Table Mountain erosion – Mountains are not forever

Jul 28, 2023

Table Mountain erosion, like mountains all around the globe, endures the erosive forces of nature – wind, rain, rivers, oceans, glaciers, earthquakes – are at work on mountains, whittling them down grain by grain, reducing them to the very sediment they were created from. Dust to dust, and mountains are not exempt. Like humans, they also have a lifespan.

Table Mountain erosion over time

Table Mountain has stood up well against the ravages of time. Seven times older than the mighty Himalayas (8 times older than the Alps and Andes; 4 times older than the Rockies), it still stands proud in its 2.6 millionth human lifetime. At the current rate of erosion, Table Mountain has another 10 million years left before it will have been reduced to beach sand. But the latest geological research on the mountain has revealed a decreased rate of erosion.

Scientists used a new dating technique that relies on cosmic particles to calculate the erosion rate. It’s complicated, but what it comes down to is that Table Mountain will be in existence a lot longer than previously believed. About 10 times longer. Based on the latest calculations, the mountain erodes 1 centimeter in height every 1000 years. So the mountain is about 5 millimeters slimmer than in 1503, when the first European climbed to the summit. At this rate, Table Mountain should still be here after the Himalayas have disappeared.

Most erosion takes place over time and on a near microscopic level. We know it’s happening but can’t see it. Every trickle of water, every flurry of wind contributes, wearing away innumerable rock particles day after day, week in and week out. Rivers draining Table Mountain, an area of 57 square kliometers, remove around 30 tons of sediment per year from each square kilometer of mountain.

But sometimes erosion is less subtle. Landslides and rockfalls do occur on the mountain, mostly during winter when cliffs are battered by storms and streams gush in full spate down ravines. Thunder also plays a role in erosion, usually as the final agent in a series of erosive forces.

Are there rockfalls from erosion?

In April 2009, during a heavy thunderstorm, a huge chunk of rock broke off from a cliff overlooking Woody Ravine (a popular route up the Twelve Apostles), razing a patch of indigenous forest and destroying a section of the path. I was climbing on the adjacent buttress earlier that day (dodging lightning bolts!) and came upon the devastation only hours after it had happened. The acrid smell generated from rock gnashed against rock, reminiscent of cordite, still lingered, and sap was still oozing from the trunks of small trees, snapped like matchwood.

This is a rare occurrence; in all the years of hiking Table Mountain, I have never witnessed a rockfall or landslide – but I have occasionally come across fresh ones, like the one in Woody Ravine.

Ironically, the piece of cliff that broke away formed part of a climbing route opened in 1916. To think climbers once scaled those cliffs, trusting the rock with their lives – rock now scattered and shattered in the ravine bed far below, just over a century later.
“Wow, it’s so quiet you can hear the mountain eroding”.

“Its so quiet – you can hear the mountain eroding”

Regarding erosion, I recall an amusing incident several years ago when descending Dark Gorge, a ravine leading up to the Saddle from the east. A friend and I were seated on a rock and savouring the setting: the ravine’s beetling sidewalls, the stillness, the mysterious gloom of the forest further down. When a pebble dropped a short distance higher up, seemingly of its own volition, we could clearly hear it clatter down the rocky slope.

My friend, lost in thought and staring into space, remarked in a reverential voice, “Wow, it’s so quiet you can hear the mountain eroding”, only to have his remark rudely refuted by a lagging friend who had snuck up on us: “It was me, you fool.”
So, with all the erosion taking place, whether from wind, water, lightning or the foot of man, it makes sense to hike Table Mountain while it’s still around. But no need to rush. A German once put it succinctly when I told him about the mountain’s ongoing erosion: “Gutt, zen wie haff time enough!”

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