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