Why is Table Mountain flat?

Why is Table Mountain flat?

When climbing Table Mountain either via Platteklip Gorge, Skeleton Gorge or using the cable car, I often get asked why is it flat? Herewith the reason:

This striking mountain, towering over Cape Town at a height of 1000 meters, is a World Heritage Site and one of the Seven Natural Wonders of the World.

One of the things that makes Table Mountain so impressive from a distance, is its almost vertical front face and flat top. It rises up from the coast very suddenly in a huge, angular mass. What many don’t realise, is that Table Mountain and the Hottentots Holland Mountains (seen across the Cape Flats to the East) both form part of a much larger mountain chain called the Cape Fold Belt. This extends over 700km to Port Elizabeth. The Cederberg Mountains to the West of Table Mountain also forms part of this range.

The Cape Fold Mountain chain formed over 200 million years ago during an ancient continental collision, where the Earth’s powerful tectonic forces pushed large masses of rock upwards. This transformed the Cape’s tidal flats into a ‘folded’ landscape, punctuated by mountain crests and valley troughs.

Table Mountain was once at the bottom of one of these valleys. So how did this happen?

Rock types of varying variety beneath the Earth’s surface played a role. There are 3 key rock groups underlying the Fold mountains in the Cape Town area: Malmesbury Shale, relatively soft sedimentary shale which is easily worn away; Cape Granite, which are very hard rocks and then Table Mountain Sandstone, which is hardened sedimentary sandstone formed from layers of compacted sand, silt and mud deposits. This was composited on top of the granite and Malmesbury Shale.

Over the years, the landscape began to weather and erode, but the exposed crests of the folds eroded before the troughs did. This meant that once the hard sandstone layer of the crest was worn away, the soft shale beneath it weathered more rapidly than the remaining sandstone troughs. The shale surrounding these troughs continued to erode further and further, leaving the hard sandstone troughs behind, eventually resulting in what was once a flat valley floor becoming today’s flat-topped Table Mountain.

 

Written by:  - 22 Jun, 2017  
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