"Anak Krakatau Erupts, Disrupting Flights and Raising Tsunami Awareness"
Composite Stratovolcano
a steep volcano built from alternating layers of lava and pyroclastic material, prone to explosive eruptions.
Flank Collapse
sudden failure of a volcano's outer slope into the sea, capable of generating tsunamis with little seismic warning.
The Sunda Strait, separating the Indonesian islands of Java and Sumatra, sits within the Circum-Pacific Belt, commonly called the Ring of Fire. This belt accounts for roughly 75% of the world's active volcanoes and is the most seismically and volcanically active zone on Earth. The intense activity results from the subduction of the Indo-Australian Plate beneath the Eurasian Plate, generating magma that fuels explosive eruptions. Indonesia alone hosts over 130 active volcanoes, making it one of the most volcanically exposed nations on the planet.
The original Krakatau erupted catastrophically in 1883 in one of the most destructive volcanic events in recorded history. The eruption generated massive tsunamis that swept coastlines across the Sunda Strait, killing approximately 36,000 people, most from tsunami waves rather than the eruption blast itself. The caldera left behind became the site of renewed activity. Anak Krakatau, meaning 'Child of Krakatau', emerged from the sea in 1927, growing within that original caldera. It is classified as a composite stratovolcano, characterised by viscous lava, explosive eruptions, and alternating layers of lava and pyroclastic material including ash, dust, sulphur compounds, and nitrogen compounds. Composite volcanoes are steeper and more explosive than shield volcanoes, which are built from fluid basaltic lava and produce far less dangerous ash dispersal.
A critical hazard Anak Krakatau poses is flank collapse: the sudden failure of a large section of the volcano's outer slope into the sea. This mechanism caused a deadly tsunami in December 2018, when a collapsing flank displaced seawater and generated waves that struck the coasts of Banten and Lampung provinces, killing at least 430 people. Unlike earthquake-generated tsunamis, which produce measurable seismic waves that activate standard early-warning systems, volcanic flank-collapse tsunamis lack a strong seismic precursor. This makes them far harder to detect and warn against in time.
Anak Krakatau is a composite stratovolcano. Its eruptions deposit alternating layers of lava and pyroclastic material. Pyroclastic material includes ash, dust, and sulphur compounds. These materials are hazardous both on the ground and in the atmosphere. Volcanic ash is particularly dangerous to aircraft because it can melt inside jet engines and cause engine failure. Aviation authorities respond to eruptions by issuing Volcanic Ash Advisory notices and rerouting or cancelling flights within affected corridors.
The volcano's location in the Sunda Strait places it near busy shipping lanes and flight paths connecting Java and Sumatra. Any significant eruption therefore has immediate consequences for aviation across western Indonesia. The ash column from an eruption can rise to altitudes that intersect standard flight levels, forcing airlines to suspend or divert services across a wide area. …
Consider the following:
1.Pyroclastic debris
2.Ash and dust
3.Nitrogen compounds
4.Sulphur compounds
How many of the above are products of volcanic eruptions?
Consider the following statements :
1.The Barren Island volcano is an active volcano located in the Indian territory.
2.Barren Island lies about 140 km east of Great Nicobar.
3.The last time the Barren Island volcano erupted was in 1991 and it has remained inactive since then.
Which of the statements given above is/are correct?
Consider the following rivers:
1.Brahmani
2.Nagavali
3.Subarnarekha
4.Vamsadhara
Which of the above rise from the Eastern Ghats?
Tungurahua Volcano, which was declared a Global Geopark by UNESCO in 2025, is situated in which one among the following countries?
Consider the following statements about volcanic eruptions:
1.Pyroclastic debris, ash and dust, sulphur compounds, and nitrogen compounds are all products of volcanic eruptions.
2.Composite (strato) volcanoes are characterised by gentle slopes and fluid lava flows.
3.The Ring of Fire accounts for approximately 75% of the world's active volcanoes.
4.Flank-collapse tsunamis are easier to detect than earthquake-generated tsunamis because they produce stronger seismic signals.
Which of the statements given above are correct?
Consider the following statements about Anak Krakatau:
1.It is located in the Sunda Strait between Java and Sumatra.
2.It emerged in 1927 within the caldera left by the 1883 Krakatau eruption.
3.The primary tsunami hazard it poses is from earthquake-triggered seabed displacement.
4.The 2018 tsunami associated with it was caused by a flank collapse into the sea.
How many of the above statements are correct?
Consider the following pairs:
Volcano / Location
1.Anak Krakatau — Sunda Strait, Indonesia
2.Barren Island — Andaman Sea, India
3.Tungurahua — Peru
4.Nyiragongo — Democratic Republic of Congo
How many of the above pairs are correctly matched?
With reference to the Sendai Framework for Disaster Risk Reduction (2015–2030), consider the following:
1.It identifies four priorities for action, including understanding disaster risk and enhancing preparedness.
2.It explicitly calls for multi-hazard early-warning systems covering both seismic and volcanic triggers.
3.It is a legally binding international treaty under the United Nations.
4.It succeeded the Hyogo Framework for Action.
Which of the statements given above are correct?
Assertion (A): A volcanic flank-collapse tsunami can strike coastal areas with little warning even when standard tsunami early-warning systems are operational.
Reason (R): Flank-collapse tsunamis are generated by gravitational failure of a volcanic edifice into the sea, producing a weak seismic signal that does not reliably trigger seismograph-based warning networks.
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