By Dr. Robert Thorson

Leap-frogging I understand. Leap-yearing I do not, unless it involves seismic tremors created by humans.

I get the concept of adding an extra day to the calendar every four years. Certainly, it’s more convenient to plan three integer-based calendar years with 365 days and a fourth one with 366, than to have four decimal-based astronomical years, each 365.24210 days long.

I get the idea of adding that extra day to the end of February, the runt of the litter of months. But for those of us who live in the mid-latitude Northern Hemisphere, why couldn’t we add an extra day of jubilant July or splendiferous September? For us, taking an extra day of February is like hitting yourself on the head with a hammer composed of black ice and chilling cold rains.

Leaping is something frogs, gazelles, puddle-jumpers and basketball players do quite well. But who or what was leaping in 45 B.C. when Julius Caesar created leap years to keep the seasonal timing of festivals on track? There’s no leaping involved in this metaphorical illusion. What actually happens is that we fall progressively behind before making the necessary correction. Adding an extra day to the year is like adding an extra minute to a race. It pushes us back.

But now there’s hope for a true and meaningful leap year. In February 2006, the national soccer team from the West African nation of Cameroon, the Lions, was playing a home game against the Ivory Coast Elephants. This match was part of a biennial pan-African tournament that qualifies teams for the World Cup.

During overtime, and with the Elephants about to win, Cameroon scored a goal, sending the match into a double-overtime shootout. So excited were the fans that they leapt up and down, creating the best-recorded “leap-quake” of all time.

This story is a case study of scientific serendipity. An unusual line of volcanoes bisects Cameroon from northeast to southwest. To investigate the properties of the crust and upper mantle in this vicinity, seismologists Garrett Euler and Doug Weins from Washington University in St. Louis installed an array of 32 seismometers across the country in January 2006, removing them for analysis in January 2007.

When examining the records, they noted several unusual tremors in February which seemed to violate every rule of seismic science. Instead of propagating outward from an epicenter with a mixture of frequencies, these tremors appeared both instantaneously and incoherently at stations throughout the country.

Baffled, they searched the geophysical archives for plausible causes, to no avail. These earthly vibrations just didn’t seem to make sense.

Luckily, Garrett’s non-seismologist girlfriend, Katy Lofton, did what many of us do each day. She searched on Google using the word Cameroon and the date of the synoptic squiggles. Bingo! A soccer match. A few more clicks revealed that a huge tournament was being played in a country absolutely crazy about the sport, and in which fans have a habit of gathering in throngs around shared television sets. Could celebrating fans leaping in unison set off the seismometers? The answer is yes!

Within a few weeks, the investigation was complete, as recently reported by the IRIS Newsletter (Integrated Research Institutions for Seismology) and the American Geophysical Union. Leap quakes less significant than the one with the overtime goal also occurred when earlier goals were scored. The strength of each was proportional to the importance for the home team. Areas with the highest populations and the best television reception experienced the strongest tremors. The tremors began and ended with the tournament. Case closed.

Had the Cameroonians been sitting in separate houses in cushioned La-Z-Boy recliners with a plates of nachos in their laps, I doubt that we would have learned this fascinating tidbit about a crowd’s ability to make the Earth move.

Perhaps the story of the Cameroonian leap-quakes – like that of Groundhog Day – can inspire a new tradition for making this bleak time of year a bit more fun. I suggest that every fourth year, the world population should simultaneously leap up to excite the Earth, and to give new meaning to the old and confusing term – leap year.