On August 27, 1883, the volcanic island of Krakatoa exploded with the force of 200 megatons of TNT, producing the loudest sound in recorded history. While the shockwave circled the globe four times, a far stranger phenomenon unfolded roughly 100 miles away in Batavia (modern-day Jakarta). Telegraph operators working for the Dutch East Indies government suddenly found their instruments behaving erratically.
Without any battery power connected, the telegraph needles violently deflected, keyers sparked uncontrollably, and submarine telegraph cables overheated to the point of near-combustion. The cataclysmic eruption sent massive plumes of ash, ionized gas, and pyroclastic debris high into the stratosphere, generating intense atmospheric electricity and massive ground currents known as telluric currents. As the massive atmospheric pressure waves rippled outward at near the speed of sound, they caused violent electrostatic discharges along suspended telegraph lines and underwater communications cables.
In Batavia's central telegraph office, bewildered operators had to completely disconnect their apparatuses as the brass equipment grew too hot to touch and lines hummed with ghost electricity. The eruption effectively converted thousands of miles of telegraph wire into giant antennas capturing the raw, terrifying electromagnetic energy of the earth tearing itself apart. It remains one of the earliest documented instances of a volcanic event generating a localized geomagnetic storm powerful enough to melt human communications technology.