The widest mountain pass on Earth sits just 140 metres above sea level
Mountain passes sound like thin, frozen notches, and some are: roads cross the Himalaya above 5,500 metres. But the widest pass in the world, the Palakkad Gap in Kerala, India, lies only 140 metres up. What makes a pass is not altitude but being the easiest way through.
A pass is simply a route that lets travellers get through or over a range or ridge. Because mountains block movement so effectively, these gaps have shaped trade, warfare and the migrations of both people and animals. Passes form where erosion by water or wind has cut down the ridge, or in the low ground between two volcanic peaks. A tight one squeezed between hills goes by the name defile.
Geographers describe the key feature as a saddle: the lowest point along a ridge that is also the highest point between two valleys, the same shape mathematicians call a saddle surface. On a topographic map it shows up as contour lines pinched into an hourglass. Real roads do not always cross at that exact spot, sometimes taking higher ground or a tunnel instead, as the Eisenhower Tunnel does beneath Loveland Pass in the Rockies. Passes often sit just above a river's source, forming a watershed, and can be a short steep climb or a valley many kilometres long whose summit only surveyors can pinpoint.
The flat top of a pass is often the only level ground around, which draws buildings, and where a border follows a crest, customs posts and soldiers follow too. Argentina and Chile share a 5,300-kilometre frontier along the Andes that crosses 42 passes. Tracks naturally converge at these points, which is why the Brenner Pass in the Alps became a classic corridor for trade and armies. Above the tree line, engineers sometimes raise roads a few metres so the wind scours snow off them.
The vocabulary is wonderfully local. Americans say gap in the southern Appalachians and notch in New England; Europe often uses col, from Old French. In Tibetan and Ladakhi a pass ends in La, as in Taglang La at 5,328 metres. Scots say bealach, the Welsh bwlch, and Lake District walkers hause. Japan's word, tōge, also names twisting mountain roads and the street racing held on them. The Mana Pass, at 5,610 metres near the China–India border, appears to carry the highest road of all.
Source: Mountain pass
