A type of geological event near an opening/vent in the Earth’s surface including volcanic eruptions of lava, ash, hot vapour, gas, and pyroclastic material.

• Ash fall 
• Lahar – Hot or cold mixture of earthen material flowing on the slope of a volcano either during or between volcanic eruptions
• Lava Flow
• Pyroclastic Flow – Extremely hot gases, ash, and
• other materials of more than 1,000 degrees Celsius that rapidly flow down the flank of a volcano (more than 700 km/h) during an eruption. 

• There are about 1500 potentially active volcanoes worldwide. 
• Volcanic activities and wildfires affected 6.2 million people and caused nearly 2400 deaths between 1998-2017.

Regions Prone to Volcanic eruptions: Barren island (A&N), Narcondam (Andaman Sea), Deccan trap in Deccan plateau, Baratang (Andaman Island), Dhinodhar hills (Gujarat), Dhosi hills (Aravali mountains), Tosham hills (Haryana).Nodal Ministry: Min. of Earth Sciences (MOES)

Types of Volcanic Eruptions:

1. Stratovolcanoes: Steep-sided with explosive eruptions. Example: Mount St. Helens.
2. Shield Volcanoes: Broad and gently sloping with non-explosive eruptions. Example: Mauna Loa.
3. Cinder Cone Volcanoes: Small, steep-sided with ash and cinder eruptions. Example: Paricutin.
4. Caldera Volcanoes: Large, basin-like depressions from explosive eruptions. Example: Yellowstone Caldera.
5. Lava Domes: Bulbous mounds from slow-moving lava. Example: Novarupta Dome.
6. Submarine Volcanoes: Form underwater. Example: Lo’ihi (Hawaii).
7. Fissure Volcanoes: Erupt along cracks. Example: Laki (Iceland).
8. Super-volcanoes: Erupt cataclysmically. Example: Yellowstone (potential supervolcano).

Criteria to Declare:

Central or State authorities declare the area as volcanically active based on these parameters:

1. Volcanic Activity: This includes volcanic eruptions, lava flows, ash emissions, and any other signs of volcanic unrest.
2. Geological Evidence: The presence of volcanic rocks, craters, calderas, lava domes, or volcanic vents features strong evidence of volcanic origin.
3. Seismic Activity: Monitoring seismic activity, including volcanic earthquakes and tremors, is crucial.
4. Gas Emissions: Measuring the composition and quantity of (SO2) or carbon dioxide (CO2), can provide insights into volcanic activity and potential hazards.
5. Ground Deformation: Detected through techniques like GPS and satellite-based interferometry, can indicate magma movement.
6. Historical Records: Historical records of past eruptions, including eyewitness accounts, written records, and geological studies, are important for assessing a volcano’s history and potential future behavior.
7. Remote Sensing: Used to monitor changes in surface temperature, volcanic ash plumes, and ground deformation.

Causes:

1. Underwater Earthquakes: When tectonic plates at subduction zones converge, they suddenly displace a massive amount of water, generating a tsunami.
2. Volcanic Eruptions: The expulsion of magma and gas from a volcano can create a sudden and forceful displacement.
3. Landslides: Landslides from coastal cliffs or mountains, can displace a significant amount of water upon impact, generating a tsunami.
4. Meteorite Impacts: Although rare, The energy released from such an impact can create powerful waves.
5. Glacial Calving: When large pieces of ice break off from glaciers and fall into the ocean, they can displace water and generate small tsunamis, known as “glacial tsunamis.”
6. Fault Zones: Faults that lie beneath the ocean can slip suddenly, displacing seawater and causing a tsunami.

Mitigation:

India had a set of official guidelines primarily related to the Barren Island volcano in the Andaman Sea. These guidelines were primarily managed by the Geological Survey of India (GSI) and the Indian Meteorological Department (IMD).

1. Monitoring and Early Warning: Continuous monitoring of volcanic activity using seismic instruments, gas analyzers, and satellite technology to detect signs of volcanic unrest.
2. Hazard Zonation: Establishment of hazard zones based on the type and potential impact.
3. Evacuation Plans: Development of evacuation plans and routes for nearby communities. Regular drills and training exercises to ensure preparedness.
4. Public Awareness and Education: Educate local communities about volcanic hazards and safety measures.
5. Coordination: Coordination between the GSI, IMD, local administration, and disaster management authorities to ensure minimal harm caused.
6. Emergency Response: Prepositioning of emergency supplies, medical teams, stockpiling food, water, medicines, and setting up emergency shelters.