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D-55: How the African Plate powers the AFAED

Updated: Mar 26, 2021

When we leave Genoa on 11 July, we will sail along the Ligurian coast with its steep hills. Already on the second day they merge with the Apennines mountains. In week two we follow the high mountains of Corsica, In week three there will be the Sardinian mountains and once over to Tunisia we will see the end of the Atlas range fading into the desert of Libya.

The existence of all these mountains is a God’s blessing for us sailors. They provide thermic winds in the morning and evening and make sailing possible. As the day gets hotter, the warm air over the mountains rises pulling in fresh air from the sea. A thermic wind is created. In the evening the process reverses. In the absence of these islands, there would just be a simmering heat as in the Sahara and no wind. Maybe an occasional light westerly breeze.

We are also lucky that we do not try to sail 20’000 years ago, during the peak of the last glaciation. With sea levels being about 120 meter lower than today, our sailing would have been much restricted.

Bathymetric map of the Mediterranean – the brown area is 100 m below today’s sea level

We could still start close to Genoa since the Ligurian coast drops off steeply. But we would have to sail straight to Corsica missing Cinque Terre and Elba. The two islands Corsica and Sardinia were linked at the time and the crossing over to Tunisia would only take two or three hours instead of a full day. But we would eventually make it to Sicily – albeit not to today’s coast but closer to the Lipari islands with the Stromboli volcano.

At least there would be some sailing. Albeit all of us would have to wear polar jackets and one of our day jobs would be the de-icing of the AFAED deck every morning!

Had we chosen to sail 6 million years earlier … there would actually be no sailing at all

The Mediterranean 5.75 m years ago with the Straits of Gibraltar closed

When the Straits of Gibraltar closed 6 million years ago, the Mediterranean evaporated and turned into an inhospitable desert. The water contribution from the big rivers Ebro, Rhone, Po and Nile is insufficient to compensate for the evaporation loss. Huge salt deposits formed at the lowest points in the Tyrrhenian and Ionian depression. All sea life had vanished and mid-day temperatures at these salt ponds soared to 70 C!

We could have visited the giant Po Canyon however which dwarfed the Grand Canyon of the Colorado River by a magnitude and stretched for 2’000 km from the Alps to Anatolia. It would be a hiking not sailing tour.

One wonders how so much change is possible in a relatively short time – geologically speaking. The change actually continues as I am writing this blog. The active volcanos of Stromboli and Aetna and the recent big earthquakes in Italy and Turkey are vivid reminders.

The answer lies in the collision of two continental plates which started a good 150 million years ago when the supercontinent Pangea was breaking apart. As the continental Plate of Africa split from South America, Antarctica and India, it began moving north. Slowly but steadily with an average speed of about 3 cm a year. Makes 4’500 km over 150 m years. Eventually the African Plate collided with the European Plate folding the sea floor of the Thetys Ocean in the process. That is the reason why so many of the Mediterranean mountains are made of limestone. They are actually the ancient sea floor of the Thetys Ocean, lifted and shoved over the underlying European Plate. If anyone ever wants to stand on the geological border between Europe and Africa, don’t come sailing with us but go skiing in the Swiss mountains. In Zermatt you will ski on the European plate one minute, the next you will be on the African plate. And all of this on 3’000 meters altitude! You still need sun glasses though!

The arrangement of the Earth’s tectonic plates about 94 million years ago

The tectonic plates in about 50 million years’ time

The movement north of Africa continues to this day. In about 2 million years, the Mediterranean will close and evaporate again. In 30 million years, Tunis will lay on top of Genoa. Geologist predict that if the current speed is maintained, the Alps will grow far beyond of what they are today. The Himalaya will become the little cousin in the East. The landmass of the African Plate is much larger than the landmass of the Indian Plate. Its oomph is thus bigger by a magnitude.

But that is far in the future. Let’s do as the Romans say “Carpe Diem” (seize the day) and let’s enjoy the geography of the Mediterranean which provides beautiful sailing winds from its mountainous islands, a hot African summer climate for swimming in the sea and ample limestone soil for the beautiful olive trees we will be watching from the sea.

Our sailboat AFAED for this summer

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2 comentarios

17 may 2020

Great post 👍🏻

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17 may 2020

Cool, the blog works! 😎 Thxs 🙏🏻

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