., Sleep, 1990) and eruption rates (Wadge, 1982).  A number of mass flux estimates, which quantify the magma supply to the surface and provide a measure of hotspot vigor over time, have been made for the Hawaiian hotspot, initially based on bathymetry and topography (Vogt, 1972; Bargar and Jackson, 1974) and later incorporating seismic and gravity data, coupled with models of crustal loading (White, 1993; Van Ark and Lin, 2004; Vidal and Bonneville, 2004; Robinson and Eakins, 2006). Although the rates calculated by these studies differ by about an order of magnitude (primarily because earlier studies had difficulty accounting for volumes obscured from bathymetry by flexure and isostatic compensation), they track one another in a gross sense and provide an ~80-million-year record of mass flux that displays variations over timescales of millions of years (Figure 2). All flux estimates also show an increase in magma supply to the surface over the past 30 million years, with the highest rates occurring at present. The flux variations probably reflect changes in lithospheric thickness—a factor that influences the extent of decompression melting—and pulsation of the plume (Vogt, 1972; White, 1993; Regelous et al., 2003; Van Ark and Lin, 2004; Vidal and Bonneville, 2004) and may correlate with the composition of the source material as reflected by geochemical changes in erupted lava (e.g., Greene et al., 2010). For example, the strong manifestation of the “Loa” and “Kea” volcanic trends—evident in both lava chemistry and geographic distribution of volcanoes (Figure 3)—over the past few million years (from Ko‘olau, on the Island of O‘ahu, to the present) occurs during a time of increasing mass flux (Weis et al., 2011).


Figure 2.  Volume flux of the Hawaiian hot spot over time as calculated by various authors.  The estimate of Bargar and Jackson (1974) is based on the volume of seamounts and islands in the Hawaiian-Emperor chain, with the timing established by Robinson and Eakins (2006).  Vogt (1972) used a similar volume-age relation.  White (1993) based his volume flux curve on crustal thickening determined seismically, coupled with the volume of seamounts and volcanoes and their underplated roots assuming Airy isostasy.  Vidal and Bonneville (2004) distinguished topography/bathymetry created by the Hawaiian swell (caused by the mantle plume) from that caused by volcanism, which is a better measure of the magma production rate.  Finally, Van Ark and Lin (2004) calculated crustal thicknesses from gravity data to compute hot spot volume flux over time.  Dashed vertical line is the location of the bend in the Hawaiian-Emperor chain of seamounts and islands (see Figure 1).


Figure 3.  Parallel compositional trends that make up the recent Hawaiian Islands. (A) Volcanoes formed over the last ~3 million years can be classified by their geochemistry as belonging to either the Kea (open triangles) or Loa (solid triangles) trends. Ko‘olau marks the start of the Loa trend, according to Tanaka et al. (2008). Before this time (grey triangles), volcanoes display characteristics of both trends. (B) Sr-Pb isotope plot of data from Hawaiian tholeiitic basalts highlighting the isotopic difference between Loa- and Kea-trend volcanoes, taken from Figure 1b inset of Weis et al. (2011).

The volume of melt provided to a volcano by the hotspot also varies on timescales of less than a million years. The Hawai‘i Scientific Drilling Project sampled nearly 500,000 years of Mauna Kea eruptive activity in a ~3.1-km-deep drill hole. Geochemical diversity in retrieved samples is consistent with repeated waxing and waning supply during the volcano’s shield-building stage, as opposed to a smoother increase and then decrease in supply as the volcano grew and was then carried away from the hotspot (Stolper et al., 2004; Rhodes et al., 2012). Models of the growth of Hawai‘i Island similarly suggest pulsed magma flow from the hotspot, based on volcano volumes and lifespans (Lipman and Calvert, 2013) and lava accumulation rates (e.g., Jicha et al., 2012).  Even shorter-term changes in supply are evident from recent volcanism.

Deformation, seismic, gas, and geologic data indicate an increase in the rate of magma supply from the mantle to Kīlauea during 2003–07 (Poland et al., 2012).  In late 2003, deformation at Kīlauea’s summit transitioned from long-term deflation to inflation, (Figure 4A).  SO2 emission rates from Kīlauea’s east rift zone (ERZ) remained nearly constant at about 1,370 tonnes per day (t/d) during this period (Figure 4B), however, suggesting no change in the amount of magma being transported from the summit to the ERZ—about 0.13 km3/yr (Sutton et al., 2003).  The inflation was therefore not caused by a decrease in effusion rate and subsequent backup in Kīlauea’s magma plumbing system, as has occurred at other times during the 1983–present Puʻu ʻŌʻō-Kupaianaha eruption (Kauahikaua et al., 1996; Miklius and Cervelli, 2003).  Since there was no precursory deflation event that would have created a pressure imbalance and a “top-down” change in magma supply, the most likely explanation for the inflation is increased magma flux from the hot spot.  Summit inflation accelerated in 2005–06 and even involved the upper part of the southwest rift zone (SWRZ; Figure 4A), accompanied by a near-doubling in ERZ SO2 emissions (indicating an increase in lava effusion from the ERZ eruption site; Figure 4B) and a large increase in seismicity in the upper rift zones and northeast of the summit caldera (Figure 4C).  Petrologic changes to lava erupted from the ERZ also reflect the magma supply increase, with increasing MgO and eruption temperatures during 2007 indicating a greater portion of “fresh” mantle-derived magma erupting from the ERZ (Figure 4D).  Perhaps the most obvious manifestation of the supply surge was a massive increase in CO2 emissions from Kīlauea.  Because CO2 exsolves from ascending magma at a depth of ~30 km and is therefore insensitive to shallow processes, it is a direct indicator of deep magma supply (Gerlach and others, 2002).  Before 2005, sporadic CO2 emission measurements yielded constant values of about 8,000 t/d, but a measurement in July 2004 was 18,200±2,500 t/d (Figure 4E), and more frequent measurements starting in 2005 averaged about 20,000 t/d for several months.  The supply surge culminated with an ERZ dike intrusion and small eruption during June 17–19, 2007, and the formation of a new long-term ERZ eruptive vent on July 21, 2007.  By the end of 2008, geological, geophysical, and geochemical data indicated a return to pre-2003 rates of magma supply. 


Figure 4.  Geophysical and geochemical time series data from Kīlauea Volcano during 2000–10.   Red dotted vertical line indicates June 17–19, 2007, ERZ intrusion and eruption.  (A) GPS data showing cross-caldera distance change (black; positive change indicates extension), vertical change at a station in the south part of the caldera (blue; positive change indicates uplift), and vertical change at a station in the southwest rift zone (red).  Uplift and extension are indicative of surface inflation. (B) ERZ SO2 emissions.  (C) Cumulative numbers of located earthquakes in the upper ERZ (black), upper SWRZ (blue), and NW of the caldera (red).  (D) MgO weight percent (left axis) and eruption temperatures from glass geothermometry (right axis) measured in lavas erupted from the ERZ.  (E) Summit CO2 emissions.  The first three measurements were made before 2000, but are shown here to indicate the consistency of pre-2004 emission rates.

The 2003–07 surge in magma supply affected not only Kīlauea, but also neighboring Mauna Loa volcano, which inflated during that time period (but which has not erupted since 1984).  The surge can therefore be modeled as an increase in magma input into an asthenospheric melt layer beneath the Hawaiian Islands that fed magma to both volcanoes (Gonnermann et al., 2012).  Such variations may also occur during the emplacement of LIPs; therefore, current and geologically recent magma variations in magma supply to Hawaiian volcanoes may provide an analog to the types of fluctuations that might occur during LIP eruptive activity.

While revealing much about how magma supply from the Hawaiian hotspot can vary over time, the inflation at both Kīlauea and Mauna Loa during the 2000s also highlighted magma storage areas beneath both volcanoes.  Coupled with geologic and other geophysical data, the deformation that accompanied the surge can be used to map the magmatic plumbing systems at these large shield volcanoes, which represent possible analogs for the types of volcanoes that might grow during LIP emplacement.

Magma Plumbing Systems

Kīlauea

The general model for Kīlauea’s magma plumbing system, first proposed by Eaton and Murata (1960) and refined by Tilling and Dvorak (1993) and other workers, is simple: magma generated in the mantle ascends and is stored in reservoirs that are one to a few kilometers beneath the summit, from which it may eventually erupt within the caldera or be transported laterally into the east or southwest rift zones as intrusions that may feed eruptions far from the summit.  While this overall depiction remains largely unchanged, the characteristics of specific parts of the magma plumbing system have been the focus of numerous studies.  Ryan (1988) used seismic data to define areas of subsurface magma transport and storage, including magma storage at 2–4 km depth beneath the summit and almost wholly molten rift zones at 3–10 km beneath the surface.  Other studies have employed deformation measurements to map the locations of magma reservoirs beneath the summit (for example, Cervelli and Miklius, 2003; Baker and Amelung, 2012).

Geodetic data collected in the 1990s and 2000s, combined with seismic and geologic data, provide improved resolution of the geometry of Kīlauea’s magma storage zones and transport pathways.  This improvement is largely due to the excellent temporal resolution of continuous ground-based sensors, including Global Positioning System (GPS) stations, and outstanding spatial resolution of deformation from Interferometric Synthetic Aperture Radar (InSAR), especially that collected during the 2003–07 magma supply increase.  Those data highlight deformation centered on a number of different points, highlighting magma storage in distinct zones beneath the summit (Baker and Amelung, 2012; Poland et al., 2012, in press; Figure 5).   


Figure 5.  Interferograms detailing surface deformation in Kīlauea’s summit area during the 2003–07 magma supply increase.  For all images, dates spanned are in the lower right, and upper left inset gives satellite, flight direction (arrow) and look direction (orthogonal line with angle in degrees from vertical).  Color scale for interpreting interferograms is in the lower right panel.  One fringe is 28.3 mm of range change along the radar line of sight (positive for increasing range, that is, ground motion away from the satellite).  (A) Uplift is focused within the caldera, near Halemaʻumaʻu Crater in the center of the caldera.  (B) Uplift has shifted to near Keanakākoʻi Crater in the SE part of the caldera.  (C) Uplift rate has increased and is centered on the south caldera and upper SWRZ.  (D) Subsidence near Halemaʻumaʻu Crater and ERZ uplift caused by magma withdrawal from the summit and intrusion into the ERZ during June 17–19, 2007.  (E) Subsidence centered in the south caldera and upper SWRZ.

Poland et al. (in press) combined geodetic data with existing seismic and geologic results to propose a refined model of magma storage and transport at Kīlauea (Figure 6).  The model contains several elements, including multiple magma reservoirs beneath the volcano’s summit and dual pairs of rift zones extending to the east and southwest, with one pair at ~3 km depth and the other at <1 km depth.  At least two reservoirs occur beneath Kīlauea’s summit: a small one (~1 km3) at ~1.5 km beneath the caldera center and a larger one (~10 km3) at ~3 km beneath the south part of the caldera.  Magma is also occasionally stored at ~3 km beneath the SE part of the caldera, near the intersection of the ERZ and caldera.  All of these magma storage zones are defined by deformation (e.g., Fiske and Kinoshita, 1969; Cervelli and Miklius, 2003; Baker and Amelung, 2012) and seismicity (e.g., Thurber, 1984; Dawson et al., 1999; Battaglia et al., 2003).


Figure 6.  Proposed structure of Kīlauea’s subsurface magma plumbing system (Poland et al., in press).  Schematic cut-away shows a cross section through Kīlauea’s summit and rift zones.  Magma pathways and storage areas are exaggerated in size for clarity.  H=Halemaʻumaʻu reservoir, K=Keanakākoʻi reservoir, SC=south caldera reservoir, SWRZ=southwest rift zone.  Plan view gives the relations of magma pathways to surface features and topography in the vicinity of Kīlauea Caldera.

Kīlauea is generally described as having two rift zones which radiate to the east and southwest from the summit.  Geologic data, however, suggest that each rift zone is comprised of two distinct magma pathways with different trends, depths, and surface expressions (e.g., Holcomb, 1987)—a model that is also supported by geophysical results.  The deeper magma pathways, located at about 3 km depth and connected to the south caldera reservoir, are the “East Rift Zone” and “Seismic Southwest Rift Zone.”  The east rift zone is by far the more dominant, both in terms of structure (it extends for over 130 km, 75 km of which are offshore; Clague et al., 1995) and recent eruptive activity (with tens of eruptions since the 1950s).  The rift zone has a molten core (Johnson, 1995b; Poland et al., 2012) from which dike intrusions can initiate (Figure 7).  The seismic southwest rift zone does not extend much beyond the coastline and is defined by seismicity that trends initially south from the caldera, then to the southwest (Figure 8).  The east and seismic southwest rift zones separate the stable north flank of Kīlauea from the unstable south flank (e.g., Cayol et al., 2000).


Figure 7.  Map of Kīlauea’s east rift zone showing intrusive activity during 1990–2011.  Seismicity (colored circles) is shown for intrusions for which little or no geodetic data are available.  Model geometries (colored lines) are given for those dikes that were detected by deformation measurements (tilt, GPS, and/or InSAR), including the 1997 Nāpau fissure eruption (Owen et al., 2000), 1999 non-eruptive dike (Cervelli et al., 2002), 2007 Father’s Day intrusion/eruption (Montgomery-Brown et al., 2010), and 2011 Kamoamoa fissure eruption (Lundgren et al., 2013).


Figure 8.  Seismicity marking discrete magmatic intrusions along Kīlauea’s seismic SWRZ.  (A) December 31, 1974–January 7, 1975.  (B) August 10–12, 1981.  (C) June 1982.  (D) March–September 2006.  Color and size of circles give depth and earthquake magnitude, respectively.  Red dashed lines in (D) indicate seismic SWRZ and volcanic SWRZ.

The shallower rift pathways radiate from the shallow magma storage area beneath the center of the caldera.  To the southwest is the “Volcanic Southwest Rift Zone,” so called because it is defined by an alignment of fissures and eruptive vents.  The most noteworthy recorded activity along this zone occurred during the 1919–20 Mauna Iki eruption, when a lava lake active in the summit caldera at the time drained into a fissure that extended southwest from the caldera.  Thomas A. Jaggar, founder of the Hawaiian Volcano Observatory, observed lava flowing in cracks just beneath the surface (and occasionally reaching the surface) at multiple locations between the caldera and Mauna Iki, attesting to its shallow nature (Jaggar, 1919).  When the summit lava lake drained again in 1922 and 1924, a fracture interpreted to be the 1919–20 conduit was exposed in the walls of Halemaʻumaʻu Crater (Figure 9)—further evidence of its shallow connection to the summit magma system.   To the east from the shallow magma storage area is the “Halemaʻumaʻu-Kīlauea Iki Trend,” named for the two craters between which it extends.  Eruptions from this rift system have occurred numerous times since the 1950s, including the spectacular 1959 Kīlauea Iki eruption (e.g., Eaton and Murata, 1960).  The trend is manifested by an alignment of eruptive vents on the floor of Kīlauea Caldera (Figure 10).


Figure 9.  Photos of the southwest wall of Halemaʻumaʻu Crater within Kīlauea Caldera showing the fissure through which the 1919–20 Mauna Iki eruption is thought to have been fed.  (A) USGS photograph by Thomas A. Jaggar taken on May 25, 1922, following a collapse of Halemaʻumaʻu Crater.  A small amount of lava is present at the base of the fissure.  (B) USGS photograph by Howard A. Powers taken on August 18, 1947, with the south flank of Mauna Loa in the background.


Figure 10.  Geologic map showing post-18th century lava flows of the summit region (warm colors are more recent than cool colors) and eruptive fissures (red hatched lines).  From Neal and Lockwood (2003). Fissures associated with the Halemaʻumaʻu-Kīlauea Iki Trend are located in the center of the map.

Based on the above evidence, the generalized east and southwest rift zones may be viewed as parallel structures, each with both shallow and deeper magma pathways that are connected to the summit magma system at different depths, and with the shallower pathways located north of the deeper pathways.  Such a geometry may be a consequence of seaward migration of both rift zones over time, as suggested by Swanson and others (1976).  The shallower rift zones are now structurally insignificant, yet mark the former locations of the deeper, more structurally significant rift zones that have been pulled southward as Kīlauea has grown.

Mauna Loa

The magma system of Mauna Loa appears simpler than that of Kīlauea in terms of geometry, probably because it is not as well-constrained owing to the relative paucity of geophysically monitored eruptive and intrusive activity compared to Kīlauea. Inter- and co-eruptive deformation data from Mauna Loa’s summit area in the 1970s–1990s clearly indicated magma storage 3–4 km beneath the south part of the caldera (Decker et al., 1983; Lockwood and Lipman, 1987; Johnson, 1995a; Miklius et al., 1995). An episode of inflation in the 2000s was well monitored by InSAR and GPS (Figure 11), and the deformation suggested that, in addition to the south caldera magma reservoir, a vertically elongated, tabular storage area underlies, and follows the trend of, the caldera below about 4-km depth (Amelung et al., 2007; Poland et al., in press). A swarm of thousands of long-period earthquakes during Mauna Loa inflation in 2002–04 was located between 30- and 50-km depth directly beneath the volcano’s summit caldera, implying the presence of a focused magma feeder conduit that extends from this depth to shallow levels that is independent of Kīlauea’s feeder system (Okubo and Wolfe, 2008). More detailed examinations of magma storage and transport await geophysical observations of future intrusive and eruptive activity at the volcano.


Figure 11.  GPS displacements from Mauna Loa during 2004–05.  Observed displacements are black, with 95% confidence ellipses, and modeled are blue.  Model sources include a point source at 3.5 km depth beneath the southeast caldera rim (red dot) with a volume increase of 4 × 106 m3/yr, and a vertical dike along the length of the caldera (red line) with a top at 3.8 km depth (the bottom is difficult to resolve but is probably no more than a few km below the top) and a volume increase of 30 × 106 m3/yr.  

Discussion

The possibility of a connection between the magmatic systems of Kīlauea and Mauna Loa has been a source of debate since the volcanoes were first described scientifically in the mid-1800s.  Petrologic differences in lava erupted from the two volcanoes provide convincing evidence that their magma sources are geochemically distinct and their magma plumbing systems are independent (e.g., Wright, 1971; Rhodes et al., 1989; Frey and Rhodes, 1993).  Observations of volcanic activity at the two volcanoes, however, highlight correlations that argue for some sort of shared magma supply.  Several authors have noted an inverse relation between eruptions of the two volcanoes (for example, Moore, 1970; Klein, 1982).  During 1934–52, for instance, Kīlauea was dormant but Mauna Loa erupted six times, while during 1955 to the present Mauna Loa only erupted twice and Kīlauea was frequently (and often continuously) active.  Klein (1982) found this anti-correlation to be statistically significant and suggested that the volcanoes were competing for a common supply of magma.  Kīlauea and Mauna Loa have also behaved sympathetically.  In May 2002, an effusive surge from Kīlauea’s ERZ occurred at the same time as the onset of inflation at Mauna Loa.  Miklius and Cervelli (2003) suggested that input of magma into Mauna Loa increased the pressure in Kīlauea’s magma system, triggering the ERZ effusive episode. 

A more direct case of sympathetic behavior between the two volcanoes is suggested by activity during 2002–07.  Mauna Loa began to inflate in 2002 after nearly a decade of deflation (Miklius and Cervelli, 2003; Amelung et al., 2007).  The inflation rate increased in late 2004 and was accompanied by a swarm of thousands of long-period earthquakes at >30 km depth (Okubo and Wolfe, 2008), but inflation waned and ceased by the end of 2009.  The fact that Mauna Loa inflation occurred at approximately the same time as a surge in magma supply to Kīlauea is an unlikely coincidence and suggests the possibility that the increase in magma supplied from the mantle affected both volcanoes.  Gonnermann et al. (2012) suggested that the two volcanoes may be dynamically linked through an asthenospheric porous melt zone.  In their model, the shallow magma plumbing systems of each volcano are distinct, and the magma feeding systems tap different parts of the mantle source (thereby explaining the overall petrologic differences in erupted lavas).  Changes in magma pressure, however, can be transmitted between crustal storage reservoirs and the asthenospheric melt zone on time scales of less than a year without requiring direct melt transport.  The model therefore provides a mechanism by which Kīlauea and Mauna Loa display complimentary modes of behavior without a shallow connection.

An asthenospheric melt zone that links Mauna Loa and Kīlauea might also explain observations of CO2 emissions at the two volcanoes.  During the 2003–07 magma supply surge and inflation of Kīlauea and Mauna Loa, CO2—which should have been emitted from both volcanoes, given that both were being supplied with magma from the mantle—was measured only at Kīlauea.  A possible explanation for this observation is that CO2 from all magma supplied by the hot spot degasses through Kīlauea’s summit.  Deep seismicity (primarily tremor and long-period earthquakes) at ~40 km depth offshore of Kīlauea’s south flank has been interpreted as the magma source that feeds the active volcanoes of Hawaiʻi (Aki and Koyanagi, 1981; Wright and Klein, 2006).  Wright and Klein (2006) further proposed that the deep feeder is linked to Kīlauea via a subhorizontal zone of magma transport at about 30 km depth, similar to the asthenospheric melt zone envisioned by Gonnermann and others (2012).  CO2 starts to exsolve at about this depth (Gerlach and others, 2002), so CO2 bubbles might ascend along the path closest to the deep conduit from the source—the nearby magmatic feeder connected to Kīlauea’s summit—regardless of the ultimate destination of the magma, be it Kīlauea, Mauna Loa, or possibly Lōʻihi.  Such a model (Figure 12) has the potential to explain why so little CO2 has been emitted from Mauna Loa, despite periods of magma accumulation and eruption (Ryan, 1995).


Figure 12.  Schematic diagram of possible magma supply pathways beneath the Island of Hawaiʻi based in part on Gonnermann et al. (2012).  Black vertical arrow represents magma supplied from the mantle hot spot to a subhorizontal melt zone at about 30 km depth (red plane), located beneath Kīlauea’s SWRZ based on long-period seismicity and tremor.  Colored arrows depict magma transport paths to the most active volcanoes of Hawaiʻi.  Most exsolved CO2 ascends with magma that is fed to Kīlauea, since that volcano is closest to the source of mantle supply, resulting in a CO2-rich plume from Kīlauea’s summit.

Above the hypothesized asthenospheric melt zone, the magma plumbing systems of the various volcanoes that make up the Island of Hawai‘i are independent.  Frequent eruptive activity and an excellent record of geophysical and geological monitoring during the period 1950–2013 have provided a high-resolution view of Kīlauea’s magma plumbing system.  Although less volcanically active during the same time period, the general outline of Mauna Loa’s magmatic system is apparent from deformation and seismicity during and between eruptive episodes.  The models presented above should prove valuable for understanding future volcanic and seismic activity at both volcanoes.  In addition, improved insights into the internal workings of Kīlauea and Mauna Loa have the potential to enhance understanding of volcanic edifices that are constructed as a consequence of LIP emplacement.  Such volcanoes have either long since eroded away or are so old and inactive that their internal architecture cannot be known.  In these cases, LIP volcano plumbing systems may be elucidated by analogy with currently active Hawaiian volcanoes.

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