Select your language

Suggested languages for you:
Log In Start studying!
StudySmarter - The all-in-one study app.
4.8 • +11k Ratings
More than 3 Million Downloads
Free
|
|

All-in-one learning app

  • Flashcards
  • NotesNotes
  • ExplanationsExplanations
  • Study Planner
  • Textbook solutions
Start studying

Volcanoes

Save Save
Print Print
Edit Edit
Sign up to use all features for free. Sign up now
Geography

In January 2022 (very recent!), an underwater volcano erupted near Tonga in the South Pacific Ocean. This is one of the most significant recorded eruptions in over 30 years, and the volcano caused a series of tsunami waves on the shores of Tonga. But what exactly is a volcano? How are they formed? What different types of volcanoes are there? Lets find out.

Volcanoes are openings of the Earths crust to the molten rock below the surface of the Earth. A mixture of hot liquid rock, gases, mineral crystals, and rock fragments – also known as magma – shoots up during a volcanic eruption.

Check out our explanation on Mount Merapi Eruption 2010 to see the damage volcanoes can cause.

How are volcanoes formed?

Convergent plate margins

The majority of volcanoes are formed at convergent plate margins where subduction occurs. As the denser plate sinks beneath the less dense plate, the temperature and pressure increase. The increase in temperature and pressure causes rocks to release water, resulting in a reduction in the melting point of the rock above. This creates magma, which rises to the surface, forming a volcano.

Hot spots from mantle plumes

Certain volcanoes are attributed to hot spots from mantle plumes instead of convergent plate margins. A mantle plume is an area under the crust of the Earth where the magma is hotter than the surrounding magma. The volcano is formed as the hotter magma melts the crust and causes magma to rise to the surface. The mantle plume remains stationary whilst the tectonic plate continues to move (this can cause a chain of volcanoes). Some examples include the Hawaiian Islands that are located far from plate boundaries.

What are the states of volcanoes?

The different states of volcanoes are active, dormant, and extinct.

  • Active volcanos are prone to eruptions. This means that they have erupted or could still erupt.
  • Dormant volcanoes are those that have not erupted for over 2000 years.
  • Extinct volcanos will never erupt again and are no longer a danger.

What are the different types of volcanoes?

The different types of volcanoes include cinder cones, composite volcanoes, shield volcanoes, and lava domes.

Cinder cones

Cinder cones are formed by the particles from lava that erupt from a single opening. When the gaseous lava is ejected into the air, small fragments solidify and form cinder. This cinder falls around the opening and forms a circular or oval cone.

Example: The Parícutin volcano in Mexico.

Volcanoes Parícutin volcano in Mexico StudySmarterParícutin volcano, Mexico, Jim Luhr, Smithsonian Institution, commons.wikimedia.org

Composite volcanoes

Composite volcanoes are formed by alternating layers of lava, volcanic ash, cinders, blocks, and bombs. They are often steep-sided and have symmetrical cones. The cone is often destroyed when the volcano becomes inactive and hardened magma blocks the opening.

Example: Mount Fuji in Japan.

Volcanoes Mount Fuji in Japan StudySmarterMount Fuji, Japan, pixabay.com

Shield volcanoes

Shield volcanoes consist mostly of fluid lava flow and are shaped (unsurprisingly!) like a shield. Basaltic lava pours out in different directions from the opening or a group of openings. This builds a gently sloping surface. Shield volcanoes are more common in oceanic settings rather than continental.

Example: Mauna Loa, Hawaii, is the world’s largest shield volcano.

Volcanoes Mauna Loa volcano in Hawaii StudySmarterMauna Loa volcano, Hawaii, U.S. Geological Survey, flickr.com

Lava domes

Lava domes are formed by lava that is too viscous to flow far. The lava often remains around the vent, building the volcano from within. This process includes the outer surface hardening, breaking, and falling down the volcanos sides. Lava domes are sometimes formed within the crater of a previous volcanic eruption.

Example: Mount Pelée in Martinique.

Mount Pelée, Martinique, pixabay.com

How do physical processes impact the magnitude and type of volcanic eruption?

Lets see how different plate margins affect the magnitude and type of volcanic eruption.

Volcanoes at divergent plate margins

Volcanoes are generally small at divergent margins because basalt lava has a high viscosity and low gas content. Currently, there are around 100 volcanoes at divergent plate margins. Some of these are extinct, but over 30 are still active.

Volcanoes at convergent plate margins

Volcanoes at convergent plate margins tend to erupt frequently and with high force. This is because the magma from the process of subduction has high gas and silica content. Ocean-ocean convergent plate margins tend to consist of volcanic islands.

The volcanoes formed at the ocean-ocean convergent plate margins are called island-arc volcanoes. The volcanoes formed at the ocean-continent convergent plate margins are called Andean-type volcanoes.

Volcanoes formed at the ocean-ocean convergent plate margins are called island-arc volcanoes.

The volcanoes formed at the ocean-continent convergent plate margins are called Andean-type volcanoes.

What are the effects of volcanoes?

The harmful effects of volcanoes include lava flows, pyroclastic flows, ash falls, gas eruptions, and further secondary hazards.

Lava flows

Volcanoes can erupt with lava flow (molten rock) and damage nearby infrastructure. However, these lava flows tend to travel slowly, which gives time for evacuation. The lava will destroy anything in its path by burning, burying, or knocking it down.

Pyroclastic flows

Pyroclastic flows are eruptions of rock, ash, and gas that are superheated. They can travel at 80km/h, significantly faster than lava flows. This means that they can travel a long way with little warning. They can threaten nearby people and cause widespread death and destruction through burning.

Ash falls

Ash falls are eruptions of ash clouds caused by the expansion of gas in the volcano. Ash falls do not tend to endanger human life but can cause issues with aviation, infrastructure, and contamination to water and agriculture.

Gas eruptions

Gas eruptions escape through soil, lava, or vents and include gases such as carbon dioxide, sulphur dioxide, hydrogen, hydrogen sulphide, and carbon monoxide. These can impact the climate and cause irritations, poisoning, breathing issues, and acidic rain.

Secondary hazards

Lets assess two types of secondary hazards from volcanoes: lahars and Jökulhlaups.

Lahars

Lahars are secondary hazards that are caused by the mixtures of volcanic material and water. They are mud and debris flows that create threats nearby the volcanoes, but they can also travel far from volcanoes along rivers and cause issues further away. They can bury or destroy natural habitats, settlements, and infrastructure. They can also generate tsunamis when they enter the sea.

Jökulhlaups

Jökulhlaups are sudden floods of water from glaciers, which can be caused by volcanic eruptions under a glacier. Therefore, they are potential secondary hazards caused by volcanic eruptions.

See our explanation on Tsunamis and how volcanoes can cause them.

Volcanoes - Key takeaways

  • Volcanoes are openings of the Earth's crust to the molten rock below the surface of the Earth.
  • The majority of volcanoes are formed at convergent plate margins where subduction occurs. Certain volcanoes are formed due to hot spots from the mantle.
  • The different types of volcanoes include cinder cones, composite volcanoes, shield volcanoes, and lava domes.
  • Volcanoes are generally small at divergent margins because basalt lava has a high viscosity and low gas content.
  • Volcanoes at convergent plate margins tend to erupt frequently and with high force.
  • The hazards caused by volcanoes include lava flows, pyroclastic flows, ash falls, gas eruptions, and further secondary hazards.

Volcanoes

The majority of volcanoes are formed at convergent plate margins where subduction occurs. As the denser plate sinks beneath the less dense plate, the temperature and pressure increase. The increase in temperature and pressure causes rocks to release water, resulting in a reduction in the melting point of the rock above. This creates magma, which rises to the surface, forming a volcano. 

Volcanoes are openings of the Earth’s crust to the molten rock below the surface of the Earth.

Volcanoes erupt at convergent plate margins where subduction occurs. As the denser plate sinks beneath the less dense plate, the temperature and pressure increase. The increase in temperature and pressure causes rocks to release water, resulting in a reduction in the melting point of the rock above. This creates magma, which rises to the surface, forming a volcano. 

We have volcanoes because of convergent plate margins where subduction occurs.

Volcanoes work by forming at convergent plate margins where subduction occurs. As the denser plate sinks beneath the less dense plate, the temperature and pressure increase. The increase in temperature and pressure causes rocks to release water, resulting in a reduction in the melting point of the rock above. This creates magma, which rises to the surface, forming a volcano. 

Final Volcanoes Quiz

Question

What are volcanoes?

Show answer

Answer

Volcanoes are openings of the Earth’s crust to the molten rock below the surface of the Earth.

Show question

Question

How are volcanoes formed at convergent plate margins?

Show answer

Answer

Volcanoes are formed at convergent plate margins due to the process of subduction. As the denser plate sinks, the temperature and pressure increase. The increase in temperature and pressure causes rocks to release water, resulting in a reduction in the melting point of the rock above. This forms magma, which rises to the surface, forming a volcano.

Show question

Question

How are cinder cones formed?


Show answer

Answer

Cinder cones are formed by the particles from lava that erupt from a single opening. In the process of the gaseous lava being ejected into the air, small fragments solidify, forming cinder. This falls around the opening and forms a circular or oval cone.

Show question

Question

How are composite volcanoes formed?


Show answer

Answer

Composite volcanoes are formed by alternating layers of lava, volcanic ash, cinders, blocks, and bombs. They are often steep-sided and symmetrical cones.

Show question

Question

How are shield volcanoes formed?


Show answer

Answer

Shield volcanoes are formed by fluid lava flow. Lava pours out in different directions from the opening or a group of openings. This builds a gently sloping surface.

Show question

Question

How are lava domes formed?

Show answer

Answer

Lava domes are formed by lava that is too viscous to flow far. Therefore, the lava often remains around the vent, building the volcano from within. This process includes the outer surface hardening, breaking, and falling down the sides of the volcano.

Show question

Question

What are the characteristics of volcanoes at divergent plate margins?


Show answer

Answer

Volcanoes are generally small at divergent margins because basalt lava has a high viscosity and low gas content.

Show question

Question

What are the characteristics of volcanoes at convergent plate margins?


Show answer

Answer

Volcanoes at convergent plate margins tend to erupt frequently and with high force. This is because the magma from the process of subduction has high gas and silica content. Ocean-ocean convergent plate margins tend to consist of volcanic islands.

Show question

Question

What are the hazards caused by volcanoes?


Show answer

Answer

The hazards caused by volcanoes include lava flows, pyroclastic flows, ash falls, gas eruptions, and further secondary hazards.

Show question

Question

How can lava flow be a threat?


Show answer

Answer

Volcanoes can erupt with lava flow (molten rock) and damage nearby infrastructure. However, it tends to travel slowly, which allows time for evacuation.

Show question

Question

How can pyroclastic flows be a threat?


Show answer

Answer

Pyroclastic flows are eruptions of rock, ash, and gas that are superheated. They can travel at 80km/h, significantly faster than lava flows. This means that they can travel a long way with little warning. Therefore, they can be a threat to nearby people and cause widespread death and destruction through burning.

Show question

Question

What are ash falls?


Show answer

Answer

Ash falls are continuous eruptions of ash clouds caused by the expansion of gas in the volcano.

Show question

Question

What are the impacts of ash falls?


Show answer

Answer

Ash falls do not tend to endanger human life but can cause issues with aviation, infrastructure, and contamination to water and agriculture.

Show question

Question

What are the impacts of gas eruptions?


Show answer

Answer

Gas eruptions of carbon dioxide, sulphur dioxide, hydrogen, hydrogen sulphide, and carbon monoxide can have an impact on the climate and can cause irritations, poisoning, breathing issues, and acidic rain.

Show question

Question

What are the secondary hazards of volcanoes?


Show answer

Answer

Lahars are secondary hazards that are caused by the mixtures of volcanic material and water. They are mud and debris flows that tend to create threats nearby the volcanoes, but they can also travel far from volcanoes along rivers and cause issues further away. Jökulhlaups are sudden floods of water from glaciers, which can be caused by volcanic eruptions under a glacier.

Show question

60%

of the users don't pass the Volcanoes quiz! Will you pass the quiz?

Start Quiz

Discover the right content for your subjects

No need to cheat if you have everything you need to succeed! Packed into one app!

Study Plan

Be perfectly prepared on time with an individual plan.

Quizzes

Test your knowledge with gamified quizzes.

Flashcards

Create and find flashcards in record time.

Notes

Create beautiful notes faster than ever before.

Study Sets

Have all your study materials in one place.

Documents

Upload unlimited documents and save them online.

Study Analytics

Identify your study strength and weaknesses.

Weekly Goals

Set individual study goals and earn points reaching them.

Smart Reminders

Stop procrastinating with our study reminders.

Rewards

Earn points, unlock badges and level up while studying.

Magic Marker

Create flashcards in notes completely automatically.

Smart Formatting

Create the most beautiful study materials using our templates.

Sign up to highlight and take notes. It’s 100% free.