The very fabric of Earth’s internal dynamics has long been a subject of fascination for geoscientists. The power and mystery behind volcanic eruptions, in particular, have continued to intrigue and baffle. Historically, the pervasive belief was that water, intertwined with shallow magma within the Earth’s crust, was the primary catalyst for these eruptions. However, the tides of understanding are shifting, offering us not only a profounder comprehension of our planet’s internal workings but also reshaping our understanding of volcanic hazards and planning.
Newly pioneered research tools at Cornell University have brought to light a revelation: carbon dioxide, often associated with global warming debates, can also be a major trigger for explosive volcanic eruptions. It’s not just about where the eruptions are sourced, but what drives them. Recent findings suggest a significant paradigm shift from crust-centric models to ones where the mantle plays a pivotal role, with carbon dioxide emerging as the main protagonist.
In the intricate dance of geological processes, the new research illuminates a path less considered, highlighting the profound implications of deep magma sources for basaltic volcanoes, typically found within tectonic plates. These revelations, spearheaded by senior author Esteban Gazel and supported by an array of distinguished scholars, are not just academic exercises. They represent a breakthrough in understanding volcanic hazards and underline the pressing need for refined prediction and planning mechanisms.
From Water to Carbon Dioxide: Rethinking the Primary Eruption Driver
Conventional Wisdom Explained: Historically, the primary driver behind volcanic eruptions was believed to be water mixed with shallow magma residing within Earth’s crust. This combination was thought to create the necessary conditions and pressures that led to an eruption. The crust, the Earth’s outermost shell, was often seen as the main theater of action, where the magma accumulated and interacted with various elements, leading to explosive outcomes. In this traditional model, water was considered the predominant force that both influenced the magma’s behavior and initiated eruptions.
The study of volcanoes, or volcanology, has ancient origins, with observations and theories stretching back to antiquity. Here are some early volcanic researchers and a brief overview of their contributions:
- Pliny the Elder (AD 23-79):
- A Roman naturalist and naval commander, he died during the eruption of Mount Vesuvius in AD 79 but left behind valuable descriptions of the event.
- His nephew, Pliny the Younger, wrote letters that provided eyewitness accounts of the eruption, offering some of the earliest detailed descriptions of a volcanic eruption.
- Aristotle (384-322 BC):
- The Greek philosopher believed that volcanic eruptions were caused by winds trapped in subterranean caves, which found an exit through the volcanoes.
- While not accurate by today’s standards, it was an early attempt to provide a natural explanation for volcanic phenomena.
- Lucretius (c. 99 BC – c. 55 BC):
- A Roman poet and philosopher who speculated about the Earth having a fiery core. He postulated that volcanic eruptions were caused by the Earth’s inner heat.
- James Hutton (1726-1797):
- Often regarded as the father of modern geology, Hutton proposed the idea of the Earth as a heat engine.
- He theorized that the internal heat of the Earth was responsible for creating various geological formations, including volcanic activity.
- Sir William Hamilton (1730-1803):
- British diplomat and volcanologist who was one of the first to make systematic observations of volcanoes.
- Studied the volcanoes of the Italian peninsula, particularly Vesuvius, and his observations contributed significantly to the early understanding of volcanic processes.
- Georges-Louis Leclerc, Comte de Buffon (1707-1788):
- A French naturalist, Buffon was one of the first to suggest that Earth began as a molten ball of metal and rock. His ideas contributed to the belief in a fiery Earth interior.
While early theories and observations were often based on limited evidence and understanding, they laid the groundwork for future researchers. As scientific methodologies evolved, so did the understanding of volcanic processes, with the realization that they are driven by the movement of tectonic plates, the melting of rocks in the mantle, and the escape of volatiles like water, carbon dioxide, and sulfur dioxide.
After Georges-Louis Leclerc, Comte de Buffon’s time, volcanic research evolved considerably as the scientific method became more rigorous and tools more sophisticated. Here’s a summary of significant developments in volcanology from the late 18th century onward:
- Determination of Volcanic Products (19th Century):
- As chemistry and mineralogy advanced in the 19th century, researchers began to analyze the materials expelled by volcanoes in detail. They recognized the diversity of volcanic rocks and began classifying them based on their chemical compositions.
- Introduction of Seismology (Late 19th to Early 20th Century):
- The development of seismology, or the study of earthquakes, led to a better understanding of the Earth’s interior. Seismographs detected the vibrations caused by moving magma, and this data offered clues about volcanic eruptions and their timings.
- Plate Tectonics Theory (Mid 20th Century):
- One of the most significant breakthroughs in geological sciences, the theory of plate tectonics, provided a comprehensive framework to understand why and where volcanoes occur. It became clear that most volcanoes are located at plate boundaries, where the Earth’s tectonic plates interact, leading to magma formation and eruption.
- Detailed Volcanic Monitoring (Late 20th Century):
- By the latter part of the 20th century, with advances in technology, volcanologists could monitor volcanoes in real-time using seismographs, gas analyzers, and ground deformation instruments. This allowed for better eruption prediction and hazard assessment.
- Understanding of Volcanic Gas Emissions:
- With advances in geochemistry, researchers started examining the gases emitted by volcanoes. They discovered that volatile substances, like water vapor, carbon dioxide, and sulfur dioxide, play crucial roles in driving eruptions.
- Remote Sensing (Late 20th to 21st Century):
- The advent of satellite technology enabled scientists to study and monitor volcanoes from space. Thermal imagery could detect heat from active lava lakes, and satellite-based radar could measure ground deformation associated with moving magma.
- Computer Modeling (21st Century):
- Modern computing allows volcanologists to simulate volcanic processes, from magma ascent to eruption dynamics. This helps predict potential eruption scenarios and assess their impact.
- Underwater Volcanology:
- The exploration of the deep ocean brought attention to underwater volcanoes and hydrothermal vents. Researchers found that these underwater volcanoes play a significant role in Earth’s heat balance and are a crucial part of the marine ecosystem.
Throughout the centuries since Leclerc, the understanding of volcanoes has become increasingly sophisticated, shifting from mere observations to a multifaceted, technology-driven discipline. These advances not only provide insights into Earth’s internal dynamics but also offer crucial information for hazard assessment and mitigation in regions vulnerable to volcanic activity.
The Role of Water: Understanding the Age-Old Belief in its Connection to Volcanic Eruptions
Historical Perspective on Water as the Trigger: For much of human history, water has been viewed as the key component driving volcanic eruptions. This belief stemmed from several foundational observations and scientific principles:
- Magma Composition: Magma, especially in subduction zones (where one tectonic plate sinks beneath another), often contains a high proportion of water. This water is introduced into the mantle from the sinking oceanic crust.
- Pressure and Expansion: As magma rises towards the Earth’s surface, the pressure decreases, allowing dissolved water in the magma to expand into steam. This rapid expansion can increase the pressure within a magma chamber, potentially leading to explosive eruptions.
- Volcanic Products: Eruptions often release vast amounts of steam, which is visible and was thus a direct, observable link between water and volcanic activity.
- Volcanic Arc Locations: Many of the world’s most active and explosive volcanoes are found in subduction zones (like the Pacific Ring of Fire). Here, water-rich oceanic crust sinks into the mantle and melts, creating magma that’s rich in water.
- Experimental Evidence: Early experimental petrology (study of rocks) showed that the melting point of rock decreased in the presence of water, suggesting that water played a role in the generation of magma.
These observations and insights positioned water at the center of volcanic processes, painting it as the primary force behind explosive eruptions. As with many scientific beliefs, it was the observable, repeatable, and explainable phenomena that solidified water’s role in the narrative of volcanology.
Carbon Dioxide’s Unveiling: Cornell’s Paradigm Shift in Volcanic Eruption Understanding
Cornell’s Insights into Carbon Dioxide (CO₂) as the Eruption Driver:
- Deep Magma Origins:
- The research indicated that basaltic volcanoes, often located within tectonic plates, are fueled by magma from deep within the mantle, about 20 to 30 kilometers beneath the Earth’s surface. This deep origin challenges the conventional wisdom that magma predominantly accumulates and erupts from shallow crustal reservoirs.
- Exsolution of CO₂:
- The researchers found that the ascent of this deep-seated magma is primarily driven by the process of exsolution of carbon dioxide. As magma rises, the reduction in pressure causes CO₂ (previously dissolved in the magma) to separate out, generating a significant force that can push the magma upwards rapidly.
- High-Precision Instruments:
- New tools developed by the Cornell team, including a high-precision carbon dioxide densimeter paired with Raman spectroscopy, allowed for accurate measurements of carbon dioxide-rich bubbles trapped within crystals from volcanic eruptions. This state-of-the-art technique provided a window into the history of the magma and its volatile content.
- Real-World Observations:
- Applying their innovative tools, the team studied volcanic deposits from the Fogo volcano in Cabo Verde. They detected a high concentration of volatiles in melt inclusions within magnesium-iron silicate crystals. The elevated levels of trapped CO₂ suggested that the magma had a deep origin, corroborating the idea of magma’s ascent from the mantle.
- Dissociation from Water:
- Esteban Gazel, a leading figure in the research, pointed out that contrary to previous models dominated by water as the main eruption driver, water plays a minimal role in these deep-origin eruptions. Instead, it’s the carbon dioxide responsible for bringing magma from the deep Earth to the surface.
- Implications for Magma Behavior:
- The low viscosity of these magmas, combined with their deep origin, means that they aren’t influenced by water in the ways that shallower volcanic systems might be. The rapid ascent of magma in such volcanoes, like Fogo, is propelled primarily by carbon dioxide, which may also influence their explosive nature.
Cornell’s groundbreaking research shifted the perspective on volcanic eruptions, suggesting that, at least for a subset of volcanoes, carbon dioxide from deep within the Earth is the driving force behind their activity, rather than water from shallower depths.
Deciphering Earth’s Fiery Breath: CO₂ Takes Center Stage
The journey of understanding Earth’s volcanic mechanisms has been long and filled with evolving theories. From ancient beliefs centered around deities expressing their wrath to the scientific consensus about water playing a pivotal role in eruptions, our comprehension of volcanoes has constantly been refined. Now, Cornell University’s groundbreaking research offers a paradigm shift, positioning carbon dioxide as the central actor for certain volcanic activities.
While this doesn’t negate the role of water in many volcanic systems, it highlights the complexity and diversity of Earth’s internal dynamics. As we continue to unravel the mysteries of our planet, it becomes increasingly evident that multiple forces, from the deep mantle to the crust, interplay to shape the world we inhabit. Such revelations not only underscore the importance of continual scientific inquiry but also hold profound implications for volcanic hazard preparedness and our broader understanding of Earth’s geological processes.
From Cornell Story: https://news.cornell.edu/stories/2023/08/carbon-dioxide-not-water-triggers-explosive-volcanoes
Image Credit: Public Domain: Tavurvur volcano eruption 2010.jpg