From shore to Promenade - a natural history

Exhibition from 12 June to 13 December 2015
Galerie des Ponchettes (an exhibition from the Natural History Museum)

Under the Promenade des Anglais lies a pebble beach, a broad grey ribbon unravelling along a 7-kilometre stretch that curves its way down from the castle hill to the mouth of the Var. Drawing on a collection of pebbles, from the ordinary to the extraordinary, this exhibition explains how the landscape shapes these pebbles: torn from the mountains that sometimes soar 3,000 metres high, drawn down by the pull of the streams and gradually whittled down along the way until they are finally deposited on the beach by the tides, forming a constantly shifting offshore bar.

Observing these pebbles and their sheer diversity is one way of telling the ancient and recent stories of the region's ever-changing landscapes and shores. The exhibition also unveils an incredibly diverse natural environment, a hidden world of irrefutable aesthetic and ecological value, and a unique heritage that deserves and requires our care.
The eternal relationship between Man and pebble is told here, from Nice's prehistoric sites to the works of contemporary artists that draw on their power.
The nature of pebbles
Pebbles of substance

The pebbles dragged down from the Alps and Prealps are rolled down to the sea by the Var and Paillon rivers and deposited on the beach by sea tides. Composed of a broad range of different mineral materials, from granite, gneiss, mudstone and arkose to sandstone and particularly limestone, they bear testimony to the region's turbulent geological past - a past that dates back hundreds of millions of years and is characterised by successive waves of landscapes, from the marine to the terrestrial, along with powerful tectonic shifts that resulted in hill and mountain formation.
The curves and planes of the pebble

Each and every pebble initially came from a large block of raw rocky and angular material, before being blunted, rounded and generally flattened by the rolling motion induced by streams and then rivers. Ultimately, a pebble's fate is to become a grain of sand like those that carpet the seabed.
Pebbles: guardians of the past

Many pebbles contain mineralised fractures that appear in the form of light-coloured veins. These intricate patterns are the result of the tectonic pressure the rock was subjected to when the Alps arose, a process that began around 20 million years ago. Veritable open-air history books, some of them bear traces of fossils, reminders of past lives and environments, with the oldest dating back hundreds of millions of years.
The ups and downs of the shore

Sea levels have been fluctuating in accordance with glacial and interglacial periods for a million years now. 400,000 years ago, the Terra Amata inhabitants built 'seafront' huts 26 metres above current sea level, opposite the castle hill that would at that time have been a small island surrounded by waves.
20,000 years ago at the peak of the last (Würm) glaciation, the sea level around our coast would have been 110 metres lower than it currently is. It gradually rose as the ice cap melted until the sea flooded the 'Gulf of Nice'. Erosion in this period was exacerbated by a drop in vegetation caused by climate change, as well as an increase in water flow and the development of human intervention (farming, cattle rearing). This triggered a huge stockpile of pebbles, which forms the bedrock of Nice's offshore bar and began to accumulate 7,000 years ago.
The baie des anges in azure and turquoise
Currents and colours

The Var and Paillon rivers gush out into the sea, abandoning their pebbles to the whims of the sea's currents. On some days, the direction they take is clearly visible: after a flurry of activity the sea takes on a strange hue featuring opalescent turquoise shades known as the Tyndall effect, an optical phenomenon in which the limestone particles ripped off the pebbles by the waves remain floating in suspension and reflect the sun's rays, resulting in the sea changing colour and contrasting beautifully with the surrounding azure blue.
The whims of the sea

The Baie des Anges is cradled by a sea that is almost tideless (tidal range of 50 cm maximum), characterised by short waves. The average height of these waves lies somewhere between 60 and 100 cm, apart from a handful of days throughout the year when surprisingly high storm waves sweep through: this violent phenomenon occurs during the spring and autumn equinoxes, such as the famous storm of 2010 that dragged in waves of almost 5 metres high that flooded the road and deposited layers of pebbles running up to the foot of the seafront buildings.
The coast's ecosystem
Under the pebbles

The pebbles form a biotope that is relatively hostile to living organisms, yet they nevertheless host a rich and often little-known biodiversity known as meiofauna, comprised of biofilms, sand fleas and other annelid worms.
Fascinating seabeds on our doorstep

The continental plateau is extremely narrow and the sea boasts significant depths mere metres away from the shore. Contrary to first appearances, they are home to incredible biodiversity and luxuriant flora and fauna such as the famous angel shark, a cartilaginous fish similar to a cross between a ray and a shark. This rare, harmless fish was once so common, it gave its name to Nice's bay. Remarkable pelagic species can be found swimming through the open sea, and the beautifully bizarre ocean sunfish can frequently be spotted sleeping close to the surface alongside a number of cetaceans such as the bottlenose dolphin, Risso's dolphin and the fin whale, an imposing creature that sometimes ventures close to the coast.
A pebble's throw from the shore, powerful upwellings haul up weird and wonderful creatures from the depths of the ocean: species such as the spectacular 4-metre long giant oarfish (or kings of herrings) that sometimes mingle here.