earth science

Volcanic landslide

Volcanic landslide 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 Volcanic landslide rather than just read about it. In short: A volcanic landslide or volcanogenic landslide is a type of mass wasting that takes place at volcanoes. Typically, the volcano builds up material in a peak that eventually becomes too high to be stable; the instability is relieved when a portion of the peak slides to a lower position.

Key takeaways

Volcanic landslide 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 Volcanic landslide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Volcanic landslide from memory before moving on to harder problems.

Reference excerpt

A volcanic landslide or volcanogenic landslide is a type of mass wasting that takes place at volcanoes. Typically, the volcano builds up material in a peak that eventually becomes too high to be stable; the instability is relieved when a portion of the peak slides to a lower position.

Occurrences

All volcanic edifices are susceptible to landslides, particularly stratovolcanoes and shield volcanoes where landslides are important processes. Volcanic landslides range in size from less than 1 km3 (0.24 mi3) to more than 100 km3 (24 mi3). The largest volcanic landslides on Earth occur from submarine volcanoes and are several times larger than those that occur on land. Submarine landslides with volumes of 100–150 km3 (24–36 mi3) have occurred in the Canary Islands within the last 43 million years, but the largest submarine landslides could have been up to 900 km3 (220 mi3) in volume. Massive submarine landslides have also taken place in the Hawaiian Islands over the last several million years, the largest of which constitute significant portions of the islands from which they originated. Smaller landslides have also been identified at volcanoes on Mars and Venus. Martian landslides reach lengths of 90 km (56 mi) and more whereas the largest Venusian landslides extend only about 50 km (31 mi). The most dramatic landslide deposits on Venus occur beneath the slopes of volcanoes. Since erosion rates on Venus are much lower than those on Earth due to the lack of water on the surface, landslides are an important mechanism in wearing down mountain regions on Venus. The rounded hills of the complexly deformed tessera, or tile-like, terrain on Venus have probably been modified by numerous landslides.

Types

At volcanoes, the term landslide is commonly used for slope movements with shear and displacement in a relatively narrow zone. They can be in the form of debris avalanches, debris flows, slumps and rockfalls. A debris avalanche is a sudden, very rapid flow of rock and soil in response to gravity. It is a common middle stage in the transformation of a cohesive debris flow from a landslide or rockslide. Debris avalanches may be restricted to grain flows or granular flows, in which flow mechanics are governed by particle interactions involving friction and collision. Debris flows, in contrast, owe much of their behaviour to excess pore-water pressure and a pore fluid that is viscous and contains fine sediment.

Sector collapses

The largest landslides from volcanoes are called sector or edifice collapses. Prehistoric sector collapses are preserved in the geological record in the form of debris avalanche deposits and collapse scars. Debris avalanche deposits can be found up to 20 km (12 mi) from the site of collapse. Collapse scars are also an indicator of sector collapse and are often described as "amphitheatre" or "horseshoe" shaped. Such collapse scars, open at one end, have long been noted in many volcanic regions around the world. The largest volcanic island sector collapse in historic times took place in 1888 when Ritter Island collapsed off the northern coast of Papua New Guinea. Edifice reconstruction generally must occur before a second sector collapse.

Prehistoric Stromboli, Sciara del Fuoco collapse Popocatépetl, Ventorrillo collapse Mount Rainier, Osceola collapse Historic Mount St. Helens, 1980 Anak Krakatoa, 2018 Mount Bandai, 1888

Flank collapses

Flank collapses are much smaller than sector collapses, but they may also yield far-reaching debris flows. Flank collapses differ from sector collapses in that they only involve the volcano flank whereas sector collapses are large enough to involve the volcano summit. The smaller size of a flank collapse indicates that there need be no repose time before another flank collapse occurs, and hence they can be treated as random events.

Prehistoric East Molokai Volcano, Wailau collapse Koʻolau Volcano, Nuʻuanu collapse Mount Garibaldi, Cheekye collapse Historic Mount Meager, 2010 Mount Elgon, 2010 Kīlauea, Hilina Slump

Causes

Several conditions can trigger landslides at volcanoes:

Intrusion of magma into a volcano Explosive eruptions Large earthquake directly beneath a volcano or nearby Saturation of the ground Hydrothermal alteration of volcanic rocks Structural discontinuities High lava accumulation rates Steep slopes

Hazards

Large landslides from volcanoes often bury valleys with tens to hundreds of metres of rock debris, forming a chaotic landscape marked by dozens of small hills and closed depressions. If the landslide deposit is thick enough, it may dam streams to form lakes. These lakes may eventually drain catastrophically to create floods and lahars downstream. Landslides that remove a large portion of a volcanic cone may abruptly decrease pressure on shallow magmatic and hydrothermal systems, which can generate explosions ranging from a small steam explosion to large steam and magma-driven directed blasts. These result in tephra and ash fall hazards for surrounding areas. Large horseshoe-shaped craters formed by landslides at volcanoes will likely direct subsequent lava flows, pyroclastic flows or lahars toward its breached opening if the primary eruptive vent is located within these deep craters. The collapse of island or coastal volcanoes from giant landslides can generate tsunamis that could potentially devastate large areas of coastal land.

Disasters

Historically, the most deadly volcanic landslide occurred in 1792 when sliding debris from Mount Mayuyama in Japan slammed into the Ariake Sea and generated a tsunami that reached the opposite shore; nearly 15,000 people were killed. The sector collapse of Ritter Island in 1888 generated a tsunami with runups of up to 15 m (49 ft) that caused damage more than 700 km (430 mi) away and killed anywhere between 500 and 3,000 people on neighbouring islands. A landslide originating from Devastation Glacier on the southern flank of the Mount Meager massif in British Columbia, Canada, buried and killed a group of four geologists at the confluence of Devastation Creek and Meager Creek in July 1975. In 1979, a landslide from the Indonesian volcano Iliwerung produced 9 m-high (30 ft) waves that killed more than 500 people. In December 2018, another landslide-induced tsunami took place in Indonesia's Sunda Strait following a collapse of Anak Krakatoa. The waves struck about 313 km (194 mi) of coastline with various heights, killing at least 373 people and damaging many buildings.

Illustrations

Worked examples

Example 1 — a first encounter with Volcanic landslide

Start with the simplest possible case. Write down what Volcanic landslide 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 Volcanic landslide 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 Volcanic landslide 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 Volcanic landslide

In research: Volcanic landslide 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 Volcanic landslide 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: Volcanic landslide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Volcanic landslides, so understanding it makes those chapters shorter.
In everyday life: Look for Volcanic landslide 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 Volcanic landslide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Volcanic landslide 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 Volcanic landslide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Volcanic landslide in simple terms?

Why does Volcanic landslide 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 Volcanic landslide?

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 Volcanic landslide.