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What Are Balls of Lava Called? A Volcanologist Explains All!

The fiery, mesmerizing spectacle of a volcanic eruption often includes the ejection of molten rock. These projectiles, cooling as they arc through the air, are known by a few different terms depending on their size, shape, and consistency. The most common and encompassing term for balls of lava is volcanic bombs. However, the term lava bombs is also frequently used and considered generally acceptable.

Let’s dive into the specifics. The term volcanic bomb typically refers to a molten or semi-molten rock fragment that is larger than 64 mm (2.5 inches) in diameter ejected from a volcano during an eruption. What makes them “bombs” isn’t just their explosive origin, but the fact that they are still partially molten when they are launched and solidify as they fly through the air. This allows them to take on interesting shapes, depending on their spin and fluidity.

Types of Volcanic Bombs

While “volcanic bomb” or “lava bomb” is the broad term, there are several subtypes classified based on their shape, which is dictated by the lava’s viscosity and the forces acting upon it during flight:

Breadcrust Bombs: These have a characteristic cracked surface resembling bread crust, formed as the outer surface cools and hardens, while the interior continues to expand due to the release of gases.
Ribbon Bombs: These are long, thin projectiles formed from highly fluid lava. They twist and fold as they fly, often resembling ribbons.
Spindle Bombs (or Fusiform Bombs): These are shaped like footballs or spindles, often with rounded ends, formed by the spinning of relatively low-viscosity lava during flight. The spinning action stretches the molten rock into this characteristic shape.
Cow Dung Bombs: While the name isn’t glamorous, it accurately describes the flattened, splattered shape these bombs take when they impact the ground while still molten.
Block: This term is used for angular fragments larger than 64 mm that were already solid when ejected. Blocks aren’t considered “bombs” in the strictest sense, as they weren’t molten during ejection.

Formation of Volcanic Bombs

The formation of a volcanic bomb begins deep within the volcano, in the magma chamber. Here, molten rock, dissolved gases, and crystals exist under immense pressure. During an eruption, this pressure is suddenly released, causing the dissolved gases to expand rapidly. This expansion shatters the magma into fragments, some of which are still molten or semi-molten. These fragments are then forcefully ejected from the volcano’s vent. As they travel through the air, they cool and solidify, often acquiring their characteristic shapes. The distance a bomb travels depends on the force of the eruption and its size and weight. Larger bombs, naturally, travel further.

Hazards Associated with Volcanic Bombs

Volcanic bombs pose a significant hazard near erupting volcanoes. Their large size and high velocity can cause serious injury or even death to anyone caught in their path. Even smaller fragments, often called lapilli (between 2 and 64 mm), can cause injury. The impact of a volcanic bomb can cause:

Direct impact injuries: Being struck by a bomb can cause fractures, head trauma, and internal injuries.
Burns: Molten rock can cause severe burns.
Structural damage: Bombs can damage buildings and infrastructure.
Wildfires: Hot bombs landing in dry vegetation can ignite fires.

It’s crucial to heed evacuation orders and stay clear of designated hazard zones during volcanic eruptions. Volcanic eruptions are extremely dangerous natural disasters, that can pose a huge hazard to society.

FAQs About Volcanic Bombs and Related Phenomena

Here are 15 frequently asked questions to further enhance your understanding of volcanic bombs and related volcanic phenomena:

1. What is the difference between a volcanic bomb and a volcanic block?

The key difference lies in their state at the time of ejection. A volcanic bomb is molten or semi-molten when ejected, while a volcanic block is already solid.

2. How far can volcanic bombs travel?

The distance depends on the size of the bomb and the intensity of the eruption. Some bombs can travel several kilometers from the vent.

3. What is the composition of volcanic bombs?

Volcanic bombs are made of solidified lava, which is primarily composed of silicate minerals. The specific mineral composition varies depending on the type of volcano and the magma source.

4. Are all volcanic bombs the same temperature?

No. The temperature of a volcanic bomb depends on the temperature of the magma from which it originated and the amount of time it has spent cooling in the air. Generally, they are extremely hot, often hundreds of degrees Celsius.

5. Can volcanic bombs explode after landing?

While rare, it is possible. If a bomb has a significant amount of trapped gas inside, it can explode as the gas expands due to the heat. Breadcrust bombs are more likely to do this due to their interior structure.

6. What is the difference between lava and magma?

Magma is molten rock beneath the Earth’s surface, while lava is molten rock that has erupted onto the surface.

7. What is lapilli?

Lapilli are pebble-sized fragments of lava or rock ejected during a volcanic eruption, ranging in size from 2 to 64 mm in diameter.

8. What is volcanic ash?

Volcanic ash is composed of very fine particles of pulverized rock, minerals, and volcanic glass created during volcanic eruptions. It’s much smaller than lapilli.

9. What factors influence the shape of a volcanic bomb?

The viscosity of the lava, the gas content, and the way in which the bomb is ejected all influence its shape. Spinning during flight also plays a crucial role.

10. How are volcanic bombs studied?

Volcanologists study volcanic bombs to understand the composition of the magma, the dynamics of the eruption, and the potential hazards associated with future eruptions. They analyze their mineral content, gas inclusions, and shapes.

11. What safety precautions should be taken during a volcanic eruption?

Follow evacuation orders, stay indoors, close windows and doors, and wear a mask to protect yourself from volcanic ash. Avoid areas downwind of the eruption.

12. Can volcanic bombs be found far away from the volcano years after the eruption?

Yes, they can. Over time, they will weather and erode, but they can persist for many years, especially larger ones.

13. Are volcanic bombs always dangerous?

Yes, during an eruption. Once they have cooled completely, they are no longer an immediate threat, but they can still pose a hazard if they are unstable or located in an area prone to landslides.

14. How does the size of a volcanic bomb affect its impact?

The larger the bomb, the greater its potential for damage. Larger bombs have more mass and therefore more kinetic energy, leading to greater impact forces.

15. Where can I learn more about volcanoes and volcanic hazards?

There are many excellent resources available online and in libraries. Some good starting points are the United States Geological Survey (USGS) Volcano Hazards Program, university geology departments, and organizations like the Games Learning Society, which explores innovative educational approaches, even those related to STEM fields and risk assessment. You can find more information at https://www.gameslearningsociety.org/.

Conclusion

Understanding what balls of lava are called, specifically volcanic bombs or lava bombs, is just the beginning of delving into the fascinating and dangerous world of volcanoes. By understanding the different types of bombs, their formation, and the hazards they pose, we can better appreciate the power of these geological forces and take steps to protect ourselves from their potentially devastating effects. Remember to always stay informed and heed the warnings of volcanologists and emergency management officials during volcanic activity.

What are balls of lava called?