The Krakatoa Volcano and Anak Krakatau

The Krakatoa volcano in the Sunda Strait of Indonesia began erupting in 1883. A German ship, the Elizabeth, was sailing past the island and reported seeing a column of smoke and ash rising some seven miles into the sky above the mountain.

The activity continued for the next few months; locals held festivals to celebrate the volcano's rumbling and spewing and occasional fiery bursts. But on August 26, a series of explosions blew the mountain—and the island—apart. Sea water had gotten into the magma chamber, and when it came into contact with the molten lava, it was like cold water hitting a red-hot skillet. The resulting explosion was heard in Sri Lanka, 4,500 miles away; the tsunami it caused rose to 130 feet and killed over 36,000 people. The massive explosion is considered one of the loudest sounds ever recorded on Earth. It was also heard as far as Australia and the island of Rodrigues near Africa. This sound level and reach are almost unprecedented.

The eruption obliterated over two-thirds of the island of Krakatoa and tsunamis devastated coastal towns in Java and Sumatra and some estimates go even higher than 36,000.

The eruption of Krakatoa remains one of the most well-documented volcanic events and serves as a powerful example of how volcanic activity can have far-reaching and long-lasting effects on the world.

The eruption released an enormous amount of volcanic ash and sulfur dioxide into the atmosphere, which spread worldwide. The particles blocked sunlight, causing a global drop in temperatures of about 1.2°C (2.2°F) over the following year. This cooling effect disrupted weather patterns for several years, leading to cooler summers and vivid red sunsets worldwide.

The volcanic ash in the upper atmosphere created striking visual phenomena. People around the world reported vivid red and orange sunsets, and a blue tint was observed in the moon. These changes in sky colors were so widespread and dramatic that they were depicted in paintings of the era, including Edvard Munch’s The Scream, which may have been inspired by the unusual red skies.

Krakatoa’s eruption provided a major case study for scientists to understand volcanic eruptions and their atmospheric effects. It led to advancements in studying tsunamis, volcanic ash dispersion, and atmospheric sciences, influencing fields as diverse as meteorology and climate science.

Krakatoa spawned a volcanic offspring before it blew up. Anak Krakatau, "child of Krakatoa," began to rise out of the sea in 1927. Today, it's about half the size of the original volcano, but it's growing every day. It's been spewing smoke, lava, and molten ash for the last several years.It is an active volcano that continues to erupt periodically.Due to its location within the Pacific "Ring of Fire"—a tectonically active area with frequent seismic and volcanic activity—Anak Krakatau is likely to continue erupting in the future.

In December 2018, a major eruption partially collapsed Anak Krakatau’s cone, triggering a deadly tsunami in the Sunda Strait. This event caused significant damage and loss of life on the coasts of Java and Sumatra.  Anak Krakatau is constantly building itself up with each eruption. This continual growth makes it unstable and prone to landslides or partial collapses, which can cause tsunamis like in 2018. As it grows, it will remain geologically active and vulnerable to explosive eruptions.

The Buried Cities of Pompeii and Herculaneum

Uncovered Pompeii with Mount Vesuvius in the background

It was long believed that August 24 in the year 79 was when Mount Vesuvius erupted. The eruption destroyed the Roman cities of Pompeii and Herculaneum. (The latter city is often left out of the story.)

Pompeii was about five miles away from the mountain. The cities are in what is now Ercolano, Campania, Italy. Pompeii was a popular resort town for Rome's wealthy and the population was about 20,000. Pompeii and Herculaneum are two of the few ancient cities to be preserved nearly intact. The ash and debris that covered the area was up to 23 feet thick in places and that protected it from looting and the elements.

Most of the residents were able to escape when noises from the volcano were heard that morning. At noon, the plume of ash, pumice rock, and debris shot up into the air and began falling on the surrounding area. Pompeii was about 5 miles from the volcano. About 5,000 people died, probably more from a blast of blistering hot, poisonous gas, rather than debris or lava. After debris fell from the initial eruption, there was already about 9 feet of ash in the streets of Pompeii but the rain of ash continued.

Herculaneum lay west of Vesuvius and it was only mildly affected by the first phase of the eruption. While roofs in Pompeii were collapsing under the weight of falling debris, only a few centimeters of ash fell on Herculaneum but it prompted most inhabitants to flee.

Pliny the Younger witnessed the eruption of Vesuvius from across the Bay of Naples, and noted that the billowing soot, rocks, and gas looked like an enormous pine tree eclipsing the sun. He wrote, "Darkness fell, not the dark of a moonless or cloudy night, but as if the lamp had been put out in a dark room."

Though he was safe across the bay, he wrote that "I believed I was perishing with the world, and the world with me."

It is said that the modern science of archaeology was born with the excavations of the two cities which were rediscovered in the 18th century. They were almost completely intact. About one-third of Pompeii is still buried and excavations continue today.

The date of the eruption is now thought to be on or after October 17 based on the excavation clues. For example, people buried in the ash were wearing heavier clothing than the light summer clothes typical of August. The fresh fruit and vegetables in the shops are typical of October and the summer fruit typical of August was already being sold in dried, or conserved form. Wine fermenting jars had been sealed, which would have happened around the second half of October. Coins found in the purse of a woman buried in the ash include one with a 15th imperatorial acclamation among the emperor's titles and could not have been minted before the second week of September.

The 1980–82 excavations in Herculaneum found many skeletons on the ancient beach in front of the city walls in what are called "boat sheds." It had been believed that the majority of the town's inhabitants had managed to flee because so few skeletons had been unearthed. This discovery led to a shift in perspective theorizing that the last inhabitants waiting for rescue by sea were probably killed instantly by the intense heat.

Boat sheds at the shore     Link

Could it happen again? Mount Vesuvius is still active. It last erupted in 1944, and experts believe it could erupt again at any time. But today, about 3 million people live within a few miles of the crater. About 600,000 of them live close enough to the volcano that they would not survive an eruption today. But our technology allows scientists to monitor the volcano continuously and there are plans to evacuate the area well in advance of any detected eruption.

crossposted at Weekends in Paradelle