It’s the question I thought literally nobody was asking, until Mrs PubChat asked on a recent trip away…
And it turns out it is a question that no one is asking, because there isn’t a proper definition or answer! Historically they have been named based on combination of overall height, steepness and general prominence
Historically Ordnance Survey used to define it based on height above sea level, with a threshold set at 610 metres (2000 feet). However over time this has evolved to how far a peak rises above the surrounding terrain. It is no longer looked at just in terms of it’s height above sea level. A hill now needs to have a significant vertical rise in relation to any nearby valleys to earn itself the grand title of “mountain” status.
Steepness and Shape
If you stop and think of what is around you, you will notice that anything called a hill will tend to have more rounded and gentle summits to it. As well as this it will have more gradual slopes that have been created by long-term weathering.
Mountains you will notice feature much sharper ridges and have more defined peaks. Alongside this they also have more steep gradients which have been shaped by over time by active tectonic uplift, glaciers, or volcanic activity.
It should be noted that historic and local convention will also at times override standard logic. A prime example of this is the Black Hills in South Dakota. The Black Hills rise over 7,000 feet above sea level. This makes them far taller than many official mountains—yet they retain “hill” in their proper name due to historical convention.
