These Rocks Are Petrified Lightning

TL;DR

Fulgurites are glass tubes formed when lightning melts rock or sand, and scientists use them to reconstruct ancient climates like the once-wet Sahara.

Key Points

• 1.Fulgurites form in milliseconds when lightning superheats the ground. Strikes carry up to one billion volts and 30,000 amps, instantly melting rock or sand into hollow glassy tubes — cooled too fast to form crystal structures.
• 2.Their shape, size, and chemistry depend entirely on local conditions. Fulgurites can be hand-sized or over 5 meters long (the record, found in Florida); they branch or curve based on soil moisture conductivity, and are often made of fused silica glass called lechatelierite.
• 3.Saharan fulgurites across 50,000 km² of Niger all date to ~15,000 years ago. Today that region gets under 20mm of rain annually, but the ancient lightning strikes indicate frequent thunderstorms, supported by evidence of soils and lakes, suggesting the tropical Sahel monsoon extended ~650 km farther north.
• 4.Air bubbles trapped in Libyan fulgurites contain CO₂ with a plant-ecosystem fingerprint. This confirms a wetter 'African Humid Period' during the Holocene, linked to orbital changes — Earth's axial tilt and elliptical orbit aligned to intensify summers and push tropical climate zones northward.