UKC

Surely, with a prominence of 672m Pen y Fan  should be in the Major Mountains list  but it's not. A mistake I think?

Isn't Pen y Fan 886m?

Yep. Though probably 885m with all the pepole eroding it!!

Pete is talking about prominence not height, a different measurement.

Ah, right. Missed that bit. Doh.

How does prominence work then? Pen y Fan is only about 500m from Corn Du which is 873m, with a bwlch between them at c.850m.

The twin summits of Pen y Fan and Corn Du are apparently counted as one mountain.
Which is news to me. 

Not an expert, sorry. I really only came across the term after walking up Garn Fadryn  on the Lleyn peninsula and being very impressed by its location and command of the surrounding area. ( Height 371 m, prominence 343 m)

Depends whether you're doing the fan dance or not! IYKYK!

https://www.ukhillwalking.com/logbook/ticklists/britains_major_mountains-24... ?

Kitp still looks to be active so I am sure they'd add it in for you.

I think Corn Du might have something to say about that! Seems a bit weird...

I agree, but Wikipedia says that it's counted as one mountain and therefore it's fact...
Maybe the fact that they are so close to each other and with very little altitude change is what makes the difference?

Prominence is the difference between the summit and the lowest contour line that doesn't contain a higher peak. So since Pen Y Fan is higher than Corn Du, Corn Du doesn't affect its prominence but Pen Y Fan would affect Corn Du.

Prominence is the difference between the height of a mountain and the highest point to which you would have to descend in order to reach a higher mountain from it.

Col depth to the next higher peak

Robert was there first so I'll add that Mont Blanc has a prominence 4697m. I'll.let you find the col?

And slightly surprisingly the Matterhorn has a prominence of only 1043m, in the Weisshorn direction.

low point somewhere around tete de Valpelline??

Col Durand, it says here:
https://www.peakbagger.com/KeyCol.aspx?pid=10027

Actually that gives the Matterhorn prominence as 1036m, rather than 1043m which is what Wikipedia has.

Maybe this spoils the game but I was interested and google found the answer for me on this page:

https://en.wikipedia.org/wiki/Topographic_prominence

The tallest hill on an island would be a Major Mountain if there was no other hill with a prominence of 600m. Eg there are two Corbetts on Rum but only one can be a Major Mountain. 

Interesting list, that. Makes you do all sorts of calculations to try and disprove various claims. 😂

I like to consider prominence as a percentage of elevation. 

So Pete's example of Pen Y Fan only achieves a 75% figure whereas my choice of the mighty Garn Fadryn gets an impressive 92% 

There are a couple of other fixes which could be made: the entry for Creag Meagaidh should be  Creag Meagaidh not  Creag Meagaidh - Puist Coire Ardair, and Moel Siabod should be removed as the most recent survey show it sadly lacking just 10cm of prominence.  You can also argue the toss about whether  Snaefell should be in the list or not. 

10cm!! Are cairns counted?

No! The folk who do these surveys will dismantle the cairn to find the highest point and then rebuild it. 

The list is "Britain's Major Mountains", so strictly speaking, The Isle of Man isn't Britain. But then neither are any of the Scottish Islands if we're talking about the island of Great Britain; Britain isn't a political entity.

Seems a shame not to have Snaefell on the list, especially if you've climbed it...

Sorry, ‘Great Britain’ does include the Scottish islands. The political entity is slightly larger again: ‘The United Kingdom of Great Britain and Northern Ireland’. Good map/diagram here:

https://www.britannica.com/story/whats-the-difference-between-great-britain...

Geographically, Great Britain refers to the single main island.
Politically, it also includes all of the islands as well.
As mountains are geographical features, you should logically assume that a list of Great Britain mountains are just those on the main island.
In reality, it would be much better to include all of the mountains.

Of course the Isle of Man isn't in the UK, (and was never in the EU). I was only talking about the hill list "Britain's Major Mountains" which doesn't include Snaefell because, presumably, the IoM isn't British, although, of course,  it is.

This is just the sort of nerdish way we hillbaggers go on. Fun isn't it?