July 04, 2020

Simon Winchester: Krakatoa – The day the world exploded:
“It was early on and warm summer’s evening, as I stood in a palm plantation high on a green hillside in western Java, that I saw for the first time, silhouetted against the faint blue hills of faraway Sumatra, the small gathering of islands that is all that remains of what was once a mountain called Krakatoa.”
The second most powerful volcanic eruption in recorded history occurs on Krakatoa, a small, uninhabited volcanic island located west of Sumatra in Indonesia, on this day in 1883. Heard 3,000 miles away, the explosions threw five cubic miles of earth 50 miles into the air, created 120-foot tsunamis and killed 36,000 people.
Krakatau (Krakatoa in Indonesian language) exhibited its first stirrings in more than 200 years on May 20, 1883. A German warship passing by reported a seven-mile high cloud of ash and dust over Krakatau. For the next two months, similar explosions would be witnessed by commercial liners and natives on nearby Java and Sumatra. With little to no idea of the impending catastrophe, the local inhabitants greeted the volcanic activity with festive excitement.
On August 26 and August 27, excitement turned to horror as Krakatau literally blew itself apart, setting off a chain of natural disasters that would be felt around the world for years to come. An enormous blast on the afternoon of August 26 destroyed the northern two-thirds of the island; as it plunged into the Sunda Strait, between the Java Sea and Indian Ocean, the gushing mountain generated a series of pyroclastic flows (fast-moving fluid bodies of molten gas, ash and rock) and monstrous tsunamis that swept over nearby coastlines. Four more eruptions beginning at 5:30 a.m. the following day proved cataclysmic. The explosions could be heard as far as 3,000 miles away, and ash was propelled to a height of 50 miles. Fine dust from the explosion drifted around the earth, causing spectacular sunsets and forming an atmospheric veil that lowered temperatures worldwide by several degrees.
The eruption is estimated to have reached 310 dB, loud enough to be heard clearly 5,000 kilometres (3,100 mi) away. It holds the record for the loudest sound ever heard. It was so powerful that it ruptured the eardrums of sailors 64 km (40 miles) away on ships in the Sunda Strait, and caused a spike of more than 2.5 inches of mercury (8.5 kPa) in pressure gauges 160 km (100 miles) away, attached to gasometers in the Batavia gasworks, sending them off the scale.
In the aftermath of the eruption, it was found that the island of Krakatoa had almost entirely disappeared, except for the southern third. The Rakata cone was cut off along a vertical cliff, leaving behind a 250-metre (820 ft) deep caldera. Of the northern two-thirds of the island, only a rocky islet named Bootsmansrots (Bosun’s Rock), a fragment of Danan, was left; Poolsche Hoed had totally disappeared. The explosion had a force 13,000 times that of the atomic bomb that was dropped on Hiroshima in 1945.
In 1927, a new island, Anak Krakatau, or “Child of Krakatoa”, emerged from the caldera formed in 1883 and is the current location of eruptive activity. This island is receiving a great deal of scientific attention, as it represents a chance to see how island ecosystems are established from scratch.
The explosion of Mount Tambora in the northern part of Sumbawa, one of the Lesser Sunda Islands of Indonesia in 1815, remains the largest ever recorded by humans, ranking a 7 on the Volcanic Explosivity Index, the second-highest rating in the index. The eruption left 100,000 dead.
(Sources: The day the wold exploded, Simon Winchester/Wikipedia/history.com)