What are fulgurites?

Fulgurites are unique structures that are formed when lightning strikes sandy soil or other siliceous materials. The immense heat generated by the electrical discharge melts the sand, creating a hollow, glass-like tube as the molten material cools and solidifies rapidly. This process is what distinguishes fulgurites from other types of geological formations, as they result specifically from electrical activity in the atmosphere rather than volcanic or biological processes.

The correct choice highlights the precise conditions that give rise to these intriguing natural phenomena, emphasizing the transformative power of lightning on the earth's surface materials. Understanding fulgurites can be important in the field of fire investigation, as their presence can often be linked to locations that have experienced electrical storms or fires ignited by lightning strikes.