Sulfuric gases convert to sulfate aerosols, sub-micron droplets containing about 75 percent sulfuric acid. Following eruptions, these aerosol particles can linger as long as three to four years in the stratosphere.
The research team ran a general circulation model developed at the Max Planck Institute with and without Pinatubo aerosols for the two years following the Pinatubo eruption.
Volcanic ash, like this from Mount St. Helens, is not really ash, but tiny jagged particles of rock and glass. It shows that volcanic aerosols force fundamental climate mechanisms that play an important role in the global change process.
This temperature pattern is consistent with the existence of a strong phase of the Arctic Oscillation, a natural pattern of circulation in which atmospheric pressure at polar and middle latitudes fluctuates, bringing higher-than-normal pressure over the polar region and lower-than-normal pressure at about 45 degrees north latitude.
Volcanic ash may be a key source of nutrients such as iron and thus capable of stimulating biogeochemical responses Duggen et al. During the week following the VEI 4 eruption of Anatahan, Northern Mariana Islands, for example, satellite-based remote sensing detected a 2—5-fold increase in biological productivity in the ocean area affected by the volcanic ash plume Lin et al. These impacts can be particularly pronounced in low-nutrient regions of the oceans.
A more indirect and longer-term impact of very large volcanic eruptions is caused by the rapid addition of CO 2 and SO 2 to the atmosphere, which affects seawater pH and carbonate saturation. Carbon-cycle model calculations Berner and Beerling, have shown that CO 2 and SO 2 degassed from the million-year-old basalt eruptions of the Central Atlantic Magmatic Province could have affected the surface ocean for 20,—40, years if total degassing took place in less than 50,—, years.
Ocean acidification from the increased atmospheric CO 2 may have caused near-total collapse of coral reefs Rampino and Self, Rapid injection of large amounts of CO 2 into the atmosphere by volcanic eruptions also provides the best analog for studying the long-term effects of 20th-century CO 2 increases on ocean chemistry.
Targeted investigations of these large eruptions have the potential to establish quantitative estimates of the volatile release and residence in the atmosphere as well as the effects on ocean acidification, carbon saturation, coral mortality, and biodiversity.
Over the long term, large eruptions can release thousands of gigatons of methane from organic-rich sediments. The latter represents a well-documented thermal maximum associated with extensive volcanism that accompanied the opening of the North Atlantic Ocean. Reconstructing the volcanic carbon emission record through geologic time and assessing the potential for large releases of reduced carbon from organic sediments is challenging and requires.
Finally, some secondary volcanic hazards are generated in the ocean. Tsunamis can be generated directly by explosive submarine eruptions e. Even small volcano-triggered tsunamis can produce significant waves e.
Volcanic eruptions can be triggered when the pressure in a subsurface magma body exceeds the confining pressure in the surrounding crust, or when underpressure initiates collapse.
The latter includes a contribution from surface loading e. An external forcing mechanism that either increases magmatic overpressure or reduces the confining pressure can potentially trigger an eruption. The sources of such perturbations operate on time scales that range from near-instantaneous stress changes associated with tectonic processes such as earthquakes, to longer-term variations due to climate change such as changes in sea level and melting of ice sheets.
A deeper understanding of external stimuli tectonics, earthquakes, changes in sea level or glaciers provides an important test of mechanisms for melt accumulation and triggering thresholds Figure 4. Tectonics influences volcanism by controlling the composition and amount of magma generated in the mantle and the thickness of the crust and the stresses that hinder or promote magma intrusion and ascent. Quantifying these connections would benefit from a better understanding of the properties of the crust that host magma bodies as well as the conditions that enable the propagation of dikes Section 2.
For example, large, silicic magma bodies that can produce caldera-. There are many exceptions, however.
Tectonic stresses also affect magma storage and the size of eruptions e. Tectonics also influences the morphology and stability of volcanoes. Volcanoes may develop on large tectonic faults e. Movement on tectonic faults intersecting volcanic edifices may increase the risk of flank collapse and the generation of debris avalanches, but at the same time may inhibit magmatic processes by relieving stress e. Regional stresses and faults may control the alignment of dikes, but the extent to which ambient stresses are modified by the development of magma reservoirs e.
On a global scale, volcanism and large earthquakes are strongly spatially correlated. Temporal coincidences between earthquakes and eruptive activity have been documented since at least the writings of Pliny his encyclopedia published in the 1st century AD. Eruption rates in the southern Andes may have increased for up to 12 months following some large earthquakes Watt et al. However, large earthquakes do not always trigger volcanic eruptions.
The possibility of delayed triggering e. Persistently active volcanoes such as Merapi, Indonesia, may be particularly prone to triggered responses e. The orientation. Eruptions have been attributed to earthquake-induced compression e. On longer time scales, earthquake-triggered ascent of deeper magmas or gases may play a role. Despite decades of study, however, the mechanisms through which seismic waves and static stress changes initiate eruptions and influence ongoing eruptions, even on short time scales, remain unknown.
Earthquakes can also trigger noneruptive unrest seismicity, gas emissions, and changes in hydrothermal systems at volcanoes e. Credit: USGS. But eruptions also impact the atmosphere. The gases and dust particles thrown into the atmosphere during volcanic eruptions have influences on climate. Most of the particles spewed from volcanoes cool the planet by shading incoming solar radiation. The cooling effect can last for months to years depending on the characteristics of the eruption.
Even though volcanoes are in specific places on Earth, their effects can be more widely distributed as gases, dust, and ash get into the atmosphere. How can volcanic eruptions be predicted? How could volcanic eruptions generate tsunamis? How did erupting volcanoes contribute to the formation of oceans? How do geologists measure volcanic eruptions? See all questions in Volcanic Eruptions. Impact of this question views around the world.
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