Origins of the Cape Fold Mountains: A Quick Mega-History

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The story of the Cape Fold Mountains, told by a non-geologist, to help you know what you’re standing on.

It was out last day walking the Agterwitzenberg Passage and our morning started with a serious climb to a small but grassy high pass. As we each reach the top, we drop our bags and rest in the grass for the others to join. All together, Johann, the trail leader for the morning, lead us in a story of these mountains. It has inspired the angle of this article as I continue.

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Imagine taking all of our Earth’s 4.5 billion years of history and hold it— stretching it from finger tip to finger tip of your open arms. At the end of one hand we have the amassing of matter into what we know as our planet and in the other hand we have us, right now. Anatomically modern humans would make up .08 mm of your arm-span, which means if  an imaginary nail file took one strike across your finger nail, we would all be gone. Our towns, governments, and all of humanity as we know it is now spread across that file.

Our pre-modern human ancestors would make up about 1.016 mm of your arm span. Mammals only about 3 inches (8.28 cm) — not even the length of most pinky fingers.

If we return our attention to the majority of Earth’s history that remained in between your outstretched arms, the mountains around us are not nearly as still and steadfast as we perceive them. Instead of the towers of heavy granite and sandstone, they resemble rolling waves, always in flux, rising up from the sea and tumbling back down, endlessly.

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These small rocks used to be mountains— that fact I knew and had wrapped my head around while walking. Big, strong mountains crack, splinter, and crumble under the unrelenting forces of wind, water, temperature extremes, and impacts like falling or being crushed. But what were the original Cape Fold Mountains like?

The Cape Fold Mountains were formed around 280-235 million years ago — about 4.5 inches (11.3 cm) along your arm span— when the continents of collided together and formed the supercontinent Pangea. Forget Cape Town, South Africa, or even Africa as we know. When the Cape Fold were born, the world was a radically different place.

But what was the Cape Fold made of?

When previous mountains eroded into the oceans, the sediments compressed under the earth’s surface in a 7 kilometer (4.3 miles) vertical pile of mud and sand. The weight of all of this turned sand into to sandstone and mud into shale. When the formation of Pangea started, most of the Cape Fold was being compressed under the earth’s surface, making the Cape Fold Mountain’s rocks malleable, able to bend without breaking. The result can be seen in the unique ‘folds’ for which the Cape Fold is named.

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The folds of the Cape Fold remain because of the very tough and weather resistant sandstones. The quartzite and other rocks composing the mountains are all about 450 million years old, about 7.2 inches (182.88 mm) of your arm span. And more than keeping the Cape Fold Mountains jagged and tough, the sandstones make for great rock climbing and erode to exceptionally poor-quality soils, without which, fynbos and life in Cape Town wouldn’t be remotely similar to what it is today.

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To end this post, I want to offer two things. First, a question: if we appreciate the Cape Fold Mountains’ ancient story, in contrast to our own short existence on this planet, can we share this story to try to end the radical behavior hurting them now?

And secondly, my favorite pictures of rocks from the Cape Fold Mountains. :-)

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