Is Kilimanjaro higher than Everest?

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

11 April 2021

What is the highest mountain Earth? The answer is Mount Everest standing at 8,849m above sea level. But what is “sea level”? Is it a fixed surface?

Of course not! The water in oceans is in constant movement, both because of the tides and also the surface waves. For this reason, scientists refer to Mean Sea Level which is the average position taking account of all the fluctuations.

However, mean sea level itself is also not the same all over the world. The reason for this is that the earth is not exactly spherical in shape. The planet bulges out at the equator due to its rotation.

The diameter measured at the equator is 12,756km while from North pole to South Pole it is 12,713km. There is a difference of 43km. In other words, when viewed from very far away (more than 50,000km in space), the earth does not appear as a circular disc. It looks like an ellipse – an oval shape.

From this point of view, the oceans are significantly “higher” near the equator that they are at the poles. But when we say “higher”, what reference point are we using?

The answer is: the centre of the planet. This question then arises: if we measured heights from this central point, would Everest still be the highest mountain or is there a higher one somewhere near the equator?

Everest is located at 28 degrees North latitude where the mean sea level is 6,378km from the centre of the Earth. This is 5km (5,000m) lower than that at the equator which is 6,378km.

When the measurements are taken from the centre of the Earth, it turns out that Everest is 6,382.3 kilometres high. Kilimanjaro, which is just 3 degrees south of the equator, is 6,384.0km from the centre of the planet. This is “higher” than Everest!

The highest point from the centre of the Earth is at Mount Chimborazo in Ecuador, South America: it is 6,384.4km high. But, from the mean sea level, this mountain does not even feature on the top-100 list of highest mountains! It is just 6,267 metres tall.

The question that remains is which of these two standards is better. Well, it depends on what you are using it for. For navigation near the earth’s surface – up to a few hundred kilometres – the heigh above sea level will do; but for space exploration, the distance from the centre is better.