Scream out loud, as loud as you possibly can. Did someone hear you about a mile away? Nope! Then you’re not loud enough. Imagine all the possible sounds that can travel farther than your voice — a rumbling engine, thunderbolt, nuclear explosion, and of course, a boar screaming. Sounds loud, right? But there’s an exceptional sound that surpasses all sounds, a volcano. Certainly, you didn’t hear the volcanic eruption of Krakatoa in 1883 — that’s the loudest sound ever recorded.
The Krakatau Volcano
Talking about volcanoes, Indonesia has a host of the world’s most active volcanoes. Krakatoa, or Krakatau in Indonesian, is a small volcanic island, or geologically, a caldera — a large volcanic crater formed by a major eruption — in the Sunda Strait between the islands of Java and Sumatra in the Indonesian province of Lampung.
It’s part of the Indonesian Island Arc. This volcanic activity is due to the subduction of the Indo-Australian tectonic plate as it moves northward toward mainland Asia. The island is about 9 kilometers wide and 5 kilometers long (3 miles wide and 5.5 miles long).
Krakatoa and the two nearby islands, Lang and Verlatan, are remnants of a previous large eruption that left an undersea caldera between them. This island is one of the most active volcanic regions in the world, which recorded the world’s most devastating volcanic eruptions in all of history.
The Volcanic Detonation
In May 1883, the captain of the Elizabeth, a German warship, reported seeing clouds of ash above Krakatoa. He estimated them to be more than 9.6 kilometers (6 miles) high above the peak. Over the next two months, commercial vessels and chartered sightseeing boats frequented the strait and reported thundering noises and incandescent clouds.
People on nearby islands held festivals celebrating the natural fireworks that lit the night sky. Unfortunately, celebrations would come to a tragic halt on August 27. The eruption of Krakatoa in the then Dutch East Indies (present-day Indonesia) occurred in the afternoon of Sunday, August 26.
The initial blast sent a cloud of gas and debris at an estimated 24 kilometers (15 miles) high into the air above Perboewatan. It is thought that debris from the earlier blast must have plugged the neck of the cone, allowing pressure to build in the magma chamber.
This triggered four more tremendous explosions in the morning of Monday, August 27, and was heard as far away as Perth, Australia, about 4,500 kilometers (2,800 miles), which plunged both Perboewatan and Danan into the caldera below the sea. Over 70 percent of the island and its surrounding archipelago collapsed into a caldera.
Additionally, seismic activity was reported to have continued until February 1884, though reports of seismic activity after October 1883 were later dismissed upon further investigations into the eruption. The Krakatoa eruption in 1883 was one of the deadliest and most destructive volcanic events in recorded history.
That’s More Than Hiroshima And Nagasaki (Combined)
The initial explosion ruptured the magma chamber and allowed seawater to contact the hot lava. As a result, it caused what is known as a phreatomagmatic event. The water flash-boiled, creating a cushion of superheated steam that carried the pyroclastic flows up to heights of 40 kilometers (25 miles), at a velocity of 100 kilometers per hour (62 miles per hour).
The eruption has been assigned a magnitude of 6 on the Volcanic Explosion Index (VEI), and it is estimated with an explosive force of nearly 200 megatons of trinitrotoluene (TNT). In comparison, the nuclear bomb that devastated both Hiroshima and Nagasaki had an explosive force of 40 kilotons — nearly ten thousand times less explosive than the Krakatoa eruption.
The pressure wave generated by the colossal explosion radiated out from Krakatoa at a velocity of 1,086 kilometers per hour (675 miles per hour). The eruption was estimated to have reached 310 decibels, loud enough to be heard clearly 5,000 kilometers (3,100 miles) away.
It was so powerful that it ruptured the eardrums of sailors 64 kilometers (40 miles) away on ships in the Sunda Strait, and caused a spike of more than 8.5 kilopascals (2.5 inHg) in pressure gauges attached to gasometers in the Batavia gasworks 160 kilometers (100 miles) away — sending them off the scale.
The pressure wave was recorded on barographs all over the world. Several barographs recorded the wave seven times over five days: four times with the wave traveling away from the volcano to its antipodal point, and three times traveling back to the volcano. Hence, the wave rounded the globe three and a half times.
The eruption hurled debris into the atmosphere an estimated 45 cubic kilometers (11 cubic miles), darkening skies up to 442 kilometers (275 miles) away from Krakatoa. In the immediate vicinity, the dawn did not return for three days. The ash was propelled to an estimated height of 80 kilometers (50 miles) and fell as far away as 6,076 kilometers (3,775 miles) landing on ships to the northwest.
The eruptions diminished rapidly after that point, and by the morning of August 28, Krakatoa was silent. Small eruptions, mostly of mud, continued into October 1883. By then, less than 30 percent of the original island remained.
The Devastating Aftermath
The Krakatoa eruption was about ten times more explosive than the Mountain St. Helens eruption of 1980 with a VEI of 5. Tephra (volcanic rock fragments) and hot volcanic gases overcame many of the victims in western Java and Sumatra, but thousands more died as a result of thermal injury from the blasts, and the tsunamis that followed.
Tidal waves created by the volcano’s collapse rose nearly 37 meters (120 feet) high above sea level. Inhabitants of the coastal towns on Java and Sumatra fled toward higher ground, fighting their neighbors for toeholds on the cliffs. One hundred sixty-five coastal villages were destroyed. The official death toll recorded by the Dutch authorities was 36,417.
For the next 13 days, a layer of sulfur dioxide and other gases began to filter the amount of sunlight able to reach Earth. The atmospheric effects made for spectacular sunsets all over Europe and the United States. Additional significant effects were also felt worldwide in the days and weeks afterward.
The average global temperatures were as much as 1.2 degrees cooler for the next five years. The combination of pyroclastic flows, volcanic ash, and tsunamis associated with the Krakatoa eruptions had disastrous regional consequences.
The Child Of Krakatoa
In 1927, some Javanese fishermen were startled as a column of steam and debris began spewing from the collapsed caldera. Krakatoa had awakened after 44 years of calm. Within weeks, the rim of a new cone appeared above sea level.
Within a year, it grew into a small island, which was named Anak Krakatoa, or Child of Krakatoa. Anak Krakatoa has continued to erupt periodically, although mildly and with little danger to the surrounding islands. The last eruption was on March 31, 2014. It registered a VEI of 1.
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Written by: Nana Kwadwo, Fri, Feb 01, 2019.