Australia

In 1991, geologists discovered a subterranean electrical current in Australia, the longest in the world, which passes through more than 3,700 mi (6,000 km) across the Australian outback. The current is conducted by sedimentary rocks in a long horseshoe arc that skirts a huge mass of older igneous and metamorphic rock comprising most of the Northern Territory. It begins at Broome in Western Australia near the Timor Sea and then dips south across South Australia before curling northward through western Queensland where it terminates in the Gulf of Carpenteria.

A side branch runs from Birdsville in South Australia near the Flinders Ranges into Spencer Gulf near Adelaide. Geologists say the current is induced by the Earth's ever-changing magnetic field and that it runs along fracture zones in sedimentary basins which were formed as the Earth's ancient plates collided. Although the fracture zones contain alkaline fluids that are good conductors of electricity, the current is weak and cannot even light a lamp. Geologists say the current might provide clues to deposits of oil and gas and help explain the geological origins of the Australian continent.