Description: It is a longstanding observation that the frequency of volcanism periodically changes at times of global climate change. The existence of causal links between volcanism and Earth's climate remains highly controversial, partly because most related studies only cover one glacial cycle. Longer records are available from marine sediment profiles in which the distribution of tephras records frequency changes of explosive arc volcanism with high resolution and time precision. Here we show that tephras of IODP Hole U1437B (northwest Pacific) record a cyclicity of explosive volcanism within the last 1.1 Myr. A spectral analysis of the dataset yields a statistically significant spectral peak at the similar to 100 kyr period, which dominates the global climate cycles since the Middle Pleistocene. A time-domain analysis of the entire eruption and delta O-18 record of benthic foraminifera as climate/sea level proxy shows that volcanism peaks after the glacial maximum and similar to 13 +/- 2 kyr before the delta O-18 minimum right at the glacial/interglacial transition. The correlation is especially good for the last 0.7 Myr. For the period 0.7-1.1 Ma, during the Middle Pleistocene Transition (MPT), the correlation is weaker, since the 100 kyr periodicity in the delta O-18 record diminishes, while the tephra record maintains its strong 100 kyr periodicity.

Description: We have applied a combination of fluid inclusion and amphibole thermobarometry to felsic tephras from highly explosive volcanic eruptions along the Central American volcanic arc (CAVA) from Guatemala through Nicaragua in order to constrain pre-eruptive magma ascent and storage conditions. We note that this is the first time a combination of pressure estimates from fluid inclusions and amphibole chemistry have been used to quantify multi-stage magma chamber processes and magma ascent velocities of large eruptions. Our data document a stepwise ascent of magmas through the crust, typically involving at least two levels of stagnation. Amphibole and fluid inclusion thermobarometry both indicate a shallow preeruptive magma storage level at 80 to 200 MPa (3-8 km depth) along the entire arc. The deeper levels of magma storage vary along-arc, with a tendency to greater maximum depths of up to 25 km in Guatemala and El Salvador, compared to maximum depths of 15 km in Nicaragua. We assume that the continental crust of about 45 km thickness in Guatemala, compared to the 30km thickness of the largely oceanic crust of Nicaragua, allowed for deeper positions of the magma chambers. Thus the observed along-arc changes in mid-crustal magma storage depths indicate a dependence between magma chamber formation and the composition and probably density of the local crust. The average composition of the pre-eruptive fluid phase for highly explosive eruptions in Central America amounts to 90% water, 5% CO2 and 5% NaCl equivalents, and show no systematic alongarc variations. The pressures obtained from the earliest fluid inclusions were taken as the pressures of fluid oversaturation and thus for the beginning of degassing. They range between 150 and 400 MPa, and do not show systematic along-arc variations. Such fluid oversaturation pressures correspond to water contents between 4-8 wt% in the felsic melts. Our results show that the depths of fluid saturation are mostly independent of crustal properties. Degassing typically started at pressures 150 to 300 MPa higher that those corresponding to the last stagnation level, providing evidence for the pre-eruptive criticality of the systems.

Description: Large explosive tropical volcanic eruptions inject high amounts of gases into the stratosphere, where they disperse globally through the large-scale meridional circulation. There is now increasing observational evidence that volcanic halogens can reach the upper troposphere and lower stratosphere. Here, we present the first study that combines measurement-based data of sulfur, chlorine and bromine releases from tropical volcanic eruptions with complex coupled chemistry climate model simulations taking radiative-dynamical-chemical feedbacks into account. Halogen model input parameters represent a size-time-region-wide average for the Central American eruptions over the last 200 ka ensuring a comprehensive perspective. The simulations reveal global, long-lasting impact on the ozone layer affecting atmospheric composition and circulation for a decade. Column ozone drops below 220 DU (ozone hole conditions) in the tropics, Arctic and Antarctica, increasing biologically active UV by 80 to 400%. Our model results could potentially be validated using high-resolution proxies from ice cores and pollen records.

Description: Large explosive volcanic eruptions from island arcs pour pyroclastic currents into marine basins, impacting ecosystems and generating tsunamis that threaten coastal communities and infrastructures. Risk assessments require robust records of such highly hazardous events, which is challenging as most of the products lie buried under the sea. Here we report the discovery by IODP Expedition 398 of a giant rhyolitic pumice deposit emplaced 520 ± 10 ky ago at water depths of 200 to 1000 m during a high-intensity, shallow submarine eruption of ancestral Santorini Volcano. Pyroclastic currents discharged into the sea transformed into turbidity currents and slurries, forming a 〉89 ± 8 km 3 volcaniclastic megaturbidite up to 150 m thick in the surrounding marine basins, while breaching of the sea surface by the eruption column laid down veneers of ignimbrite on three islands. The eruption is one of the largest recorded on the South Aegean Volcanic Arc, and highlights the hazards from submarine explosive eruptions.

Description: Despite their global societal importance, the volumes of large-scale volcanic eruptions remain poorly constrained. Here, we integrate seismic reflection and P-wave tomography datasets with computed tomography-derived sedimentological analyses to estimate the volume of the iconic Minoan eruption. Our results reveal a total dense-rock equivalent eruption volume of 34.5 ± 6.8 km³, which encompasses 21.4 ± 3.6 km³ of tephra fall deposits, 6.9 ± 2 km³ of ignimbrites, and 6.1 ± 1.2 km³ of intra-caldera deposits. 2.8 ± 1.5 km³ of the total material consists of lithics. These volume estimates are in agreement with an independent caldera collapse reconstruction (33.1 ± 1.2 km³). Our results show that the Plinian phase contributed most to the distal tephra fall, and that the pyroclastic flow volume is significantly smaller than previously assumed. This benchmark reconstruction demonstrates that complementary geophysical and sedimentological datasets are required for reliable eruption volume estimates, which are necessary for regional and global volcanic hazard assessments.

Description: The Lonquimay Volcanic Complex (LVC) in South Central Chile (38.38°S, 71.58°W) is part of the Southern Volcanic Zone of the Andes, which formed in response to the subduction of the Nazca Plate beneath the South American Plate. During the last 10200+-70 years of its magmatic evolution, the LVC produced 23 explosive eruptions documented in the succession of widespread tephra deposits. We investigated this stratigraphic sequence for matrix glass, mineral and bulk rock compositions of the juvenile components. Furthermore, melt inclusions were analyzed for their major element and volatile contents. The tephra succession reflects six mafic replenishments of the LVC magma reservoir followed by progressive magmatic differentiation. Each cycle has been successively tapped by several eruptions. Compositionally zoned tephras were typically deposited early in a cycle, whereas late eruptions discharged more evolved magmas. Intermediate compositions typically contain mixed disequilibrium mineral assemblages. The maximum degree of fractionation reached during a cycle increases with younger ages. Our investigations of melt inclusions, in order to reconstruct the pre-eruptive volatile inventories of the LVC magma chamber, reveal the exsolution of two separate fluid phases. One S-rich fluid phase released from mafic melts in the middle crust and one Cl-rich aqueous phase, released from more ifferentiated melts that resided in the upper part of LVC´s plumbing system. The pre-eruptive saturation state of the LVC melts indicates that felsic eruptions may have been triggered by H2O-supersaturation whereas mafic melts seem to have experienced a complex replenishment history potentially exciting LVC´s mafic eruptions.

Description: Caldera-forming eruptions of silicic volcanic systems are among the most devastating events on Earth. By contrast, post-collapse volcanic activity initiating new caldera cycles is generally considered less hazardous. Formed after Santorini’s latest caldera-forming eruption of ~1600 bce , the Kameni Volcano in the southern Aegean Sea enables the eruptive evolution of a recharging multi-cyclic caldera to be reconstructed. Kameni’s eruptive record has been documented by onshore products and historical descriptions of mainly effusive eruptions dating back to 197 bce . Here we combine high-resolution seismic reflection data with cored lithologies from International Ocean Discovery Program Expedition 398 at four sites to determine the submarine architecture and volcanic history of intra-caldera deposits from Kameni. Our shore-crossing analysis reveals the deposits of a submarine explosive eruption that produced up to 3.1 km 3 of pumice and ash, which we relate to a historical eruption in 726 ce . The estimated volcanic explosivity index of magnitude 5 exceeds previously considered worst-case eruptive scenarios for Santorini. Our finding that the Santorini caldera is capable of producing large explosive eruptions at an early stage in the caldera cycle implies an elevated hazard potential for the eastern Mediterranean region, and potentially for other recharging silicic calderas.