"Anak Krakatau Erupts in Sunda Strait; Tsunami Risk Assessed by Authorities"
Flank collapse
sudden failure of a volcano's outer slope into the sea, displacing water and generating tsunami waves
Composite volcano (stratovolcano)
a steep-sided volcano built of alternating lava and pyroclastic layers, prone to explosive eruptions
The Sunda Strait, located between 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 region's intense activity results from the subduction of the Indo-Australian Plate beneath the Eurasian Plate, generating magma that fuels composite (stratovolcano) eruptions.
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, causing approximately 36,000 deaths, most of them from the tsunami waves rather than the eruption blast itself. The caldera left behind by that collapse became the site of renewed volcanic activity in the 1920s. Anak Krakatau, meaning "Child of Krakatau", emerged from the sea in 1927, growing within the original caldera. It has experienced frequent eruptions since then and is classified as a composite (stratovolcano) type, characterised by viscous lava and explosive eruptions that deposit alternating layers of lava and pyroclastic material.
Volcanic eruptions do not automatically generate tsunamis. The specific mechanism that makes Anak Krakatau particularly dangerous is flank collapse, the sudden failure of a large section of the volcano's outer slope into the sea. When a volcanic edifice is destabilised by sustained eruption activity, internal magma pressure, or hydrothermal weakening of rock, an entire flank can slide into the ocean. This sudden displacement of a large volume of water generates tsunami waves that radiate outward with little warning.
The critical distinction from earthquake-generated tsunamis is the absence of a seismic signal. Earthquake-triggered tsunamis produce measurable seismic waves that activate early-warning systems, giving coastal populations some lead time. A volcanic flank collapse produces no comparable seismic precursor. …
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?
What are Tsunamis? How and where are they formed? What are their consequences? Explain with examples.
Mention the global occurrence of volcanic eruptions in 2021 and their impact on regional environment.
Discuss the geophysical characteristics of Circum-Pacific Zone.
Consider the following statements about Anak Krakatau:
1.It is located in the Sunda Strait between Java and Sumatra.
2.It emerged from the sea in 1927 within the caldera left by the 1883 Krakatau eruption.
3.A partial collapse of its flank in 2018 generated a tsunami that struck coastal areas of Banten and Lampung.
4.A volcanic flank collapse generates a tsunami with a strong seismic signal that activates early-warning systems.
How many of the above statements are correct?
With reference to the 1883 Krakatau eruption, which of the following statements is/are correct?
1.The eruption occurred in the Sunda Strait between Java and Sumatra.
2.Most of the approximately 36,000 deaths were caused by tsunami waves rather than the eruption blast itself.
3.Anak Krakatau emerged from the sea immediately after the 1883 eruption.
Select the correct answer using the code below:
Consider the following pairs:
Volcano / Location
1.Anak Krakatau — Sunda Strait, Indonesia
2.Barren Island — Andaman and Nicobar Islands, India
3.Tungurahua — Peru
4.Fagradalsfjall — Iceland
How many of the above pairs are correctly matched?
Consider the following statements about volcanic eruption products:
1.Pyroclastic debris consists of fragments of solidified lava and rock ejected during eruptions.
2.Sulphur dioxide released into the stratosphere can cause short-term regional cooling by forming aerosols.
3.Composite volcanoes (stratovolcanoes) are characterised by low-viscosity basaltic lava and low-explosivity eruptions.
4.Ash and dust from volcanic eruptions can disrupt aviation over wide areas.
Which of the statements given above are correct?
Which of the following best explains why a volcanic flank-collapse tsunami is more dangerous than an earthquake-generated tsunami from an early-warning perspective?
Want the full note, Prelims Facts & MCQ answers?
Create a free account — takes less than a minute.
Create free account