Marilyn makes things prominent

Your generosity continues to impress me. Courtesy of Jonathan, Gib, Chris, Adam (who's recently completed a cross-channel charity swim), Paul, Alex and Nini, our fundraising is now into distinctly tartan territory. Not counting Gift Aid, we are about a metre shy of the summit of Beinn a' Bhùird, a Munro in the Cairngorms and the 11th highest mountain in Britain.

The Munros, as you may know, are the mountains in Scotland with a height of over 3000ft, named for a list drawn up by Sir Hugh Munro. I should qualify that by saying that we are talking about absolute height here - that is, the height of the summit above sea level. But that isn't the only measure of height that mountaineers care about. They also deal in the currency of prominence (or relative height).

Prominence is measured by looking at how far you would have to descend before you could start climbing to a higher peak. If that sounds a bit esoteric, we can make it more concrete by thinking about the South Summit of Everest. At 8.,749m, it's actually the second highest summit on Earth - and yet it's not on many people's lists of mountains to climb and the first people to reach it aren't much remembered [1]. The reason is that the summit itself stands only about 10m clear of the southeast ridge. You could probably walk out of your front door right now and find a hill with more prominence in a few minutes. Even if you live in Norfolk. 

So, prominence matters to mountaineers, and sufficiently that they have all sorts of lists drawn up around it. There is a list of British mountains with a prominence of at least 150m. They are known as the Marilyns, which tells you a lot about mountaineers' sense of humour. 

One consequence of thinking of mountains in terms of prominence is that the list of most prominent mountains is very different from the list of highest mountains. All of the world's really big mountains are part of a group of ranges forming a giant C shape around the Tibetan plateau, and so the "key cols" that you have to descend to before you can start your next ascent tend to be quite high in their own right. Prominence lists tend to prioritise mountains on islands, or the highest points on each continent. K2 is only the 22nd most prominent mountain. Aconcagua, by virtue of lording it over the Americas, is the second most prominent peak. 

Sorry about that. I'd intended the prominence discussion to be a brief intro to talking about the kit you need for this sort of expedition, but clearly my British male obsession with statistics has taken over once again. And now it's late, and I have an early flight, so you'll have to wait until next time to hear about size 13 boots, crampon extenders, and why they are a real headache for my baggage allowance.

[1] It was Charles Evans and Tom Bourdillon, who reached it as part of the first summit attempt by the 1953 expedition that put Hillary and Tensing on the main summit.