There is no consensus on the definition of mountain, but in Britain and Ireland it is often taken to be a summit over 2,000 ft, or more latterly, 600 m. There is less consensus about the topographical prominence requirement (e.g. the change in elevation required between neighbouring mountains), which can vary between . Prominence is even strongly debated regarding UIAA classification of Himalayan mountains. In the alps, the UIAA requires a prominence of over 30 m to be a peak and over 300 m to be a mountain.