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  • 1
    Electronic Resource
    Electronic Resource
    The formation of circular littoral cones from tube-fed pāhoehoe: Mauna Loa, Hawai'i (1996)
    Springer
    Bulletin of volcanology 57 (1996), S. 471-482 
    Details
    ISSN: 1432-0819
    Keywords: Littoral cones ; Mauna Loa ; Volumetric flow rate ; Lava tubes ; Lava-water interaction ; Lava delta ; Bench collapse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Pyroclastic cones along the southwest coast of Mauna Loa volcano, Hawai'i, have a common structure: (a) an early formed circular outer rim 200–400 m in diameter composed mostly of scoria and lapilli, and (b) one or more later-formed inner rims composed almost exclusively of dense spatter. The spatter activity locally fed short lava flows that ponded within the outer rims. Based on various lines of evidence, these cones are littoral in origin: relationships between the cones and associated flows; the degassed nature of the pyroclasts; and (although not unequivocal) the position of the cones relative to known eruptive vent locations on Mauna Loa. Additional support for the littoral interpretation comes from their similarity to (smaller) littoral cones that have been observed forming during the ongoing Kilauea eruption. The structure of these Mauna Loa cones, however, contrasts with that of “standard” Hawaiian littoral cones in that there is (or once was) a complete circle of pyroclastic deposits. Furthermore, they are large even though associated with tubefed pāhoehoe flows instead of 'a'ā. The following origin is proposed: An initial flow of tube-fed pāhoehoe into the ocean built a lava delta with a base of hyaloclastite. Collapse of an inland portion of the active tube into the underlying wet hyaloclastites or a water-filled void allowed sufficient mixing of water and liquid lava to generate strong explosions. These explosions broke through the top of the flow and built up the outer scoria/lapilli rims on the solid carapace of the lava delta. Eventually, the supply of water diminished, the explosions declined in intensity to spattering, and the initial rim was filled with spatter and lava.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00304433
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  • 2
    Electronic Resource
    Electronic Resource
    Volcán Ecuador, Galapágos Islands: erosion as a possible mechanism for the generation of steep-sided basaltic volcanoes (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 271-283 
    Details
    ISSN: 1432-0819
    Keywords: Key words: Galápagos ; erosion ; steep slopes ; eruption hiatus ; rift zone ; magma supply ; caldera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract. Volcán Ecuador (0° 02′ S, 91° 35′ W) consists of two strongly contrasting components: the eroded and vegetated remnant of a once-circular main volcano with a probable caldera, and a prominent rift zone extending to the northeast that is neither strongly eroded nor weathered. There are about 20 young-looking flows and vents on this caldera floor but only one on the higher remnant of the main volcano. The southwest half of the main volcano is faulted into the ocean. The main part of Volcán Ecuador possesses steep erosional slopes (average 30–40°) that cut into a sequence of flows that dip radially outward at 〈10°. In contrast, the northeast rift zone consists entirely of young flows and vents. The upper 10 km of the rift zone forms a peninsula about 7.5 km wide that connects Volcán Ecuador to Volcán Wolf. The rift zone bends to the southeast and the lower 8 km is tangential to the coast of Volcán Wolf. The rift zone axis dips away from the northeast edge of the main volcano, and its flanks slope roughly northwest and southeast at 〈4°. The rift zone is the Galápagos structure that most closely resembles a Hawaiian rift zone because it is constructed of lavas from subparallel linear vents, shows evidence of a deep feeder conduit, and has changed its direction to avoid a direct intersection with neighboring Volcán Wolf. The steep erosional slopes extending around the perimeter of the main volcano (except to the southwest where slumping occurred) were probably generated by marine erosion during a prolonged period of eruptive inactivity (perhaps 20 000–30 000 years). Only a few post-erosional eruptions have taken place at the main volcano in and near what was once the caldera. The entire rift zone postdates the period of prolonged erosion. Using the evidence for prolonged inactivity at Volcán Ecuador, we propose that erosion may have helped to produce steep slopes on the other western Galápagos volcanoes. On these more active volcanoes, however, numerous subsequent eruptions have completely mantled the erosional slopes with lava. The mechanism by which the volcanoes may shut off for long periods of time is unknown, but the fact that the Galápagos hotspot is presently supplying nine active volcanoes suggests that the magma supply at an individual volcano could vary greatly over periods of (tens of?) thousands of years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302080
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  • 3
    Electronic Resource
    Electronic Resource
    Thick lava flows of Karisimbi Volcano, Rwanda: insights from SIR-C interferometric topography (1998)
    Springer
    Bulletin of volcanology 60 (1998), S. 239-251 
    Details
    ISSN: 1432-0819
    Keywords: Key words Karisimbi ; Virunga ; Viscous lava flows ; Lava rheology ; Remote sensing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  We use a digital elevation model (DEM) derived from interferometrically processed SIR-C radar data to estimate the thickness of massive trachyte lava flows on the east flank of Karisimbi Volcano, Rwanda. The flows are as long as 12 km and average 40–60 m (up to 〉140 m) in thickness. By calculating and subtracting a reference surface from the DEM, we derived a map of flow thickness, which we used to calculate the volume (up to 1 km3 for an individual flow, and 1.8 km3 for all the identified flows) and yield strength of several flows (23–124 kPa). Using the DEM we estimated apparent viscosity based on the spacing of large folds (1.2×1012 to 5.5×1012 Pa s for surface viscosity, and 7.5×1010 to 5.2×1011 Pa s for interior viscosity, for a strain interval of 24 h). We use shaded-relief images of the DEM to map basic flow structures such as channels, shear zones, and surface folds, as well as flow boundaries. The flow thickness map also proves invaluable in mapping flows where flow boundaries are indistinct and poorly expressed in the radar backscatter and shaded-relief images.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050230
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  • 4
    Electronic Resource
    Electronic Resource
    Topographic analyses of K*lauea Volcano, Hawai'i, from interferometric airborne radar (1999)
    Springer
    Bulletin of volcanology 61 (1999), S. 1-14 
    Details
    ISSN: 1432-0819
    Keywords: Key words Digital elevation model ; TOPSAR ; Interferometry ; Eruption volume ; Digital topography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  We analyze digital topographic data collected in September 1993 over a ∼500-km2 portion of K*lauea Volcano, Hawai'i, by the C-band (5.6-cm wavelength) topographic synthetic aperture radar (TOPSAR) airborne interferometric radar. Field surveys covering an ∼1-km2 area of the summit caldera and the distal end of an ∼8-m-thick 'a'* flow indicate that the 10-m spatial resolution TOPSAR data have a vertical accuracy of 1–2 m over a variety of volcanic surfaces. After conversion to a common datum, TOPSAR data agree favorably with a digital elevation model (DEM) produced by the U.S. Geological Survey (USGS), with the important exception of the region of the ongoing eruption (which postdates the USGS DEM). This DEM comparison gives us confidence that subtracting the USGS data from TOPSAR data will produce a reasonable estimate of the erupted volume as of September 1993. This subtraction produces dense rock equivalent (DRE) volumes of 392, 439, and 90×106 m3 for the Pu'u '*'*, K*pa'ianah*, and episode 50–53 stages of the eruption, respectively. These are 124, 89, and 94% of the volumes calculated by staff of the Hawaiian Volcano Observatory (HVO) but do not include lava of K*pa'ianah* and episodes 50–53 that flowed into the ocean and are thus invisible to TOPSAR. Accounting for this lava increases the TOPSAR volumes to 124, 159, and 129% of the HVO volumes. Including the ±2-m uncertainty derived from the field surveys produces TOPSAR-derived volumes for the eruption as a whole that range between 81 and 125% of the USGS-derived values. The vesicularity- and ocean-corrected TOPSAR volumes yield volumetric eruption rates of 4.5, 4.5, and 2.7 m3/s for the three stages of the eruption, which compare with HVO-derived values of 3.6, 2.8, and 2.1 m3/s, respectively. Our analysis shows that care must be taken when vertically registering the TOPSAR and USGS DEMs to a common datum because C-band TOPSAR penetrates only partially into thick forest and therefore produces a DEM within the tree canopy, whereas the USGS DEM is adjusted for vegetation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050258
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  • 5
    Electronic Resource
    Electronic Resource
    Channel overflows of the Pōhue Bay flow, Mauna Loa, Hawai'i: examples of the contrast between surface and interior lava (1995)
    Springer
    Bulletin of volcanology 57 (1995), S. 117-126 
    Details
    ISSN: 1432-0819
    Keywords: Key words Channel overflows ; Shear rates ; Viscosity ; Lava types ; 'a'ā ; pāhoehoe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  A number of overflows from a large lava channel and tube system on the southwest rift zone of Mauna Loa were studied. Initial overflows were very low viscosity gas-rich pāhoehoe evidenced by flow-unit aspect ratios and vesicle sizes and contents. Calculated volumetric flow-rates in the channel range between 80 and 890 m3/s, and those of the overflows between 35 and 110 m3/s. After traveling tens to hundreds of meters the tops of these sheet-like overflows were disrupted into a surface composed of clinker and pāhoehoe fragments. After these 'a'ā overflows came to rest, lava from the interiors was able to break out on to the surface as pāhoehoe. The surface structure of a lava flow records the interaction between the differential shear rate (usually correlated with the volumetric flow-rate) and viscosity-induced resistance to flow. However, the interior of a flow, being better insulated, may react differently or record a later set of emplacement conditions. Clefts of toothpaste lava occurring within fields of clinker on proximal-type 'a'ā flows also record different shear rates during different times of flow emplacement. The interplay between viscosity and shear rate determines the final morphological lava type, and although no specific portion of lava ever makes a transition from 'a'ā back to pāhoehoe, parts of a flow can appear to do so.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301402
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  • 6
    Electronic Resource
    Electronic Resource
    Pahoehoe and aa in Hawaii: volumetric flow rate controls the lava structure (1990)
    Springer
    Bulletin of volcanology 52 (1990), S. 615-628 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The historical records of Kilauea and Mauna Loa volcanoes reveal that the rough-surfaced variety of basalt lava called aa forms when lava flows at a high volumetric rate (〉5–10 m3/s), and the smooth-surfaced variety called pahoehoe forms at a low volumetric rate (〈5–10 m3/s). This relationship is well illustrated by the 1983–1990 and 1969–1974 eruptions of Kilauea and the recent eruptions of Mauna Loa. It is also illustrated by the eruptions that produced the remarkable paired flows of Mauna Loa, in which aa formed during an initial short period of high discharge rate (associated with high fountaining) and was followed by the eruption of pahoehoe over a sustained period at a low discharge rate (with little or no fountaining). The finest examples of paired lava flows are those of 1859 and 1880–1881. We attribute aa formation to rapid and concentrated flow in open channels. There, rapid heat loss causes an increase in viscosity to a threshold value (that varies depending on the actual flow velocity) at which, when surface crust is torn by differential flow, the underlying lava is unable to move sufficiently fast to heal the tear. We attribute pahoehoe formation to the flowage of lava at a low volumetric rate, commonly in tubes that minimize heat loss. Flow units of pahoehoe are small (usually 〈1 m thick), move slowly, develop a chilled skin, and become virtually static before the viscosity has risen, to the threshold value. We infer that the high-discharge-rate eruptions that generate aa flows result from the rapid emptying of major or subsidiary magma chambers. Rapid near-surface vesiculation of gas-rich magma leads to eruptions with high discharge rates, high lava fountains, and fast-moving channelized flows. We also infer that long periods of sustained flow at a low discharge rate, which favor pahoehoe, result from the development of a free and unimpeded pathway from the deep plumbing system of the volcano and the separation of gases from the magma before eruption. Achievement of this condition requires one or more episodes of rapid magma excursion through the rift zone to establish a stable magma pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301212
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  • 7
    Electronic Resource
    Electronic Resource
    The 1919–1920 eruption of Mauna Iki, Kilauea: chronology, geologic mapping, and magma transport mechanisms (1993)
    Springer
    Bulletin of volcanology 55 (1993), S. 190-203 
    Details
    ISSN: 1432-0819
    Keywords: Lava lakes ; dikes ; plumbing ; tilt ; eruptive characteristics ; gas conent ; satellitic shield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Utilizing historical accounts, field mapping, and photogeology, this paper presents a chronology of, and an analysis of magma transport during, the December 1919 to August 1920 satellitic shield eruption of Mauna Iki on the SW rift zone of Kilauea Volcano, Hawaii. The eruption can be divided into four stages based on the nature of the eruptive activity. Stage 1 consisted of the shallow injection of a dike from the summit region to the eventual eruption site ∼10 km downrift. During stage 2, a low ridge of pahoehoe formed in the vent area; later a large a'a flow broke out of this ridge and flowed ∼8.5 km SW at an average flow front velocity of 0.5 km/day. The eruption continued until mid-August producing almost exclusively pahoehoe, first as gas-rich overflows from a lava pond (stage 3), and later as denser tube-fed lava (stage 4) that reached almost 8 km from the vent at an average flow-front velocity of 0.1 km/day. Magma transport during the Mauna Iki eruption is examined using three criteria: (1) eruption characteristics and volumetric flow rates; (2) changes in the surface height of the Halemaumau lava lake; and (3) tilt measurements made at the summit of Kilauea. We find good correlation between Halemaumau lake activity and the eruptive stages. Additionally, the E-W component of summit tilt tended to mimic the lake activity. The N-S component, however, did not. Multiple storage zones in the shallow summit region probably accounted for the decoupling of E-W and N-S tilt components. Analysis of these criteria shows that at different times during the eruption, magma was either emplaced into the volcano without eruption, hydraulically drained from Halemaumau to Mauna Iki, or fed at steady-state conditions from summit storage to Mauna Iki. Volume calculations indicate that the supply rate to Kilauea during the eruption was around 3 m3/s, similar to that calculated during the Mauna Ulu and Kupaianaha shield-building eruptions, and consistent with previously determined values of long-term supply to Kilauea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301516
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  • 8
    Electronic Resource
    Electronic Resource
    The formation of circular littoral cones from tube-fed pāhoehoe: Mauna Loa, Hawai`i (1996)
    Springer
    Bulletin of volcanology 57 (1996), S. 471-482 
    Details
    ISSN: 1432-0819
    Keywords: Key words Littoral cones ; Mauna Loa ; Volumetric flow rate ; Lava tubes ; Lava ; water interaction ; Lava delta ; Bench collapse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Pyroclastic cones along the southwest coast of Mauna Loa volcano, Hawai`i, have a common structure: (a) an early formed circular outer rim 200–400 m in diameter composed mostly of scoria and lapilli, and (b) one or more later-formed inner rims composed almost exclusively of dense spatter. The spatter activity locally fed short lava flows that ponded within the outer rims. Based on various lines of evidence, these cones are littoral in origin: relationships between the cones and associated flows; the degassed nature of the pyroclasts; and (although not unequivocal) the position of the cones relative to known eruptive vent locations on Mauna Loa. Additional support for the littoral interpretation comes from their similarity to (smaller) littoral cones that have been observed forming during the ongoing Ki¯lauea eruption. The structure of these Mauna Loa cones, however, contrasts with that of "standard" Hawaiian littoral cones in that there is (or once was) a complete circle of pyroclastic deposits. Furthermore, they are large even though associated with tube-fed pāhoehoe flows instead of `a`ā. The following origin is proposed: An initial flow of tube-fed pāhoehoe into the ocean built a lava delta with a base of hyaloclastite. Collapse of an inland portion of the active tube into the underlying wet hyaloclastites or a water-filled void allowed sufficient mixing of water and liquid lava to generate strong explosions. These explosions broke through the top of the flow and built up the outer scoria/lapilli rims on the solid carapace of the lava delta. Eventually, the supply of water diminished, the explosions declined in intensity to spattering, and the initial rim was filled with spatter and lava.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00304433
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  • 9
    Electronic Resource
    Electronic Resource
    Calculation of lava effusion rates from Landsat TM data (1998)
    Springer
    Bulletin of volcanology 60 (1998), S. 52-71 
    Details
    ISSN: 1432-0819
    Keywords: Key words TM ; Lava flow ; Thermal flux ; Effusion rates ; AVHRR ; Pu'u 'O'o ; Kupaianaha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  We present a thermal model to calculate the total thermal flux for lava flowing in tubes, on the surface, or under shallow water. Once defined, we use the total thermal flux to estimate effusion rates for active flows at Kilauea, Hawaii, on two dates. Input parameters were derived from Landsat Thematic Mapper (TM), field and laboratory measurements. Using these parameters we obtain effusion rates of 1.76±0.57 and 0.78±0.27 m3 s–1 on 23 July and 11 October 1991, respectively. These rates are corroborated by field measurements of 1.36±0.14 and 0.89±0.09 m3 s–1 for the same dates (Kauahikaua et al. 1996). Using weather satellite (AVHRR) data of lower spatial resolution, we obtain similar effusion rates for an additional 26 dates between the two TM-derived measurements. We assume that, although total effusion rates at the source declined over the period, the shut down of the ocean entry meant that effusion rates for the surface flows alone remained stable. Such synergetic use of remotely sensed data provides measurements that can (a) contribute to monitoring flow-field evolution, and (b) provide reliable numerical data for input into rheological and thermal models. We look forward to being able to produce estimates for effusion rates using data from high-spatial-resolution sensors in the earth observing system (EOS) era, such as Landsat 7, the hyperspectral imager, the advanced spaceborne thermal emission spectrometer, and the advanced land imager.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050216
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  • 10
    Electronic Resource
    Electronic Resource
    Channel overflows of the Pōhue Bay flow, Mauna Loa, Hawai'i: examples of the contrast between surface and interior lava (1995)
    Springer
    Bulletin of volcanology 57 (1995), S. 117-126 
    Details
    ISSN: 1432-0819
    Keywords: Channel overflows ; Shear rates ; Viscosity ; Lava types ; 'a'ā ; pāhoehoe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A number of overflows from a large lava channel and tube system on the southwest rift zone of Mauna Loa were studied. Initial overflows were very low viscosity gas-rich pāhoehoe evidenced by flow-unit aspect ratios and vesicle sizes and contents. Calculated volumetric flow-rates in the channel range between 80 and 890 m3/s, and those of the overflows between 35 and 110 m3/s. After traveling tens to hundreds of meters the tops of these sheet-like overflows were disrupted into a surface composed of clinker and pāhoehoe fragments. After these 'a'ā overflows came to rest, lava from the interiors was able to break out on to the surface as pāhoehoe. The surface structure of a lava flow records the interaction between the differential shear rate (usually correlated with the volumetric flow-rate) and viscosity-induced resistance to flow. However, the interior of a flow, being better insulated, may react differently or record a later set of emplacement conditions. Clefts of toothpaste lava occurring within fields of clinker on proximal-type 'a'ā flows also record different shear rates during different times of flow emplacement. The interplay between viscosity and shear rate determines the final morphological lava type, and although no specific portion of lava ever makes a transition from 'a'ā back to pāhoehoe, parts of a flow can appear to do so.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301402
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