The eruption of the Krakatoa volcano in 1883 was heard thousands of kilometers away due to the phenomenal force of the eruption, which sent shock waves through the atmosphere, spreading over long distances and being amplified by the different atmospheric layers.
The eruption of Krakatoa in 1883 was incredibly violent, one of the fiercest in recent history. In just a few hours, the explosion released a power equivalent to about 13,000 times that of the atomic bomb dropped on Hiroshima. The volcano propelled tons of ash, rocks, and scorching gases several dozen kilometers into the atmosphere, sending a massive shockwave around the globe. The entire island literally collapsed, swept away by the force of this titanic explosion. It is this extreme and sudden devastation, releasing a phenomenal amount of energy in a very short moment, that largely explains why the sound was audible thousands of kilometers away, even in Australia.
During an explosion as intense as that of Krakatoa, very powerful sound waves propagate in all directions at a speed of about 1230 km/h, which is approximately the classic speed of sound in air. When the initial energy released is colossal, these sound waves can travel thousands of kilometers without significantly losing intensity. Even though a large amount of sound energy obviously dissipates along the way, some remains strong enough to be distinctly heard at impressive distances, exceeding 4000 kilometers in the case of Krakatoa. These waves easily travel through the air in the form of pressure variations, pushing and pulling air molecules in front of them like a gigantic invisible shock wave. The more violent an eruption is, the more intense and lasting this phenomenon becomes, explaining why populations located far from the eruption site were able to distinctly hear a sound comparable to that of a cannon fire.
The warm air expelled by the Krakatoa eruption rose very high into the atmosphere and encountered colder air layers below. This unusual temperature inversion — known as a thermal inversion — acts like a true acoustic mirror that reflects sound back to the ground rather than allowing it to escape into space. Because of this, sound waves were guided over vast distances, bouncing between these layers of air with varying densities like a ping-pong ball between two surfaces. Other atmospheric phenomena present at the time, such as fast jet streams, further facilitated the sound by channeling it even farther than is usually possible. All of this combined made the explosion clearly heard thousands of kilometers away from the volcano.
When the very powerful sound wave emitted by the eruption of Krakatoa propagated, it encountered solid ground, the surface of the sea, and various atmospheric layers. Upon hitting these obstacles, part of the sound waves was reflected, dispersing in other directions or bouncing upward and then back down further away, particularly between the ocean and certain atmospheric layers. These effects, combined with rare phenomena of acoustic resonance (a kind of amplification due to the waves adding together as they overlap), allowed the sound to travel impressive distances. One can easily imagine these sound waves bouncing from one atmospheric layer to another, traveling farther than they would have in a straight line. It's somewhat like the sound continued its path by making a series of giant skips, significantly extending its range.
Following the eruption of Krakatoa, volcanic ash caused spectacular sunsets around the world for several years, notably inspiring the artist Edvard Munch in his famous painting The Scream.
The energy released during the eruption of the Krakatoa volcano is equivalent to approximately 13,000 times the power of the atomic bomb dropped on Hiroshima in 1945.
The Krakatoa disaster in 1883 not only generated sounds audible thousands of kilometers away, but also triggered an atmospheric shockwave detected by barometers all around the planet multiple times.
The considerable amount of ash expelled by Krakatoa caused a temporary decrease in the average global temperature of about 0.5 to 1°C during the five years following its eruption.
Although other volcanoes such as Tambora in 1815 or Mount St. Helens in 1980 had powerful eruptions, none produced an audible noise at such a distance as that of Krakatoa. This makes the eruption of 1883 a unique sound phenomenon in contemporary history.
Scientists were able to estimate the sound intensity based on historical accounts from various points around the globe, the study of the atmospheric shockwave recorded by barographs at the time, and modern theoretical calculations based on the physics of acoustic waves.
The noise produced by the Krakatoa explosion in 1883 was heard up to 4,800 km away, making it one of the most powerful sound events ever recorded.
A sound wave is an acoustic disturbance that propagates through a fluid like air, while a shock wave is a wave that carries much more energy, traveling faster than sound and capable of causing significant damage. The eruption of Krakatoa generated both sound waves (audible) and an atmospheric shock wave measured by instruments.
The eruption of Krakatoa in 1883 caused a temporary global cooling due to the ashes projected into the atmosphere. It also generated devastating tsunamis that killed over 36,000 people and produced spectacular sunsets observable worldwide for several months.
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