Timeline of the history of Gibraltar
The history of Gibraltar portrays how The Rock gained an importance and a reputation far exceeding its size and shaping the people who came to reside here over the centuries. Evidence of hominid inhabitation of the Rock dates back to the Neanderthals. A Neanderthal skull was discovered in Forbes' Quarry in 1848, prior to the "original" discovery in the Neander Valley. In 1926, the skull of a Neanderthal child was found in Devil's Tower. Mousterian deposits found at Gorham's Cave, which are associated with Neanderthals in Europe, have been dated to as as 28,000 to 24,000 BP, leading to suggestions that Gibraltar was one of the last places of Neanderthal habitation. Modern humans visited the Gibraltar area in prehistoric times after the Neanderthal occupancy. While the rest of Europe was cooling, the area around Gibraltar back resembled a European Serengeti. Leopards, lynxes and bears lived among wild cattle, deer, ibexes and rhinos – all surrounded by olive trees and stone pines, with partridges and ducks overhead, tortoises in the underbrush and mussels and other shellfish in the waters.
Clive Finlayson, evolutionary biologist at the Gibraltar Museum said "this natural richness of wildlife and plants in the nearby sandy plains, shrublands, wetlands and coastline helped the Neanderthals to persist." Evidence at the cave shows the Neanderthals of Gibraltar used it as a shelter "for 100,000 years." Cro-Magnon man took over Gibraltar around 24,000 BCE. The Phoenicians are known to have visited the Rock circa 950 BC and named the Rock "Calpe"; the Carthaginians visited. However, neither group appears to have settled permanently. Plato refers to Gibraltar as one of the Pillars of Hercules along with Jebel Musa or Monte Hacho on the other side of the Strait; the Romans visited Gibraltar. Following the fall of the Western Roman Empire, Gibraltar was occupied by the Vandals and the Goths kingdoms; the Vandals did not remain for long although the Visigoths remained on the Iberian peninsula from 414 to 711. The Gibraltar area and the rest of the South Iberian Peninsula was part of the Byzantine Empire during the second part of the 6th century reverting to the Visigoth Kingdom.
711 30 April – The Umayyad general Tariq ibn Ziyad, leading a Berber-dominated army, sailed across the Strait from Ceuta. He first failed. Upon his failure, he landed undetected at the southern point of the Rock from present-day Morocco in his quest for Spain, it was here. Coming from the Arabian words Gabal-Al-Tariq. Little was built during the first four centuries of Moorish control. 1160 – The Almohad Sultan Abd al-Mu'min ordered that a permanent settlement, including a castle, be built. It received the name of Medinat al-Fath. On completion of the works in the town, the Sultan crossed the Strait to inspect the works and stayed in Gibraltar for two months; the Tower of Homage of the castle remains standing today. 1231 – After the collapse of the Almohad Empire, Gibraltar was taken by Ibn Hud, Taifa emir of Murcia. 1237 – Following the death of Ibn Hud, his domains were handed over to Muhammad ibn al-Ahmar, the founder of the Nasrid kingdom of Granada. Therefore, Gibraltar changed hands again. 1274 – The second Nasrid king, Muhammed II al-Faqih, gave Gibraltar over to the Marinids, as payment for their help against the Christian kingdoms.
1309 – While the King Ferdinand IV of Castile laid siege on Algeciras, Alonso Pérez de Guzmán was sent to capture the town. This was the First Siege of Gibraltar; the Castilians took the Upper Rock from. The garrison surrendered after one month. Gibraltar had about 1,500 inhabitants. 1310 31 January – Gibraltar was granted its first Charter by the king Ferdinand IV of Castile. Being considered a high risk town, the charter included incentives to settle there such as the offering of freedom from justice to anyone who lived in Gibraltar for one year and one day; this fact marked the establishment of the Gibraltar council.1316 – Gibraltar was unsuccessfully besieged by the Nasrid caid Yahya. 1333 June – A Marinid army, led by Abd al-Malik, the son of Abul Hassan, the Marinid sultan, recovered Gibraltar, after a five-month siege. King Alfonso XI of Castile attempted to retake Gibraltar aided by the fleet of the Castilian Admiral Alonso Jofre Tenorio. A ditch was dug across the isthmus. While laying the siege, the king was attacked by a Nasrid army from Granada.
Therefore, the siege ended in a truce, allowing the Marinids to keep Gibraltar.1344 March – After the two-year Siege of Algeciras, Algeciras was taken over by the Castilian forces. Therefore, Gibraltar became the main Marinid port in the Iberian Peninsula. During the siege, Gibraltar played a key role as the supply base of the besieged. 1349 – Gibraltar was unsuccessfully besieged by the Castilian forces led by the king Alfonso XI. 1350 – The siege was resumed by Alfonso XI. It was again unsuccessful due to the arrival of the Black Death, which decimated the besiegers, causing the death of the king. 1369 – As the Civil War in Castile came to an end, with the murder of king Peter I by the pretender Henry, the Nasrid king of Granada, Muhammad V, former ally of Peter, took over Algeciras after the 3-day Siege of Algeciras. Ten years the city was razed out to the ground, its harbour made unusable; this fact increased again the importance of Gibraltar, yet in Marinid hands, i
The Iberian Plate with the microcontinent Iberia encompassed not only the Iberian Peninsula but Corsica, the Balearic Islands, the Briançonnais zone of the Penninic nappes of the Alps. Nowadays, the Iberian plate is a part of the Eurasian plate; the Iberian plate came into existence during the Cadomian Orogeny of the late Neoproterozoic, about 650–550 Ma, on the margin of the Gondwana continent, involving the collisions and accretion of the island arcs of the Central Iberian Plate, Ossa-Morena Plate, South Portuguese Plate. The three plates have never separated from each other since that time. In the Mesozoic, Late Jurassic Africa started moving east, the Alpine Tethys opened. Subsidence related to this caused deep deposits of sediments on the east and some sediment remnants in pop downs in central parts of Spain. Two stages of rifting occurred in the east, one from Later Permian to Triassic, the second from Late Jurassic to early Cretaceous. On the south side deposits of carbonates and clastic sediments formed a shelf in shallow water during late Triassic and Liassic times.
This was rifted in Toarcian times. Active rifting was complete by 160 Ma. After this thermal subsidence occurred till the end of Cretaceous. During this time rifting separated North America from Africa forming a transform zone. In the late Triassic and early Jurassic there were two stages of rifting involving extension and subsidence on the western margin of Iberia, it extended the western margin. The Iberian Abyssal Plain, off the west coast of Portugal and Spain, formed 126 Ma; this separated Newfoundland's Grand Banks, with Flemish Cap being split at 118 Ma. By Early Cretaceous, 110 Ma rifting occurs on west and north west edges. During the time of the supercontinent Pangea, the Iberian plate was joined to Armorica. During the break-up of Pangea, in the early Cretaceous, the Bay of Biscay started opening around 126 Ma and completed by 85 Ma; this created the Biscay Abyssal Plain, parted the Iberian plate from the Trevelyan Escarpment. During this time Iberia rotated anticlockwise relative to Eurasia.
This caused the subduction of the Ligurian Basin onto the eastern side. This formed the Betic nappe stack. After 85 Ma the Atlantic Ocean opening started between Greenland; this left the Bay of Biscay as a failed rift. The rotation of the Iberia and its relation to the formation of the Pyrenees has been difficult to decipher with certainty. Detailed aeromagnetic measurements from the sea floor offshore of the Grand Banks of Newfoundland to show that Iberia moved as part of the African plate from late Cretaceous to mid-Eocene time, with a plate boundary extending westward from the Bay of Biscay; when motion along this boundary ceased, a boundary linking extension in the King's Trough to compression along the Pyrenees came into existence. Since the late Oligocene, the Iberian plate has been moving as part of the Eurasian plate, with the boundary between Eurasia and Africa situated along the Azores–Gibraltar fracture zone. Continued rotation of the Iberian plate in the early Miocene once again separated the Iberian plate from Eurasia opening the Betic Corridor a strait of water connecting the Mediterranean Sea with the Atlantic Ocean.
As the Iberian plate rotated, it closed the Betic Corridor 5.96 million years ago during the Messinian period of the Miocene, precipitating the Messinian Salinity Crisis, a period when the Mediterranean Sea evaporated or completely. The core of the Iberian Peninsula consists of a Hercynian cratonic block known as the Iberian Massif. On the northeast this is bounded by The Pyrenean fold belt, on the southeast it is bounded by the Betic Foldchain; these twofold chains are part of the Alpine belt. To the west, the peninsula is delimited by the continental boundary formed by the magma poor opening of the Atlantic Ocean; the Hercynian Foldbelt is buried by Mesozoic and Tertiary cover rocks to the east, but outcrops through the Iberian Chain and the Catalan Coastal Ranges. List of tectonic plates – A list of the moving sections of the lithosphere of the Earth
Geology of the Iberian Peninsula
The geology of the Iberian Peninsula consists of the study of the rock formations on the Iberian Peninsula, which includes Spain, Portugal and Gibraltar. The peninsula contains rocks from every geological period from Ediacaran to Holocene, many types of rock are represented. World-class mineral deposits are found there; the core of the Iberian Peninsula consists of a Hercynian cratonic block known as the Iberian Massif. On the northeast this is bounded by The Pyrenean fold belt, on the southeast it is bounded by the Betic Foldchain; these twofold chains are part of the Alpine belt. To the west, the peninsula is delimited by the continental boundary formed by the opening of the Atlantic Ocean; the Hercynian Foldbelt is buried by Mesozoic and Cenozoic cover rocks to the east, but outcrops through the Iberian Chain and the Catalan Coastal Ranges. The Iberian Massif consists of rocks from the Paleozoic Era, it was assembled about 310 Ma. Several zones occur in the Iberian Massif; these were the pieces.
On the north coast of Spain occurs the Cantabrian Zone. To the west and in the Iberian Chain and Catalan Coastal Ranges is the West Asturian-Leonese Zone; the Central Iberian Zone appears near A Coruña, through the north of Portugal, through the middle of Spain, including the Montes de Toledo. The Ossa-Morena Zone outcrops out to the east of Lisbon; this includes some Precambrian rocks. The furthest south part is the South-Portuguese Zone; the Variscan Orogeny occurred as the European Hunic Terrane and Laurentia-Baltica continents collided. In Iberia this occurred in pre-Stephanian Carboniferous; the external part of the orogeny was the Cantabrian Zone. This was deformed in the upper crustal layers; the West Asturian Leonese Zone and Central Iberian Zone are the external parts of the orogeny and are more deformed and metamorphosed, intruded. These three zones are part of one terrane; the Ossa-Morena Zone and South Portuguese Zone are two different terranes. In the Mesozoic this was covered with other sediments, which have since eroded.
The Cantabrian Zone consists of older Paleozoic unmetamorphosed rocks. It is bounded on the west and south-west sides by a concave arc of Precambrian rocks called the Narcea window, the Villabandin window in the Narcea antiform; the Herreria Formation from the Lower Cambrian consists of shale and feldspathic sandstone alternating, with some conglomerate. These have a thickness of 1 to 1.5 km. The Lancara Formation consists of a couple of hundred metres of limestone; the lower part was formed in peritidal zones in the Lower Cambrian, the upper member from the Middle Cambrian contains fossils and is red or green glauconictic and nodular limestone. The Oville Formation from Middle to Upper Cambrian contains alternating sandstone. Trilobite fossils are common in the shale; the Barrios Formation is Arenigian and up to 500 metres thick. It consists of a white massive quartzite; the Penas and Vidrias area, close to the western boundary of the Cantabrian zone has a complete succession of Ordovician deposits.
Black shales from Llanvirnian times are found in the Central Coal Basin eastern side. But in the Ordovician Period, this zone was above water and eroding; the Formigoso Formation dates from Middle Llandovery time in the Silurian. It is up to 150 m thick; the San Pedro and Furada Formations are up to 300 metres thick and consists of shale and iron bearing sandstone interbedded, These are from Wenlock Ludlow and Lower Gedinian times. In the Devonian Period deposition occurred on the western side, with dolomite, argillaceous limestone and shale from the Raneces Complex or La Vid Formation, it is 600 metres thick and Gedinian to Emsian in age. The Santa Lucia Formation is of limestone, it contains coral near the Narcea Antiform in the west and has peritidal facies in the east near the Central Coal Basin. The Huergas Formation alternates between red sandstone and shale and is of Couvinian to Givetian age; the Portilla formation is of coralline limestone of Givetian to Frasnian age. This is topped off by sandstone layers up to 500 m thick from the Frasnian to Fammenian age.
Devonian sediments are not found to the east of the central coal basin, are thickest in the west. A pelagic facies comes from the Pisuerga-Carrion province. In Carboniferous times deposition started with black shales and cherts from the Tournaisian age, red limestone, red shale and radiolarites were formed in the Visean age. Mountain Limestone is a thick black lifeless limestone of Serpukhovian age. Turbidites with olistoliths appear in the Serpukhovian, indicating the first sign of the Hercynian tectonic events; these first events happened in the Pisuerga-Carrion province. Variscan compression lifted the west side. Over time the compressed zone moved towards the east. In the Namurian A stage, the Olleros formation was byukt from turbidites in a trough in front of the orgen, the Barcallente formation was a carbonate platform further off shore. In the Namurian B stage the trough was forming San Emillano Formation, the Valdeteja Formation was offshore, but in deeper marine conditions. During Westphalian A time the trough was filled and deposits of terrestrial material formed the San Emiliano Formation and Sama Group and the Lena group being thickest in the Central Coal Basin Unit.
Further east in the Picos de Europa it remained covered in shallow water with continuous formation of a carbonate platform. The Westphalian age is represented by 5000 m of the Central Coal Basin, which as the name su
A transform fault or transform boundary is a plate boundary where the motion is predominantly horizontal. It is connected to another transform, a spreading ridge, or a subduction zone. Most of these faults are hidden in the deep ocean, where they offset divergent boundaries in short zigzags resulting from seafloor spreading, the best-known being those on land at the margins of continental tectonic plates. A transform fault is the only type of strike-slip fault, classified as a plate boundary; these faults are known as conservative plate boundaries, since they neither create nor destroy lithosphere. Geophysicist and geologist John Tuzo Wilson recognized that the offsets of oceanic ridges by faults do not follow the classical pattern of an offset fence or geological marker in Reid's rebound theory of faulting, from which the sense of slip is derived; the new class of faults, called transform faults, produce slip in the opposite direction from what one would surmise from the standard interpretation of an offset geological feature.
Slip along transform faults does not increase the distance between the ridges it separates. This hypothesis was confirmed in a study of the fault plane solutions that showed the slip on transform faults points in the opposite direction than classical interpretation would suggest. Transform faults are related to transcurrent faults and are confused. Both types of fault are side-to-side in movement. In addition, transform faults have equal deformation across the entire fault line, while transcurrent faults have greater displacement in the middle of the fault zone and less on the margins. Transform faults can form a tectonic plate boundary, while transcurrent faults cannot; the effect of a fault is to relieve strain, which can be caused by compression, extension, or lateral stress in the rock layers at the surface or deep in the Earth's subsurface. Transform faults relieve strain by transporting the strain between ridges or subduction zones, they act as the plane of weakness, which may result in splitting in rift zones.
Transform faults are found linking segments of mid-oceanic ridges or spreading centres. These mid-oceanic ridges are where new seafloor is created through the upwelling of new basaltic magma. With new seafloor being pushed and pulled out, the older seafloor slides away from the mid-oceanic ridges toward the continents. Although separated only by tens of kilometers, this separation between segments of the ridges causes portions of the seafloor to push past each other in opposing directions; this lateral movement of seafloors past each other is where transform faults are active. Transform faults move differently from a strike-slip fault at the mid-oceanic ridge. Instead of the ridges moving away from each other, as they do in other strike-slip faults, transform-fault ridges remain in the same, fixed locations, the new ocean seafloor created at the ridges is pushed away from the ridge. Evidence of this motion can be found in paleomagnetic striping on the seafloor. A paper written by geophysicist Taras Gerya theorizes that the creation of the transform faults between the ridges of the mid-oceanic ridge is attributed to rotated and stretched sections of the mid-oceanic ridge.
This occurs over a long period of time with the spreading center or ridge deforming from a straight line to a curved line. Fracturing along these planes forms transform faults; as this takes place, the fault changes from a normal fault with extensional stress to a strike slip fault with lateral stress. In the study done by Bonatti and Crane and gabbro rocks were discovered in the edges of the transform ridges; these rocks are created deep inside the Earth's mantle and rapidly exhumed to the surface. This evidence helps to prove that new seafloor is being created at the mid-oceanic ridges and further supports the theory of plate tectonics. Active transform faults are between faults. Fracture zones represent the active transform-fault lines, which have since passed the active transform zone and are being pushed toward the continents; these elevated ridges on the ocean floor can be traced for hundreds of miles and in some cases from one continent across an ocean to the other continent. The most prominent examples of the mid-oceanic ridge transform zones are in the Atlantic Ocean between South America and Africa.
Known as the St. Paul, Romanche and Ascension fracture zones, these areas have deep identifiable transform faults and ridges. Other locations include: the East Pacific Ridge located in the South Eastern Pacific Ocean, which meets up with San Andreas Fault to the North. Transform faults are not spreading centers; the best example is the San Andreas Fault on the Pacific coast of the United States. The San Andreas Fault links the East Pacific Rise off the West coast of Mexico to the Mendocino Triple Junction off the coast of the Northwestern United States, making it a ridge-to-transform-style fault; the formation of the San Andreas Fault system occurred recently during the Oligocene Period between 34 million and 24 million years ago. During this period, the Farallon plate, followed by the Pacific plate, collided into the North American plate; the collision led to the subduction of the Farallon plate underneath the North American plate. Once the spreading ce
MV Fedra was a Liberian-registered bulk-carrier cargo ship. It ran aground and smashed against Europa Point, the southernmost tip of Gibraltar on 10 October 2008 following severe gale force winds measuring 12 on the Beaufort scale. Spanish and Gibraltarian emergency services mounted a joint rescue operation, Gibraltar declared a Major Incident and requested the standby of additional statutory and voluntary emergency services, although due to the safe rescue of all crew from Fedra they were not needed. Five of its 31 crew members were airlifted to safety by a Spanish coast guard helicopter and the rest were hoisted up by an improvised crane system; the vessel broke in half shortly thereafter. About half of its 300 tons of fuel spilled into the sea; some of such oil washed ashore along Gibraltar's western coast in the area of Rosia Bay and Camp Bay. Spanish sources said that some fuel from Fedra had washed up on some Campo beaches having drifted as far as Tarifa. There were oil slicks in the Bay of Gibraltar.
Fedra avoided becoming a permanent shipwreck when the forward section was re-floated and towed round into the Bay of Gibraltar in February 2009. It was moored alongside the South Mole in Gibraltar Harbour; the superstructure was cut away from the hull of the aft section, was placed the dockside at HM Naval Base. A report was released by the Gibraltar Maritime Association in January 2012 which reveals how the Company undermined the Master of Fedra and his authority in his attempts to save both the crew and the ship; the report explains the various aspects which led to the demise of MV Fedra. MV New Flame Searle, Dominique. "Cargo ship hits Gibraltar rocks in heavy seas". Reuters. Retrieved 11 October 2008. "Bulk Carrier FEDRA runs aground in severe weather". Gibfocus. Archived from the original on 15 October 2008. Retrieved 11 October 2008. "El vertido de fuel se extiende por el Estrecho y llega hasta Ceuta". El País. Retrieved 15 October 2008
A passive margin is the transition between oceanic and continental lithosphere, not an active plate margin. A passive margin forms by sedimentation above an ancient rift, now marked by transitional lithosphere. Continental rifting creates new ocean basins; the continental rift forms a mid-ocean ridge and the locus of extension moves away from the continent-ocean boundary. The transition between the continental and oceanic lithosphere, created by rifting is known as a passive margin. Passive margins are found at every ocean and continent boundary, not marked by a strike-slip fault or a subduction zone. Passive margins define the region around the Atlantic Ocean, Arctic Ocean, western Indian Ocean, define the entire coasts of Africa, Greenland and Australia, they are found on the east coast of North America and South America, in western Europe and most of Antarctica. East Asia contains some passive margins; this refers to whether a crustal boundary between oceanic lithosphere and continental lithosphere is a plate boundary or not.
Active margins are found on the edge of a continent. These are marked by uplift and volcanic mountain belts on the continental plate. Less there is a strike-slip fault, as defines the southern coastline of W. Africa. Most of the eastern Indian Ocean and nearly all of the Pacific Ocean margin are examples of active margins. While a weld between oceanic and continental lithosphere is called a passive margin, it is not an inactive margin. Active subsidence, growth faulting, pore fluid formation and migration are all active processes on passive margins. Passive margins are only passive in plate boundaries. Passive margins consist of both onshore coastal plain and offshore continental shelf-slope-rise triads. Coastal plains are dominated by fluvial processes, while the continental shelf is dominated by deltaic and longshore current processes; the great rivers drain across passive margins. Extensive estuaries are common on mature passive margins. Although there are many kinds of passive margins, the morphologies of most passive margins are remarkably similar.
They consist of a continental shelf, continental slope, continental rise, abyssal plain. The morphological expression of these features are defined by the underlying transitional crust and the sedimentation above it. Passive margins defined by a large fluvial sediment budget and those dominated by coral and other biogenous processes have a similar morphology. In addition, the shelf break seems to mark the maximum Neogene lowstand, defined by the glacial maxima; the outer continental shelf and slope may be cut by great submarine canyons, which mark the offshore continuation of rivers. At high latitudes and during glaciations, the nearshore morphology of passive margins may reflect glacial processes, such as the fjords of Norway and Greenland; the main features of passive margins lie underneath the external characters. Beneath passive margins the transition between the continental and oceanic crust is a broad transition known as transitional crust; the subsided continental crust is marked by normal faults.
The faulted crust transitions into oceanic crust and may be buried due to thermal subsidence and the mass of sediment that collects above it. The lithosphere beneath passive margins is known as transitional lithosphere; the lithosphere thins seaward. Different kinds of transitional crust form, depending on how fast rifting occurs and how hot the underlying mantle was at the time of rifting. Volcanic passive margins represent one endmember transitional crust type, the other endmember type is the rifted passive margin. Volcanic passive margins are marked by numerous dykes and igneous intrusions within the subsided continental crust. There are a lot of dykes formed perpendicular to the seaward-dipping lava flows and sills. Igneous intrusions within the crust cause lava flows along the top of the subsided continental crust and form seaward-dipping reflectors. Passive margins are characterized by thick accumulations of sediments. Space for these sediments is called accommodation and is due to subsidence of the transitional crust.
Subsidence is caused by gravitational equilibrium, established between the crustal tracts, known as isostasy. Isostasy controls the uplift of the rift flank and the subsequent subsidence of the evolving passive margin and is reflected by changes in heat flow. Heat flow at passive margins changes over its lifespan, high at the beginning and decreasing with age. In the initial stage, the continental crust and lithosphere is stretched and thinned due to plate movement and associated igneous activity; the thin lithosphere beneath the rift allows the upwelling mantle to melt by decompression. Lithospheric thinning allows the asthenosphere to rise closer to the surface, heating the overlying lithosphere by conduction and advection of heat by intrusive dykes. Heating elevates the lower crust and lithosphere. In addition, mantle plumes may cause prodigious igneous activity. Once a mid-oceanic ridge forms and seafoor spreading begins, the original site of rifting is separated into conjugate passive margins and migrates away from the zone of mantle upwelling and heating and cooling begins.
The mantle lithosphere below the thinned and faulted continental oceanic transition cools