These Rocks Are Petrified Lightning

Geologists study fulgurites, or "petrified lightning," which are rocks formed instantaneously by lightning strikes. Lightning, occurring 45 times per second globally, involves charged particles in clouds and on the ground. When these charges connect, up to a billion volts and 30,000 amps flow for less than a quarter-second, heating the ground by thousands of degrees. This melts rock, which then rapidly cools into a glassy, hollow tube called a fulgurite. Fulgurites vary in size, shape, and chemical composition based on the strike's location and ground makeup. They can be a few centimeters to over 5 meters long, with shapes determined by the lightning's path through the ground. Their chemical makeup reflects the local soil or rock, often containing fused grains and silica glass (lechatelierite) in sandy areas, but differing in limestone. These formations are crucial for paleolightning studies, helping researchers determine past weather and climate conditions. For example, fulgurites in the Saharan desert, dating back 15,000 years, indicate a much wetter climate during the Holocene's "African Humid Period." Air bubbles trapped within fulgurites from Libya show atmospheric compositions consistent with active plant ecosystems, suggesting the Sahel's wet climate extended 650 kilometers further north than today. This shift in climate zones is linked to Earth's orbital changes, making summers more intense and expanding tropical zones.