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  • 1
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    The Miocene Galápagos ash layer record of Integrated Ocean Drilling Program Site Legs 334 and 344: Ocean-island explosive volcanism during plume-ridge interaction (2015)
    GSA (Geological Society of America)
    In:  Geology, 43 (7). pp. 599-602.
    Details
    Publication Date: 2019-10-24
    Description: Drilling at Integrated Ocean Drilling Program Site U1381 on the Cocos Ridge offshore Costa Rica recovered 67 primary Miocene (ca. 8 Ma to ca. 16.5 Ma) marine fallout ash layers. Geochemical, volcanological, and geological criteria link these ashes to Plinian eruptions that carried ash to at least 50–450 km from the Galápagos hotspot. These ash layers are the first documentation of highly explosive Miocene Galápagos hotspot volcanism. This volcanism is bimodal with two-thirds of the tephra layers generated by basaltic magmas (glass compositions 〈57 wt% SiO2) and one-third by rhyolitic magmas. The temporal distribution of the tephra layers, inferred from sediment accumulation rates calibrated by 40Ar/39Ar and biostratigraphic ages, reveals a distinct increase in eruption frequency and hence increased volcanic activity of the Galápagos hotspot after 14 Ma which we interpret in the context of dynamic interaction between the Galápagos plume and spreading ridge.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1130/G36645.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Cyclic volcanism at convergent margins: linked to aarth orbital parameters or climate changes? (2010)
    Copernicus
    In:  [Talk] In: EGU General Assembly 2010, 02.05.-07.05.2010, Vienna, Austria . Geophysical Research Abstracts .
    Details
    Publication Date: 2019-09-23
    Description: EGU2010-13373 The frequency of volcanic activity varies on a wide rangeof spatial and temporal scales, from 〈1 yr. periodicities in single volcanic systems to periodicities of 106 yrs. in global volcanism. The causes of these periodicities are poorly understood although the long-term global variations are likely linked to plate-tectonic processes. Here we present evidence for temporal changes in eruption frequencies at an intermediate time scale (104 yrs.) using the Pleistocene to recent records of widespread tephras of sub-Plinian to Plinian, and occasionally co-ignimbrite origin, along the Pacific Ring of Fire, which accounts for about half of the global length of 44,000 km of active subduction. Eruptions at arc volcanoes tend to be highly explosive and the well-preserved tephra records from the ocean floor can be assumed to be representative of how eruption frequencies varied with time. Volcanic activity along the Pacific Ring of Fire evolved through alternating phases of high and low frequency; although there is modulation by local and regional geologic conditions, these variations have a statistically significant periodicity of 43 ka that overlaps with the temporal variation in the obliquity of the Earth’s rotation axis, an orbital parameter that also exerts a strong control on global climate changes. This may suggest that the frequency of volcanic activity is controlled by effects of global climate changes. However, the strongest physical effects of climate change occur at 100 ka periods which are not seen in the volcanic record. We therefore propose that the frequency of volcanic activity is directly influenced by minute changes in the tidal forces induced by the varying obliquity resulting in long-period gravitational disturbances acting on the upper mantle.
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Talk
  • 3
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    Combined bromine and chlorine release from large explosive volcanic eruptions: A threat to stratospheric ozone? (2013)
    GSA (Geological Society of America)
    In:  Geology, 41 (6). pp. 707-710.
    Details
    Publication Date: 2019-10-24
    Description: Large explosive volcanic eruptions inject gases, aerosols, and fine ashes into the stratosphere, potentially influencing climate. Emissions of chlorine (Cl) and bromine (Br) from such large eruptions play an important role for catalytic destruction of ozone in the stratosphere, but hitherto the global effects of simultaneous catastrophic release of volcanic Br and Cl into the stratosphere have not been investigated. The Br release from 14 large explosive eruptions throughout Nicaragua covering an entire subduction zone segment in the past 70 ka was determined with petrologic methods. Melt inclusions in volcanic phenocrysts were analyzed using a new optimized synchrotron–X-ray fluorescence microprobe set-up. Single eruptions produced Br outputs of 4–600 kt, giving an average Br emission of 27 kt per eruption. Using the assumption that 10% of the emitted halogens reach the stratosphere, the average Br and Cl loading to the stratosphere would be 3 ppt and 1500 ppt, respectively, which together would account for 185% of the preindustrial equivalent effective stratospheric Cl loading. We thus conclude that many large tropical volcanic eruptions had and have the potential to substantially deplete ozone on a global scale, eventually forming future ozone holes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/G34044.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Lifetime and cyclicity of fluid venting at forearc mound structures determined by tephrostratigraphy and radiometric dating of authigenic carbonates (2008)
    GSA (Geological Society of America)
    In:  Geology, 36 (9). pp. 707-710.
    Details
    Publication Date: 2019-10-24
    Description: At convergent margins, fluids rise through the forearc in response to consolidation of the upper plate and dewatering of the subducting plate, and produce various cold-seep–related features on the seafloor (mud diapirs, mud mounds). At the Central American forearc, authigenic carbonates precipitated from rising fluids within such structures during active venting while typical mixed-mud sediments were ejected onto the surrounding seafloor where they became intercalated with normal pelagic background sediments, indicating that mud mounds evolved unsteadily through alternating active and inactive phases. Intercalated regional ash layers from Plinian eruptions at the Central American volcanic arc provide time marks that constrain the ages of mud ejection activity. U/Th dating of drill core samples of authigenic carbonate caps of mud mounds yields ages agreeing well with those constrained by ash layers and showing that carbonate caps grow inward rather than outward during active venting. Both dating approaches show that offshore Nicaragua and Costa Rica (1) active and inactive phases can occur simultaneously at neighboring mounds, (2) mounds along the forearc have individual histories of activity, but there are distinct time intervals when nearly all mounds have been active or inactive, (3) lifetimes of mounds reach several hundred thousand years, and (4) highly active periods last 10–50 k.y. with intervening periods of 〉10 k.y. of relative quiescence.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/G24806A.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    PalVol v1: A proxy-based semi-stochastic ensemble reconstruction of volcanic stratospheric sulfur injection for the last glacial cycle (130,000–50 BP) (2023)
    Copernicus
    Details
    Publication Date: 2023-12-18
    Description: Perturbations in stratospheric aerosol due to explosive volcanic eruptions are a primary contributor to natural climate variability. Observations of stratospheric aerosol are available for the past decades, and information from ice cores has been used to derive estimates of stratospheric sulfur injections and aerosol optical depth over the Holocene (approximately 10,000 BP to present) and into the last glacial period, extending back to 60,000 BP. Tephra records of past volcanism, compared to ice cores, are less complete, but extend much further into the past. To support model studies of the potential impacts of explosive volcanism on climate variability over across timescales, we present here an ensemble reconstruction of volcanic stratospheric sulfur injection (VSSI) over the last 130,000 years that is based primarily on terrestrial and marine tephra records. VSSI values are computed as a simple function of eruption magnitude, based on VSSI estimates from ice cores and satellite observations for identified eruptions. To correct for the incompleteness of the tephra record we include stochastically generated synthetic eruptions, assuming a constant background eruption frequency from the ice core Holocene record. While the reconstruction often differs from ice core estimates for specific eruptions due to uncertainties in the data used and reconstruction method, it shows good agreement with an ice core based VSSI reconstruction in terms of millennial-scale cumulative VSSI variations over the Holocene. The PalVol reconstruction provides a new basis to test the contributions of forced vs. unforced natural variability to the spectrum of climate, and the mechanisms leading to abrupt transitions in the palaeoclimate record with low-to-high complexity climate models. The PalVol volcanic forcing reconstruction is available at https://doi.org/10.26050/WDCC/PalVolv1 (Toohey, Schindlbeck-Belo, 2023).
    Type: Article , NonPeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - without review
  • 6
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    PalVol v1: a proxy-based semi-stochastic ensemble reconstruction of volcanic stratospheric sulfur injection for the last glacial cycle (140 000–50 BP) (2024)
    Copernicus
    Details
    Publication Date: 2024-04-04
    Description: Perturbations in stratospheric aerosol due to explosive volcanic eruptions are a primary contributor to natural climate variability. Observations of stratospheric aerosol are available for the past decades, and information from ice cores has been used to derive estimates of stratospheric sulfur injections and aerosol optical depth over the Holocene (approximately 10 000 BP to present) and into the last glacial period, extending back to 60 000 BP. Tephra records of past volcanism, compared to ice cores, are less complete but extend much further into the past. To support model studies of the potential impacts of explosive volcanism on climate variability across timescales, we present here an ensemble reconstruction of volcanic stratospheric sulfur injection (VSSI) over the last 140 000 years that is based primarily on terrestrial and marine tephra records. VSSI values are computed as a simple function of eruption magnitude based on VSSI estimates from ice cores and satellite observations for identified eruptions. To correct for the incompleteness of the tephra record, we include stochastically generated synthetic eruptions assuming a constant background eruption frequency from the ice core Holocene record. While the reconstruction often differs from ice core estimates for specific eruptions due to uncertainties in the data used and reconstruction method, it shows good agreement with an ice-core-based VSSI reconstruction in terms of millennial-scale cumulative VSSI variations over the Holocene. The PalVol reconstruction provides a new basis to test the contributions of forced vs. unforced natural variability to the spectrum of climate and the mechanisms leading to abrupt transitions in the palaeoclimate record with low- to high-complexity climate models. The PalVol volcanic forcing reconstruction is available at https://doi.org/10.26050/WDCC/PalVolv1 (Toohey and Schindlbeck-Belo, 2023).
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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