Terminology: Height vs Elevation vs Climbing Height vs Prominence

How best to describe and understand how big a mountain is before you climb

May 21, 2019

Quick Summary

Height: The vertical dimension of something from wherever you consider its top and bottom.

Tallness: The distance between the ground and the top of something standing on the ground.

Elevation: The height of something standing – like a building or a mountain – relative to (usually) sea level.

Altitude: The height of something suspended – like a plane or a cloud – relative to (usually) sea level, most commonly estimated by air pressure.

Climbing height: The height one would climb to relative to the height one climbs from.

Prominence: The minimal amount one would need to descend from a peak before being able to ascend a higher peak.

World’s Highest Mountains

Highest mountain on earth by elevation: Mount Everest

Highest mountain by distance from the centre of the earth: Mount Chimborazo

Most prominent mountain on earth: Aconcagua

Most dry-prominent mountain on earth: Mauna Kea

What’s the big deal?

It’s not a great idea to stress out about terminology, but sometimes it can make such a big difference, that we better get it right. Terminology around elevation is one such example.

On Summits.com we will give you what we call the “height” (in metres and feet) of a mountain, because that’s the world people generally use to look it up. But what we really mean by “height,” is actually “elevation.” And a lot of the time, what you really want to know is “climbing height”, which we will usually give you, unless we give you “prominence” instead.

So what gives?! Well, it gets complicated real quick.

To help illustrate the point before we get to the added complexities of mountains, let’s take the Petronas Towers in Kuala Lumpur, Malaysia as an example.

Petronas Towers in downtown Kuala Lumpur.

Height, Elevation, and Altitude

Height

Let’s take the Petronas Towers in Kuala Lumpur, for example. Googling them will tell you that they are 451.9 metres high. That’s the height between the top of the towers and the ground around them. But, does that include the spindly little telephone tower at the top?

And does that include the 5 floors of space the towers go underground?

The point is that height is relative. The upper point is usually known in the case of buildings and mountains, but when it comes to the lower point, we have to ask how high it is “relative to what.” Note: When referring to the height of something relative to the ground, we usually refer to how tall it is.

Elevation

Elevation, however, usually refers to the height relative to sea level. So, given that the Petronas Towers sit on land that’s 56 metres above sea level, you might say that the top of the Petronas Towers have an elevation (above sea level) of 507.9 metres. But of course, they’re not that high. So elevation is a more specific concept to use because it compares height with the widely accepted concept of sea level.

However, sea levels fluctuates with tides, and even with waves and ripples if you want to get pedantic. Most people get that we consider an average sea level globally, but its actually difficult to understand this, or at least measure it, when the sea is thousands of kilometres away and well over the horizon, as is the case for the Himalayas. And of course, we’re living in an era where sea levels are rising, so are mountains shrinking?

Here’s an idea: Let’s instead measure the height of a mountain relative to the centre of the earth. Well, interestingly, the world is not spherical. It’s actually a bit squashed – bulging out towards the equator. Actually, by this measure, Mount Everest is the 10th “highest” peak on earth. Mount Chimborazo in Ecuador has much more land under it, as do 7 other mountains in the Peruvian and Ecuadorian Andes and Mount Kilimanjaro.

Mount Kilimanjaro above the plains of Tanzania.

Altitude

Like elevation, altitude seeks to explain the height of something relative to sea level. But where elevation is usually used to describe the vertical dimension of a standing structure, altitude is usually used to describe the vertical dimension of the lowest point of a structure suspended in the air, usually an aircraft. So we generally wouldn’t talk about the altitude of, say, the Petronas Towers, nor that of a mountain.

Altitude is also usually measured differently. An altimeter estimates altitude based on air pressure. This isn’t a bad idea because air pressure correlates with elevation, but not perfectly. Other variables that affect air pressure, such as the weather, need to be accounted for or they will cause a less accurate measure.

You also might ask “are we measuring the altitude from the bottom of the object or the top?” Well, it’s not clear, but you’re probably not going to have an altimeter so accurate, or an aircraft so high (or should I say tall) that it’s going to make all that much of a difference. So long as your pilot understands what’s going on, you should be fine.

Summits.com’s dodgy hand-drawn diagram of mountain height terminology

Climbing Height, and Prominence

Climbing height

Climbing height is, of course, the height that you will climb to relative to that from which you begin the climb. If you’re going from sea level to the summit, then the climbing height would equal a mountain’s elevation. That’s actually possible in Southeast Asia, where many mountains jut up out of the sea. But I doubt there are any climbers that would have climbed the full 8,848 metres of Mount Everest, because that would require walking quite some distance before starting to climb. Most people start climbing in Lukla, which is already 2,860 metres above sea level and a few hundred kilometres from the sea.

At Summits.com, to get an estimate of the climbing height, we often just subtract the elevation of the starting point or trail head from the elevation of the summit. But this measure of climbing height doesn’t actually represent the amount that one will need to physically climb to reach the summit. That’s because almost all mountains on earth will require you to do a bit of up and down before reaching the summit. The sum of the ups will be the real amount of climbing up you need to do (which incidentally should be exactly equal to the amount of climbing down if you are going back to the same place).

Sometimes, when there are multiple trails and starting points for a mountain, or if the up-and-down nature of the trail is so great that climbing height is kind of irrelevant, we might instead offer a mountain’s prominence.

Prominence

We often use the word prominence when referring to people favourably – “she’s a prominent writer,” or “he’s a prominent architect,” or “they’re prominent zombies.” Essentially, we’re saying that they stand out, in some important but often unnamed quality, above others around them. This term is taken directly from topographic geography where we use it to describe the extent to which a mountain sticks out vertically above those around it.

However, the exact definition of prominence is a bit more complicated: The prominence of a peak is the minimum amount that one would need to descend from the summit before being able to ascend a higher peak.

When applying it to people, it makes no sense at all. When applying the concept to the Petronas Towers, you might notice that the Skybridge of the Petronas Towers connects the two towers at 170 off the ground. So assuming that one tower is ever so slightly shorter than the other (as surely must be the case), then the shorter tower would then have a prominence of 281.9 metres. If we were to assess the prominence of the taller tower, it would be equal to its height above whatever minimum elevation you would need to descend to if you were walking to The Exchange 106 – the tower about 1km away that has taken over the Petronas Towers as the tallest building in Southeast Asia.

But this definition of prominence doesn’t always work so well. Take Mount Everest, for example, because there is no higher peak than Everest, the concept of prominence doesn’t apply to it because you couldn’t descend any distance to climb a higher peak because there simply isn’t any higher peak (relative to sea level).

K2, which is considered the second tallest mountain in the world, has a prominence of only 4,020 metres because it shares the Himalayas with Everest. Yet, this is less than the prominence of Mount Kinabalu, which isn’t even the tallest mountain in Southeast Asia.

The concept of prominence can be useful. Take, for example, the South Summit of Everest, which is only 360 metres away from the main Everest summit, and only 99 metres shorter. You could consider this the second highest peak in the world because it’s still far taller than K2. But because you only have to descend 11 metres from the South Summit before being able to ascend the main Everest summit, the South Summit only has a prominence of 11 metres. In short, it’s not a very prominent peak.

Mount Everest, with the South Summit visible on the right.

The most prominent mountain on earth?

You might then be asking, “If the concept of prominence doesn’t really apply to Everest because it is the most elevated point on earth, what’s the mountain with the highest prominence on earth?” Given that every other mountain in the Himalayan range is kind of clumped together like K2, this title goes to Aconcagua – the highest point in the Andes, the second highest mountain range.

Yet, if we really want to get annoyingly nit-picky, the minimal descent to get from Aconcagua to Everest would have you crossing either the Pacific or Atlantic ocean. But if we follow the terrain down to the bottom of the sea – what we refer to as the “dry prominence” – you only have to descend 55 metres into the Bering Strait to bridge from the Americas to Asia before ascending into higher points in the Himalayas. But to get to a higher point from Mauna Kea – the 4,207 metre high volcano in Hawaii – you would have to descend 5,125 metres under water, giving it a dry prominence of 9,330 metres, which is more than the height, elevation, altitude, or climbing height of Everest!

Sunset from the top of Mauna Kea.