6.3 Lava Domes and Cryptodomes
4 min read•july 30, 2024
Lava domes and cryptodomes are unique volcanic structures formed by viscous magma. These features shape volcano morphology, creating bulbous mounds or hidden intrusions that can lead to explosive eruptions and hazardous collapses.
Understanding lava domes and cryptodomes is crucial for assessing volcanic risks. Their formation, growth mechanisms, and potential for catastrophic failure highlight the complex interplay between magma properties and volcanic landforms, influencing eruption styles and hazard potential.
Lava Domes and Cryptodomes: Growth and Structure
Lava Dome Formation and Characteristics
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Frontiers | Internal Structures and Growth Style of a Quaternary Subaerial Rhyodacite Cryptodome ... View original
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Frontiers | Textural Insights Into the Evolving Lava Dome Cycles at Santiaguito Lava Dome, Guatemala View original
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Frontiers | Load Stress Controls on Directional Lava Dome Growth at Volcán de Colima, Mexico View original
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Frontiers | Internal Structures and Growth Style of a Quaternary Subaerial Rhyodacite Cryptodome ... View original
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Frontiers | Textural Insights Into the Evolving Lava Dome Cycles at Santiaguito Lava Dome, Guatemala View original
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Top images from around the web for Lava Dome Formation and Characteristics
Frontiers | Internal Structures and Growth Style of a Quaternary Subaerial Rhyodacite Cryptodome ... View original
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Frontiers | Textural Insights Into the Evolving Lava Dome Cycles at Santiaguito Lava Dome, Guatemala View original
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Frontiers | Load Stress Controls on Directional Lava Dome Growth at Volcán de Colima, Mexico View original
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Frontiers | Internal Structures and Growth Style of a Quaternary Subaerial Rhyodacite Cryptodome ... View original
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Frontiers | Textural Insights Into the Evolving Lava Dome Cycles at Santiaguito Lava Dome, Guatemala View original
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- Lava domes develop when highly viscous, silica-rich magma extrudes from a volcanic vent and accumulates around the opening rather than flowing away as a lava flow (rhyolitic or dacitic magmas)
- Cryptodomes are lava domes that form beneath the Earth's surface, causing the ground above to swell and bulge upwards (, Japan)
- Lava domes and cryptodomes often display a combination of endogenous and exogenous growth throughout their development leading to complex internal structures
- The outer surface of lava domes and cryptodomes usually consists of a carapace of brittle, fractured lava ranging from blocky and massive to highly brecciated and unconsolidated
Endogenous and Exogenous Growth Mechanisms
- Endogenous growth happens when magma is injected into the interior of the dome causing it to expand from within
- Results in various internal structures such as shear lobe boundaries, magma tubes, and radial fractures
- Exogenous growth occurs when magma extrudes onto the outer surface of the dome frequently forming short, thick lava flows called coulees
- Leads to a layered or "onion-skin" internal structure
- As lava domes and cryptodomes grow, they can become oversteepened and unstable resulting in partial or complete collapse
- Collapses generate hazards like , pyroclastic flows, and (Unzen volcano, Japan)
Hazards of Lava Dome Collapse and Cryptodome Eruptions
Pyroclastic Flows, Surges, and Debris Avalanches
- collapses can produce devastating pyroclastic flows and surges which are hot, ground-hugging mixtures of ash, gas, and rock fragments traveling at high velocities and covering extensive areas (, Indonesia)
- Larger lava dome collapses can also generate debris avalanches which are rapidly moving masses of rock debris and ash capable of traveling tens of kilometers from the source
- The hazards associated with lava domes and cryptodomes can persist for long periods as these features can remain active and unstable for months to years after their initial formation
Explosive Cryptodome Eruptions and Lateral Blasts
- eruptions can be especially hazardous due to their sudden and explosive nature
- As magma intrudes beneath the surface, it can cause the overlying rock to fracture and bulge upwards potentially leading to a sudden decompression and explosive fragmentation of the magma (, USA)
- Cryptodome eruptions can generate powerful lateral blasts which are highly destructive, ground-hugging currents of hot ash, gas, and rock fragments capable of leveling forests and destroying infrastructure over a wide area
- Both lava dome collapses and cryptodome eruptions can be accompanied by the release of volcanic gases, particularly sulfur dioxide leading to respiratory hazards and acid rain formation
Magma Viscosity and Lava Dome Formation
Role of Magma Viscosity in Dome Formation
- Magma plays a crucial role in controlling the formation of lava domes and cryptodomes
- High-viscosity magmas, typically rich in silica and dissolved gases, are more likely to form these features than low-viscosity, mafic magmas (andesitic or basaltic magmas)
- High-viscosity magmas resist flow and tend to accumulate around the vent forming a mound or dome-shaped extrusion
- The magma's ability to trap gases also contributes to the formation of a cohesive, spiny or blocky dome
- Lower-viscosity magmas within the lava dome or cryptodome can sometimes extrude through fractures in the cooler, more viscous outer shell forming short lava flows or spines
Factors Influencing Magma Viscosity and Dome Formation
- The relationship between magma viscosity and dome formation can be influenced by factors such as:
- Magma composition (silica content)
- Temperature
- Gas content (volatile content)
- Rate of magma supply
- Configuration of the volcanic conduit
- The high viscosity of the magma can also lead to the buildup of gas pressure within the dome or cryptodome increasing the likelihood of explosive decompression and collapse
Notable Examples of Lava Domes and Cryptodomes
Lava Dome Examples
- The on the island of Montserrat has been producing a series of lava domes since 1995 with numerous collapses generating pyroclastic flows and ash plumes
- , Guatemala, is a complex of four lava domes that have been actively growing since 1922 often producing small to moderate explosive eruptions and pyroclastic flows
- Lava domes are a common feature in the crater of Mount Merapi, Indonesia, one of the most active and hazardous volcanoes in the world
- Frequent dome collapses at Merapi generate deadly pyroclastic flows and lahars
- The eruption of 1912 in Alaska, USA, formed a lava dome within the vent area following the cataclysmic eruption that produced the Valley of Ten Thousand Smokes ash flow deposit
Cryptodome Examples
- The 1980 eruption of Mount St. Helens, USA, involved the catastrophic failure of a cryptodome resulting in a massive lateral blast, debris avalanche, and pyroclastic flows
- The 1951 eruption of Mount Lamington, Papua New Guinea, involved the explosive destruction of a cryptodome generating devastating pyroclastic flows that claimed over 3,000 lives
Key Terms to Review (26)
Andesitic lava: Andesitic lava is a type of volcanic rock characterized by its intermediate silica content, typically between 53% and 63%. It is known for being more viscous than basaltic lava, resulting in a slower flow and the formation of distinct geological features such as lava domes and cryptodomes. The composition often includes minerals like plagioclase feldspar, pyroxene, and hornblende, which contribute to its unique properties.
Bulbous shape: A bulbous shape refers to a rounded, swollen appearance often associated with certain geological features formed by volcanic activity. In the context of volcanic structures, this shape is typically seen in lava domes and cryptodomes, where viscous lava accumulates and solidifies, creating a bulb-like form. These features are characterized by their steep sides and overall dome-like structure, which distinguishes them from other types of volcanic formations.
Cryptodome: A cryptodome is a type of volcanic dome that forms beneath the surface of the ground, primarily from the accumulation of magma that does not reach the surface. These structures are often hidden from direct view and can exert significant pressure on overlying rock layers, leading to deformation and the potential for explosive eruptions. Understanding cryptodomes is crucial because they provide insights into the subsurface processes of volcanic activity and can indicate impending volcanic hazards.
David P. Hill: David P. Hill is a prominent volcanologist known for his extensive research on volcanic processes, particularly concerning magma chamber dynamics and the formation of calderas. His work has significantly influenced our understanding of how magmatic systems evolve over time, contributing to the assessment of volcanic hazards and the study of recent significant eruptions.
Debris avalanches: Debris avalanches are rapid flows of a mixture of water, soil, rock, and vegetation that occur when the stability of a slope is compromised. These events can be triggered by various factors, such as heavy rainfall, volcanic activity, or earthquakes, leading to the collapse of material from steep terrains. In the context of volcanic features, debris avalanches can significantly impact the landscape and pose threats to surrounding areas by altering the topography and potentially creating lahars or other hazards.
Deformation: Deformation refers to the process of change in shape or size of rocks due to stress, which can occur from tectonic forces acting upon them. This process is essential in understanding the formation of various volcanic features, such as lava domes and cryptodomes, where the movement and alteration of material can create distinct geological structures. The study of deformation helps in assessing volcanic activity and predicting potential hazards associated with these formations.
Exsolution: Exsolution is a geological process where a solid solution, typically in a mineral, separates into two distinct phases. This often occurs when temperature and pressure conditions change, allowing certain components of the mineral to crystallize out, leading to the formation of new minerals or textures. In the context of lava domes and cryptodomes, exsolution plays a significant role in the evolution of magma and the stability of these features.
Hot Rockfalls: Hot rockfalls refer to the rapid descent of hot volcanic materials, such as rocks and pyroclastic debris, from a volcanic structure, typically associated with lava domes and cryptodomes. These events occur when unstable slopes of accumulated material collapse under the influence of gravity, resulting in hazardous flows that can travel considerable distances and pose significant risks to nearby areas. They are especially prevalent during explosive eruptions or dome growth phases.
Lahar: A lahar is a destructive volcanic mudflow composed of a mixture of water, volcanic ash, and debris that flows down the slopes of a volcano. These flows can occur during or after an eruption, especially when heavy rainfall mobilizes volcanic materials, leading to rapid and often devastating movements of sediment.
Lava dome: A lava dome is a steep-sided, mound-like volcanic structure formed by the slow extrusion of viscous lava, typically andesitic, dacitic, or rhyolitic in composition. These formations are created when the lava is too thick to flow far from the eruption site, leading to the accumulation of lava near the vent. Lava domes can be associated with explosive eruptions, and they often exhibit unique growth patterns and collapse features, making them significant in understanding volcanic processes.
Lava extrusion: Lava extrusion refers to the process by which molten rock (lava) is expelled from a volcano during an eruption, typically forming various geological features like lava flows, lava domes, or cryptodomes. This process is crucial in shaping the landscape and can significantly influence volcanic hazards and landforms. The characteristics of the lava, including its viscosity and temperature, determine the style and extent of the extrusion, affecting both the eruption's dynamics and the resultant formations.
Magma accumulation: Magma accumulation is the process by which molten rock, or magma, builds up in a specific location beneath the Earth's surface. This accumulation often occurs in magma chambers, which can influence volcanic activity and the formation of surface features such as lava domes and cryptodomes. Understanding how magma accumulates helps to explain the dynamics of volcanic eruptions and the behavior of lava flows.
Merapi Volcano: Merapi Volcano is an active stratovolcano located on the island of Java in Indonesia, known for its frequent eruptions and significant lava dome formation. It is one of the most active volcanoes in the world, continuously shaping its landscape through the growth and collapse of lava domes that are formed by the slow extrusion of viscous lava.
Mount St. Helens: Mount St. Helens is an active stratovolcano located in the state of Washington, known for its catastrophic eruption on May 18, 1980, which significantly altered the surrounding landscape. This volcano is a classic example of stratovolcanic activity and provides insights into volcanic behavior, pyroclastic flows, and tephra dispersal patterns associated with eruptions.
Novarupta-Katmai: Novarupta-Katmai refers to a significant volcanic eruption that occurred in 1912 at Novarupta volcano, located in the Katmai National Park in Alaska. This eruption is one of the largest of the 20th century and is notable for the formation of a large caldera and extensive lava domes that resulted from the volcanic activity, showcasing the dynamic processes associated with explosive eruptions.
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.
Rhyolitic lava: Rhyolitic lava is a type of volcanic rock that is highly viscous and rich in silica, which makes it thick and slow-moving. This lava typically results from the melting of continental crust and is associated with explosive volcanic eruptions. Its high viscosity contributes to the formation of various volcanic landforms, including lava domes and cryptodomes, where the lava piles up near the vent instead of flowing away.
Robert I. Tilling: Robert I. Tilling is a prominent volcanologist known for his research on volcanic eruptions, lava domes, and cryptodomes. His work has significantly advanced the understanding of the formation and behavior of these volcanic features, particularly in relation to eruptive processes and hazards associated with dome-building eruptions.
Santiaguito: Santiaguito is a volcanic dome that formed as a result of the continuous extrusion of lava at the foot of the active stratovolcano, Santa María, in Guatemala. This dome is a classic example of a lava dome, characterized by its steep sides and relatively small size compared to larger stratovolcanoes. Its formation is primarily due to the accumulation of viscous lava that does not flow far from the vent, leading to a conical structure that often exhibits explosive activity.
Seismic Monitoring: Seismic monitoring refers to the use of instruments and technologies to detect, measure, and analyze seismic waves produced by earthquakes and volcanic activity. This process is crucial for understanding the behavior of volcanoes, assessing hazards, and developing early warning systems to protect communities from potential eruptions.
Soufrière Hills Volcano: The Soufrière Hills Volcano is an active stratovolcano located on the Caribbean island of Montserrat, which has been erupting since 1995. Known for its lava dome formations, this volcano has significantly shaped the landscape of Montserrat and impacted its population through volcanic eruptions and pyroclastic flows.
Steep-sided: Steep-sided refers to the sharp and abrupt slopes typically found in certain volcanic landforms, particularly lava domes and cryptodomes. These formations are characterized by their tall, towering profiles and steep inclines, which result from the accumulation of viscous lava that piles up near the vent. The steepness of these sides is a crucial factor in understanding how these volcanic structures behave and evolve over time.
Thermal imaging: Thermal imaging is a technique that uses infrared cameras to detect and measure the heat emitted by objects, allowing for the visualization of temperature differences in real-time. This technology is particularly useful in monitoring volcanic activity, as it can reveal changes in surface temperatures that indicate lava flow movement, pyroclastic flow hazards, and other thermal phenomena associated with eruptions.
Usu volcano: An usu volcano is a type of stratovolcano characterized by its steep, conical shape and the explosive nature of its eruptions. These volcanoes typically form from alternating layers of lava flow, ash, and volcanic rock, leading to a complex structure that can become quite hazardous during eruptions due to the potential for pyroclastic flows and ashfall.
Viscosity: Viscosity is a measure of a fluid's resistance to flow, which in the context of magma, plays a crucial role in determining how it behaves during eruptions and the types of volcanic products formed. The viscosity of magma is influenced by its temperature, composition, and gas content, impacting everything from magma generation to eruption styles and hazards associated with lava flows.
Volcanic Eruption: A volcanic eruption is a geological event in which molten rock, ash, and gases are expelled from a volcano, often resulting in significant hazards to the surrounding environment and communities. These eruptions can take various forms, including explosive eruptions that produce pyroclastic flows and effusive eruptions that generate lava flows. Understanding the characteristics and impacts of eruptions is essential for assessing the types of hazards they pose, managing lava flow risks, recognizing the formation of structures like lava domes, and analyzing different pyroclastic deposits.