The Geology of Choosing Your Race

This fun blog brought to you by Team TriSports athlete Liz Miller (who also happens to be a geologist). Follow her on Twitter – FeWmnLiz.

What factors do you consider when signing up for races? How close the race is to where you live? Or whether the race destination would also make for a good vacation? Most triathletes like to plan and give careful consideration to every race that we sign up for, but sometimes even the best-laid plans can get sidetracked. Just in 2012, the Oschner Ironman 70.3 New Orleans swim was cancelled due to unsafe water conditions, and the bike course at Boise 70.3 was shortened to just 12 miles due to SNOW on the course (in June!). Some of the pro men even rode in their wetsuits, due to the 47 degree air temperature! But the chance of cold weather or choppy water isn’t the only thing that you should consider when signing up for your next race. I’d like to propose another factor to consider – geology! I know this is a triathlon blog, but how about we “switch gears” and talk some science.

I should preface this blog post by pointing out that geology has indeed affected some Ironman races in the past. Just 6 days before the 2006 Ironman World Championship race in Kona, a magnitude 6.9 earthquake struck the island. Reports say that in the days before the earthquake hit, Kona was unusually hot and humid, and in the days after the earthquake, the area got slammed with torrential downpours. On the day of the race, skies were overcast and winds were light – a beautiful day for racing. But, at about 7:20 PM, a torrential downpour happened on Ali’i Drive. Some athletes had to wade through knee deep water just to make it to the finish line. Within an hour the downpour had stopped and the water receded. So earthquakes really can affect your race, even if the quake doesn’t actually happen on race day!

Now, in order to determine which races are safer (geologically speaking), we need a quick geology introduction. The Earth’s outer shell is made up of plates which are constantly moving. Most geologic activity occurs as a result of the interaction between these plates. There are three types of plate boundaries:

1. Convergent boundaries are boundaries where plates collide. At these boundaries, plates are colliding to form mountain ranges, or one plate is diving down beneath the other plate in a process called subduction.

2. Divergent boundaries are boundaries where two plates are moving away from each other. Magma can rise to the surface at divergent boundaries, forming new crustal material.

3. Transform boundaries are boundaries where two plates slide past each other. As the plates slowly move past one another, pressure builds until the plates rupture in one big movement, causing an earthquake. The San Andreas fault in California is a transform boundary and is responsible for the frequency of earthquakes in California.

Here’s the United States Geological Survey’s simplified map of plate tectonics; the red arrows indicate plate direction. Arrows pointing towards each other represent convergent boundaries; arrows pointing in opposite directions represent divergent boundaries; arrows that are side-by-side represent a transform boundary.

The other geologic hazard that should be considered before registering for a race is hot spots – the kind formed by liquid hot magma, not the painful ones on your feet at the end of a marathon. Hot spots are areas where magma is able to make its way up to the surface and form volcanic features. The Hawaiian Islands are one of the best known examples of hot spot volcanism – these islands have formed as the Pacific Plate moves over the Hawaiian hotspot. AND hot spots can also experience seismic activity.  In the image below, the Hawaiian Island chain is visible in the center of the picture; this chain has formed as the Pacific Plate has slowly moved over the Hawaiian hot spot.

Now, let’s compare the geologic maps to TriMapper’s map of Ironman races around the world.

The Australian races are probably safe. Australia sits on a large plate of its own, and the plate boundaries are a significant distance from the continent itself. Ironman New Zealand could be problematic – the plate boundary runs right through the north and south islands! The earthquake that hit Christchurch in 2011 was in February, and Ironman New Zealand is typically early March. Japan is also at risk, since it is located on a plate boundary. In 2011, a very large earthquake hit Japan, causing tsunamis, structural damage, and a nuclear release. I wouldn’t want to be racing in that environment! Additionally, Japan has historically had some of the largest earthquakes, causing the most damage and casualties.

Most of the North American races are in the clear, except for Ironman Canada – Whistler is located near the triple junction of the North American plate, Juan de Fuca plate, and Pacific Plate.

The Ironman races in Mexico aren’t looking too promising – Cabo San Lucas is near the triple junction of the North American plate, Cocos plate, and Pacific plate, and Cozumel sits pretty close to a plate boundary too. In fact, the United States Geological Survey calls Mexico one of the world’s most seismically active areas. But further to the south, Ironman Brazil looks to be in the clear, since Brazil is located near the center of the South American plate.

Ironman South Africa and Lanzarote are both centrally located on the African plate and are probably safe bets.

Some of the European races might be a little risky – Ironman Wales and UK are probably far enough away from a plate boundary, as well as Ironman Kalmar and the Ironman European Championship. But Ironman Switzerland, Austria, and France are getting a little close to the Eurasian and African plate boundary.

So, out of 29 Ironman events worldwide, at least 8 Ironmans are located at or near plate boundaries. That’s nearly 30%! Not to mention the fact that the Ironman World Championship race is located on an island that is still being formed by an active volcano. I certainly won’t complain about making it to Kona one day to race, but in the meantime, I might stick with the North American races (or convince my boyfriend to buy a plane ticket to Australia…).

Here’s a map of all the Ironman 70.3 races – I’ll leave it up to you to figure out which races are safer than others!