Our aim on these pages, presently embryonic, is to suggest the impact geology has
rather than deliver scientific information but with some of both. Although the area
is in one sense homogeneous it has interesting origins which have evolved much intricacy.
At its most fascinating is along the coastal ways and the beaches where marine erosion
reveals a multitude of minerals and evolutionary clues. The whole complex is a chunk
of oceanic abyss displaced by plate migrations (see my Cosmic Myth). So not only
does it have the fusion elements from deep sea volcanoes but also seismic crunches
as it grounded up against the Spanish massif. Quite how much subsequent erosion there
has been is not clear but many forms suggest submarine action.
Parts of a jasper collection
A fascinating feature here is the presence of fossil reefs, fossil beaches and fossil
dunes visibly overlying vulcanism. Dunes are at Los Escullos, Rodalquilar Playazo,Cala
Higuera and Playa de los Genoveses. At Playazo additional interest arises from the
presence of lava bombs embedded in fossil sandbanks. A conventional reading for the
Cerro de Cabo de Gata is a submarine volcanic plate with marine sedimentation, subsequent
seismic events and aerial erosions. At best these lava bombs fell through shallow
water into softened sand. They were certainly aerial in origin which seems to indicate
vulcanism after the plate was elevated above sea level. Quite where the source might
have been one cannot say, slightly west judging from the slant. At Los Escullos (which
means ‘breakwaters’) there are fossil dunes but no obvious fossil beach above sea
level. At Genoveses the fossil beach, containing evidence of marine fauna, is backed
by fossil dunes & a fossil dune headland cap over basalts.
This sequence of images shows fossil evidence of fauna in a typical sandy sheltered
beach. The top left image resembles very closely a razor clam’s breather holes. The
2nd & 3rd images are most likely those of worms. The bottom right hole is 6 cm across
in the fossil beach, a large marine invertebrate that burrowed vertically into wet
sand. The cap of Genoveses headland is said to be an oolithic dune but it is set
on a volcanic base that extends westwards.
Reading this image: foreground low fossil dunes on the western edge leading to flat
fossil beaches around the inlet; in the background huge fossil dunes on the eastern
side created presumably by severe westerlies.
This detail of a fossil beach shows a tidal shell bank not significantly different
in its molluscs from modern ones except that the shells are larger. There is one
conch fossil, not exposd when these images were made.
These fossil dunes between Rodalquilar and Las Negras are enormous and if one allows
for settlement and subsequent fossilisation would originally have been truly mountainous.
Some appears to be sedimentary. More info needed!
Minerals on Genoveses - ochres, bentonite, other clays and an area of talc on which
walking is precarious. The 3rd image shows a typical mixture of hot pyroclast flows
with fused material & eroded basalt residue topped by fossil dune. Pyroclasts, domes,
magma & basalt dominate between here and the western massif.
This sequence of images shows lava bombs that have plummeted molten into a soft beach.
There is a little evidence of them in the dunes that back this zone which might suggest
a time sequence if not a period. They vary in size but the really significant thing
is that they lie in a beach that contains modern fossil shells. Their (semi)molten
state is clearly indicated by the ‘egg splats’.
Cala Higuera belongs to the Fraile complex. It lies at the sea end of a long barranca
and a rambla. It is of pyroclasts and white pumice cliffs that erode in chunks, the
strange eau-de-nil coloured powdery outflow seen in many area of Fraile and tufa
filled with volcanic glass fragments. Amongst the pebbles are interesting semi-precious
For the present purposes of these pages the Cabo de Gata is best identified geologically
as 3 distinct zones, though they blend. From east to west they would be Carboneras
which is volcanic underlying limestones up to Las Negras; Rodalquilar caldera; Frailes
complex caldera including Genoveses which is mainly lavas and abyssal pyroclasts.
Possibly the most complex is the Frailes zone the two cones being upthrust through
the andesite while still submarine. It includes the small caldera Majada Redonda.
Genoveses I have taken for the time being as the focus of the western zone (map to
Probably the best places to see the geology without excavation (which is not allowed)
are from the coastal paths and coves and the zone around Rodalquilar mines where
minute quantities of gold were extracted, alum and sulphur along with small quantities
of other minerals. The UNESCO museum there is the best source of information.
◄These cliffs at Cala Carbon are volcanic dust interspersed with magma & granite
layers, fossil dune whilst in the foreground the shelf is black lava, full of underwater
funnels and small caves.
The zone of which Cala Carbon forms a part is mainly massive lava flows full of fumaroles
and passages of which these kids give the scale, craggy and hard rock through which
run large jasper dykes.
These images give the scale of the western zone that overlooks Cabo de Gata village.
It is scrambling country and fairly uniform in its basic geology of magma flows.
But there are areas that contain iron, lodestone, lead and other related minerals.
It also has a very small remote remnant of temperate rainforest on one of the north
facing steep slopes.
West from Cala Carbon
Many of the lower hills in the Fraile zone are volcanic cinder mounds in which fascinating
varieties of quartz fragments can be found amongst the rubble.
Between Carboneras and San Miguel (east-west) the Cape divides broadly more or less
conveniently into 3 zones. Carboneras has a predominance of fossil limestones overlying
vulcanism; Los Frailes consists of later volcanic cones in a previously established
large andesite caldera embracing the Genoveses plain; the Western massif consists
mainly of magma caldera walls landwards with pyroclastic mounds, basalt, lava flows
and fossil dunes seawards. Mesa de Roland is the highest point by Carboneras, mainly
chalky limestone over basalt. The large Holcim cement works combined with power station
and desalination plant are there. Part of the Frailes zone is the popular small recognisable
caldera of Majada Redonda, its interior a well publicised hike. The western crags
make precipitate scrambles.
The rim of Genoveses is characterised by magma dykes extending radially into the
Erosion of conglomerate pyroclasts exposes what were once either treacly outflows
or ‘smokers’. Scrambling country!
This dyke extends down to the sea where it forms an impenetrable barrier to walking
the coastal shelf From it one can look over Calas Carbon and Monsul to Genoveses
Note: these pages are written piecemeal under constant revision & extension! - work
Detailed mineral information for the Rodalquilar zone is available on the mindat
Calderas:Genoveses(?), Majada, Rodalquilar, Frailes Cones: Frailes -resurgent cones
in old caldera.
SKETCH MAP SHOWING CALDERAS & CONES
These two maps attempt to show the main geomorphological features as seen. Their
content needs more research than has been possible to this stage. One of the intriguing
aspects of the quest is the intricacies in timescale of dynamic events between the
emergence of the oceanic igneous plate and later geological times. For the author
this is an ongoing thing so nothing here is in any way finite, only a start! One
thing is certain though; the intricate ecology of the Cabo de Gata park arises as
much from variations in chemistry as to its numerous microclimates induced by topography.
This mass of porphyritic rock is to be found near Las Negras at the base of a limestone
formation. Photography doesn’t do justice to the range of colour found in it nor
the infinite opportunity for inspiring abstract painting! ►
Panorama of the caldera Majada Redonda
El Fraile and Majada Redonda
Face each other across a wide hilly valley. Here they are viewed from another peak.►▼
◄▲ A stiff steep scramble brings one to the rim of Majada Redonda. The slopes are
a mixture of scree, palmetto thickets and tumbled volcanic boulders. The rim itself
has fields of eroded volcanic debris interspersed with gnarled crags of solidified
heat fused oozes of one sort or another, mainly granite. Amongst the latter are many
small meadows filled with flowers much enjoyed by butterflies ‘topping’ in late spring
as the temperatures rise in lower zones. The reason for this flowering in spite of
its exposure and altitude is the prevalence of hilltop fogs at all times of the year.
Sometimes they enforce descent!
The area between Agua Amarga and Carboneras is largely limestone reefs which overlay
lava and granite flows, prominent in coastal zones. Carboneras itself, an attractive
and popular resort, lies in an alluvial basin beyond which is the eastern mass of
vulcanism and limestones.
A visit to the UNESCO geology museum throws some doubt on calling Genoveses a caldera.Frailes is not immediately recognisable as a caldera. But more detailed exploration
is revealing. The two cones are resurgence volcanoes. The UNESCO display is skilful,
professional and excellently informative.
Collecting mineral pebbles here is a quiet pastime followed by many. Only certain
coves produce semi precious stones but those that do reward searches with rich variety.
The amethysts (right) were part of a shared collection amassed in an hour. The jaspers
The seaward side of El Fraile, the south east, has precipitate slopes, ravines and
chasms that plunge into the sea in a tumult of geological emissions, hard and soft.
Steep coves result. Apparently it has good grazing for goats, since flocks are regularly
visible on these slopes. Only two years ago the goatherds walked with the flock but
these days they sit in vans watching and send waiting dog(s) out to keep it under
control when necessary. The goats seem to follow pre-arranged routes known to the
lead animals. At least that is what observation leads one to think!