A Geological and
Geomorphological Review
of the Maltese Islands with
Special Reference to the
Coastal Zone
Odette Magri
Geography Division, Mediterranean
Institute, University of Malta, Msida
MSD06, Malta
odette.magri@um.edu.mt
Territoris (2006), 6:
7-26
Territoris
Universitat de les Illes Balears
2006. Núm. 6, pp. 7-26
ISSN: 1139-2169
A GEOLOGICAL AND
GEOMORPHOLOGICAL REVIEW OF THE
MALTESE ISLANDS WITH SPECIAL
REFERENCE TO THE COASTAL ZONE
Odette Magri
ABSTRACT: Relationships between tectonics, geology and landforms are very evident in the Maltese Islands. Two
rift systems belonging to different ages and having different trends dominate the structural setting of the Islands. The
older rift generation creates a horst and graben structure north of the Great Fault. The second rift generation –the
Maghlaq Fault– is associated with the Pantelleria Rift. The fault determines the south-west littoral of Malta and is
responsible for the north-east tilt of the Islands. The geology is made up of Tertiary limestones with subsidiary marls
and clays. The geological formations are very distinctive lithologically and this is reflected in characteristic
topography and vegetation. The main focus of this paper is on the coastal zone where the relationship between
geology and geomorphology is particularly evident. The coast although being only about 190 km long features a large
variety of landforms. Lower Coralline Limestone forms vertical plunging cliffs reaching more than 200 m in some
places. Globigerina Limestone features cliffs which in most cases are fronted by shore platforms. Blue Clay displays
itself as slopes which extend from the base of the Upper Coralline Limestone plateau to sea-level. Where Greensand
occurs at the coast this does not produce any particular landform as it is often assimilated into the base of the Upper
Coralline Limestone plateau. The latter runs parallel to the coast in north-west Malta. Moreover tectonics play a very
important role especially in the formation of bays and cliffs. During the Quaternary period there has been tilting of
Malta towards the north-east together with a general subsidence of the archipelago which is probably still going on.
KEYWORDS: tectonics, geology, geomorphology, coastal zone, Maltese Islands.
RESUM: A les illes Malteses s’observa de forma evident la relació entre tectònica, geologia i paisatge. Dos sistemes
de fractures (rift) de diferent edat i que mostren direccions diferents dominen la disposició estructural de les Illes. El
sistema de rift més antic va crear una estructura en horst i graben al nord de la Gran Falla. La segona generació de rift
–la falla Maghlaq– s’associa amb el rift de Pantelleria. Aquesta fractura condiciona el litoral del sud-oest de Malta i és
la responsable del basculament cap al nord-est de les Illes. La constitució geològica està formada per calcàries del
Terciari i, de forma subsidiària, per margues i argiles. Les formacions geològiques són litològicament molt diferents,
la qual cosa es reflecteix de forma característica en la topografia i la vegetació. El principal objectiu d’aquest treball se
centra en la zona costanera, on es fa particularment evident la relació entre geologia i geomorfologia. Encara que la
costa té 190 km i escaig de longitud presenta una gran varietat de paisatges i morfologies. La calcària coral·lina
inferior forma penya-segats verticals que poden arribar a superar els 200 m d’altitud. Les calcàries amb globigerines
formen penya-segats que en molts de casos desenvolupen en la seva part frontal plataformes litorals. Les calcàries
blaves desenvolupen pendents que s’allarguen des de la base de la plataforma de les calcàries coral·lines superiors fins
al nivell de la mar. La costa no presenta cap paisatge particular quan afloren les «arenes verdes», que sovint
Magri, Odette
A Geological and Geomorphological Review of...
s’assimilen a la base amb la plataforma de les calcàries coral·lines superiors. Aquestes darreres van paral·leles a la
costa al nord-oest de Malta. Malgrat tot, la tectònica hi fa un paper molt important, especialment en la formació de
badies i penya-segats. Durant el Quaternari hi ha hagut un basculament de Malta cap al nord-est juntament amb una
subsidència general de l’arxipèlag que probablement continua avui dia.
PARAULES CLAU: tectònica, geologia, geomorfologia, zona costanera, illes Malteses.
1. Overview of the Maltese Islands
coasts of Tripoli and Libya. Geophysically
the Maltese Islands and the Ragusa penin-
The Maltese Islands are located in the
sula of Sicily are regarded as forming part of
central Mediterranean region between Italy
the African continental plate. The
and North Africa, at a latitude of 35º48’28”
archipelago is linked to the Ragusa penin-
to 36º05’00” North and a longitude of 14°
sula in the Sicilian Channel by a submarine
11’ 04” to 14° 34’ 37” East (Schembri,
ridge, which reaches a maximum depth of
1993). The archipelago consists of three
200 m below the present sea level and is
main islands – Malta, Gozo and Comino –
mostly less than 90 m deep. The sea depth
and several small uninhabited islets which
between the Islands and North Africa is
include Cominotto (Maltese: Kemmunett),
much deeper, sometimes reaching more than
Filfola (Maltese: Filfla), St.Paul’s Islands
1000 m (Morelli et al., 1975 in Schembri,
(Maltese: Il-Gzejjer ta’ San Pawl or Sel-
1993). Spratt (1867) claims that the
munett Islands), Fungus Rock (Maltese: Il-
submarine ridge was an epicontinental land
Hagra / Il-Gebla tal-General or General’s
bridge during the Pleistocene and facilitated
Rock) and few other minor rocks (Figure 1).
the migration both northwards and
The Islands have a total land area of 316
southwards of exotic fauna.
km2 (Malta: 245.7 km2, Gozo: 67.1 km2,
The Maltese Islands were settled
Comino: 2.8 km2) and a coastline about 190
continuously from the middle Neolithic
km long, with a submerged area (up to 100
onwards. Important stone temples were
m) of 1940 km2 (Schembri, 1990). The
constructed in the period 2600 – 1700 BC
length of the whole archipelago is 45 km;
(Evans, 1971 in Alexander, 1988). Since
Malta being 27 km long, Gozo 14.5 km long
then the Islands have been occupied by
and Comino 2.5 km. The North Comino
Phoenicians, Greeks, Carthaginians,
Channel, separating Gozo from Comino, is 1
Romans, Arabs, Normans, Angevins, Ara-
km wide whereas the South Comino
gonese, the Knights of St. John, French and
Channel, separating Comino from Malta is 2
finally the British. Malta became an
km wide.
independent country in 1964. In 2005 when
The Islands lie approximately 96 km
the last population census was carried out the
from Sicily to the north, 290 km from North
Islands had a population of 404,039 (Census,
Africa to the south, 1836 km from Gibraltar
2005). The latter shows an increase of
to the west and 1519 km from Alexandria,
25,907 persons (6.9%) over ten years when
Egypt to the east (Figure 1). The archipelago
the Islands had a population of 378,132
is situated on a shallow shelf, the Malta-
(Census, 1995). This figure results in a
Ragusa Rise, part of the submarine ridge
population density of 1282 persons per
which extends from the Ragusa peninsula of
square kilometre, one of the highest in the
Sicily southwards to the North African
world and the highest in the European Union.
10
Territoris, núm. 6. 2006
A Geological and Geomorphological Review of...
Magri, Odette
The aim of this paper is to provide a
activity is also a predominant factor on
review on the geology and geomorphology of
landform development and its role is
the Maltese Islands with special reference to
especially evident at the coastal zone where
the coastal zone. The physical landscape is
despite the restricted coastal length of the
characterised by distinct lithologies which
Islands, various landforms have been
have developed different landforms. Tectonic
developed.
Figure 1. Location of the Maltese Islands.
Source: Alexander, 1988
2. Geology of the Maltese Islands
valley loams, sands and gravels. Deposition
occurred in the following simple succession.
The Maltese Islands are entirely com-
1. Upper Coralline Limestone
posed of Tertiary limestones with subsidiary
2. Greensand
marls and clays. Quaternary deposits, mostly
3. Blue Clay
Pleistocene in age, are limited to few
4. Globigerina Limestone
localities and include cliff breccias, cave and
5. Lower Coralline Limestone
Territoris, núm. 6. 2006
11
Magri, Odette
A Geological and Geomorphological Review of...
Table I shows the litho- and chronos-
thin but intensively cultivated and hillslopes
tratigraphy of the Maltese Islands. The
on it are densely terraced. The Blue Clay
geological succession represents a varied
produces slopes that tend to slide over the
cross-section of Oligo-Miocene lithologies
underlying Globigerina Limestone
and facies, but consists almost entirely of
Formation. It forms the most fertile bedrock
carbonates. The geological formations of the
on the Islands, especially where springs seep
Islands are very distinct lithologically and
from the overlying Upper Coralline
this is reflected in characteristic topography
Limestone. The latter, which also includes
and vegetation (House et al., 1961a). The
Greensand, forms massive cliffs and
Lower Coralline Limestone is responsible for
limestone pavements with karstic topography
forming spectacular cliffs, some reaching
similar to Lower Coralline Limestone. This
140 m in height, which characterize the
formation caps tabular hills and mesas
Islands especially in the west. Inland the
reaching a maximum height of 253 m above
Lower Coralline Limestone forms barren
sea level at Ta’ Zuta, near Dingli in south-
grey limestone-pavement topography. The
west Malta (Pedley et al., 1978). Figure 2
succeeding Globigerina Limestone, which is
represents the spatial distribution of the
the most extensive formation on the Islands,
different geological formations of the
forms a broad, rolling landscape. The soil is
Maltese Islands.
Table I. Stratigraphy of the Maltese Islands
Epoch Stage
Years BP
Formation
Maximum thickness (m)
U. Miocene
Tortonian
Upper Coralline Limestone
104-175
(12-7.5 Ma)
Greensand
0-16
M. Miocene
Serravallian
Blue Clay
0-75
(13-12 Ma)
M. Miocene
Langhian
Upper Globigerina Limestone
5-20
(15-13 Ma)
Upper Main Conglomerate (C2)
L. Miocene
Burdigalian
Middle Globigerina Limestone
0-110
(20-15 Ma)
Lower Main Conglomerate (C1)
L. Miocene
Aquitanian
Lower Globigerina Limestone
5-110
U. Oligocene
Chattian
Lower Coralline Limestone
140
Lithostratigraphy mainly after Murray (1890); chronostratigraphy after Felix (1973)
Sources: Pedley et al., 1978; Alexander, 1988
12
Territoris, núm. 6. 2006
A Geological and Geomorphological Review of...
Magri, Odette
Figure 2. The geology of the Maltese Islands.
Source: House et al., 1961a
The lithostratigraphy of the Maltese
The sequence of rock units of limestones
Islands has been well known since the time
and associated marls represents a succession
of Spratt (1843) due to its simple structure
of sediments deposited within a variety of
and the gentle regional dips. The current ter-
shallow marine environments (Pedley et al.,
minology applied to the individual
1978). In many respects these resemble the
formations originated from the detailed work
mid-Tertiary limestones occurring in the
of Murray (1890). Although Murray’s
Ragusa region of Sicily and North Africa.
lithostratigraphy is still generally accurate,
The succession gives the impression that the
work by Pedley (1975) has substantially im-
depositional area first subsided and then
proved the detailed understanding of both
there was a gradual shallowing (Felix,
lithostratigraphy and palaeoecology,
1973). The sequence starts with the Lower
especially within the two Coralline Li-
Coralline Limestone, deposited in a shallow
mestone formations. Spratt (1867) was the
gulf-type area followed by a sea with shoals.
earliest worker to publish on the Quaternary
The Globigerina Limestone and Blue Clay
geology. A more detailed study was carried
show a deepening in an open marine
out by Trechmann (1938).
environment, to a maximum depth of 150 m
Territoris, núm. 6. 2006
13
Magri, Odette
A Geological and Geomorphological Review of...
to 200 m, as suggested by the foraminiferal
agricultural development. The most
fauna. The upper two formations, the
accessible sections in Malta are along the
Greensand and Upper Coralline Limestone
Qammieh coastline, northern Malta. In Gozo
and their foraminiferal associations, indicate
the formation is well exposed in the valley
a gradual shallowing to an area with shoals
gorges around San Lawrenz, western Gozo.
but still in an open marine environment.
The formation shows marked thickness
variations ranging from 23 m near Fort
2.1. The Geological Formations
Chambrey, southern Gozo, to about 207 m
around Marsaxlokk, southern Malta. The
2.1.1. Lower Coralline Limestone
usual colour of the formation is pale-yellow.
The Lower Coralline Limestone is the
A pale-grey subdivision, bounded both
oldest formation visible on the Islands.
above and below by phosphorite conglo-
Outcrops are mainly limited to coastal
merate horizons, occurs in the middle of the
sections along the western sides of Malta
sequence. The Globigerina Limestone
and Gozo (Pedley et al., 1976). Vertical
provides most of the building stone in Malta
cliffs extend up to 140 m in south-west
and in local terminology is referred to as
Gozo and about 100 m in the sections
Franka (Pedley et al., 1976). This formation
is further subdivided into Lower, Middle
between Fomm ir-Rih and Benghisa Point in
and Upper Globigerina Limestone separated
western and southern Malta respectively.
by two phosphorite conglomerate horizons.
Inland exposures are mostly associated
either with valley-gorge sections, as in
2.1.3. Blue Clay
southern Malta, or with faulted inliers such
The Blue Clay Formation comprises a
as at Naxxar. The upper part of the Lower
sequence of alternating pale grey and dark
Coralline Limestone Formation is exploited
grey banded marls, with lighter bands
in quarries (Pedley et al., 1978). The lowest
containing the highest proportion of carbo-
horizons of the formation are exposed in
nate (Pedley et al., 1978). The formation
cliff sections around Maghlaq, south-west
never contains more than 30 per cent
Malta (Pedley et al., 1976). Pedley (1978)
carbonate material (Murray, 1890). This
has subdivided the Lower Coralline
lithology is found throughout the Islands and
Limestone Formation into four members:
possibly also at the base of the cliffs on the
Maghlaq Member (oldest), Attard Member,
island of Filfla, off the western coast of
Xlendi Member and Il-Mara Member
Malta (Pedley et al., 1976). The maximum
(youngest). The name attributed to each
thickness of the Blue Clay Formation is
member indicates the site where the member
approximately 75 m recorded at Xaghra,
is best exposed. Local terminology for this
northern Gozo, and on the western coast of
formation is Zonqor.
Malta north of Fomm ir-Rih Bay (Pedley et
al., 1976, 1978). Marked thinning occurs
2.1.2. Globigerina Limestone
towards the south and east, where the
The Globigerina Limestone Formation is
formation has been mostly removed by
given this name due to the high percentage
erosion. Fossils are common but are res-
of planktonic foraminifera present in the
tricted to microfauna or crushed specimens
rock (Pedley et al., 1976, 1978). The
of macrofauna, except in the upper horizons
formation covers large areas of central and
of the Blue Clay around northern Malta and
southern Malta and Gozo. The outcrops are
southern Gozo (Pedley et al., 1976).
frequently obscured by housing and
14
Territoris, núm. 6. 2006
A Geological and Geomorphological Review of...
Magri, Odette
2.1.4. Greensand
of approximately 100 m of strata is present
The Greensand Formation is composed
in a lithological sequence, which can be
of thickly bedded, coarse, glauconitic,
divided into three divisions (Pedley et al.,
bioclastic limestones (Pedley et al., 1978).
1978). Pedley (1978) divides the Upper
In unweathered sections the green and black
Coralline Limestone Formation into four
glauconite grains are visible. Usually due to
members, each member consisting of several
the release of limonite upon weathering and
beds: Ghajn Melel Member, Mtarfa
oxidation of the glauconite, the rock
Member, Tal-Pitkal Member and Gebel
possesses a characteristic orange-brown
Imbark Member. The Maltese terminology
colour. The transitional change upwards
used for this formation is Tal-Qawwi.
from the Blue Clay is frequently sharp, par-
ticularly in the western areas of the Islands.
2.1.6. Quaternary Deposits
In eastern parts assimilation of the top of the
Trechmann (1938) carried out a detailed
Greensand into the base of the overlying
study of the quaternary deposits of the
Upper Coralline Limestone, as a result of
Maltese Islands and has classified them into
bioturbation, has produced the effect of a
valley loams and breccias, coastal conglo-
gradual change in sedimentation (Pedley et
merates and breccias, and ossiferous
al., 1976). The maximum development of
deposits in caves and fissures. The earliest of
the Greensand Formation is found at Il-
the deposits are the Pleistocene ossiferous
Gelmus in west-central Gozo, where 16 m
deposits of various cave systems in Malta,
can be measured (Pedley et al., 1976).
which have yielded numerous interesting
Throughout the rest of Malta and Gozo the
animal remains (Pedley et al., 1978). Ghar
formation, is usually less than 1 m thick and
Dalam cave, southern Malta, is the most
shows extensive reworking and assimilation
well-known. The oldest fauna include
into the overlying strata (Pedley et al.,
Pleistocene dwarf hippopotami, pygmy
1978). The formation largely consists of ma-
elephants, dormice and swans. A later
terial transported and deposited into shallow
deposit features horse and deer (House et al.,
water marine conditions from areas of
1961a). The presence of so many land
erosion outside the present confines of the
quadrupedal animals is taken as evidence
Islands (Pedley et al., 1976).
that there was land communication between
Sicily and Malta at this period (Pedley et al.,
2.1.5. Upper Coralline Limestone
1978). Later deposits which possess a
The Upper Coralline Limestone is the
distinct red colour, include alluvial fans,
youngest Tertiary formation of the Maltese
caliche soil profiles and calcreted breccias
Islands and is similar in many aspects to the
and conglomerates. All are stained red by
Lower Coralline Limestone Formation,
iron oxidation.
especially in colour and coralline algal
content (Pedley et al., 1976). It is a durable
sequence, frequently weathering into steep
3. Geomorphology of the Maltese
cliffs and featuring a well-developed karst
Islands
topography. Outcrops occur on all islands of
the Maltese archipelago and the formation is
The geomorphology of the Maltese
extensively developed especially in western
Islands has been discussed by House et al.
Malta, Comino and east-central Gozo, where
(1961b), Vossmerbäumer (1972) and
it displays a wide range of lateral and ver-
Alexander (1988). Coastal geomorphology
tical facies variations. A maximum thickness
is dealt with in the studies of Guilcher and
Territoris, núm. 6. 2006
15
Magri, Odette
A Geological and Geomorphological Review of...
Paskoff (1975), Paskoff and Sanlaville
2. Blue Clay slopes: these occur at coastal
(1978), Ellenberg (1983) and Paskoff
areas and in valleys which separate the
(1985). More recent sources are lacking.
plateau uplands from the surrounding areas.
The predominant control on landforms in
Blue Clay slopes in Malta occur mostly at the
Malta is undoubtedly that of tectonic activity
coast at the foot of the Upper Coralline
including faulting, up-arching and subsi-
Limestone plateau. Inland, Blue Clay
dence (Alexander, 1988). The highest land,
corresponds with the location of dry valleys
around south-west Malta and western Gozo,
which have watercourses during the wet
occurs at the intersection of the rift system
season only, although some have perennial
shoulders (Illies, 1980). Isopachyte maps
springs which flow throughout the year
published by Pedley et al. (1976) indicate
(Schembri, 1993) due to the impermeability
that the extinct NE-SW trending rift system
of Blue Clay. In Gozo, Blue Clay outcrops in
left eminences of the Lower and Middle
coastal slopes and valley slopes and floors
Globigerina Limestone at the south-east and
which cut through Coralline plateaus and
north-west ends of the archipelago. The
Globigerina Limestone plains.
latter was removed by erosion on south-east
3. Rdum or undercliff areas: these are
Malta. The present relief of the Islands
found where Blue Clay slopes descend
corresponds most closely with the iso-
steeply to the sea from beneath the Upper
pachytes of the Lower Coralline Limestone,
Coralline Limestone cliffs, which mark the
which reflects all stages of subsidence and
edge of the limestone outcrop. Faulting and
up warping that the various land areas have
jointing in the bedding planes of the limes-
gone through. Both main Islands are tilted
tone result in rockfall of the Upper Coralline
towards the north-east. The highest point in
Limestone Formation onto the Blue Clay. In
Malta is 253 m above sea level located at
Malta these landforms are situated mainly
Ta’ Zuta on Dingli Cliffs, south-west Malta,
on the western coast, although there are
whereas in Gozo the highest point is 191 m
some present on the north-east coast. In
found at Dbiegi, western Gozo.
Gozo rdum areas occur on the eastern coast.
House et al. (1961b) classify the physical
4. Flat-floored basins: in most cases these
landscape of the Maltese Islands into five
are the result of faulting, such as Pwales
categories.
Valley, or downwarping, such as Bingemma
1. Coralline Limestone plateaus: these
Basin. Sometimes flat-floored basins occur
form the highest areas and are bounded by
due to erosion and subsequent alluvial
well-marked escarpments. These uplands
deposition, such as Wied il-Ghasel, limits of
range in size from the massive triangular
Mosta, central Malta. The region north of the
plateau of western Malta to the small mesas
Victoria Lines Fault consists of a series of
of north-west Gozo. In western Malta, the
ridges and valleys. From north to south, the
Coralline Limestone plateaus range in heights
major divisions are: Marfa Ridge, Mellieha
from 180 m to 245 m. Eastwards the plateaus
change into undulating areas developed on
Valley, Mellieha Ridge, Mizieb Depression,
Globigerina Limestone, mostly having a
Bajda Ridge, Pwales Valley, Wardija Ridge
height of 120 m. The western plateaus are
and Bingemma Basin (Figure 3).
flanked by deeply incised valleys which have
5. Globigerina Limestone hills and
cut back into the upland. The south-west edge
plains: these include large areas of gently
has been least affected by such action and the
sloping land which, in Malta, consist of a
regular line of cliffs is broken only in one
series of low ridges and shallow valleys and
place, where the valley complex of Imtahleb
in Gozo have a more varied topography. The
forms a deep embayment.
central, southern and eastern regions of
16
Territoris, núm. 6. 2006
A Geological and Geomorphological Review of...
Magri, Odette
Malta mostly consist of areas of gentle
occurring around the head of Marsa Creek
relief, although steep slopes occur in a
(eastern Malta), Ta’ Qali (central Malta) and
number of places. Flat land is very limited,
Luqa airfield (southern Malta).
Figure 3. Ridge and valley topography north of the Great Fault.
Source: Ransley and Azzopardi, 1988
4. Coastal geomorphology of the
detail. In spite of the small size, the Maltese
Maltese Islands
Islands display a large variety of coastal
features. Bays in northern Malta correspond
to downthrown blocks that were partially
Two studies by Paskoff and Sanlaville
submerged. High cliffs which characterize
(1978) and Ellenberg (1983) have made a
the south-west coast are associated with a
significant contribution to understanding the
major fault (Figure 4). Beaches are rare and
coastal geomorphology of the Maltese
constitute only 2.4 % of the coastline
Islands.
(Schembri, 1990) (Figure 5). Low limestone
Paskoff and Sanlaville (1978) claim that
coasts display interesting examples of both
the general outline of the Maltese littoral
mechanical and chemical processes such as
zone has been determined by tectonics.
hydraulic pressure and corrosion (Figure 6).
Lithology and advanced karstification have
Most of the coasts have a high relief and
to be considered when studying the coast in
Territoris, núm. 6. 2006
17
Magri, Odette
A Geological and Geomorphological Review of...
show different types of cliffs. Some are
5. The presence of immersed levels about
associated with wave-cut platforms (Figure
9-11 m, 17-21 m, 25-30 m and 33-40 m at
7). Others plunge directly into the sea
the foot of high cliffs on the south-west
(Figure 4) or are skirted by landslides.
coast (Martineau, 1965 in Paskoff and
Since its definitive emersion after the
Sanlaville, 1978).
Tortonian, the Maltese archipelago has been
affected by karstification, now found at an
Faults resulting from tectonic activity
advanced stage of development, which is
determine the outline of the Maltese coasts.
evident at the south of Malta, Comino and
Some faults are perpendicular to the littoral
western Gozo. In Malta, for example, one
zone. Horsts at the north of the Island
finds important circular depressions such as
(Wardija, Bajda, Mellieha and Marfa Ridges
the doline structure of Il-Maqluba, near
and the island of Comino) are separated by
Qrendi, south-west Malta, which is 60 m wide
sunk blocks which the sea has partially (at
and 40 m deep. Long caves, such as Ghar
St.Paul’s and Mellieha Bays) (Figure 3) or
Hasan, south of Hal-Far and especially Ghar
totally overrun (North Comino and South
Dalam, close to Birzebbuga, explored to
Comino Channels). Ras ir-Raheb at the end
about 100 m and famous for its palaeon-
of the projection in Fomm ir-Rih Bay,
tological richness in bone fossils, are also
western Malta coincides with the western
found (Paskoff and Sanlaville, 1978). The
extremity of the Great Fault of the Victoria
karstification, remarkable in underground
Lines (Figure 3).
structures, is principally cut in Coralline
The south-west littoral zone of Malta is
Limestone, which is very sensible to actions
determined by the Maghlaq Fault (Figure 8),
of solution because of its purity in calcium
oriented WNW-ESE, and starting from
carbonate and its dense fractures and
where the Island has been tilted towards the
thickness (Paskoff and Sanlaville, 1978). In
north-east (Paskoff and Sanlaville, 1978).
subterranean cavernous areas of karstic origin,
The result is a striking contrast between a
revealed by cliff retreat, wave action during
south-west coast featuring sheer cliffs of a
storms may provoke roof collapse, which
rectilinear aspect (Figure 4), more than 200
forms roughly semi-circular coves. Blue
Grotto (Figure 8), in southern Malta, is an
m high near Dingli, and a rocky but shallow
example of such a landform (Paskoff, 1985).
north-east coast (Figure 6), gradually
There is evidence of past processes in-
descending under the sea. Other evidence of
volved in the subsidence of Malta during the
the tilting is the water drainage division
Quaternary period accompanied by a tilting
which runs near the south-west coast and the
movement. The following facts support this
location of the highest point of the Island
idea:
(253 m) at Ta’ Zuta, near Dingli, south–west
1. General topography and stratigraphic
Malta (Figure 8).
sequence are inclined towards the north-east.
The role of tectonics is not as important
2. Sinking of the bays on the north-east
in Gozo. However numerous faults are
coast.
located on the southern coast of the Island
3. Traces of Neolithic cart ruts passing
and very likely determine its outline
below sea level in Marsaxlokk Bay, southern
(Paskoff and Sanlaville, 1978).
Malta.
4. Stalactites hanging at the ceiling of
4.1. Coastal features
caves which today are found below sea level
The main coastal features of the Maltese
at the entrance of Grand Harbour in Valletta
archipelago can be divided into five
(Hyde, 1955).
categories. These include cliffs, rdum areas,
18
Territoris, núm. 6. 2006
A Geological and Geomorphological Review of...
Magri, Odette
low rocky coastline, semi-circular coves and
cliffs are generally cut in the Lower
sinkholes and drowned valleys. Each
Coralline Limestone and lack shore
category is discussed in more detail in the
platforms at their feet, such as at Ghar
sections that follow.
Hasan, southern Malta. These cliffs are
vertical, rectilinear and probably of tectonic
4.1.1 Cliffs
origin (Paskoff and Sanlaville, 1978).
Steep cliffs, more than 50 m high and in
Marine erosion appears to be biochemical
some places more than 200 m (Figure 4),
and inefficient. At sea level, an undercut
represent half the length of the Maltese
notch is formed. It is quite regular and
coastline (Guilcher and Paskoff, 1975;
measures between 0.80 m to 1.50 m in depth
Paskoff and Sanlaville, 1978). They
and width (average 0.60 m). The immersed
characterize southern and south-west Malta,
lower part features an irregular sloping
eastern Comino, and most of the coast of
pavement with a cavity formed by waves.
Gozo (Ellenberg, 1983). Vertical plunging
Figure 4: Plunging cliffs developed in Lower Coralline Limestone characterize the south and
south-west coasts from Benghisa to Fomm ir-Rih. These cliffs are associated with the Maghlaq
Fault and reach a height of 200 m in some parts.
Territoris, núm. 6. 2006
19
Magri, Odette
A Geological and Geomorphological Review of...
Figure 5: Sandy beach backed by clay slopes at Ghajn Tuffieha Bay. This Bay which is popular
and frequented both by locals and tourists has been designated by the Malta Environment and
Planning Authority as an area of ecological importance and is a protected site.
Figure 6: Low rocky shore cut in Lower Coralline Limestone on the north-east coast. Pools
and lapiés which produce a very irregular surface are the result of corrosion.
20
Territoris, núm. 6. 2006
A Geological and Geomorphological Review of...
Magri, Odette
Where cliffs are cut in the Globigerina
4.1.2 Rdum areas
Limestone they are fronted, in most cases,
The rdum areas constitute a very original
by shore platforms produced by mechanical
and spectacular element of the Maltese
action of waves, mainly through hydraulic
coasts and correspond to a type of marine
pressure that dislodge and remove blocks
cliff related to a specific geological structure
from stratified and jointed rocks (Figure 7).
that is prone to mass movements. The rdum
Between Marsaxlokk Bay (southern Malta)
areas occur where Blue Clay crops out at sea
and St.Thomas Bay (south-east Malta), the
level and is overlaid with the massive strata
Globigerina Limestone features a perfectly
of Upper Coralline Limestone (Figure 9).
The clay is easily eroded by wave action. In
vertical cliff which reaches a height of more
addition, rainwater percolates through
than 50 m. At sea level a structural platform,
fissures of the limestone into the underlying
above which there is a notch, is the result of
clay. This causes the Blue Clay to become
mechanical erosion. The rock here is quite
plastic and unstable. Jointing and faulting in
uniform which helps to maintain the
the Upper Coralline Limestone causes the
steepness of the cliff, and rather soft
latter to dislodge and eventually break up,
allowing marine erosion to work efficiently
falling on the clay. The landforms are
(Paskoff and Sanlaville, 1978).
characterised by a boulder scree at sea level
Figure 7: Low cliff and shore platform formed in Globigerina Limestone, characteristic of the
southern coast. Globigerina Limestone being a softer material than Coralline Limestone
displays a smoother surface. This is mainly the result of the mechanical action of waves,
especially hydraulic pressure.
Territoris, núm. 6. 2006
21
Magri, Odette
A Geological and Geomorphological Review of...
and larger landslides at the foot of the scarp
cavern and gallery systems in all formations,
face. As a result cliff retreat is probably
especially in the Coralline Limestone.
slow, since a certain time is necessary for
In Qawra, western Gozo (Figure 8), there
the removal of the boulders. The huge limes-
is a large (400 m in diameter and 70 m deep)
tone blocks are too large to be displaced by
elliptical sinkhole structure of complex
the sea and form a strong protective
origin (Pedley, 1974 in Paskoff, 1985),
buttressing to the clayey part of the cliff.
bounded by vertical walls and developed in
This type of cliff probably retreats much less
the Lower Coralline Limestone. Its bottom
quickly than Globigerina Limestone cliffs
has been partially inundated because a
(Paskoff and Sanlaville, 1978). Rdum areas
karstic gallery connects the depression with
are especially found north of the Victoria
the open sea and allows small boats to pass.
Lines Fault and in eastern Gozo (Figure 8).
Dwejra Bay (Figure 8), close to Qawra is
another former closed depression, measuring
4.1.3 Low rocky coastline
approximately 340 m in diameter. It has
In north-east Malta and northern Gozo,
largely been invaded by the sea and only its
cliffs are largely absent. Long tracts of low,
eastern half has been preserved. An islet,
rocky coastlines of corrosion (Paskoff, 1985)
Fungus Rock, is the last remnant of its
are found (Figure 6). Pools and lapiés give an
western wall, destroyed by marine erosion.
extremely irregular topography to shore
platforms, particularly when they are cut in
4.1.5 Drowned valleys
Coralline Limestone (Figure 6). Chemical
Malta and Gozo display inlets that are
and biological weathering are the prevailing
partially drowned valleys (also known as
processes in the formation of such coasts.
calanques) of subaerial erosion. Typical
Evidence of abrasion is absent. Structural
calanques are found: Wied iz-Zurrieq in
controls account for the simultaneous
southern Malta and Il-Bajda in south-west
development of several platforms at different
Gozo are narrow, shore inundated valleys
levels up to more than 10 m above the sea.
with steep sides cut in Lower Coralline
This is evident in northern Gozo, where the
Limestone. Wider and more developed
Globigerina Limestone crops out. On exposed
inlets, such as Salina Bay in north-east Malta
coasts large boulders dislodged by storm
and Marsascala Bay in south-east Malta,
waves lie scattered on the shore platform, and
correspond to finger-shaped, broad and more
corrosion microforms are less developed.
open valleys, subaerially eroded in the soft
Globigerina Limestone and subsequently
4.1.4 Semi-circular coves and sinkholes
submerged (Figure 8). Changes in sea level
Semi-circular coves, such as Qawra, near
have also submerged the mouth of some
Dwejra Point and Dwejra Bay in western
drainage channels on the coast, giving rise to
Gozo (Figure 8), the two creeks on the
headlands, creeks and bays, especially
western coast of Comino, Blue Grotto on the
evident on the north-east coasts, since the
southern coast of Malta, and Paradise Bay
seaward tilt of the Island is in that direction.
on the north-western coast of Malta re-
Especially important is the system of
present a conspicuous feature of the Maltese
drowned valleys which form the creeks of
coastline. They originate from widely
the two main harbours of Malta, Marsamxett
distributed typical karstic landforms inun-
Harbour and Grand Harbour, separated by
dated by the sea (Paskoff, 1985). Post-
the Valletta headland. Important examples of
Miocene solution of carbonates has reached
inundated river valleys in Gozo include
an advanced stage, producing well-deve-
Mgarr ix-Xini (southern Gozo) and Xlendi
loped sinkholes and extensive subterranean
Bay (south-west Gozo).
22
Territoris, núm. 6. 2006
A Geological and Geomorphological Review of...
Magri, Odette
Figure 8. Predominant coastal landforms in the Maltese archipelago.
Source: Paskoff, 1985
Key
1. high cliff (more than 100 m high)
5. sandy beach
2. cliff (less than 100 m high)
6. sinkhole structure
3. rdum type cliff
7. major fault
4. low rocky coast
8. height in metres from datum line
Figure 9: Il-Qarraba is a peninsula separating Gnejna Bay from Ghajn Tuffieha Bay on the
north-west coast. It features an rdum landform and its shape is unique in the Maltese Islands.
Il-Qarraba is linked to the mainland by clay slopes and has been assigned the highest level of
conservation and protection by the Malta Environment and Planning Authority.
Territoris, núm. 6. 2006
23
Magri, Odette
A Geological and Geomorphological Review of...
5. Conclusion
slopes which extend from the base of the
Upper Coralline Limestone plateau to sea
This paper has showed that in Malta
level. Where faulting and jointing in the
there are very clear relationships between
Upper Coralline Limestone plateau occurs,
tectonics, geology and landforms. The mor-
this results in the breaking of the formation
phological response to superimposed phases
with consequent rockfall taking place. The
of strike-slip faulting and rifting, with
boulders fall on the Blue Clay underneath
associated uparching and downwarping can
forming a characteristic feature of the
be observed. Stream channel formation and
Maltese littoral – rdum areas. These areas
incision, coastal geomorphology, erosion
are characterised by a boulder scree at sea
surface formation and scarp morphology
level and larger landslides at the foot of the
have all responded sensitively to the tectonic
scarp face. Greensand does not produce any
events of the last 15 Ma (Alexander, 1988).
particular landform where it occurs at the
The structural setting of the Maltese
coast as this is often assimilated into the
Islands is dominated by two rift systems of
base of the Upper Coralline Limestone
different ages and trends (Illies, 1981). The
plateau which runs parallel to the coast in
older rift generation, the Great Fault, trends
north-west Malta. Besides there are few
in a NE-SW to ENE-WSW direction. This
outcrops of this formation across the whole
creates a horst and graben structure in
archipelago.
northern Malta, Comino and eastern Gozo.
The role of tectonics has been recognized
The second rift generation – the Maghlaq
by Paskoff and Sanlaville (1978) who claim
Fault – is associated with the Pantelleria Rift
that the general outline of the Maltese
and trends in a NW-SE direction. This fault
littoral has been determined by tectonic
determines the south-west littoral of Malta
activity. Bays in northern Malta correspond
and is responsible for the north-east tilt of
to downthrown blocks that were partially
the Islands.
submerged. High cliffs on the south-west
The geological succession represents a
coast are related to a major fault. Some cliffs
varied cross-section of Oligo-Miocene
are associated with wave-cut platforms.
lithologies and facies but consists almost en-
Others plunge directly into the sea or are
tirely of carbonates. The geological
skirted by landslides. Landslides and slope
formations of the Islands are very distinctive
instability are especially evident on the
lithologically, reflected in characteristic
western coast north of the Great Fault of the
topography and vegetation (House et al.,
Victoria Lines. Landslides occur both in
1961a). The NE-SW trending horsts and
Upper Coralline Limestone and Blue Clay
graben cut through the entire Tertiary rock
Formations. The former feature translational
succession.
and rotational slides whereas the latter
The relationship between geology and
displays mudslides (Magri, 2001).
geomorphology is particularly evident at the
Moreover, as far as Malta is concerned,
coast. The Lower Coralline Limestone forms
there has been tilting of its lengthwise axis
spectacular vertical plunging cliffs reaching
towards the north-east in addition to the
more than 200 m in some places. These are
general subsidence of the archipelago during
probably of tectonic origin and lack shore
the Quaternary period. No trace of former
platforms. Globigerina Limestone features
shorelines higher than the present one has
cliffs which in most cases are fronted by
been found in spite of careful investigations
shore platforms produced by the mechanical
(Paskoff and Sanlaville, 1978). Emerged
action of waves. Blue Clay displays itself as
wave-cut terraces or notches as well as
24
Territoris, núm. 6. 2006
A Geological and Geomorphological Review of...
Magri, Odette
marine deposits seem to be entirely lacking.
(Eds.), Malta: Background for development.
Formerly reported raised beaches (Hyde,
University of Durham, págs. 34-42.
1955) are in fact pediment features. At
HYDE, H.P.T. (1955): The geology of
St.Paul’s Bay, cart tracks of Neolithic age
the Maltese Islands. Lux Press, Malta.
enter the sea at one side and emerge on the
ILLIES, J. H. (1980): «Form and
opposite side of the inlet (Hyde, 1955). The
formation of graben structures: The Maltese
situation suggests evidence of recent crustal
Islands», in CLOSS, H., GEHLEN, K. V.,
subsidence, which is probably still in
ILLIES, J. H., KUNTZ, E., NEUMANN, J.
progress.
and SEIBOLD, E. (Eds.), Mobile earth.
Harald Boldt Verlag, Bonn, págs. 161-184.
ILLIES, J. H. (1981): «Graben formation
References
–the Maltese Islands– a case history».
Tectonophysics, no 73, págs. 151-168.
ALEXANDER, D. (1988): «A review of
MAGRI, O. (2001): Slope instability
the physical geography of Malta and its
along the north-west coast in Malta.
significance for tectonic geomorphology».
Unpublished MSc dissertation, University of
Quaternary Science Reviews, no 7, págs. 41-
Durham.
53.
MURRAY, J. (1890): «The Maltese
CENTRAL OFFICE OF STATISTICS.
Islands with special reference to their
(1997): Census of population and housing
geological structure». Scottish Geographical
Malta 1995. Vol.1: Population, age, gender
Magazine, no 6, págs. 449-488.
and citizenship. Central Office of Statistics,
PASKOFF, R. (1985): «Malta», in BIRD,
Malta.
E.C. and SCHWARTZ, M.L. (Eds.), The
ELLENBERG, L. (1983): «Die küsten
world’s coastlines. Van Nostrand Reinhold
von Gozo». Essener Geographische
Company, New York, págs. 431-437.
Arbeiten, no 6, págs. 129-160.
PASKOFF, R. and SANLAVILLE, P.
FELIX, R. (1973): «Oligo-Miocene
(1978): «Observations géomorphologiques
stratigraphy of Malta and Gozo».
sur les côtes de l’archipel Maltais».
Mededeelingen Landbouwhogeschule
Zeitschrift für Geomorphologie, no 22, págs.
Wageningen Nederlands, no 73, págs. 1-103.
310-328.
GUILCHER, A. and PASKOFF, R.
NATIONAL STATISTICS OFFICE
(1975): «Remarques sur la géomorphologie
(2006): Census of population and housing
littorale de l’archipel Maltais». Bulettin de
2005 - Preliminary report. National
l’Association de Géographes Français, no
Statistics Office, Malta.
427, págs. 225-231.
Available online at:
HOUSE, M.R., DUNHAM, K. C. and
http://www.census2005.gov.mt/reports/
WIGGLESWORTH, J. C. (1961a): «Geo-
(Accessed on 12/10/2006).
logy and structure of the Maltese Islands»,
PEDLEY, H. M. (1975): The Oligo-
in BOWEN-JONES, H., DEWDNEY, J.C.
Miocene sediments of the Maltese Islands.
and FISHER, W.B. (Eds.), Malta:
Unpublished PhD thesis, University of Hull.
Background for development. University of
PEDLEY, H. M. (1978): «A new
Durham, págs. 24-33.
lithostratigraphical and palaeoenvironmental
HOUSE, M.R., DUNHAM, K. C. and
interpretation for the Coralline Limestone
WIGGLESWORTH, J. C. (1961b): «Relief
Formations (Miocene) of the Maltese
and landforms», in BOWEN-JONES, H.,
Islands». Overseas Geology and Mineral
DEWDNEY, J. C. and FISHER, W. B.
Resources, no 54, págs. 1-17.
Territoris, núm. 6. 2006
25
Magri, Odette
A Geological and Geomorphological Review of...
PEDLEY, H. M., HOUSE, M. R. and
SCHEMBRI, P. J. (1993): «Physical
WAUGH, B. (1976): «The geology of Malta
geography and ecology of the Maltese
and Gozo». Proceedings of the Geologists’
Islands: A brief overview», in Options
Association, no 87, págs. 325-341.
Méditerranéennes, Malta: Food, agricul-
PEDLEY, H. M., HOUSE, M. R. and
ture, fisheries and the environment.
WAUGH, B. (1978): «The geology of the
CIHEAM, Montpellier, no 7, págs. 27-39.
Pelagian Block: The Maltese Islands», in
SPRATT, T.A.B. (1843): «On the
NAIRN, A.E.M., KANES, W. H. and
geology of the Maltese Islands». Pro-
STEHLI, F. G. (Eds.), The ocean basins and
ceedings of the Geological Society of
margins. Vol. 4B: The Western Medi-
London, no 4, págs. 1-8.
terranean. Plenum Press, London, págs.
SPRATT, T.A.B. (1867): «On the bone
417-433.
caves near Qrendi, Zebbug and Mellieha in
RANSLEY, N. and AZZOPARDI, A.
the island of Malta». Quarterly Journal of
(1988): A geography of the Maltese Islands,
the Geological Society of London, no 23,
4th edition. St.Aloysius’ College, Malta.
págs. 283-297.
SCHEMBRI, P. J. (1990): «The Maltese
TRECHMANN, C. T. (1938):
coastal environment and its protection», in
«Quaternary conditions in Malta». Geolo-
Atti dell’Ottavo Convegno Internazionale:
gical Magazine, no 75, págs. 1-26.
Mare e Territorio, La protezione
VOSSMERBÄUMER, H. (1972):
dell’ambiente Mediterraneo ed il piano
«Malta, ein beitrag zur geologie und geo-
della Commissione delle Comunità Europee.
morphologie des Zentral-mediterranean
Università degli Studi di Palermo, Palermo,
raumes». Würzburger Geographische
págs. 107-112.
Arbeiten, no 38, págs. 1-213.
26
Territoris, núm. 6. 2006
|
