When lightening strikes sand, the heat sometimes fuses the sand into long, slender glass tubes called fulgurites
When lightning strikes sand or sediment, the path followed by the bolt can fuse into a glassy tube called a fulgurite
Now, scientists are studying fulgurites in Egypt to piece together a history of the region's climate.
Amid the region's sandy dunes, however, fulgurites are common.
However, the lumps and tubes of glass that litter the region's shifting dunes are proof that lightning, the only source of fulgurites, frequently touched down there in the past.
Because fulgurites are mainly glass, they're chemically stable and aren't very susceptible to erosion, says Barbara Sponholz, a physical geographer at the University of Wurzburg in Germany.
Thus, the first thing one saw on entering the gallery was not the fulgurites themselves but a shelf of "Supplemental Didactics": sixty-six paper booklets, identically bound in drab tan.
McCollum made his "assisted" fulgurites by firing rockets into thunderheads, triggering lightning bolts directed into a special barrel--in effect, forcing lightning to strike in the same place repeatedly.
They found some quite unusual fulgurites
(lightning-generated tubes of fused sand) as well as mineral specimens that were eye-catching.
Some, which resemble fulgurites
, are nearly a meter long, and are believed to have formed in worm burrows in a limey sediment.
In Soviet experiments reported in 1977, laboratory researchers used up to 12,000 volts to vaporize the inner walls of tubes of ice or plastic that served as models of fulgurites
While it seemed a long shot, the team hit pay dirt after sampling glassy lightning-seared rocks - known as fulgurites
- from just five locations.