Culture
A geological haven: how much do you know about the rock that makes up 'The Rock'?
Taking a closer look at this island's age!

Melanie Drury

Walking around the Maltese Islands, for anybody interested in geology, is pure pleasure. But even somebody that has zero knowledge about geological strata will, as a minimum, notice a wide variety of rocky features that are sure to captivate interest.

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Geological features in Malta may include caves carved in limestone through centuries of weathering, rolling hills of blue clay meandering into the sea and dramatic cliff faces revealing various different rock layers that are evident even to the untrained eye.

Malta is affectionately known as The Rock locally. Indeed, the tiny islands seem to be nothing but rocks jutting out of the heart of the Mediterranean. They appear tilted, with descending gradients towards the northeast and steep cliffs on the southwest coast.

The break causing the cliffs is because Malta is made up of a crest on the tilted edge of the Malta graben. A graben is an elongated block of the earth's crust lying between two faults that have displaced upwards and downwards. The Maltese archipelago was created through an uplift of sedimentary rocks that happened in the late Miocene and Pliocene periods, some 5 million years ago.

Much older, the making of Malta’s own ‘bones’ is only partly figuratively speaking, because its predominantly limestone rock is made from deposits of shells, coral, algal and fecal debris in marine waters. This organic sedimentary rock is composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite and the crystal known as honey calcite is commonly found in Malta. The oldest sedimentary layer of limestone in Malta is from the late Oligocene, around 25 million years ago.

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In fact, five distinct rock layers are sandwiched on top of each other to create the Maltese Islands. The oldest geological strata from the Oligocene is known as the Lower Coralline Limestone formation. In the Miocene, there was the formation of the Globigerina Limestone, Blue Clay, Greensand and Upper Coralline Limestone. Starting with the oldest, the rock layers of Malta are as follows:

1. Lower Coralline Limestone (Maltese: Żonqor)

The oldest exposed rock layer is 28-23 million years old and has a maximum thickness of 162 metres. It can be seen in the lower parts of cliffs in the south-west of the archipelago, such as at Dingli. This hard limestone is pale grey in colour.

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2. Globigerina Limestone (Maltese: Franka)

This soft, gold-coloured limestone becomes rosy when exposed to air and browns with the formation of a protective patina. It contains many fossils and is one of the main building materials used in Malta. It is 23-14 million years old and ranges in thickness from 23 metres to 207 metres.

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3. Blue Clay (Maltese: Tafal)

Clearly visible near Gnejna Bay and Selmun but completely missing on the eastern parts of the island, this impermeable blue-gray mudstone is 15-10 million years old and measures up to 65 metres thick.

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4. Greensand (Maltese: Ġebla s-Safra)

Yellow-green in colour due to the presence of glauconite, an iron potassium phyllosilicate mineral, this sandstone takes on an orange tint when exposed to air. This very fragile, thin layer, ranging from a few centimetres up to 11 metres in thickness, is 10-7 million years old.

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5. Upper Coralline Limestone (Maltese: Qawwi ta' Fuq)

The top layer is 7-5 million years old and around 140 metres thick. The hard, pale grey limestone was used in constructions requiring great strength, such as fortifications. The western end of Comino has cliffs of Upper Coralline Limestone.

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Fun fact

The Maltese archipelago is linked to Sicily by an underwater plateau of depths of less than 100 metres. During various marine regressions of the Mediterranean, when the sea level was much lower, Malta was connected to Sicily.


Melanie Drury
Written by
Melanie Drury
Melanie was born and raised in Malta and has spent a large chunk of her life travelling solo around the world. Back on the island with a new outlook, she realised just how much wealth her little island home possesses.

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