The eruption of Krakatoa in Indonesia in 1883 was truly awesome. The sound was, by far, the loudest sound ever recorded; the loudest sound in modern history. It travelled more than 3000 km to central Australia, where it woke up sleeping people, and 4800 km to islands in the Indian Ocean, where they thought there was a gunbattle offshore.
While the eruption itself was awesome, it was the tsunamis that caused all the deaths – so how were these tsunamis formed? Nobody really knows the exact mechanism, since no one was there at the time. One theory is that, after the caldera had been formed, a side of the volcano slumped into the sea, causing the tsunamis. A second theory is that, when the magma chamber collapsed, huge volumes of sea water poured into the space and then slopped out again, causing
the tsunamis. If this last theory is correct, you can recreate your own ‘Krakatoan tsunamis’ in the classroom, as demonstrated by these Spanish students.