🇬🇧 English: The Porous Columns of Tirana
Welcome to Mother Teresa Square in the heart of Tirana! One of the eye-catching buildings here is the Archaeological Institute, with its many columns made of pale stone. If you look closely, you'll notice the stone shows distinct layering and many holes. This EarthCache will help you discover why.
🪨 About the Rock
The stone used for the columns is travertine – a form of freshwater limestone that forms not in oceans, but at springs and thermal waters, especially where water is rich in dissolved calcium carbonate and CO₂.
When such water reaches the surface, it releases CO₂ into the atmosphere due to temperature and pressure changes. This causes calcium carbonate (CaCO₃) to precipitate and form solid limestone deposits. Over time, these build up in layers.
During this process, air or CO₂ bubbles may get trapped, forming round cavities. Additionally, organic materials such as mosses, algae, or plant roots can become embedded in the forming stone. When this material later decays, it leaves behind irregular holes, channels, or tubular voids – the characteristic porous texture of travertine.
Because of this origin, travertine often appears layered and full of holes. It comes in colors ranging from white to beige, light yellow, or brown, depending on mineral content.
Travertine has been used as a decorative and structural stone since ancient times – famously in the Colosseum in Rome. The travertine in Tirana may have been imported from Italy (e.g., Tivoli), particularly during the period of Italian occupation in the late 1930s.
🔍 Your Task On Site
Please answer the following questions. Send them via message or include them in your log (no spoiler pictures please).
1. Describe the stone on the columns:
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What does the surface look like?
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Which colors and layers do you see?
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How frequent and large are the holes?
2. Describe the holes more closely:
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Evenly or unevenly distributed?
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Round, oval, or elongated?
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Do some connect to each other?
3. In your opinion, how did these holes form?
4. How does the stone feel when you touch it?
5. Optional:
Take a photo of yourself or your GPS at one of the columns (no close-ups of holes, please).
📚 Sources
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