Day 172: İstanbul

Sept 22 - Lots of rain today. Decide to give Odette a break from palaces/churches/mosques/castles and go the Istanbul Aquarium. It is about an hour west along the coast of the Marmara Sea, just past the old airport.

The aquarium had some very large tanks, good viewing windows, and otherwise a satisfying experience for die-hard fans of aquatic animals. Good thing, since tickets ran about $55 for the three of us.

They had a few rooms dedicated to explaining the ecosystem of the Black Sea. This required an explanation of how the Black Sea formed. I’ve always found this, along with the Mediterranean, a source of pre-historical fascination, so I will share it with you now.

The above maps shows the various bodies of water and the land around them. The Bosphorus (hidden under the dot for Istanbul), is just the width of a river, not even comparatively visible.

To start things off, the Mediterranean Sea has filled and emptied several times, due to its almost completely enclosed form. The Straits of Gibraltar have acted in the past as a barrier to the Atlantic Ocean. When land bridges have existed across the straits, the Med has dried out, leaving only flat, salty basins between Europe and Africa. When sea levels rise and the straits are breached, the ocean flows in and fills it up. The last time this happened, the oceans kept rising, and over time, put stress on the little isthmus where Istanbul is today.

At the time, what we know as the Black Sea was a freshwater lake, with shorelines well below current sea level. Many pre-historic people lived here. About 5600 BCE, the pressure from the filling Mediterranean (really the Sea of Marmara) finally broke through like a dam, causing a flood of legendary proportions into the Black Sea basin. It is thought that sea levels in the basin rose about 15 cm per day, fast enough that bewildered tribes along the shores probably fled, not having any understanding of what was going on. At any rate, the influx of salt water would have killed off their food sources within a few weeks.

This was all hypothesized, until a group of researchers took cores of bottom sediments in several key locations around the basin and found a succession of material exactly as would be predicted by the ‘sudden flood’ model. As confirmation, some preserved human-made abodes have also been found at depths of hundreds of meters.

Another amazing fact about the Black Sea is the pronounced chemical stratification. Being such a restricted basin, there are basically no vertical convention currents. There is a great deal of inflow from freshwater sources, so the top 100 meters or so is less saline than the Mediterranean. This less dense water never mixes with that below 100 meters, so salinity is much higher at depth. Lack of convection also means that there is no dissolved oxygen at depth, so only anaerobic organisms can live there. It is basically toxic to nearly all sea life. When ancient sunken ships are found at these depths, they are almost perfectly preserved.

On the way back, get off the bus just at the entrance to the new undersea traffic tunnel, and turn up the hill. Here we stop by the Church of Saints Sergius and Bacchus, which is basically a miniature version of the famous Hagia Sophia less than 2 km away. It was built by Justinian I in 527-36. In 1497 it was converted to a mosque by the Ottomans, and remains so today.

Tonight finally locate a much more ‘local’ place to eat, where the prices are about 60% of those in the more touristed areas. Turkish food is such a relief for us, with plenty of soups, fresh vegetable dishes, and spicy chicken kebabs.