Apparently most people go to Fátima for religious reasons. I went there for the caves.

Fátima is really lucky to have two networks of caves nearby. I originally planned to go to Grutas de Mire de Aire (one of the 7 wonders of Portugal) however, upon discovering a taxi would cost upwards of €50 and there was no other mode of transport, I decided to go to the caves where I could get a free ride from the hotel.

Grutas da Moeda translates to ‘The Coin Caves’. They got their name from a two step process:

1. A wealthy man from the region was attacked by a band of robbers and fell through a sinkhole trying to protect his money. This sinkhole became known as ‘Algar da Moeda’, Coin Sinkhole.
2. In 1971, two hunters followed a fox into this sinkhole and discovered the caves. After exploration and the making of pathways, it was opened to the public in 1974.

The Coin Sinkhole (otherwise known as the Water Sinkhole) can be seen in the Sheppard’s Room. If you look carefully you will be able to see roots, searching for water and nutrients, climbing down the walls.

To support this as being the main/original entrance there were animal bones discovered nearby (although I doubt they were originally found so neatly):

Cave formations like these are actually quite rare but most commonly found where limestone is present. This particular set is within the Estremenho Limestone Massif.

The deepest, accessible section of the caves is 45m below the entry point. There are still rivers below which feed into the Lis River Spring, for the town of Leira.

The limestone for these caves was formed about 168 million years ago in a shallow sea of warm, calm, crystal clear water. The rock is formed through the deposition of sediments that are rich in calcium carbonate eg. Shells and algae. You can clearly see these layers throughout time, especially in the below picture. The lines between the layers are called stratification joints.

Caves, themselves, are formed when:

• Water has absorbed carbon dioxide from the rain and/or soil, making it acidic.
• The limestone, which easily reacts, features.
• The fractures in the rock aid water movement, helping to create underground rivers and thus accelerating the formation of caves. An example of this can be seen in the ‘Lake of Happiness’. If you look at the ceiling it looks like a river.

Speleothems (Stalagmites etc.) are created when the water infiltrates the limestone and calcite (one of the forms of Calcium Carbonate CaCO₃) is deposited elsewhere. The average growth rate is 0.3mm per year or 1cm per century. It took this column, which stands at 2.2m, approximately 22 thousand years to be produced in the Maritime Room:

So, the next time you feel like you aren’t making progress with something,that you can’t see any progress, think of this moment and how lots of small repetitive actions add up over time.

The way that the water flows really affects the type of speleothem that is created. You’ve got your standard:

• Stalagmites, where a deposit grows from the ground upwards.
• Stalactites which hang from the ceiling like a leg from a pair of tights. You can also get eccentric stalactites where something, eg. The air current, is irregular so the growth is not in one uniform direction. The red colour here is created by clay being present and rich in iron oxide.

• Columns, where stalagmites and stalactites have been growing at the same time and join together.

Then there are some which you may not have heard of:

• A wax-like mantle can be created when there is continuous water flow as opposed to drips:

• Flags are formations that stick out of walls due to water run-off:

• Gours are tiny basins where calcite crystals shine when it’s dry.
• Broccoli are formed by water splashes and look a bit like the texture of the plant:

The green colours in the image below are due to mosses and ferns growing in the presence of the artificial light:

I don’t feel like these pictures have done the caves justice but I hope you’ve enjoyed them none-the-less, I know I did. Plus, every day’s a school day!