30 August 2025
The Spectacular Basaltic Prisms of Santa María Regla
If you ask the average person for two words that they associate with Mexico, it’s unlikely that they will be basaltic prisms. Yet, a few hours drive from Mexico City is an outstanding example of this geological structure. These tall columnar joints, some over 40 meters in height, line a ravine – and through that ravine waters flow which end in not one but two waterfalls. It is almost like visiting another world. Image Credit
The formations themselves were created millions of years ago during intense volcanic activity in the region. As lava poured from the earth and began to cool, it did so unevenly. The outer layers solidified first, while the molten rock inside contracted as it cooled more slowly. This process created tension, and the rock fractured into long, vertical cracks.
Remarkably, the fractures spread in a pattern that produced
strikingly regular geometric shapes – usually hexagons, though some columns
have four, five or even seven sides. Over time, erosion by wind and water
exposed these structures more clearly, carving the ravine and allowing
waterfalls to cascade dramatically over the prisms. What began as a raw
volcanic outpouring was slowly sculpted into one of Mexico’s most extraordinary
natural wonders.
Naturally (or not, as it were), reminders that you are still on planet Earth are everywhere. In the two centuries since naturalist and explorer Alexander von Humboldt captured the public imagination with his topographical drawings of the prisms, tourism has rocketed, particularly in this century. And so did the number of people slipping on the wet stone and injuring themselves in their fall.
As such, certain adaptations have been made to balance visitor access with environmental preservation. Walkways, paths and stair concentrate the movement of visitors in certain areas, which prevents erosion, prevents any damage to the basalt columns and allows local plant life to fully take hold. Vegetation can be spotted in a number of places, springing up from cracks in the structure.
There are also safety barriers to stop people from climbing. Again, it is a measure put in place to preserve both the natural formations and the lives of any visitors foolhardy enough to imagine themselves as agile as a mountain goat (and even those would have trouble here).
Of course, some will ignore the signs but rock gets slippery when wet.
Although cafes, souvenir shops and hotels are kept at a
distance from the main geological site, don’t expect the place to be all virgin
territory. In order to maintain the site, the necessary evils of commercial
development certainly have a presence, but waste management is firmly in place
and the visual impact is kept to a minimum. However, as you can see from the pictures, the site is kept in pristine condition, despite nature's occasional incursions.
So, while the Basaltic Prisms of Santa María Regla may not
be the first image that springs to mind when thinking of Mexico, they are
without doubt one of its most jaw-dropping natural treasures. Few places on
Earth allow you to stand at the meeting point of fire, water, and time – gazing
at lava frozen into perfect symmetry while waterfalls thunder past. It’s
geology turned into sculpture, a reminder that nature can be every bit as
precise, dramatic, and astonishing as any work of art.
