Y2 Geog: Volcanoes

EYA

Name the parts of the volcano and what they are (there are 5 main ones)

• Magma chamber

  • reservoir of molten rock within or beneath the earth’s crust

• Pipe/Conduit

  • passage in a volcano through which magma and volcanic gases rise towards the surface

• Crater 

  • bowl-shaped depression produced by impact of volcanic activity on summit of volcano

• Vent

  • any opening at the Earth’s surface through which magma and volcanic gases rise toward the surface

• Secondary cone

  • smaller cones that build up on the sides of a volcano

What are the characteristics of stratovolcanoes VS shield?

Stratovolcanoes

• Cone-shaped

• Concave (steep at top, gentler at base)

• Alternate layers of acid lava and ash + cinder

Shield volcanoes

• broad-based

• cone-shaped

• gentle slopes

What is the lava of stratovolcanoes VS shield?

Stratovolcanoes

• acid lava

• viscous

• acidic

• flows slowly

• presence of ash & cinder

Shield volcanoes

• fluid/runny

• basic

• flows faster than acidlava

• cools and solidifies slowly

What is the eruptions of stratovolcanoes VS shield like?

Stratovolcanoes

• violent

• lava may escape through secondary cones

Shield volcanoes

• frequent

• quiet and gentle(due to easier release of gases from basic lava)

What are the hazards of stratovolcanoes vs shield?

Stratovolcanoes

• Pyroclastic flow - fast flowing clouds of hot gas & volcanic matter

• gases - often poisonous, released from mantel dur. eruption

• lahar - fast flowing river of volcanic mud

• ash cloud

• lava flow

Shield volcanoes

• gases

• Lava flow

how are volcanoes formed?

• Magma forces its way between two plate tectonic boundaries

• Lava cools and turns into rock. Many years later magma forces its way up again.

• The process repeats over and over again. The cooled lava forms layers of rock.

• In between, the volcano spews out ash and steam. The ash settles on the volcano and cements into rock.

• Over millions of years, the layers build up to form a volcano.

What are the primary hazards of volcanoes? (There are 6) name them

• lava flows

• Volcanic gases

• Ash clouds

• Pyroclasticflows

• Lahars/floods

• Tsunamis

What is the definition, impacts of lava flows

definition - streams of molten rock erupted onto the surface

Impacts

• destruction of infrastructure - burning, crushing

• loss of agricultural land production

• spark regional forest fires

• melt snow caps, spark secondary lahars

What is the impact of volcanic gases

• suffocation - of unsuspecting wild life and humans in low valleys

• acidic sulfur emissions - destroy crops far away

• acid rain - created due to mixed atmospheric gases, aerosols -> can destroy fabrics up to 2000km from sourcesuffocation - of unsuspecting wild life and humans in low valleys

• acidic sulfur emissions - destroy crops far away

• acid rain - created due to mixed atmospheric gases, aerosols -> can destroy fabrics up to 2000km from source

What is the definition and impact of ash clouds

definition - Large quantities of solid and molten rock fragments fall back down to Earth after being forcefully thrown into the air by volcanic explosions

Impacts

• property damage -  Causes burial and structural collapse of infrastructure, telephone lines, and power grids, this leads to collapses, killing many people

• massive clean-up needed - requires massive clean-up operations using water hosing, dump trucks, and dedicated disposal sites.

• affects transport - cloud and destroys jet engines -> widespread civil aviation shut down, high frequency ash -> complete darkness -> hazardous driving conditions

  • impacts crops & animals - impacts many: ash disperses widely in the atmosphere -> destroys vast crop fields, poison grazing livestock

What is the definition and impact of pyroclastic flows

• DEFINITION -  Concentrated, superheated avalanches of volcanic rocks, ash, and gases moving in direct contact with the ground surface.

• IMPACTS

  • kills instantly - Burial, incineration, high impact of fragments

  • destroys animals and plants - extreme, scalding lateral air surges

What is the definition, triggers and impacts of lahars/floods

• DEFINITION -  A rapidly moving, high-density mixture of volcanic rock debris and water racing down river valleys.

• TRIGGERS

  • Eruptions at snow-covered volcanoes

  • volcanoes with crater lakes

  • intense rainfall

• IMPACTS

  • mass destruction - lifts and displaced buildings, bridges, cars, river beds -> forms unstable dammed lakes, worsens future floods

What os the definition, triggers, and impacts of tsunami

• DEFINITION -  Gigantic ocean displacement waves triggered by sudden marine disruptions during volcanic events.

• TRIGGERS

  • volcanic earthquakes

  • big structural landslides calving into shallow bays

  • caldera collapse

  • high volume pyroclastic flows displacement entering ocean water

• IMPACTS 

  • Kills people - high waves

What are the socio-economic reasons why people stay near volcanoes? (5 reasons)

• fertile soils for agriculture

• Mining for resources: precious stones and minerals; employment opportunities

• Tourism revenue

• Geothermal energy

• Poverty

Explain how fertile soils for agriculture gets people to stay near volcano

• lava that has weathered down to form soils and ash that has settled on the ground are rich in nutrients to aid plant growth

• people have a livelihood by earning an income through the sale of crops

• as food is grown, this provides access to food and food security

• examples:

  • rice farming @ Mt Mayon, Phillippines

  • vineyard @ foot of Mt Etna, Italy

How does mining for resources get people to stay near volcano?

• working as sulphur miners is employment for people to earn income

• sulphur is sold for revenue

• industrial uses such as making fertilisers, disinfectant, black gun powder

• examples:

  • sulphur mining @crater of Mt Ijen, Indonesia

How does tourism revenue get people to stay near volcano

• tourism industry makes use of the scenic beauty and attractions provided by the volcanic landscape, like the volcano and its hot springs

• People can be employed  as hotel employees and tour guides or earn a livelihood by running businesses such as cafes near these attractions

• hot springs/onsens are tourist attractions, where people visit to have a bath. Hot spring operators earn revenue from providing this service. Hotels are booked based on the quality of their hot springs.

• Tourists enjoy doing these recreational activities

• examples:

  • hot springs @ Mt Fuji, Japan

  • full-day private tour @ Nagano (Japan?)

How does geothermal energy get people to stay near volcanoes

• Geothermal energy is heat within the earth, a renewable energy source because heat is continuously produced inside the earth. It is used for bathing, heating buildings, and generating electricity 

• generation of electricity is needed for:

  • industrial and commercial development as electricity is needed to drive machinery and equipment, and for the use of electrical appliances

  • domestic consumption for heating in winter and cooling in summer in homes

how does poverty get people to stay near volcanoes?

• no means to relocate

• Do not have the financial means/resources to move

• E.g. Hawaii

What is one cultural reason for staying near volcanoes? Provie an example.

• Spiritual attachment to the volcano

  • Mount Merapi @ Indonesia

Name 5 monitoring tools and techniques to predict volcanic eruptions, and how each technique works.

• Seismometers: Measure earthquakes occurring near a volcano as magma moves upward.

• Tiltmeters & GPS Satellites: Detect ground deformation and surface swelling caused by rising magma.

• Thermal & Infrared Imaging: Monitor rising temperatures and heat sources within the volcanic vent or magma chamber.

• Gas Monitoring ("Spiders"): Robots measure escaping gases (like increased sulfur dioxide emissions).

  • Precursors & Patterns: Observing increased earthquake frequency/intensity and studying past eruption patterns.

what is the limitation of these measures to predict volcanic eruptions?

• eruptions are unpredictable, scientists can only offer probabilities, and precursor signals may subside without an eruption

Name 4 prevention strategies and how they work.

• Hazard Mapping: Identifies high-risk zones around a volcano based on past flow paths and hazard potential.

• Land-Use Regulations: Prevents new buildings, homes, or critical infrastructure from being constructed in designated danger zones.

• Exclusion Zones: Prohibits public access to high-risk areas before, during, or after an eruptive event.

What is one limitation of the prevention strategies?

Prevention cannot stop the actual volcanic eruption from happening; it only limits human exposure and land usage in danger zones.

Name 3 preparedness strategies.

• building codes

• Public education and emergency planning

• Redistribution of losses and response

give 3 examples of building codes as a preparedness strategy

• Requiring steeply pitched roofs and smooth materials (e.g., sheet metal or glass) to shed volcanic ash easily.

• Designing roofs to support heavy weight loads (similar to snow loads) to prevent structural collapse.

  • Avoiding roof obstructions (such as chimneys or solar panels) where drifting ash can accumulate.

  • 
    

give 2 examples how public education and emergency planning is a preparedness strategy

• Conducting regular emergency drills in public buildings to teach evacuation routes and reduce panic.

• Preparing household emergency kits (including masks, goggles, flashlights, and battery-operated radios).

give 3 examples how redistribution of losses and response can be a preparedness strategy

• Subsidized insurance schemes and public relief funds to spread financial losses across taxpayers and assist poor/remote communities.

• Short-Term Response: Immediate search and rescue, evacuation, and emergency aid.

• Long-Term Response: Rebuilding homes, schools, and infrastructure to restart the economy.

Describe the distribution of fold mountains around the world, providing some examples.

• Distributed in long, elevated linear mountain belts across continental interiors or along continental margins.

• Found along continental collision zones across Southern Asia (e.g., Himalayas) and along the eastern boundary of the Pacific Ring of Fire (e.g., Andes).

• Example: Himalayas (passing through India, Pakistan, China, Bhutan, and Nepal) or the Andes Range.

Account for the formation of fold mountains, describing the plate boundary and tectonic process.

• Plate Boundary: Convergent boundary between two Continental plates (or Oceanic & Continental plates).

• Tectonic Process: When two continental plates collide, both have equal low density so no subduction takes place. Compressional forces buckle, fold, and uplift the rock layers into massive mountain ranges.

Describe the distribution of volcanoes.

• Linear Belts along Margins: Volcanoes are not randomly distributed; they are heavily concentrated in narrow, linear belts along tectonic plate boundaries.
  
  

• Pacific Ring of Fire: The primary concentration forms a horseshoe-shaped belt around the Pacific Ocean basin, known as the Pacific Ring of Fire. This spans the west coasts of North and South America, as well as the east and southeast coasts of Asia.
  
  

• Mid-Ocean Spreading Lines: Submarine volcanoes form continuous underwater chains running down the center of ocean basins (e.g., down the middle of the Atlantic Ocean).
  
  

  • Intraplate Hotspots: A smaller number of isolated volcanoes occur within the interior of tectonic plates, far away from plate margins (e.g., the Hawaiian Islands in the Pacific Ocean).
    

Account for thee formation of these volcanoes, giviing some examples.

• Subduction at Convergent Boundaries: Where a denser oceanic plate subducts beneath a continental or oceanic plate into the mantle, rising magma ascends through fractures in the crust to erupt as volcanic island arcs or coastal volcanoes (e.g., Mariana Islands and Cotopaxi Volcano).
  
  

• Plate Separation at Divergent Boundaries: Where oceanic plates pull apart under tensional forces, magma continuously wells up from the mantle to fill the gap at spreading centers, cooling in seawater to build submarine volcanoes and ocean ridges (e.g., Mid-Atlantic Ridge).
  
  

• Mantle Plumes at Hotspots: Stationary plumes of superheated mantle material melt directly through the middle of an overlying plate, erupting to build active volcanoes directly over the plume (e.g., Mauna Loa in Hawaii).

Describe the distribution of mid-oceanic ridges, giving some examples.

• Distributed as continuous underwater mountain chains running down the center of ocean basins.

• Located along ocean spreading centers outside the main Pacific Rim, such as running down the middle of the Atlantic Ocean.

• Example: Mid-Atlantic Ridge in the Atlantic Ocean (between North American Plate and Eurasian Plate) / Azores.

Account for the formation of mid-oceanic ridges, describing the plate boundary and tectonic process.

• Plate Boundary: Divergent boundary between two Oceanic plates.

  • Tectonic Process: Oceanic plates pull away from each other under tensional forces, forming a spreading center. Magma wells up from the mantle into the gap, cooling in seawater to build underwater ridges, submarine volcanoes, and volcanic islands.
    

Describe the distribution of oceanic trenches.

• Distributed in long, narrow, extremely deep V-shaped depressions along ocean basin margins.

• Traces the outer edges of the Pacific Ring of Fire, including the west coasts of North and South America, the east/southeast coasts of Asia, and the northeast coast of Australia.

• Example: Peru-Chile Trench (between Nazca Plate and South American Plate).

Account for the formation of oceanic trenches, describing the plate boundary and tectonic process.

• Plate Boundary: Convergent boundary between an Oceanic plate & Continental/Oceanic plate.

• Tectonic Process: As the denser oceanic plate subducts into the mantle, it flexes and plunges downward at the collision zone, creating a deep trough on the seafloor.