The Maltese archipelago consists of three inhabited islands, namely Malta, Gozo and Comino, and a number of uninhabited islets: Kemmunett, Filfla, Selmunett (St. Paul´s Islands) and Fungus Rock, together with some large rocks, among them Il-Gebla tal-Halfa and Hagret il-Fessej.

The surface areas are:

Malta - 245.7 km²
Gozo - 67.1 km²
Comino - 2.8 km²
Selmunett - 10.1 ha
Filfla - 2 ha
Fungus Rock - 0.7 ha

Size and position

The Maltese Islands are a group of small, low-lying islands situated almost at the centre of the Mediterranean Sea
( 35°48'28'' to 36°0'0'' N; 14°11'04'' to 14°34'37'' E ). They are about 96km south of Sicily and 290km north of the Libyan coast.

The sea between Malta and Sicily (the Sicilian Channel) is generally less than 90m in depth, although the maximum depth reaches nearly 200m. The Malta Channel, between Malta and North Africa, is deeper and at some points reaches depths in excess of 1000m.

Geology

The islands are composed of sedimentary rocks, mostly limestones, which were laid down in the sea during the Oligo - Miocene period. This accounts for the presence of large numbers of marine plant and animals fossils in Maltese rocks. These are the remains of organisms such as a algae, molluscs, echinoderms, crustaceans and fish which were preserved in bottom sediments which later became rock. The five principal types of rock exposed are listed below in order of decreasing age:

Lower Coralline Limestone -
found exposed in strata up to 140m thick. Formed between 25 and 30 million years ago.

Globigerina Limestone -
found exposed in strata of thicknesses ranging
between 23 and 207m. It is subdivided into three layers by two intervening pebble layers.

Blue Clay -
exposed in layers of varying thickness up to 65m

Greensand -
the thinnest stratum, with exposed thickness up to 12m

Upper Coralline Limestone -
exposed in strata up to 162m thick. This is a complex of calcareous rocks that were laid down not long before the land rose out of the sea about 10 million years ago.


In some localities Quaternary deposits of the Pleistocene Epoch (1.9-0.01 million years ago) are to be found, especially in valleys, on the coast and in caves and fissures.
These were formed on land or in fresh water after Malta emerged completely from beneath the sea.

The soil

The material making up the soil is very similar to that forming the rocks. The different soil types present are derived from Coralline Limestone, Blue Clay, Globigerina Limestone and the Quaternary deposits.

Three main soil types are encountered in Malta: Terra soils, Xerorendzina soils and Carbonate Raw soils. Although these can still be found in the areas where they were originally formed from the underlying rocks, extensive movement of soil by humans took place over the years, so that it is now possible to find a mixture of all soil types in the same locality.

Terra Soils are the oldest and were formed during the Pleistocene. They are found mainly on Coralline Limestone, both Lower and Upper. In the natural state, therefore, Terra soils are found mainly in the northern and southeastern parts of the island of Malta, in the coastal areas of Gozo and on Comino.

Xerorendzinas and Carbonate Raw Soils are derived mainly from Globigerina Limestone and Blue Clay. The former are found principally in the central parts of Malta, particularly in the valleys, and were produced mainly from Globigerina Limestone. Carbonate Raw Soils, which are whitish owing to their high calcium carbonate content, were formed mainly from Blue Clay.

Geomorphology

Rain, wind, storms, wave action and ceaseless temperature fluctuations, together with geotectonic movements, have played a great part over the years in the formation of the Maltese Islands as we know them. Erosion of the different types of rock led to the creation of a characteristic topography.

The Lower Coralline Limestone forms natural bastions of rock in the southern and western parts of the islands. Inland, this type of rock forms flat surfaces riddled with depressions, ridges, holes, crevices and ledges. These were formed when groundwater, slightly acidic because of its carbon dioxide content, dissolved the calcium carbonate. The same thing happened in the case of the Upper Coralline Limestone.

Globigerina Limestone, where exposed, gives rise to a different type of landscape which plains of generally smooth rock, while the Blue Clay forms slopes covering the underlying rocks. Greensand is not a very robust rock, and is usually found on clay which easily subsides. Thus much of the Greensand crumbles and rolls downwards, usually with a simultaneous collapse of the Upper Coralline Limestone. This process leads to the formation of screes, with broken rocks and boulders under cliff faces, especially evident on the Gozitan hillsides.

The islands have an inclination from the southwest, where the highest points are found, towards the northeast, where the land slopes gently into the sea. The islands lack montains, the highest point Ta´Zuta, near Dingli Cliffs, which is 253m above sea level. The highest point in Gozo - Ta´Dbiegi - has an altitude of 191m. Lakes and rivers are lacking, with only a few freshwater springs to be found.

Geotectonic movements, which started to occur millions of years ago, played an important part in moulding the islands. Large tracts of land were raised, while others subsided, so that faults were created throughout the islands. A major fault is Xaqq il-Maghlaq, which traverses the islands from the northwest to the southeast coasts. Another major fault lies between Madliena and Fomm ir-Rih, while in Gozo the principal fault crosses from Ras il-Qala to Mgarr ix-Xini. Between the two latter faults, several minor faults are to be found running parallel to the major ones. Land subsidence led to the formation of hills and valleys such as the ridges at Wardija, Mizieb, Mellieha and L-Ahrax, and the valleys of Pwales, Mistra and Ghadira in between.

The topography of Gozo is more complex, and is marked by a number of hilly plateaux formed from Upper Coralline Limestone, between which are plains where erosion has exposed the Globigerina Limestone. The hillsides are covered with clay slopes, while the plains slope away into valleys.

The climate

The Maltese Climate is typically Mediterranean with mild, wet winters and hot, dry summers. Annual rainfall is very variable, the average for the last 40years being 53cm. The wet season lasts from October to March, with about 85% of the rain falling in this period. The period from April to September constitutes the dry season.

Temperatures are moderate, the average being 18.8°C, with the monthly average ranging from 12.3° to 26.3°C. Relative humidity is high throughout the year, generally between 65-80%. Malta is renowned for its sunshine, and days in which the sun does not appear are few and far between. The mean daily hours of sunshine is 8.5. Windy conditions are the norm, with only about 8% windless days in the year. The prevailing wind is the mistral or northwesterly, which blows on 18% of windy days. Other wind directions are more or less equally represented.

Water resources

Natural water resources are totally dependent on rainwater which percolates through the rock and forms underground reservoirs (aquifers). From here it seeps through cracks and fissures, or else is pumped up by man. It is believed that between 16% and 25% of the annual rainfall finds its way into the rocks to form these natural subterranean water reserves. The major water source is found in the Globigerina and Coralline Limestone layers at sea level. Fresh water percolates through the rock and, being lighter, floats on the salty water which infiltrates from the sea.

Other water reserves are found on clay strata which trap the water percolating through the rocks above. Where the Coralline and Clay layers are exposed together at the surface, water from these reserves seeps out of the aquifer and flows downhill, forming streamlets which meander through the valley watercourses. In the past, many of these springs flowed all the year around, although their output was reduced considerably during the summer months. Nowadays many of them have dried up completely because of overpumping of water from underground sources or diversion for other uses, mainly irrigation.

During the last fifty years, many valleys have been dammed for the catchment and storage of rainwater for irrigation. More recently, many farmers have excavated large reservoirs over clay strata in order to store rainwater to be used for irrigation during the dry period.