The land of lost volcanoes

I’m standing on soft sand, scattered with smooth, polished quartz pebbles of different sizes. The large sandstone outcrop in front of me is glowing a honey-orange in the afternoon sun. The light casts shadows on the rock, giving definition to features formed through natural weathering. Those shadows also highlight impossibly straight lines, and perfect angles. Lines carved by humans around 2000 years ago, into the solid stone outcrop. I see a man holding parchments made from vine leaves with sketches, symbols, and even scribbles: what they have drawn and designed is calculated down to the millimeter. He shouts, and the workers run around in some kind of organized chaos. A man high up on the rock outcrop, beads of sweat on his brow, glinting in the sun. He has been gently hitting his stone hammer into the sandstone; carefully removing rock straight down this huge outcrop, cautious that each strike could easily destroy days of working. This team of workers are slowly, carefully carving a tomb inside the rock.

A gentle gust of cool breeze brings me back. I’m at Hegra, in AlUla. A place where you get lost in the history immersed in the landscape. Here, around 2000 years ago, the Nabataeans expanded their range south of Petra, and built their second largest city. Their shops, homes, alleys, are now all gone, with only tantalizing glimpses of their foundations protruding out of the desert sand. The enormous tombs are still standing proud. They are carved into the isolated sandstone outcrops that dot the landscape. The tombs have such beautiful detail, with such incredible precision: they are something from another time. This is the first site in Saudi Arabia to be designated a UNESCO World Heritage Site, and with over 110 tombs and active archaeology happening every year, it is a place full of stories.

Those stories, and my somewhat vivid imagination recreating the past, go even further back in time than the Nabataeans. Looking out on the landscape, my mind sees the wind and the rain slowly breaking down larger outcrops of sandstone to create the outcrops (it will take tens of thousands of years for these elements to reduce these beautiful tombs to dust). An expanse of sandy desert plains, with islands of outcrops of different shapes and sizes scattered; a desert archipelago slowly being ravished by the wind. ?

But there is something strange. An anomaly in the landscape. In the distance, there is a dark, flat ridge, expanding for miles, and it’s much higher than where I stand. Like a dark-rich cherry icing on the top of a sponge cake, it can be seen from left to right. What is this dark plateau (or should we say gateau)?

One of the most wonderful things about AlUla is the incredibly rich geology. It’s not all just beautiful sandstone outcrops. In the south of AlUla, there are igneous and metamorphic rocks, sharp, dark; a little reminiscent of their almost billion year old history.

That dark plateau is something different. Something more recent. Something that was borne from the fiery depths of the earth.

We need to go back to where it all began. Not as far back as those rocks in the south. Or as far back as when the sandstones formed. For this story, we only need to go back to just around 30 million years ago.

Around this time, there were tectonic shifts in the earth’s crust happening. Literally tectonic. Rifting in East Africa had begun, and this slowly pushed the Arabian Peninsula eastwards. (Very, very slowly. Tectonic plates are moving right now, about the same rate your fingernails grow in a year. It is slow but so powerful.) This was the beginning of the Red Sea. The force crumpled the Arabian Peninsula, and over a few million years, the rock that was once hidden underground, out of sight from any early mammalian ancestor, was slowly thrust up. If you stood in AlUla around this time, you would be standing on the top of a massive sandstone plateau. Stretching for hundreds of miles in all directions; there were no valleys, no sandy desert plains. It would have been a world very different to what you see today.

All of this activity, the pushing apart of the earths crust, the new sea forming, the crumpling of the Arabian Peninsula, caused a rumbling inside the earth, as if our planet had eaten one too many falafels. Underneath the solid crust is hot liquid rock (called magma). This generally slowly flows, creating convection currents that we will never see. But the opening of the Red Sea created shifts, changing those convection currents, messing with the gentle flow of the unfathomably hot liquid rock's natural movements. Like a lava lamp on a gigantic scale, bubbles of this magma began to slowly rise to the surface. When they hit the solid crust, they pushed against it: slowly heaving and gently forcing its way through cracks, giving birth to volcanoes.

Yes, volcanoes. There were volcanoes in AlUla.

Dozens of them began erupting around 10 million years ago. These volcanoes spewed out lava, spreading across hundreds of miles, covering parts of that sandstone plateau that had been so rudely awakened from its slumber. This is basalt lava; a dark igneous rock that has cooled fast, so the minerals are small. These were not the large explosive volcanoes glorified in movies. They would have been more similar to those volcanoes on Hawaii, erupting large amounts of lava; flowing rivers of lava, and fountains silently spurting, glowing brightly against the starry night.

We know there were large amounts of lava erupted, because we can see it today. Dark, sometimes rugged, sometimes smooth, basaltic rock stretching for hundreds of miles. It poured. It flowed. It burnt the young soil that had only just begun to form on the sandstone plateau. It covered the sandstone. It would have been a spectacular thing to witness. And then around half a million years ago they stopped. Today, these volcanoes are dead, the bubbles of magma hardened: they are a relic of a forgotten time.

Basalt is an igneous rock, so it is hard. A lot harder than sandstone. As lava cools, crystals grow, and as they grow, they fuse into each other. Tightly packed together, the wind and the rain take a long time to break it down. Sandstone on the other hand, is made up of lots of grains cemented together: water getting into that natural cement breaks it down, and the grains fall out.

And here’s the super interesting thing. The lava that erupted and spread across the sandstone plateau, protected the sandstone underneath. All around, the rest of that massive block of sandstone that was thrust up when the Red Sea opened, has slowly been broken down by wind and rain. Today we have sand dunes, expanses of desert plains: all sand that was originally a part of that that plateau.

There are several of these fields of basalt, called harrats, in AlUla, and the largest is Harrat Uwayrid; the largest of AlUla’s five nature reserves, and a UNESCO Man and Biosphere Reserve.

It is mesmerizingly beautiful standing on the top of the harrat; more so if you are sharing that view with someone special, because you are taking in that experience together. The landscape up here is completely different. It is darker, more rough and harsh than the softer looking sand plains below. It is the views that take your breath away. Standing near the edge of the harrat, behind you are flat basalt flows, with the ghostly figures of long sleeping volcanoes in the distance. And in front of you is the spectacular landscape of AlUla: those stunning sandstone formations, the sand dunes, the expanses of desert plains scattered with shrubs. It’s like the perfect painting.

From here, you can see how the landscape of AlUla formed. Before these volcanoes erupted, there was just one large sandstone plateau: no stunning sandstone formations, no sand dunes, no expanses of desert plains scattered with shrubs. The lava poured out, covering some of this plateau, but not all of it. The parts of the sandstone plateau that was not covered by the hard basalt were broken down by the wind and the rain, slowly shaping the landscape we see today.

Volcanoes seeping rivers of glowing hot rock. Lava erupting in bright fountains across the landscape. The wind gently shaping the rocks around us. A lost sandstone plateau, like something out of an Arthur Conan Doyle novel. Reaching a view point here, either by car up to the top of the harrat, or a hike and climb through the silent, ancient, age-old trodden goat paths, you can begin to see that history.

The stories of the landscape can come alive with a little imagination.