Mount Anak Krakatau and the Sunda Strait Tsunami
One afternoon, June 29, 1927, nearly 95 years have passed since the cataclysmic eruption of its mother, Mount Krakatoa. A fisherman pulling a net after a long day of paddling, witnessed something extraordinary and unexpected.
With a rumble, enormous waves of gas suddenly rise to the surface of the sea. The bubbles, in strange and random combinations, appeared everywhere, surrounding the boat. The fisherman was confused and scared. The bubbles exploded, spitting out ash and a foul-smelling sulfur gas.
The bubbles, according to journalist Simon Winchester in Krakatoa: When the World Exploded, 27 August 1883, were the first indications on the surface that a new volcano lurking deep in the ocean floor was trying to establish itself.
Its growth is so fast and its activities change. In addition to the bubbles that became more violent, black foam, steam, rock, and even flames appeared. Finally, on January 26, 1928, the volume of bubbles and flames turned to solid ash and rock, and came to the surface: a new, curved thin layer of land appeared for the first time above sea level. The new land grew, black and sickle-like, until it finally formed an island.
The number of explosions is getting bigger. On February 3, 1928 no less than 11,791 explosions for 24 hours. Even the number increased on June 25, 1928 to reach 14,269 explosions or about ten explosions per minute for a day and a night.
The first researcher to observe the birth of the new mountain was a Russian geophysicist, WA Petroeschevsky. Later he came to build a bunker of cast concrete and iron on Panjang Island to observe the activity of the new mountain.
"He gave him a name that still sticks with him today: Anak Krakatoa," Simon wrote
According to Simon Petroeschevsky's observation post proved invaluable for monitoring Child Krakatoa's development: it grew from a baby 20 feet tall and half a mile long, started life in 1930, to a peak 500 feet high and a mile long and a mile wide in 1950, and now became a monster island 1,500 feet high and two craters.
On maps of the area, Simon continued, hydrographers from various navies changed the island's markings from "blue" dots meaning "new, temporary, and uncertain" to "dark black" meaning "established, permanent, and settled."
"It has always been an extraordinarily active volcano, one that has grown rapidly and unstoppably since its birth," Simon wrote.