Are there any terms in English, either colloquial or scientific, to describe the highest and lowest points of elevation on a given object (particularly a planet)?

For example, one could say that the deepest point on Earth, the Mariana Trench, is 11,034 meters below sea level, or you could say that Earth's sea level is 11,034 meters above Earth's... what? Similarly, the peak of Mt Everest is 8,848 meters above sea level, which means that Earth's sea level is 8,848 meters below its... what?

This is particularly tricky for other planets, which don't have a sea level as a convenient baseline: "The Martian landing site is at a very high elevation, just 2,000 meters below the summit of Olympus Mons, which is the ________ of Mars."

Do those terms exist? Or do we have to use longer phrases like "highest point" or "greatest elevation"?

  • 'Apex' and 'acme' are standard words for highest point. You might use 'nadir' or 'trough' for lowest point, although, originally, I don't think they connoted elevation.
    – DyingIsFun
    Sep 8, 2015 at 16:37
  • Highest and lowest point are what I have always heard.
    – Robusto
    Sep 8, 2015 at 16:44
  • @Silenus Yeah, I thought of "nadir", but the problem is that that already has an astronomical definition: the point on the celestial sphere directly below an observer.
    – Nerrolken
    Sep 8, 2015 at 16:44
  • 1
    'Nadir' has a geological meaning, given here: en.wikipedia.org/wiki/Nadir_(topography)
    – DyingIsFun
    Sep 8, 2015 at 16:48
  • There is some ambiguity, because there is relative to sea level, but there is also relative to the mass center of the planet (and this can create counter intuitive locations, because planets are not perfect spheres).
    – jxh
    Sep 8, 2015 at 17:29

1 Answer 1



a. The topmost part, top; the vertex, apex; †the crown (of the head), boss (of a shield), umbo (of a shell). OED


a. fig. Highest point or state, culmination, climax, acme. OED

  • +1/2 (rounded to 1) for "summit" because I think "the Earth's summit" is fairly idiomatic for the "Earth's [surface] highest point." But what about a word for its lowest point?
    – Papa Poule
    Jan 8, 2016 at 18:29

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