Lightning
Lightning protection in cities, especially in the high-income countries, is so effective that many of the inhabitants forget that lightning is a hazard at all. But Earth’s surface is actually struck by more than 300 million bolts of lightning each year, causing grass, brush and forest fires every day. The spread of lightning risk is uneven – the northernmost parts of Europe, Asia and North America have less than 5 lightning days a year, northern Europe has 20–30 lightning days, the Mediterranean area 30–50, and the equator area 150–250. The number of lightning strikes in a certain area is partly determined by average temperature, but also by other factors, such as altitude. Quito in Ecuador—located 2850 meters above sea level—has more than 300 lightning days a year.
Lightning has set most cities in the world on fire at some time or other, and many have burned completely to the ground, such as Worms in Germany. Countless tall buildings—towers, churches, minarets, mosques, Buddhist and Hindu temples—have been destroyed by lightning-induced fire.
Among the victims of lightning we can find emperors and kings, bishops and generals, ship captains and mountaineers. About ten thousand people a year are struck by lightning, the majority of which survive without permanent injury. The number of animals killed is in the millions. In the United States and Brazil (large countries with good statistics) we find that 200 people a year are killed by lightning, in Europe less than 100 in each country but usually—like in Finland, Sweden, Norway and Denmark—less than 10. A hundred times more people are killed in traffic.
Lightning is attracted to the highest point in an area and to metal. Golfers are at risk, as are soccer players, referees and spectators in small and medium-sized stadiums without lightning rods. Long metal rails are very dangerous during thunderstorms. All outdoor sporting activities including horseback riding should be interrupted when there is a risk of lightning.
If you see a bolt of lightning strike a beach and decide to bring a shovel to excavate the spot, you will see immediately how we can calculate lightning patterns for past times. A hollow tube with glass lining its inner surface is formed when the sand melts. The tube, known as a fulgurite, is usually a centimeter wide and a few decimeters long, but can be up to 4–5 cm wide and extend up to a few meters down.
Sand melts at 1800° C. The energy in a bolt of lightning is equal to the energy of the Hiroshima bomb, and although the discharge happens within a thousandth of a second the temperature can reach almost 30 000° C and a huge explosive force can be produced. When lightning strikes a mountain peak it melts the rock, which will shine like glass, like the original tops of the pyramids were known to shine.
Our database TRITON has details on thousands of particularly important lightning events. We recommend that anybody moving to a warmer climate or to a mountainous area check the frequency of lightning there.