There’s no denying that Petra is a place that inspires superlatives. It’s one of the world’s über-famous archaeological sites, and like most first-time visitors, we were astounded. With vibrant red, white and pink sandstone cliffs carved into beautiful, ornate temples and tombs, the city is absolutely awe-inspiring.
We were so impressed that we wrote three posts (see the links below) on the hand-carved tombs and Bedouins who live in the area. But the ancient Nabataeans aren’t the only ones who whittled away at the striking cliffs. Mother nature’s relentless sculptors – water and wind – have also been on the job for millions of years.
Petra, now and for all its history has been a desert. A meager 6 inches of rain falls here each year, but because the city sits in a valley surrounded by rugged mountain terrain, most of the water ends up in Petra. As a result, millennia of wind and flash floods have eroded the colorful sandstone cliffs to produce strange and wonderful rock formations, some of which are downright artistic.
These elegant swirls of ochre and terra cotta are called “Liesegang rings.” Exactly how these strangely beautiful rocks are formed has geologists scratching their heads, but understanding the process isn’t necessary to appreciate their unique appeal.
This light brown wedding-cake formation is a result of “differential erosion.” This is geo-speak for what happens when some parts of the rock wall weather faster or slower than others; softer means fast, and harder means slow.
If visitors haven’t seen differential erosion before they arrive in Petra, they certainly will after the long walk along the bottom of the canyon. All it requires is a gaze up the cliff wall.
In a few locations the human carvers have been helped along by nature’s relentless duo. What were once flat walls and precise columns have been reshaped by water and wind into wavy, wonky rooms that would make Dr. Seuss proud.
But not to worry, understanding a bit about the geology of Petra is only a speck of icing on an already well-slathered cake. The complex colors and shapes of the canyon walls are just another reason that Petra has inspired and amazed people for thousands of years.
For the closet geeks out there, if you want to know a bit more about the geology of Petra, geologist Munim Al-Rawi has written a layman-friendly blog post.
And don’t forget, you heard it here: Petra Rocks!
James & Terri
8. Etan J. Tal via Wikimedia Commons