Peña de Bernal from Bernal town, Queretaro, Mexico (Barry Evans)

“In time the Rockies may crumble, Gibraltar may tumble, They’re only made of clay…” according to Nat King Cole. Well no, if they really were made of clay – a soft sedimentary rock – they’d be long gone. In the case of the Rock of Gibraltar (limestone), or for that matter El Capitan (granite) and this week’s topic, Peña de Bernal (igneous), we’re talking tougher stuff.

There’s nothing like a really big chunk of rock to remind me how insignificant I am, despite the illusion that I’m at the center of everything running the show. If you’ve stood beneath El Cap, you know what I mean – it’s one gigantinormous lump of granite, about as vertical as you can get, pulling us humans down to size. I can confirm the same is true of, for instance, Gibraltar and Stawamus Chief in British Columbia, and other huge rocks. Other world-class monoliths (from the Greek “one stone”) would include Ayers Rock (more properly Uluru) in central Australia, Rio’s Sugarloaf Mountain, Sigiriya in Sri Lanka, and, closer to home, Morro Rock in Morro Bay.

I’m writing this in our hotel in the small town of Santiago de Bernal in Mexico, home of Peña de Bernal, another Really Big Monolith, and the highest in the world, according to some accounts. We climbed it yesterday, as thousands of pilgrims do every year, to the chapel a couple of hundred feet below the top (it gets a tad hairy beyond that point). When we were here ten years ago, the official story – as told on several signboards at the base of the rock – is this the huge monolith was formed some 100 million years ago as a pluton, that is, solidified magma.

Turns out, it’s only about nine million years old, according to a recent chemical analysis by the National Autonomous University of Mexico (UNAM). It’s still igneous, but formed of dacite, like Mount St. Helens. Both Peña de Bernal and Mount St. Helens owe their existence to the tectonic subduction of denser oceanic plate beneath lighter continental plate. The friction of the two plates rubbing against each other generates heat, resulting in magma that subsequently rises to the surface.

Deciding which of several contenders counts as “the world’s tallest monolith” is tricky. It’s easy enough to measure the peak, but where do you start measuring from down at the base? According to new measurements by UNAM, La Pena de Bernal is 433 meters, or 1,421 feet, high, making it a tad higher than Gibraltar (1,398 ft.), which until now held the crown. That’s according to a two-year old article in LiveScience resolutely titled, “Mexican Monolith Is World’s Tallest Freestanding Rock.”

But c’mon. El Cap soars 3,000 feet above the valley floor. Bukit Kelam is another 3,000 ft. rock in Indonesia. Stawamus Chief is a 2,300 ft. high. So what counts as a monolith? The giant Easter Island heads are called monoliths, as are the individual elements that make up Stonehenge. Heck, there’s a monolith orbiting Jupiter, if you recall the MacGuffin, which ended up dominating 2001: A Space Odyssey.

I suspect it’s all about semantics. Geologists avoid the word monolith, preferring instead “inselberg” (“island mountain”) which has a more precise meaning. Me, I think from now on I’ll stick to Stonehenge and the Easter Island statues before making any claims about nature’s Really Big Stuff.

###

Barry Evans gave the best years of his life to civil engineering, and what thanks did he get? In his dotage, he travels, kayaks, meditates and writes for the Journal and the Humboldt Historian. He sucks at 8 Ball. Buy his Field Notes anthologies at any local bookstore. Please.