The regular readers of my blogs may have noticed my interest in sea level changes over the ages. In 2019 when we travelled from Corfu to Venice, we would have become hikers after Zadar. The Adria did not reach to Venice and the Po River was far longer. Last year the first half of our journey would have been a leisurely walk following fresh water lakes, mountain ranges and Anatolian rivers. Would we have been able to reach the Baleares without getting wet feet at the peak of the last ice age as well?
Mallorca's West Coast is rocky but the Seas surrounding the Baleares are quite shallow
Sea level changes during the ice ages were common. At the peak of the last ice age, sea levels were 120 meters below today’s. The large glaciers captured 42 x 10^6 cubic kilometers of water. The rising seas did not only swallow the Persian Gulf, which was probably the Bible's Garden of Eden, but also Sundaland in Southeast Asia and the large Indus Delta – both also home to sophisticated societies. The sea also flooded the Black Sea, a fresh water lake until that time. Also, Malta was connected to Sicily so was Corsica to Sardinia.
The core Areas were Land during the last Ice Ages - they were flooded 12'000 years ago
In the western Mediterranean, changes were less drastic. The Balearic Ridge was too low and remained flooded during the ice ages. We could not have walked from Spain to Ibiza. It was a land bridge though during the Messalina Salinity Crisis 6 million years ago when the Betics mountains separated the Mediterranean from the Atlantic. In the 19th century, people found bones of giant rabbits, the Nuralagus Rex, on Mallorca. The species is now extinct but clearly migrated from the Iberian peninsula to the Baleares. Menorca and Mallorca were one island though 12’000 years ago. We would not have to cross in week three.
The Nuralagus was a Giant Rabbit who lived on the Baleares - it migrated from the Iberian Peninsula and grew massively in the Absence of Predators - a normal Rabbit to the Right
The Ligurian coast from La Spezia to Marseille was not very different from today. The mountains drop to sharply into the sea. The shore lines were only a few hundred meters further out. The drop off of the Ligurian Mountains was too steep
The Drop off of the Ligurian Mountains is so steep that the Shoreline did not change
It was very different though for the large Rhone River Delta which extends several dozen kilometers into the sea. An area of 10’000 square kilometers, about quarter of Switzerland, was above sea level. It must have looked like the northern part of the Adria. Nordic forests intersected with marshes and grass land. It must have looked spectacular – a delta like the ones we find nowadays in Siberia and Alaska. Am sure it was populated with great game which was a perfect source of food for the early Humans living there.
The dotted line represents the Shoreline during the last Ice Age - Sand deposits are grey
One thing I did not grasp until recently was that the Rhone River would deposit its sediments only when reaching the sea – meaning 50 – 70 kilometres further out. The landscape of today’s Rhone Delta was a normal river landscape – the decline was minimal though and the Rhone River must have meandered quite a bit. But there was still a drop of 120 meters to go resulting in a decline of 0.2 %. At the end of the ice age, the sea levels rose faster than the Rhone could fill the new bay. Researchers assume that the sea reached up to Viviers, an old Bishop town south of Montélimar. 12’000 years ago we could have sailed easily to Avignon.
The Sea reached almost Montelimar in 10'000 BC
The Rhone’s contributories carry large quantities of sediments and deposited them when they hit the still water of the north reaching bay. Two of them, the Ardèche and the Durance, move significant volumes of stones, gravel and sand towards the Rhone Valley. By 6’000 BC the northern bay was closed off and the building of the Rhone Delta as we know it began.
The rapid Advance of the Delta's Shoreline over the last few Millenia
That the growth of the Rhone River Delta was fast is evidenced by Hannibal’s crossing of the river on his way to Italy in 218 BC. His army crossed somewhere between Orange and Avignon, 4 days of marching distance from the sea. The new delta was still too swampy to be crossed by his army of 38’000 Infantry, 8’000 Cavalry and 40 Elephants.
Hannibal had to cross the Rhone far North since the new Delta was not passable
This year, we won't be sailing along the Rhone River Delta though. The shores are too shallow and there are only a few good places to anchor for the night. We will take a short cut, stop in Marseille and fly over to Menorca to continue our journey with another boat. We thus will miss beautiful places like Aigues-Mortes, Agde, Beziers, Narbonnes and Rosas. But postponed is not cancelled. They stay on the list for future visits.
The Rhone River Delta is still growing - sea becomes marshes - marshes wet land - wet land eventually arable land. The progress is unstoppable. .