DRRM ♡ Volcanoes

Volcano

• rupture in the earth's crust

• allows molten rock, ash, and gases to escape from below the surface

• vent through which magma, once it reaches the surface, becomes lava

  • along with other volcanic materials, are expelled

Types of Volcanoes

• shield volcanoes

• composite volcanoes (stratovolcanoes)

• lava domes

• cinder cones

Shield Volcanoes

• characterized by their broad, gently sloping sides, resembling a warrior's shield

• formed by effusive eruptions of highly fluid basaltic lava

  • flows easily and spreads out over large areas

• large broad slopes, fluid lava flow

• ex. Mauna Loa, Hawaii

Composite Volcanoes (Stratovolcanoes)

• tall & conical volcanoes

• built up by many layers of hardened lava, tephra, pumice, and volcanic ash

• known for explosive eruptions due to the viscous nature of their magma, which traps gases

• steep & symmetrical, explosive eruptions

• ex. Mayon, Philippines

Lava Domes

• circular mounds resulting from the slow extrusion of viscous lava from a volcano

• thick lava piles up around the vent because it is too sticky to flow far

  • creating a dome-like structure

• small with steep sides oozes viscous lava

• ex. Showa Shinjan, Japan

Cinder Cones

• simplest type of volcano

• small and steep-sided cones built from ejected lava fragments (cinders)

  • that fall back around the vent

• often formed during single, relatively short-lived eruptive events

• smallest, single vent, erupts cinders, ash, & rocks

• ex. Sunset Crater, Arizona

Potential Volcano-related hazards

• lahar

• ashfall

• pyroclastic flow

• ballistic projectile

• volcanic gas

• lava flow

Lahar

• dangerous fast-moving mixtures of volcanic debris, rock, & water

• flow down slopes of a volcano

• triggered by heavy rainfall or melting snow/ice

• can travel great distances

• highly destructive engulfing everything in their path

Ashfall

• fragments of pulverized rock minerals and volcanic glass from an explosive eruption

• fall to the ground after eruption

• can cause

  • respiratory problems

  • contaminate water supplies

  • collapse roofs

  • disrupt transportation & communication

Pyroclastic flow

• fast-moving currents of hot gas & volcanic debris

  • ash, pumice, rock fragments

• rushing down volcano flanks

• extremely dangerous

• temperatures of several hundred degrees celsius

• speeds of hundreds of kilometers per hour

• incinerate and bury everything in their path

Ballistic projectile

• rocks and other fragments ejected from a volcano during eruption

• follow a ballistic trajectory through the air

• range in size from small pebbles to large blocks

• can cause significant damage and injury even at a considerable distance from the vent

Volcanic gas

• released from volcanoes into the atmosphere

• include water vapor, carbon dioxide, sulfur dioxide, hydrogen sulfide, & hydrogen halides

• in high concentrations can be toxic to humans and animals

• contribute to acid rain

• affect climate

Lava flow

• streams of molten rock pouring from a volcanic vent

• flow down the volcano's slopes

• generally slow-moving and predictable

• can destroy infrastructure vegetation and homes by incineration and burial

Phreatic Eruption

• meaning spring

• type of volcanic eruption driven by explosive expansion of steam

• occurs when groundwater or surface water contacts hot volcanic materials

• water rapidly heats up boils and flashes to steam

Warning Signs of a Volcanic Eruption

• seismic activities

• ground deformation

• volcanic gas emissions

• changes in hydrothermal systems

• visible changes at the crater or summit

Seismic Waves

• increased frequency & intensity of earthquakes

  • caused by magma rising & cracking rock underground

• volcanic tremors (harmonic tremors)

  • cont. vibrations caused by magma movement

  • more rhythmic than typical quakes

• long-period earthquakes

  • pressure changes in magma chambers and fluid movement

• monitoring tool: seismograph

Seismograph

• complete system includes seismometer and recording device

• historically used paper or film now typically digital

• recording device converts electrical signals from seismometer into a visible record called a seismogram

Ground Deformation

• land around a volcano changes shape as magma accumulates

• ground swelling (inflation)

• ground tilting

• ground fissuring

• monitoring tools: gps insar (satellite radar) tiltmeters

Ground Swelling (Inflation)

surface bulges as magma pushes upward

Ground Tilting

instruments may detect the slanting of the land

Ground Fissuring

cracks appear in the ground as stress builds

Volcanic Gas Emissions

• gases escaping from a volcano can signal changes underground

• increased Steaming/Fumarolic Activity

  • steam or gas vents may appear

• changes in gas composition and abundance

  • sulfur dioxide can signal rising magma

• smell of sulfur (rotten-egg smell) may indicate sulfur gases

• monitoring tools: gas spectrometers drones direct sampling

Changes in Hydrothermal Systems

• hot springs & crater lakes can react to volcanic heat and pressure

• increased temperature

• variations in chemical content in water sources

• drying up of springs or wells from underground changes

• monitoring tools: temperature probes water sampling kits pH meters

Visible Changes at the Crater or Summit

• physical signs that can be observed directly

• crater glow

• localized landslides

• observation methods: satellite imagery drones direct observation

Crater Glow

red or orange glow at night due to hot magma or gases

warning signs & monitoring

• often preceded by increased seismic activity, ground deformation, gas emissions, changes in hydrothermal systems, & visible surface changes

• monitoring these indicators with scientific instruments and data analysis helps assess hazards and mitigate risks to communities

Before an Eruption

• stay updated with local news

• know community warning systems and emergency plans

• discuss emergency protocols and roles with household members

• prepare 72-hour emergency supply kit

  • first aid kit, clothes, food, water, flashlight, radio, medicines, dust masks, goggles, sturdy shoes

• secure livestock

• follow local authority announcements and evacuation orders

During an Eruption

• follow evacuation orders from local authorities and remind family of disaster plan

• do not return home until declared safe

• if advised to stay indoors, seal windows and doors with a damp cloth to block ash and smoke

• wear long-sleeved shirts and long pants

• use goggles to protect eyes

• use dust mask or hold a damp cloth over face to prevent inhalation of ash and volcanic particles

• avoid low-lying regions and river areas where debris may accumulate

• keep updated via radio television text messages or social media

After an Eruption

• get clearance from local government before returning home

• check house for damage; avoid entry if unsafe

• avoid ashfall areas if you have respiratory issues

• inspect electrical wiring, appliances, and gas tanks before use

• ensure drinking water is safe

• stay updated on emergency news

• wear protective gear when cleaning ash and debris