The catastrophic eruption of Krakatoa in August 1883 is renowned for sending shockwaves around the planet four times and darkening global skies. Less known, however, is the bizarre electrical anomaly experienced by telegraph operators in Batavia (modern-day Jakarta), located roughly 100 miles from the volcanic island. Hours before the final apocalyptic blast, undersea telegraph lines connecting Java to Sumatra began behaving erratically.
Operators reported that receiving needles were twitching violently without any human input at the transmitting end. As the eruption reached its peak, vast underwater pyroclastic flows raced across the seabed of the Sunda Strait, burying and superheating the gutta-percha insulation of the submarine telegraph cables. The extreme thermal surge caused the copper wires inside to melt and short-circuit, generating massive atmospheric and ground voltage spikes that fried equipment in the local offices.
Operators in Batavia watched in horror as sparks showered from their telegraph keys, severing real-time communication with the outside world at the exact moment the island disintegrated into the ocean.