Mountains are not forever

All around the globe, 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 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 3.6 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, so I won’t go there, 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 every 1000 years. So Table 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 kilometers, 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 the ravines. Thunder also plays a role in erosion, usually as the final agent in a series of erosive forces. 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 12 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 on 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 the early 1900s. To think climbers once scaled those cliffs, trusting the rock with their lives – rock now scattered and shattered in the ravine bed far below.

On the subject of erosion, I recall an amusing incident a few years ago while descending Dark Gorge, a ravine leading up to the Saddle from the east. A friend and I were seated on a rock, resting our weary legs while savoring the setting: the ravine’s beetling sidewalls, the stillness, the mysterious gloom of the forest further down. So 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 even 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 damn 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 up. Like a German put it when I told him about it while hiking up Table Mountain: “Gutt, zen wie haf time enough!”

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