Postcards from Krakatau

Dear Reader,

With so much grim news from around the world, I haven’t heard much about the eruption of Krakatau, or Krakatoa, earlier this month. Krakatau is among the world’s better-known volcanoes, listed alongside Japan’s Mt. Fuji, Italy’s Mt. Vesuvius or Mt. Etna, and Hawai’i’s Kīlauea. Yet it isn’t just the cataclysmic eruptions that have sealed Krakatau’s reputation among fiery giants — its explosive history has taught us so much about tectonic and natural history processes, as well as inspired art and literature.

I’ve written about Indonesia’s volcanoes before, and looked at how volcanoes have inspired the English language:

• Volcano Trails, Indonesia

• Landscape Lexicon: Volcanoes

In this edition, I want to retrace Krakatau’s influence far beyond the archipelago nation of Indonesia, as a series of postcards through time. We’ll briefly look at how this tiny volcano has shaped not just its own topography through violent outbursts, but also inspired fiery art and literature in places as far away as Norway and England, and shaped our understanding of island biogeography and evolution.

The Latest Eruptive Chapter - 5th September 2026

Plumes of ash and volcanic gases drift westwards from the tiny island of Krakatau, captured by infrared imaging on 5th September, 2026. Image credit: NASA Earth Observatory/Michala Garrison.

Since June this year, Anak Krakatau, located in the Sunda Strait between the islands of Sumatra and Java in Indonesia, has seen a seismic uptick. Satellites picked up thermal signals, and a few gases escaped — the slumbering giant was astir! Through July, moderate eruptions continued, with daily outbursts like a child throwing a tantrum and ash clouds reaching 100–400 meters (~330–1,300 feet). On 4th September, from 5 pm to around midnight, an explosive, spectacular eruption sent a towering fountain of lava for hours, with an ash column rising to 15 kilometres (9 miles) high.

The following day, satellite images showed not just the trail of smoke floating over the Indian Ocean, but also the island's shape changing. Over the next few days, authorities warned residents near and far to mask up and stay indoors, and suspended air traffic across eight airports, grounding over 3000 flights. Between 6th-11th September, 14 Strombolian eruptions — mild blasts with a Volcanic Explosivity Index between 1-2 — were recorded. Since then, volcanic activity has slowed, but Krakatau remains an active, erupting volcano, with a high alert level in place.

🌊 Sunda Strait Tsunami - 22 December 2018

On 22 December 2018, between noon and six in the evening, 423 eruptions were recorded at Anak Krakatau — a sign of something cataclysmic unfolding. At around nine in the evening, the volcano erupted. The eruption was so violent that the volcano's southwestern flank broke off and fell into the sea, triggering a giant tidal wave, or tsunami, of 13.4 metres (44 ft), later known as the Sunda Strait tsunami.

Captured more than a month after the December 2018 eruption, this image shows a deformed Anak Krakatau trailing sediments. Image Credits: Sentinel Hub.

The 1929 ashy plume is typical of the shallow explosions that marked the submarine birth of a new volcano, christened Anak Krakatau. Image Credits: Photo by C.E. Stehn, 1929 (courtesy Volcanological Survey of Indonesia), CC BY-NC.

The Birth of Anak Krakatau - June 11, 1929

After forty-four years of dormancy, some underwater activity was detected at the caldera or depression of Krakatau. On 29 December 1927, jets of water and ash erupted along the Sunda Strait from depths of 180 meters; these eruptions continued, building a new wall that finally breached the surface as a new island. Nicknamed ‘Anak Krakatau,’ or the child of Krakatau, perhaps with the hope that it would be less explosive than its parent, it was officially designated on 11th June 1929. After that, it grew at an alarming pace of 5 to 9 meters (16 to 30 feet) per year, till another collapse in 2018. Since then, the pace has decreased, yet the volcano continues to expand.

🌋 Krakatau goes Kaboom - 27 August 1883

After the 1883 Krakatau volcano, an English artist, William Ascroft, was commissioned by the Royal Society of London to paint the spectacular skies, tinted by ash and sulphur dioxide. As the event occurred years before colour photography was invented, this painting, among 300 others, bears witness to the post-Krakatau sunsets. Image Credits: Public Domain.

Krakatau’s 1883 eruption ranks among the fifth most explosive in the Earth’s history. The other contenders, Mt Toba and Tambora on Sumatra and Sumbawa islands of present-day Indonesia, Taupo in New Zealand, and Katmai in Alaska, erupted well before known or surviving records of human history. The Krakatau supervolcano was recorded by geologists and climatologists, captured by global news agencies, painted by artists, and written about in poems!

Halfway across the world, an English poet, Gerard Manley Hopkins, wrote about the burnished post-Krakatau skies, as did other poets like Algernon Swinburne, Robert Bridges and Alfred Tennyson. In London, William Ascroft rendered 300 works of fevered skies, and in Oslo, Edvard Munch drew inspiration for his expressionist masterpiece, The Scream. Richard Hamblyn’s article, The Krakatau Sunsets in the Public Domain Review, captures these inspirations beautifully.

This watercolour study titled ‘Hereroland’ was painted by Pechuël-Loesche on 4th September 1884, in present-day Namibia. It was included in a book by German physicist Johann Kiessling, who wrote about the twilight phenomena caused by the atmospheric-optical disturbances after the Krakatau eruption. Read Adam Green’s ‘Studies on Twilight Phenomena, after Krakatoa (1888).’

During the explosion, the volcanic peaks of Perbuwatan, Danan, and Rakata collapsed, triggering 30-meter tsunamis that claimed over 36,000 lives. The explosion's sound was recorded as far as 4,800 km (3,000 mi) away. For months after, the ashy aftermath resulted in fiery sunsets and hazy, blue moons worldwide. Beneath the Sunda Strait, a massive hollow magma chamber yawned open — 44 years later, Anak Krakatau would rise from these depths.

🕷️ The lone spider at Rakata - May 1884

When Krakatau erupted, biologists were discussing whether volcanic eruptions obliterate or sterilize life, or if some species cling on. In May 1884, when the first researchers surveyed the islands, they found a lone spider on the Rakata island. Since then, we’ve learned that spiders have a penchant for ‘ballooning’ — they toss silk threads into the air and can be carried aloft for great distances. The discovery of the lone spider sparked studies on how isolated islands are colonised. In the months that followed, other expeditions to the islands observed how life takes root, the waves of colonizing species, and a few extinctions that eventually create a complex ecosystem.

I’ve written about Krakatau and volcanoes’ role in shaping island biogeography before.

Studies of species recolonisation on Krakatau allowed Robert MacArthur and E.O. Wilson to test their theory of island biogeography, which accounts for waves of immigration and extinction that create unique, new habitats.

📖 Book Recommendation