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C - 18 : Why are the Ancient Harbours in Dalmatia not silted?

Updated: Apr 29, 2021

Remember our experience in Lydia in 2017 and 2018 when we found ancient ports 4 to 5 miles inland, far away from the current shores? Even small rivers from the Anatolian plateau created large alluvial plains over the last 2'000 years and eventually closed them off.

The completely silted harbour of Kaunos which we visited in 2017 during our 3rd week

During our voyage along the Dalmatia coast we will be sailing into many harbours which dates back to Illyrian or Roman time: Durres, Kotor, Dubrovnik, Split and Pula to name a few. Why are they not silted? There are rivers in Dalmatia as everywhere else?

Dalmatia's five rivers which reach the Mediterranean

The answer lies in the nature of Dalmatia's geology which we discussed already several times. The karst, limestone soil can not retain water and is bone dry. It still rains though. Where is the water going? A look at the existing rivers provide the answer.

Krka river near Sebrenice

The Dalmatian Rivers are all shallow and only grow larger when it rains heavily. They all lose water to the surrounding soil. Some of them do not even reach the sea.

Karstfield illustration from Wikipedia

Limestone gets eroded by the slight acidity of rain. When it rains, rain drops chemically react with Carbon oxide (CO2) in the atmosphere and form tiny amounts of Carbonic Acid (H2CO3). Compared to other acids, carbonic acid is harmless. We even put it into our seltzer and drink it. However, o er long periods it dissolves limestone (CaCO3) and creates large, complex cave systems. And this is exactly what happens in Dalmatia every day. Water drains into these caves and runs off underground. Dalmatia has mighty rivers - we just don't see them. And given that they dissolve the livestock bedrock chemically, there are no sediments.

The famous Blue Caves - we are going to visit them in week 2

There are a few places where these caves can be visited without crawling through miles of muddy caverns. In a few places such as Vis they are accessible by boat. Inside the caves there is no sunlight - of course. The indirect sunlight is filtered by water which absorbed everything from the spectrum except blue. Scuba divers know this - below 20 m depth everything turns blue. These caves are thus bathed in magnificent blue.

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