7.2 Types of Calderas and Their Evolution
5 min read•july 30, 2024
Calderas come in three main flavors: collapse, explosion, and erosion. Each type forms differently and has unique features. Understanding these differences is key to grasping how supervolcanoes shape our planet's surface.
Calderas evolve through stages, from pre-caldera buildup to post-caldera quiet periods and potential reawakening. This lifecycle helps us predict future volcanic activity and assess risks to nearby communities. It's a crucial part of studying supervolcanoes.
Caldera Types and Formation
Collapse Calderas
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- Form when a magma chamber is partially emptied, leading to the unsupported roof collapsing into the void
- Examples include (USA) and (Japan)
- Typically larger than explosion calderas, as they are related to the size of the underlying magma chamber
- Often associated with silicic magmas (rhyolitic to dacitic)
Explosion Calderas (Krakatoa-type)
- Form during explosive volcanic eruptions when the magma chamber is completely emptied, and the overlying rock is blasted away
- Examples include (Indonesia) and (Greece)
- Usually smaller than collapse calderas and may have a more irregular shape due to the explosive nature of their formation
- Can be associated with a wider range of magma compositions (basaltic to rhyolitic)
Erosion Calderas (Glencoe-type)
- Form when a volcanic edifice is heavily eroded, exposing the underlying magma chamber
- An example is (Scotland)
- Have a more irregular or dissected morphology compared to the more circular or elliptical shape of collapse and explosion calderas
- Formation process differs from collapse and explosion calderas, as they form through erosion rather than a singular eruptive event
Caldera Morphology
- Varies depending on the formation process and can be characterized by size, shape, and the presence of resurgent domes or
- Collapse calderas are typically larger and more circular or elliptical in shape
- Explosion calderas are usually smaller and may have a more irregular shape
- Erosion calderas have a more irregular or dissected morphology due to the erosional processes involved in their formation
Caldera Development Stages
Pre-caldera Volcanism
- Involves the buildup of a volcanic edifice through repeated eruptions from a central vent or multiple vents
- Characterized by the accumulation of lava flows, pyroclastic deposits, and the growth of a magma chamber
- Sets the stage for the caldera-forming eruption by creating an unstable magmatic system
Caldera-forming Eruptions
- Occur when the magma chamber becomes unstable, leading to large-scale evacuation of magma and the collapse of the overlying rock
- Can be highly explosive and produce extensive pyroclastic deposits
- Result in the formation of the caldera structure, which may be a , , or
Post-caldera Quiescence
- Immediately following the caldera-forming eruption, the caldera may experience a period of reduced activity
- The caldera floor may be filled with volcanic deposits, water (forming a ), or sediments
- This stage represents a period of relative stability in the caldera system
Post-caldera Volcanism
- Can occur within the caldera or along its margins
- May include the formation of resurgent domes, lava domes, or cinder cones, as well as the eruption of lava flows and pyroclastic materials
- Indicates that the magmatic system is still active and evolving
- The presence and nature of post-caldera volcanism can vary between caldera types
Long-term Evolution
- The caldera may undergo further collapse or erosion over time, modifying its original morphology
- Hydrothermal activity and mineralization may also occur during the post-caldera stage
- The caldera system continues to evolve over time, influenced by factors such as magma recharge, regional stress fields, and erosional processes
Caldera Types: Comparison and Contrast
Formation Mechanisms
- Collapse calderas form due to the emptying and collapse of a magma chamber
- Explosion calderas form during explosive eruptions that completely evacuate the magma chamber
- Erosion calderas form through the erosion of a volcanic edifice rather than a singular eruptive event
Size and Shape
- Collapse calderas are typically larger than explosion calderas, related to the size of the underlying magma chamber
- Explosion calderas are usually smaller and may have a more irregular shape due to the explosive nature of their formation
- Erosion calderas have a more irregular or dissected morphology compared to the more circular or elliptical shape of collapse and explosion calderas
Post-caldera Volcanism
- Collapse calderas often experience resurgent doming and the formation of lava domes
- Explosion calderas may have more dispersed post-caldera volcanism along the caldera margins
- The presence and nature of post-caldera volcanism can vary between caldera types
Magma Composition
- Collapse calderas are often related to silicic magmas (rhyolitic to dacitic)
- Explosion calderas can be associated with a wider range of magma compositions (basaltic to rhyolitic)
- The composition of the magma can influence the style and intensity of eruptions, as well as the morphology of the resulting caldera
Caldera Activity: Future Potential
Factors Influencing Future Activity
- The presence of an active magma chamber, the rate of magma recharge, and the state of stress in the overlying rock
- Increased seismicity, ground deformation, and changes in gas emissions may indicate magma movement or pressurization of the system
- The recurrence interval of and the time elapsed since the last major eruption can provide a general guide to the potential for future activity
Monitoring Techniques
- Seismicity monitoring, particularly earthquake swarms or tremor, may indicate magma movement or pressurization
- Ground deformation, detected through GPS, InSAR, or tiltmeters, can reveal inflation or deflation of the caldera floor related to magma intrusion or withdrawal
- Gas emission monitoring, such as SO2 or CO2 flux, can suggest magma degassing and potential unrest
- These techniques provide insights into the current state of a caldera system and help assess the likelihood of future eruptions
Indicators of Potential Future Activity
- The presence of active hydrothermal systems, resurgent doming, or recent post-caldera volcanism may indicate a higher likelihood of future activity
- Calderas that have been dormant for long periods may have a lower potential for future activity compared to those with recent unrest
- However, each caldera system is unique, and the timing of eruptions can be highly variable
Multidisciplinary Approach
- Evaluating the potential for future activity in caldera systems requires integrating geological, geophysical, and geochemical data
- Developing a comprehensive understanding of the system's behavior and evolution over time is crucial for assessing future eruption potential
- Collaborations between volcanologists, geophysicists, geochemists, and other experts are essential for effective caldera monitoring and hazard assessment
Key Terms to Review (26)
Aso: Aso is a volcanic caldera located in Kumamoto Prefecture, Japan, known for its vast size and active volcanic system. It features one of the world's largest calderas, formed by multiple volcanic eruptions that created a large depression filled with volcanic landforms. The caldera is significant in understanding volcanic activity and the processes that shape calderas over time.
Caldera Development: Caldera development refers to the process by which a large volcanic depression, typically formed after the eruption of a volcano, evolves and changes over time. This can include the collapse of the ground surface following a massive eruption, leading to a large basin-like feature, and subsequent geological processes that shape its morphology, such as erosion and sedimentation. Understanding caldera development is essential in grasping how volcanic systems behave over time and their impact on surrounding ecosystems and human activities.
Caldera Lake: A caldera lake is a large, basin-like depression that forms when a volcano erupts and collapses, often filling with water over time. These lakes can provide insights into volcanic activity and ecology, as they often host unique ecosystems and sediment layers that reveal the geological history of the area.
Caldera morphology: Caldera morphology refers to the shape, structure, and physical features of a caldera, which is a large depression formed when a volcano erupts and collapses. The study of caldera morphology helps in understanding the processes that lead to their formation and evolution, including factors such as eruption magnitude, magma chamber dynamics, and subsequent geological activity. Understanding caldera morphology is crucial for assessing volcanic hazards and predicting future volcanic behavior.
Caldera-forming eruptions: Caldera-forming eruptions are large volcanic eruptions that result in the collapse of the ground above a volcanic chamber, creating a depression known as a caldera. These eruptions often produce massive amounts of volcanic material, which can lead to significant changes in the surrounding landscape and environment. Understanding these eruptions helps in grasping the types of calderas that form and their subsequent evolution over time.
Collapse caldera: A collapse caldera is a large depression formed when a volcanic eruption leads to the emptying of a magma chamber, causing the ground above it to sink or collapse. This geological feature often occurs after a massive explosive eruption, which drains significant amounts of magma from the chamber, resulting in the roof of the chamber becoming unsupported and collapsing into it. The formation of collapse calderas can significantly alter the landscape and can lead to the development of new volcanic features.
Crater Lake: A crater lake is a type of lake that forms within a volcanic caldera, typically resulting from the collapse of the volcano following an explosive eruption or from the accumulation of water in the depression left by the volcanic activity. These lakes are often characterized by their deep blue color and clarity, making them unique geological features. They provide insights into volcanic processes and the evolution of calderas.
Erosion caldera: An erosion caldera is a large depression formed as a result of volcanic activity that has been significantly modified by erosion processes over time. These calderas can develop when a volcano collapses after an eruption, but their shape and features are further altered by natural forces such as water, wind, and glacial activity, leading to distinct characteristics that reflect both volcanic and erosional processes.
Explosion caldera: An explosion caldera is a large, basin-like depression formed when a volcano erupts with such force that the magma chamber below collapses. This type of caldera typically results from explosive volcanic activity, which can eject significant amounts of volcanic material, leading to a dramatic reshaping of the landscape. The formation of an explosion caldera often signifies the release of high-energy eruptions that can have widespread impacts on the environment and human activities.
Geochronology: Geochronology is the science of determining the age of rocks, sediments, and fossils through various dating methods. This field plays a vital role in understanding geological time and the history of the Earth, particularly in the context of volcanic activity and caldera systems. By accurately dating geological formations, scientists can unravel the timing of significant events, such as eruptions and the evolution of landforms.
Glencoe Caldera: The Glencoe Caldera is a large volcanic depression located in the Scottish Highlands, formed by a significant explosive eruption around 60 million years ago. This caldera is a classic example of a caldera created by the collapse of land following a volcanic eruption, which plays an important role in understanding caldera evolution and related volcanic activity.
Krakatoa: Krakatoa is a volcanic island located in the Sunda Strait between Java and Sumatra in Indonesia, known for its catastrophic eruption in 1883 that is considered one of the deadliest volcanic events in recorded history. This eruption had a significant impact on global climate, atmospheric conditions, and volcanic science, influencing our understanding of stratovolcanoes, pyroclastic deposits, and caldera formation.
Long-term evolution: Long-term evolution refers to the gradual changes and adaptations that occur in geological formations and volcanic systems over extensive periods, often influenced by tectonic activity, climate change, and magma dynamics. This concept is crucial for understanding how different types of calderas develop and transform due to eruptive histories and environmental factors over time.
Phreatomagmatic Eruption: A phreatomagmatic eruption occurs when magma interacts with water, leading to explosive volcanic activity. This type of eruption often produces a mixture of volcanic ash, steam, and gas, and is characterized by the rapid expansion of water vapor generated from heated water coming into contact with hot magma. These eruptions are particularly significant in understanding the explosive potential of different volcanic systems and can create various landforms and deposits.
Post-caldera quiescence: Post-caldera quiescence refers to a period of relative inactivity that follows the formation of a caldera after a significant volcanic eruption. During this phase, volcanic activity diminishes as the caldera stabilizes and the geological landscape adjusts to the changes caused by the eruption. This phase can last for decades to thousands of years, allowing for recovery of the surrounding ecosystems and the development of new geological features.
Post-caldera volcanism: Post-caldera volcanism refers to volcanic activity that occurs after the formation of a caldera, typically involving the eruption of new magma through the caldera floor or along its rim. This type of volcanism can lead to the development of new volcanic features, such as resurgent domes, lava flows, and smaller eruptive centers, significantly altering the landscape and geological characteristics of the area. Understanding post-caldera volcanism is crucial for comprehending the evolutionary stages of calderas and their long-term activity patterns.
Pre-caldera volcanism: Pre-caldera volcanism refers to the volcanic activity that occurs prior to the formation of a caldera. This phase includes the eruption of lava, ash, and other volcanic materials that contribute to the development of the volcanic structure before a significant collapse happens. Understanding this term is crucial as it provides insights into the evolution of calderas and helps in recognizing the patterns of volcanic behavior leading up to a caldera formation.
Pyroclastic flow: A pyroclastic flow is a fast-moving current of hot gas and volcanic matter, such as ash and rock fragments, that flows down the slopes of a volcano during an explosive eruption. This deadly phenomenon is characterized by its high temperatures and speeds, making it one of the most hazardous volcanic phenomena.
Remote Sensing: Remote sensing refers to the acquisition of information about an object or phenomenon without making physical contact. In volcanology, it plays a crucial role in monitoring volcanic activity, assessing hazards, and mapping changes in the landscape over time, helping to enhance our understanding of various volcanic processes and their impacts.
Resurgent Dome: A resurgent dome is a raised area within a caldera formed by the upward movement of magma and volcanic material following a major eruptive event. This geological feature often results from the collapse of the caldera floor after an explosive eruption, creating a hollow that can be filled with magma. Over time, the pressure from the underlying magma chamber can cause the floor to uplift, leading to the formation of a dome-like structure, which indicates volcanic activity beneath the surface.
Santorini: Santorini is a volcanic archipelago in the Aegean Sea, known for its stunning caldera formed by a massive eruption around 1600 BCE. The island is a prime example of a caldera's evolution, showcasing both geological processes and the impact of volcanic activity on human settlement and culture. The dramatic landscape features steep cliffs, white-washed buildings, and a rich history tied to one of the largest volcanic eruptions in recorded history.
Supereruption: A supereruption is an extremely large volcanic eruption that ejects more than 1,000 cubic kilometers of material, including ash and magma, into the atmosphere. These massive eruptions can have catastrophic consequences for the environment and climate, often leading to widespread ash fall and significant disruptions to ecosystems. Supereruptions are associated with caldera-forming events and play a crucial role in understanding the evolution and behavior of major volcanic systems.
Toba Caldera: Toba Caldera is a large volcanic caldera located on the island of Sumatra in Indonesia, formed by a super-eruption approximately 74,000 years ago. This cataclysmic event is significant for its massive ash deposits and its impact on global climate, making it one of the largest known volcanic eruptions in Earth's history. The caldera itself, which spans about 100 kilometers (62 miles) in length, is filled by Lake Toba, one of the largest volcanic lakes in the world, illustrating the explosive nature and geological evolution associated with such caldera systems.
Volcanic ash fall: Volcanic ash fall refers to the deposition of fine particles ejected from a volcanic eruption, which can spread over vast distances due to wind and atmospheric conditions. This phenomenon can have significant impacts on the environment, human health, and infrastructure, particularly in relation to the formation and evolution of calderas. The accumulation of volcanic ash is an important factor in understanding the dynamics of caldera formation, as it contributes to the weight of the volcanic edifice and can influence future eruptions.
Volcanic dome: A volcanic dome is a mound-shaped protrusion formed by the slow extrusion of highly viscous lava from a volcano. These structures are typically created by the accumulation of lava that is too thick to flow easily, resulting in a steep, dome-like shape. Volcanic domes can significantly influence volcanic activity and hazards due to their formation processes and potential for collapse or explosive eruptions.
Yellowstone Caldera: The Yellowstone Caldera is a massive volcanic caldera located in Yellowstone National Park, formed by a series of explosive volcanic eruptions over the past 2.1 million years. It is one of the largest active volcanic systems in the world and plays a crucial role in understanding caldera formation and evolution, as well as volcanic hazards associated with such systems.