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The Blue Grotto - Il-Hnejja EarthCache

Hidden : 11/05/2008
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Geocache Description:

The Blue Grotto is an amazing natural cave and arch which can be seen from land and also explored by small boats.

The Blue Grotto, known as Il-Hnejja (meaning 'The Arch') in Maltese, was given its English name by a British soldier who thought it was similar enough to Grotta Azzuzza (The Blue Grotto) in Capri to deserve the same name. It is located near "Wied iz-Zurrieq" south of the town of Zurrieq. (Bus number 39 will take you there.)
The Blue Grotto is only one of many coastal caves found in the area. However, the Arch over it is a truly remarkable natural geological feature formed through the relentless pounding of the sea. The cavern is 40 metres in circumference, extends back to a depth of 26 metres and has an immense arch reaching a height of 42 metres. The whole system consists of six caves, of which the Blue Grotto is the largest and most impressive. The water appears to be an intense cobalt blue colour, because of the reflection of the sky off the white sandy bottom. The Blue Grotto itself faces east and, especially in the morning, the rays of sunlight reflect off the water and cave walls, revealing an incandescent beauty. There are stalactites on the roof and waters are so clear, it is like looking into an aquarium full of fish. The intense blue reflections in the sea are spectacularly augmented by the orange, purple and green of the various minerals present in the rocks. It is possible to enter into the Blue Grotto and the other caves on "Dghajjes", which are small Maltese boats. The Dghajjes are piloted by expert boatmen who know the surrounding waters and caves very well.

The Dghajjes

The Technical Bit

Malta stands on an underwater ridge that extends from North Africa to Sicily. Millions of years ago the island was fully submerged, as shown by the marine fossils embedded in the rock found at the highest points of Malta. The western side of Malta is characterised by high sheer cliffs such as the Dingli Cliffs. These were formed by the uplifting of land due to the Pantelleria rift that developed between Malta and the Pelagian islands. As the tectonic plates of Africa and Europe collided and the straits of Gibraltar closed, the underwater ridge was pushed up and the Maltese archipelago was created.
The Maltese cliffs are made up mostly of Coralline Limestone, which is not a very resistant rock, and the caves and arches have been formed by wave erosion. Wave erosion is the wearing away and removal of loose material by the constant pounding of the waves. This pounding becomes far more damaging when the waves carry with them quantities of abrasive rocks, stones and sand. Additionally the “joints”, or cracks and crevices, in the cliff face are constantly being subjected to stresses, because of the hydraulic pressure of the huge volumes of water, which are regularly forced into them by the waves. Initially the waves attack the bottom of a cliff and form what is known as a “notch”. Eventually when the notch grows deeper, the overhanging rock above it becomes too heavy to remain suspended and it collapses, dumping blocks of stones into the sea at the base of the cliff. These blocks are then picked up by the waves and smashed against the base of the cliffs, which they undercut even further. Coralline Limestone is a rock that naturally has many “joints” in it. When the rock fractures along these joints more blocks fall into the sea. Water is forced into the joints or crevices and compresses the air trapped within them, which puts pressure on the walls of the joint. When allowed to expand suddenly, the air “explodes” and by a continuous process of expansion and contraction it turns the joints into cracks, then into crevices, then into notches and finally into caves. This results in what is known as cliff retreat. When waves act on both sides of a protruding headland, erosion occurs on both sides forming caves. When these caves erode back into the cliff they can meet in the middle. In this way a natural arch may be produced.

It is not essential but please take a picture of yourself at the viewpoint holding your GPS with the Blue Grotto Arch behind you.

What you need to do to log this cache When you are standing at the viewpoint what is your height above sea level in either feet or metres? Send the answer to me within 48 hours of posting your log.

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First To Find honours go to Drastak from the Czech Republic! Congratulations!

Additional Hints (Decrypt)

Fgnaq ng gur ivrjcbvag naq ernq gur nygvghqr sebz lbhe TCF erpvrire.

Decryption Key


(letter above equals below, and vice versa)