Sebastian Lüning (UK)
Morocco is a popular tourist destination. Most people travel to the white beaches of Agadir to sunbathe and relax, to watch the magicians on Djemaa el-Fna square in Marrakech, or to go shopping in the UNESCO-protected Osouk of Fes. However, Morocco has much more to offer. Some of the most attractive specimens found at international fossil fairs originate from this country. Morocco is home to exceptionally well-preserved trilobites and attractive Orthoceras assemblages from the Palaeozoic. The beds containing these fossils are systematically mined in the Anti-Atlas. Other fossils, such as goniatites and ammonites, complement the diverse palaeontological national treasure.
These fossils are part of an exciting geological past. This article aims to guide you through the highlights of Morocco’s geological history, exploring the stories behind the country’s natural wonders and its multi-million-year-old inhabitants. Concealed in its spectacular mountain chains are some fascinating snapshots from the past. Our trip will commence at the very beginning of this history and will take us gradually forward through time. We will visit various sites on a route starting in the Precambrian of the Anti-Atlas, in the southern part of the country, and then moving northwards to the Triassic and later periods of the High and Middle Atlas. Where necessary, the journey will involve some hopping about, to enable stratigraphic continuity.
Much of Morocco is covered by mountains. These are exposed scars that are testimony to the awesome power of continental collisions. The Anti-Atlas, soaring as high as 2,500m, dominates the south-east of the country. The High Atlas Mountains rise above central Morocco and are the Alps of the Maghreb. This mountain chain is 700km long and reaches heights of over 4,000m. It remains a formidable barrier and you can count the number of passes through it on the fingers of one hand. North of the High Atlas is its somewhat smaller twin, the Central Atlas and in the far north of the county, the Rif Mountains watch over the straits leading into the Mediterranean Sea.
Precambrian rock melt from the deep
Morocco’s oldest rocks date from the earliest era of the Earth’s geological history: the Precambrian. Granites from this time can be found around the town of Tafraoute, located one kilometre above sea level in the western Anti-Atlas. Nature and her tools – wind, temperature fluctuations and water – have etched the rocks into bizarre forms. Steep, barren mountain slopes surround an ancient granite dome, and the pink granite is shaped into astonishing rock needles, spheres, towers and sugar loaves.
The piled stones look as if they could fall down at any moment. The Chapeau de Napoléon (Napoleon’s hat), two kilometres south of Tafraoute, is the masterpiece of this open-air museum. ‘As hard as granite’ – the old saying, seems not to apply here. Granite consists of grains of minerals, between which are tiny cavities that make the rock porous to air and water. The grains are made up mainly of the minerals feldspar, quartz and mica. The water that penetrates the rocks attacks those minerals that are more easily dissolved – feldspar and mica – and causes the granular decay of the granite.
However, just as important for the formation of the rock sculptures of Tafraoute is their regular fracture pattern. Cooling and pressure relief in the mountains formed the fractures and joints in the granite. The stone was split into blocks and the corners were slowly rounded off by nature. Chemical weathering penetrated the rock and, layer-by-layer, the outer surface of the granite was eroded away, almost like the peeling of an onion. That’s exactly how geologists refer to it: ‘onion skin weathering’. The shape of the blocks and the stone statues follows the prevailing pattern of the fracture system. The vertical joints, lying close to one another, give rise to the formation of needle rocks, whereas square blocks tend to become spheroidal forms.
The granite of Tafraoute was formed 550mya as several continental blocks collided and Africa was born. High temperatures in the mountains’ cores led to the melting of the rock in some places. Hot magma travelled upwards along the fractures, but came to a halt at some depth. The liquid rock solidified and formed large granite domes. Over millions of years, the mountains above were slowly eroded and today the granite lies exposed on the Earth’s surface.
Not content to let nature work her magic alone, Belgian artist Jean Verame decided to make his mark on this landscape. In 1984, he and a group of Moroccan fire fighters set to work with 18 tons of blue, red, violet and white paint. Equipped with solar-powered spray guns, they spent three months transforming a stretch of granite blocks, three kilometres north of Tafraoute, into a work of art he called ‘Les Pierres Bleues’ – the blue stones. Today, the colour is fading, but natural decay is part of Verame’s artistic concept. He created similar works in the Tibesti Mountains in Chad and also in Corsica.
Besides granite, there are other Precambrian rocks found in the Anti-Atlas. Schists, quartzites and serpentinites – all these take us deep into Morocco’s distant past. Almost without exception, these old rocks were once buried at enormous depths. The tremendous pressures and extremes of temperature experienced at these depths caused the rocks to melt, deform and harden again. They then followed a tortuous route, and finally ended up at the Earth’s surface. It is often impossible to say what the geological origins of these metamorphic rocks was.
Walking over the Cambrian sea floor: stromatolite colonies near Ouarzazate
Shortly after the granites of Tafraoute were created, destruction of the newly formed mountain chains began and rubble piled up in the hinterland of the southern supercontinent of Gondwana. Huge river systems cut into the landscape for thousands of kilometres. They carried endless deposits of pebbles, sand and mud, some of which flowed over Morocco as they went, creating the country’s oldest sediments. The detritus of half a continent piled up here, washed up from the furthest corners of Gondwana. However, eventually, the supply of debris from the large African hinterland faded away.
Sometime during the Early Cambrian a new age dawned – an age of slime! The oldest and most successful organisms (certainly, in terms of longevity) in Earth’s history took over Morocco: microbial mats made of colonies of cyanobacteria – masses of them. Fossilized as stromatolites, today they can be found close to the Tizin-Tinififft Pass in the Anti-Atlas – just as the sea left them behind in ancient times. Large parts of the Anti-Atlas consist of limestone made of these microbial mats.
Photosynthesis within the cyanobacteria and the resulting removal of carbon dioxide from the water led to the precipitation of calcium carbonate on their surfaces. Layer after layer was deposited, forming the typical layered stromatolite structure. Mud particles were also trapped and incorporated. It must have been paradise: there was virtually nothing around to eat the stromatolites, as more complex life forms had not yet developed in this early phase of evolution. Their worst enemy was the debris washed into the sea by rivers. This regularly covered the slime mats and sometimes killed them off.
A few million years later and the golden era for Morocco’s stromatolites was over. The rivers suddenly began to transport so much sediment into the seas that their dominance came to an end. Now, sand, gravel and mud began to pile up in regular layers. South-east of the city of Ouarzazate, in the Tizin-Tinififft Canyon, a wadi has cut deep into a fascinating archive of this part of the Earth’s distant past. Geological history can be read, layer-by-layer, on the walls of the gorge like a book, and wind and water have sculpted the surrounding mountain peaks, transforming them into incredible shapes.
On the other side of the pass is the fertile valley of the River Draa. This is a desert river that has its source in the High Atlas, the water of which very rarely reaches the Atlantic. A million date palms line the banks of this, Morocco’s longest river. Fortresses in this area – the Kasbahs – are made of red clay and were the key to power within a chain of oases. It was from here that the local Berber rulers controlled the trade routes; routes that stretched as far as Timbuktu in the golden days.
Late Ordovician glacial times
Steep, strangely layered cliffs enclose the Draa Valley. A natural cake made of layers of hard sands and softer clays, laid down during the Ordovician period, in a shallow ocean. The composition of the marine sediments changed with the rhythm of the fluctuating sea level. During the latest Ordovician, the sea suddenly began to freeze. Temperatures fell dramatically and a huge ice shield formed over Morocco and the Sahara. It was a glaciation that also made its mark in England and Wales, and as far away as Saudi Arabia, both continental fragments then located close to North Africa. Glacial scratches and grooves from this time can still be found in Morocco. In addition, the enormous power of catastrophic melt waters washed away some of the sediment layers below. The remnants of this phase of destruction are silent witnesses within the mountains of this tranquil valley.
Graptolites of the Silurian sea
Two hundred thousand years later, this ice age came to an end. The glacial ice thawed and the huge volume of meltwater caused sea level to rise by about 100m. Ice age sands were drowned and layers of mud covered the sea floor – but the ocean was sick. The sea floor was lifeless, consisting of nothing but a foul black layer of this mud. The oxygen in the lower part of the water column was being consumed faster than it could be replaced from above. Massive numbers of animal corpses – graptolites – sank from the well-aerated upper layers of the water column into the mud. T
he harsh environmental conditions in the Silurian period forced these graptolites to quickly optimise their shapes and adapt. Today, that quick succession of changes enables us to precisely reconstruct events in this ancient ocean. The graptolites are a fossil clock, unmatched by any other means of measurement. By correlating graptolite species, scientists have proved that this black mud was deposited at the same time in other countries of North Africa. The organic ingredients of the clay formed from the mud are the rich source of the oil fields in the Algerian and Libyan Sahara, most of the product of which is exported to Europe.
The Orthoceras lagerstätte
A few kilometres from the town of Tazzarine, a modest ridge rises out of the desert. It is mouse-grey and half-buried by sand dunes. The clock has moved on about 20 million years. The sea still has Morocco tightly in its grip and oxygen has become a rarity once again. The ridge consists of a limestone that takes on a grey-black hue when freshly uncovered. It is a limestone that has made the Anti-Atlas and Morocco famous the world over and is a rock that can be found in every fossil collection around the world. Embedded within it are strange arrow-like creatures, packed closely together and each divided into many small chambers.
There are millions of them: these are Orthoceras or ‘the straight horned’ to translate directly from the Latin. They were squid-like creatures with long, stretched shells. Orthoceras bear a very close resemblance to the ammonites, except that ammonites have spiral shells. The animal itself lived in the last and largest chamber, with the other chambers serving to regulate the creature’s buoyancy. These could be filled with either water or gas to help it rise or sink. Wherever Orthoceras are dug from the ground in the Anti-Atlas, busy hands are to be found breaking up the rock into more manageable blocks of about one cubic metre – the valuable raw material for an amazing range of crafted products.
Erfoud – the fossil factory
Most of the excavated Orthoceras limestone is transported to Erfoud, in the centre of the eastern Anti-Atlas. Besides the cultivation of dates, many of the 18,000 inhabitants make a living, either directly or indirectly, from the region’s rich fossil deposits. Everywhere you go, people are sawing, hammering, filing and gluing. It’s hard work, but the people are proud to be part of this privileged caste of craftsmen.
And the fossils of Erfoud are famous. If you haven’t heard of this town, you will probably have come across the unique objects made of Orthoceras fossils somewhere. With great skill, multicoloured varieties of Orthoceras limestone are pieced together. Among the objects the workers of Erfoud make are beautiful bathroom tiles that can be found in many top class Moroccan hotels. Another popular product consists of the beautifully crafted Orthoceras pillars that create a shining and exquisite living room decor.
Mounds of mud
Fifteen kilometres south-east of Erfoud, a group of mysterious cones poke out of the landscape along the Hamar Lakhdad Ridge (Fig. 9). Clustered in a narrow strip, three and a half kilometres long, a total of 48 carbonate mud mounds stick up, some as high as 50m. It’s still not clear when this Kess-kess chain of hills was formed and, despite extensive research, experts disagree about the mechanism behind their creation. Some scientists believe the cones are shallow sea reefs and others say they’re the remains of deep-water mud. What is clear is that 410mya, during the Devonian, a volcano erupted on the seabed.
Once the volcanic activity had subsided, animal life established itself on the sides of the volcano under the sea – Ammonoidea, mussels and Orthoceras. A new theory suggests that hot volcanic springs on the seabed played an important role in the creation of the mud mounds. These hot springs may have triggered precipitation of finely crystalline carbonate that accreted to form their distinctive cone shapes. Similar mounds were formed in the Devonian period in other parts of Northwest Africa, for example, in neighbouring Algeria.
Morocco caught in the Pangaean collision
Three hundred million years ago, late in the Carboniferous period, the sea disappeared from Morocco. The region rose up and its rocks were bent and crushed by enormous forces inside the Earth. Africa, North America and Europe collided and became welded together. A massive mountain chain came into being, stretching right across the newly formed supercontinent of Pangaea. Apart from the Anti-Atlas, only a few remnants of the former massif are left in Morocco today. The mountains were worn away over the subsequent 100 million years. They collapsed and huge cracks and basins opened up that quickly filled with red debris.
The red Triassic
Wind, water and violent fluctuations in temperature broke down the mountains into their constituent parts and the sediments that were deposited in Morocco at that time were all red. Red stones crashed down from the mountains’ scree fans. Rivers and small dunes pushed red sand ahead of them, and red clay settled on flood plains and in lakes. The red is rust – the debris contains large amounts of oxidised iron that gives the stone its intense red hue. One of the most impressive red Triassic landscapes can be found in the Argana Valley, 40km north of Agadir. Just as it did back then, a river babbles through the valley, and the cliffs consist of cross-bedded sandstone layers that show the direction of flow of the old river system.
Eventually, this river-bisected landscape was reconquered by the ocean. Sea level rose and a tropical coral environment was established. Siliceous sponges formed huge reefs in the warm water. The carbonate sea of the Jurassic period nestled in a huge rift. Where today the High and Central Atlas tower into the sky, tectonic forces endeavoured to rip apart North Africa and, indeed, the supercontinent of Pangaea. The Atlantic Ocean came into being and also played a part in ripping open the African continent. Enclosed by steep slopes, the tropical ocean washed into a broad gash through the heart of Morocco 1,000km long and 100km wide – the ancient ‘Atlas Gulf’. Ultimately, however, these forces were unable to split North Africa apart.
Some time later, Africa found itself on an unstoppable collision course with Europe that resulted in the creation of long mountain chains on both continents, among them, the High Atlas. Corals, sponges, mussels and snails – the former inhabitants of the tropical ocean – found themselves in a huge natural elevator and now they sit on top of mountains, at an altitude of several kilometres.
High Atlas canyon land
Huge gorges cut into the southern edge of the majestic High Atlas. Here, rivers have etched deep trenches into the Jurassic massif, some of them 500m deep. These allow a rare view into the core of this mountain belt. The Gorge de Dadés is Morocco’s Grand Canyon. There is a road that follows the gorge’s river, but some parts of the gorge are so narrow that, in these places, its route had to be blasted out of the bare rock.
No matter how uniform they may look from a distance, these mountains are far from homogenous. They consist of a layer cake, with alternating hard limestone beds and softer clay layers that have been incised to varying degrees. Where the rock is soft, the gorge broadens out into a basin that has been settled and cultivated by man.
But how did the River Dadés work its magic on these great mountains? When and how were the gorge systems at the southern edge of the High Atlas established? The answer lies in the deeply entrenched high altitude meanders of the area. Shifting river beds are usually common to quite different landscapes, that is, lowland plains. So why does the River Dadés meander through these mountains and not simply cut a straight path? Because the river must have existed, and created its bends and loops, before the High Atlas was created.
When the mountains began to form, the Dadés was already etching itself into the ground. This meant the river maintained its course and its original meanders despite the creation of the mountains. It has done so for many millions of years, up to the present day. A hundred and fifty kilometres to the east, there is another large canyon in the High Atlas which carves its way through the Jurassic limestone: Wadi Ziz. The Romans used this gorge as a pass and today it is still one of the most important routes across the mountain chain.
In a region of steep gorges made of hard Jurassic limestone, waterfalls can never be very far away. Indeed, on the northern edge of the High Atlas, 170km north-east of Marrakech, a river plunges hundreds of metres down the Wadi el-Abid in several cascades. It is without doubt the most spectacular waterfall in Morocco and is called the Cascades d’Ouzoud. Translated from the Berber language, this means the ‘the Olive Falls’ – olive trees being a key part of the agriculture in this region.
A permanent rainbow hangs over the gorge as sunlight is refracted in the spray of the plummeting waters. Curtains of calcareous sinter adorn the rocks. This limestone was dissolved somewhere in the depths of the Jurassic massif in the High Atlas and is redeposited here as the water loses carbon dioxide during free fall. At the foot of the Cascades d’Ouzoud, lies an idyllic natural swimming pool, providing Morocco’s children with a first class bathing spot and a welcome opportunity to cool off.
A waterfall in a similar setting can be found on the cedar-covered slopes of the Middle Atlas, north-east of Khenifra. These mountains are also composed of Jurassic limestone and reach heights of more than three kilometres. The limestone is full of cracks that allow rain and meltwater to penetrate underground. Here, we find the River Oum-er-Rbia that is fed by 40 springs, giving rise to its other name ‘Quarante Sources’. A pretty waterfall tumbles down a steep escarpment. In terms of its construction, it is similar to the Cascades d’Ouzoud, but not quite as high. Impressive calcareous sinter deposits have formed here as well. And the Quarante Source is just as good for swimming or washing in as its larger brother in the High Atlas.
Middle Atlas underground worlds
On the northern edge of the Middle Atlas, near the small town of Taza in the mountains of Jebel Tazzeka, lies the answer to the origins of the dissolved limestone in the mountain streams. Rough Jurassic limestone peaks surround a broad, shallow valley 1,500m up in the mountains. The valley floor consists of very fertile soil and is known as the plain of Dayet Chiker. Up here, the Berbers make a living from arable farming and cattle rearing. The valley is what is known as a ‘polja’. Acidic subterranean watercourses have dissolved the limestone here and etched huge hollows in the stone. Bit by bit, the water has worked its way below ground. At some point, the mass of rock above the hollows no longer had enough support, and the cave system collapsed. The pattern continued upwards, creating a visible hole in the landscape.
Close to the polja, a smaller collapse has left a hole 20m wide that leads 180m vertically into the ground. It is the shaft of Friouato, a karst doline. Limestone erosion and subsequent collapses have created a narrow access into the core of the mountain. Ferns and mosses have populated the opening of the shaft in the damp twilight. It remains cool here even in the height of summer. A steep stone staircase leads visitors down into the darkness. Light barely penetrates down to the floor of the shaft and this is where the adventurous part of our trip into the underworld begins. Hidden in one dark corner is a black opening of about chest-width, which is the entrance to an exciting cave tour.
The caves were first explored by the French in 1934. Since then, hardly anything about the 270m long subterranean labyrinth has changed. Dozens of tourists visit the Friouato Caves every day, but there is no permanent lighting down here – torches are the only source of light. The first stalactites appear out of the darkness. In a similar manner to the limestone curtains at the waterfalls, carbon dioxide degasses out of water as it drips from the cave ceilings. Over many years, long spikes have grown down from the roof. Water splashing onto the cave floor from above also leaves deposits, creating stalagmites that grow in tower and candle shapes. Just three and a half kilometres north is the Chiker Cave. At a length of almost four kilometres, it is one of the largest cave systems in North Africa. Experts believe that the Chiker Cave is somehow linked to the Friouato karst shaft underground.
Only a few of the millions of tourists that flock to Agadir’s beaches every year know that they are spending their holiday close to a very unusual natural spectacle. When the wind gets up, the coastal rocks of nearby Cape Rhir suddenly come alive. A powerful jet of water is forced, under enormous pressure, through a hole in the rocks and fountains of seawater shoot out of the ground at regular intervals. These structures are known as blowholes and are a natural phenomenon reminiscent of geysers.
However, they are not related to any kind of volcanic activity, but are the result of the pressure of the breaking waves on the rocks. Blowholes of this quality are rare and you would have to go to Australia’s West Coast or Tonga to find their equal. The blowholes occur as aggressive seawater has gouged out existing cracks and etched small tunnel systems into the limestone. The limestone itself was formed 160mya in the Jurassic Period. During those times, there was a sea here too, although it must have been much warmer than today. Tropical coral reefs and shallow lagoons provided a rich environment for sea creatures and aquatic plant life and their fossilized remains can be seen in the coastal cliffs of Cape Rhir.
Source Bleu de Meski
During the Cretaceous, a carbonate-rich sea continued to wash over Morocco and formed rocks that are very similar to those of the preceding Jurassic period. Twenty-five kilometres south of the town of Er-Rachidia, water reflects off the walls of a grotto carve into chalky layers. The water is from the Source Bleue de Meski: the blue spring. Warmed to a temperature of 18°C, it bubbles out of the ground here after a journey from the High Atlas, down through the limestone. The spring is the continuation of the Ziz River that forms a deep gorge in the mountains. There, the Ziz disappears underground and returns to the Earth’s surface at this spring. It then continues towards the broad expanse of the Sahara where it eventually dries up without ever reaching the sea.
We briefly return to the blowhole coast near Agadir to study the high cliffs to the south that preserve millions of years of Cretaceous history. The rocks are composed of limestones and marls. At one point, we find the remains of huge oyster banks that once colonised the ocean floor. Today, 90 million years later, the oyster shells are again washed by ocean waves at high tide. You have to look closely to realize that these artfully shaped coastal inhabitants are actually multi-million-year-old fossils.
Birth of the High and Middle Atlas
Seventy million years ago, towards the end of the Cretaceous, the sea gradually receded. Rocked by large earthquakes, the seabed was slowly uplifted. Forty-five million years later, Africa collided with Europe. The Straits of Gibraltar found itself in the centre of a tectonic battlefield. The rock layers of Morocco and Spain were compressed between the continents as if in a clamp. The rocks were uplifted several kilometres and the High and Middle Atlas and the Rif Mountains were born.
Morocco had entered turbulent times. The high pressure in the mountains heated the rocks deep in the crust to such an extent that parts of it began to melt. This pressure also forced the molten rock to the surface, through cracks and fissures. The result was the volcanic landscape of the Paysage d’Ito in the Middle Atlas. Here, we find six-sided basalt columns – whole batteries of them, like organ pipes, which were produced as the lava cooled. Long shrinkage cracks formed vertical to the cooling surface, leading to the creation of the typical pillar shape.
Erosion as a new beginning
After the birth of the Atlas Mountains, the process of weathering and erosion began. Water, wind and temperature fluctuations began to take their effect. The resulting debris formed huge fans. Streams transported the rubble downhill in large quantities. In the mountain valleys of the High Atlas, some of the debris hardened. However, here again, the forces of nature got to work, sculpting elegant structures out of it. This is how the imposing cliffs of the Amesfrane, located in a remote part of the High Atlas, were formed.
Today, there are still villages here that can only be reached by footpaths. The wall of the Amesfrane rises 500m out of the wooded slopes of its wadi. Early travellers dubbed the cliffs here ‘La Cathedral’ because of the resemblance of their shape and walls to the facade of a gothic church and bell tower. Erosion has etched slim pillars and natural ledges into the walls, blessing the huge rock dome with a graceful exterior.
There are similar natural works to admire on the south side of the High Atlas. Huge forces must have been operating where the entrance of the Dades gorge is now situated, as the strata here soar vertically into the sky. The high pressures within the mountains have also created an impressive fracture pattern. Subsequently, nature has carved beautiful forms out of the area’s gravelly sand, including shapes like chimneys, towers and mushrooms.
Merzouga sand dunes
The end product of these destructive forces is quartz sand, trillions of grains of which are now blown about the deserts of Morocco to pile up into huge sand dunes. Fifty kilometres south of Erfoud, near the Oasis of Merzouga in the Anti-Atlas, is the migrating dune of Erg Chebbi, towering 100m above the stony plain. It is the largest dune in Morocco, over 30km long and up to 10km wide but is only a taste of the gigantic sand dune systems that dominate the central Sahara in neighbouring Algeria and Libya.
And so we’ve reached the present and our journey through time comes to an end. We have seen that the rocks upon which this impressive country is built go back many millions of years. Their history is diverse and their story is narrated, chapter-by-chapter, in the breathtaking landscapes of modern Morocco.
This article is based on the documentary film Natural Wonders of the Maghreb by the same author, which is available on DVD (www.seven-continents.com/morocco.htm). The film script was written in co-operation with Steven Taylor (www.britishvoice.de). I thank Roy Bullard for his encouragement to publish this geological overview.
Contacting the author
Sebastian Lüning can be contacted at: Sebastian.Luning@gmx.net.