雅思阅读 077：Anak Krakatau — A Volcano Seen from Space

Adapted from "Indonesian volcano erupts with enough force to see from space" by Mary Randolph, Scientific American, 10 September 2026.

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Reading Passage

In the sea between the Indonesian islands of Java and Sumatra lies Anak Krakatau — "Child of Krakatau" — a volcanic island that emerged from the submerged caldera of one of the most famous eruptions in history.

The original Krakatoa eruption of 1883 was cataclysmic. It lasted more than five months, ejected an estimated 25 cubic kilometres of rock and ash, and generated tsunamis up to 30 metres high that killed tens of thousands of people across the Sunda Strait. The explosion was heard 4,800 kilometres away — described by some scientists as the loudest sound ever recorded by modern humans. By the time the dust settled, most of the island had collapsed beneath the waves.

Anak Krakatau began to rise from that submerged crater in 1927. It broke the surface in 1928 and formed a small, permanent island by 1930. Since then it has remained one of the most active volcanoes on Earth, growing at a rate of around seven metres per year as repeated eruptions pile lava and ash onto its flanks. It has also been one of the most dangerous: in December 2018, a sudden collapse of the island's south-western flank triggered a tsunami that swept across nearby coastlines, killing more than 400 people and injuring thousands.

On 5 September 2026, Anak Krakatau roared back to life. For more than 24 hours, it erupted continuously, shooting gas and ash high into the tropical sky. Images captured by the NASA–USGS Landsat 8 satellite showed a vast plume of ash billowing westward across the Indian Ocean, easily visible from orbit. According to Indonesia's meteorological agency, the ash column reached 20,000 feet east of the volcano and as high as 50,000 feet to the west — high enough to enter commercial airspace.

The eruption forced the closure of eight airports across Java and Sumatra and disrupted thousands of flights. Airlines were forced to reroute services, leaving hundreds of passengers stranded. Authorities issued the second-highest alert level on Indonesia's four-point scale and urged residents within a six-kilometre radius of the crater to evacuate. For several days, ash fell like grey snow on nearby towns, dusting rooftops, roads and the windows of cars.

Geologists were not surprised by the eruption itself — Anak Krakatau erupts somewhere between ten and twenty times per year — but they were struck by its intensity and duration. "This was a major eruptive episode, not a typical day-to-day degassing event," says a volcanologist at Indonesia's National Volcanology Agency. The 2018 tsunami, which followed a similar flank collapse, has left scientists nervous about whether a large explosion could trigger another catastrophic landslide.

Anak Krakatau sits in the Pacific Ring of Fire, a 40,000-kilometre horseshoe of tectonic boundaries that encircles the Pacific Ocean and contains roughly 75 percent of the world's active volcanoes. The Ring of Fire is also the source of around 90 percent of the world's earthquakes. Indonesia alone has more than 130 active volcanoes — more than any other country on Earth.

As of mid-September 2026, flights have resumed and the alert level remains elevated but stable. Indonesian authorities say they will continue monitoring the volcano around the clock using seismometers, tiltmeters and satellite imagery. For the millions of people who live within sight of the volcano, however, the eruption is a vivid reminder that beneath the calm tropical waters of the Sunda Strait, one of the most volatile geological systems on the planet continues to stir.

Questions 1–5

Choose the correct letter, A, B, C or D.

1. The original 1883 Krakatoa eruption is notable because it

   • A. created the island of Anak Krakatau.
   • B. was possibly the loudest sound in human history.
   • C. killed more than 400 people instantly.
   • D. lasted only a few hours.

2. When did Anak Krakatau first appear above sea level?

   • A. 1883
   • B. 1927
   • C. 1928
   • D. 1930

3. The 2018 event at Anak Krakatau was caused by

   • A. a powerful earthquake in Sumatra.
   • B. a flank collapse and resulting tsunami.
   • C. a thermal explosion beneath the crater.
   • D. a landslide on the opposite coast.

4. How high did the ash plume reach west of the volcano in September 2026?

   • A. 20,000 feet
   • B. 30,000 feet
   • C. 50,000 feet
   • D. 130,000 feet

5. What proportion of the world's active volcanoes lies within the Ring of Fire?

   • A. About one half
   • B. About two thirds
   • C. About three quarters
   • D. About 90 percent

Questions 6–10

Do the following statements agree with the information given in the passage?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

6. The 1883 Krakatoa eruption ejected less than 10 cubic kilometres of material.
7. Anak Krakatau grows by roughly seven metres each year.
8. The September 2026 eruption caused more than 400 fatalities.
9. The 2026 eruption forced the closure of eight airports.
10. Indonesia has the largest number of active volcanoes of any country.

Questions 11–13

Complete the sentences below. Choose NO MORE THAN TWO WORDS from the passage for each answer.

11. The volcanic island lies between the Indonesian islands of Java and ____________.
12. The 2018 tsunami followed a sudden ____________ of the island's south-western flank.
13. Authorities monitor the volcano using seismometers, tiltmeters and ____________.

Answers

1. B — "described by some scientists as the loudest sound ever recorded by modern humans."
2. C — "It broke the surface in 1928."
3. B — "a sudden collapse of the island's south-western flank triggered a tsunami."
4. C — "as high as 50,000 feet to the west."
5. C — "roughly 75 percent of the world's active volcanoes."
6. FALSE — The passage says 25 cubic kilometres, not less than 10.
7. TRUE — "growing at a rate of around seven metres per year."
8. NOT GIVEN — Fatalities mentioned refer to 2018; 2026 deaths are not stated.
9. TRUE — "forced the closure of eight airports across Java and Sumatra."
10. TRUE — "Indonesia alone has more than 130 active volcanoes — more than any other country."
11. Sumatra
12. collapse
13. satellite imagery

Key Vocabulary