earth science

Lava dome

Lava dome is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lava dome rather than just read about it. In short: In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings.

Key takeaways

Lava dome belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lava dome to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lava dome from memory before moving on to harder problems.

Reference excerpt

In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on Earth form lava domes. The geochemistry of lava domes can vary from basalt (e.g. Semeru, 1946) to rhyolite (e.g. Chaiten, 2010) although the majority are of intermediate composition (such as Santiaguito, dacite-andesite, present day). The characteristic dome shape is attributed to high viscosity that prevents the lava from flowing very far. This high viscosity can be obtained in two ways: by high levels of silica in the magma, or by degassing of fluid magma. Since viscous basaltic and andesitic domes weather fast and easily break apart by further input of fluid lava, most of the preserved domes have high silica content and consist of rhyolite or dacite. Existence of lava domes has been suggested for some domed structures on the Moon, Venus, and Mars, e.g. the Martian surface in the western part of Arcadia Planitia and within Terra Sirenum.

Dome dynamics

Lava domes evolve unpredictably, due to non-linear dynamics caused by crystallization and outgassing of the highly viscous lava in the dome's conduit. Domes undergo various processes such as growth, collapse, solidification and erosion. Lava domes grow by endogenic dome growth or exogenic dome growth. The former implies the enlargement of a lava dome due to the influx of magma into the dome interior, and the latter refers to discrete lobes of lava emplaced upon the surface of the dome. It is the high viscosity of the lava that prevents it from flowing far from the vent from which it extrudes, creating a dome-like shape of sticky lava that then cools slowly in-situ. Spines and lava flows are common extrusive products of lava domes. Domes may reach heights of several hundred meters, and can grow slowly and steadily for months (e.g. Unzen volcano), years (e.g. Soufrière Hills volcano), or even centuries (e.g. Mount Merapi volcano). The sides of these structures are composed of unstable rock debris. Due to the intermittent buildup of gas pressure, erupting domes can often experience episodes of explosive eruption over time. If part of a lava dome collapses and exposes pressurized magma, pyroclastic flows can be produced. Other hazards associated with lava domes are the destruction of property from lava flows, forest fires, and lahars triggered from re-mobilization of loose ash and debris. Lava domes are one of the principal structural features of many stratovolcanoes worldwide. Lava domes are prone to unusually dangerous explosions since they can contain rhyolitic silica-rich lava. Characteristics of lava dome eruptions include shallow, long-period and hybrid seismicity, which is attributed to excess fluid pressures in the contributing vent chamber. Other characteristics of lava domes include their hemispherical dome shape, cycles of dome growth over long periods, and sudden onsets of violent explosive activity. The average rate of dome growth may be used as a rough indicator of magma supply, but it shows no systematic relationship to the timing or characteristics of lava dome explosions. Gravitational collapse of a lava dome can produce a block and ash flow.

Related landforms

Cryptodomes

A cryptodome (from the Greek κρυπτός, kryptos, "hidden, secret") is a dome-shaped structure created by accumulation of viscous magma at a shallow depth. Two examples of cryptodomes were the ones leading to the 1956 eruption of Bezymianny and the 1980 eruption of Mount St. Helens. In each case, the explosive eruption began after the cryptodome caused the side of the volcano to bulge outward and led to a sector collapse, in turn leading to explosive decompression of the subterranean cryptodome.

Lava spine/Lava spire

A lava spine or lava spire is a growth that can form on the top of a lava dome. A lava spine can increase the instability of the underlying lava dome. A recent example of a lava spine is the spine formed in 1997 at the Soufrière Hills Volcano on Montserrat.

Lava coulées

Coulées (or coulees) are lava domes that have experienced some flow away from their original position, thus resembling both lava domes and lava flows. The world's largest known dacite flow is the Chao dacite dome complex, a huge coulée flow-dome between two volcanoes in northern Chile. This flow is over 14 kilometres (8.7 mi) long, has obvious flow features like pressure ridges, and a flow front 400 metres (1,300 ft) tall (the dark scalloped line at lower left). There is another prominent coulée flow on the flank of Llullaillaco volcano, in Argentina, and other examples in the Andes.

Examples of lava domes

References

External links

Global Volcanism Program: Lava Domes USGS Photo glossary of volcano terms: Lava dome

Illustrations

Worked examples

Example 1 — a first encounter with Lava dome

Start with the simplest possible case. Write down what Lava dome claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lava dome before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lava dome ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lava dome

In research: Lava dome appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lava dome in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lava dome is common in secondary-school and first-year university syllabi. It links to neighbouring topics Lava domes, Volcanic landforms, so understanding it makes those chapters shorter.
In everyday life: Look for Lava dome outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lava dome in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lava dome means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lava dome out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lava dome in simple terms?

Why does Lava dome matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lava dome?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lava dome.