A Living Fossil in the Petrified Forest

It’s a Welwitschia!  Nestling among 280 million year old fossil tree trunks, this is the rare plant I have been searching for. Two wonders of the natural world – the living, sprawling Welwitschia and the ancient, petrified trees – have fortuitously come together here in Namibia. Separated by more than an immense period of time, they also bear witness to completely different environments. Welwitschia is adapted to the extremes of dryness and heat of a desert while the archaic trees once lined a great floodplain and were felled by melting glacial waters. However, in spite of their many differences, these two plants share a hidden secret. Between them, they reveal the fascinating story of a gigantic landmass that broke apart over 100mya.

Petrified log showing segmentation caused by compressional stress.

The ancient southern supercontinent of Gondwana existed for hundreds of millions of years and embraced South America, Africa, Madagascar, Australia, Antarctica and parts of Asia. By 280mya, vast cool temperate forests of Cordaites trees covered parts of Gondwana. Cordaites is a primitive relative of the conifers that grew to 30m in height and is best known from the coal swamp forests of 325 to 295mya in Europe and North America. As Gondwana emerged from a great ice age, Cordaites trees lining river floodplains were engulfed by melting glacial waters. This catastrophic flooding resulted in their burial under hundreds of metres of sediment. Over an immense period of time, silica dissolved in groundwater replaced the original woody tissue and turned to quartz. Traces of iron stained the quartz beautiful shades of red, brown and yellow. This process of petrification preserved, in exquisite detail, features such as growth rings, bark and even branch attachments.

Close up of beautifully coloured silicified growth rings.

Only with the break up of Gondwana were the logs finally re-exposed. Around 120mya, tectonic movements caused South America and Africa to separate and lifted western Namibia by as much as 1,000m. Erosion increased dramatically. Over many tens of millions of years, vast amounts of sedimentary rock were eroded away until the ancient trees once again saw the light of day.

One of the largest Welwitschia plants in the Namib Desert, measuring 1.4m tall & 4m wide.

Today, the idea of catastrophic flooding seems about as far removed as you can get from the site of the petrified forest near Khoraxis in north-western Namibia. The land is parched. Vegetation is sparse and stunted. Any plants that do survive have been shaped by millions of years to cope with the harsh conditions. Here and there, sprawling among the petrified logs, is one of the world’s most celebrated plants. Welwitschia mirabilis elicits an extreme reaction from pretty well everyone who sees it. The Daily Mail newspaper recently dedicated a full page feature to Welwitschia, describing it as ‘the most hideous plant on Earth’. It has even had an obscure Belgian film named after it: The Curse of Welwitschia.

Petrified wood showing branch attachment.

Why should an obscure desert plant attract such hyperbole? For a start, it doesn’t look remotely like any other living plant. Nor does it behave like a typical desert plant. It lives only in the Namib Desert and neighbouring dry lands in a narrow strip along the southwest coast of Africa.

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