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54-463: The coaster was built as a smaller-scale prototype to the larger Giant Cyclone Safety Coasters (the "Terrifying Triplets") which Traver built in 1927. In addition to its innovative all-steel frame (described by promotional material as being "[s]trong as the Rock of Gibralter [ sic ]"), the coaster was also innovative in its use of aluminum-body roller coaster trains. The aluminum alloy used in

108-636: A Neanderthal woman's skull was found at Forbes' Quarry , located on the north face of the Rock. However, its significance was not recognized until after the 1856 discovery of the type specimen in the Neander Valley . Excavations in Gorham's Cave , located near sea level on the eastern side of the Rock, found evidence it was used by Neanderthals, and plant and animal remains in the cave gave evidence of Neanderthals' highly varied diet. The Eastern Face of

162-560: A combined uplift of about 26.5 metres (87 ft) in the past 250,000 years. Today, the Rock of Gibraltar forms a peninsula jutting out into the Strait of Gibraltar from the southern coast of Spain . The promontory is linked to the continent by means of a sandy tombolo with a maximum elevation of 3 m (9.8 ft). To the north, the Rock rises vertically from sea level up to 411.5 m (1,350 ft) at Rock Gun Battery . The Rock's highest point stands 426 m (1,398 ft) near

216-421: A fold axis is called a cylindrical fold . This term has been broadened to include near-cylindrical folds. Often, the fold axis is the same as the hinge line. Minor folds are quite frequently seen in outcrop; major folds seldom are except in the more arid countries. Minor folds can, however, often provide the key to the major folds they are related to. They reflect the same shape and style, the direction in which

270-541: A half years. The Germans never got close to capturing the rock and so the men were never sealed inside. The team was disbanded to resume civilian life when the war ended. The saying "solid as the Rock of Gibraltar" is used to describe an entity that is very safe or firm. The motto of the Royal Gibraltar Regiment and Gibraltar itself is Nulli Expugnabilis Hosti ( Latin for "No Enemy Shall Expel Us"). Approximately 40% of Gibraltar's land area

324-444: A hinge need to accommodate large deformations in the hinge zone. This results in voids between the layers. These voids, and especially the fact that the water pressure is lower in the voids than outside of them, act as triggers for the deposition of minerals. Over millions of years, this process is capable of gathering large quantities of trace minerals from large expanses of rock and depositing them at very concentrated sites. This may be

378-427: A mechanism that is responsible for the veins. To summarize, when searching for veins of valuable minerals, it might be wise to look for highly folded rock, and this is the reason why the mining industry is very interested in the theory of geological folding. Anticlinal traps are formed by folding of rock. For example, if a porous sandstone unit covered with low permeability shale is folded into an anticline, it may form

432-629: A planar detachment without further fault propagation, detachment folds may form, typically of box-fold style. These generally occur above a good detachment such as in the Jura Mountains , where the detachment occurs on middle Triassic evaporites . Shear zones that approximate to simple shear typically contain minor asymmetric folds, with the direction of overturning consistent with the overall shear sense. Some of these folds have highly curved hinge-lines and are referred to as sheath folds . Folds in shear zones can be inherited, formed due to

486-513: A series of unique views of the Bay of Gibraltar , the isthmus, and Spain. When World War II broke out in 1939, the authorities evacuated the civilian population to Morocco , the United Kingdom , Jamaica , and Madeira so that the military could fortify Gibraltar against a possible German attack. By 1942 there were over 30,000 British soldiers, sailors, and airmen on the Rock. They expanded

540-541: A strong axial planar cleavage . Folds in the rock are formed about the stress field in which the rocks are located and the rheology , or method of response to stress, of the rock at the time at which the stress is applied. The rheology of the layers being folded determines characteristic features of the folds that are measured in the field. Rocks that deform more easily form many short-wavelength, high-amplitude folds. Rocks that do not deform as easily form long-wavelength, low-amplitude folds. Layers of rock that fold into

594-435: A thrust fault cuts up section from one detachment level to another. Displacement over this higher-angle ramp generates the folding. Fault propagation folds or tip-line folds are caused when displacement occurs on an existing fault without further propagation. In both reverse and normal faults this leads to folding of the overlying sequence, often in the form of a monocline . When a thrust fault continues to displace above

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648-523: A very minor part of the Rock of Gibraltar. The Little Bay Shale Formation consists of dark bluish-gray, unfossiliferous shale, which is interbedded with thin layers of grit , mudstone , and limestone. It predates the Gibraltar limestone. The Dockyard Shale Formation is an undescribed variegated shale of unknown age that lies buried beneath the Gibraltar's dockyard and coastal protection structures. Although these geological formations were deposited during

702-593: Is a monolithic limestone mountain 426 m (1,398 ft) high dominating the western entrance to the Mediterranean Sea . It is situated near the end of a narrow 9 kilometres (5.6 mi) long promontory stretching due south into the Mediterranean Sea and is located within the British territory of Gibraltar , and is 27 km north-east of Tarifa , Spain, the southwestern tip of Europe on

756-788: Is a migratory bottleneck, or choke point, for an estimated 250,000 raptors that cross the Strait annually, and because it supports breeding populations of Barbary partridges and lesser kestrels . Fold (geology) In structural geology , a fold is a stack of originally planar surfaces, such as sedimentary strata , that are bent or curved ( "folded" ) during permanent deformation . Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur as single isolated folds or in periodic sets (known as fold trains ). Synsedimentary folds are those formed during sedimentary deposition. Folds form under varied conditions of stress , pore pressure , and temperature gradient , as evidenced by their presence in soft sediments ,

810-504: Is accommodated by slip between the pages of the book. The fold formed by the compression of competent rock beds is called "flexure fold". Typically, folding is thought to occur by simple buckling of a planar surface and its confining volume. The volume change is accommodated by layer parallel shortening the volume, which grows in thickness . Folding under this mechanism is typical of a similar fold style, as thinned limbs are shortened horizontally and thickened hinges do so vertically. If

864-417: Is also a feature of many igneous intrusions and glacier ice. Folding of rocks must balance the deformation of layers with the conservation of volume in a rock mass. This occurs by several mechanisms. Flexural slip allows folding by creating layer-parallel slip between the layers of the folded strata, which, altogether, result in deformation. A good analogy is bending a phone book, where volume preservation

918-643: Is also possible that the original Gibraltar macaques are a remnant of populations that are known to have spread throughout Southern Europe during the Pliocene , up to 5.5 million years ago. Some animals of the Rock have been reintroduced by the Alameda Wildlife Conservation Park who have three Barbary macaques . The Rock of Gibraltar, at the head of the Strait , is a prominent headland , which accumulates migrating birds during

972-425: Is relatively weak. When rock behaves as a fluid, as in the case of very weak rock such as rock salt, or any rock that is buried deeply enough, it typically shows flow folding (also called passive folding , because little resistance is offered): the strata appear shifted undistorted, assuming any shape impressed upon them by surrounding more rigid rocks. The strata simply serve as markers of the folding. Such folding

1026-719: Is the Tower of Homage , a massive building of brick and very hard concrete called tapia . The upper part of the tower housed the former occupants' living apartments and Moorish bath. A unique feature of the Rock is its system of underground passages, known as the Galleries or the Great Siege Tunnels . The first of these was dug towards the end of the Great Siege of Gibraltar , which lasted from 1779 to 1783. General Elliot , afterwards Lord Heathfield, who commanded

1080-454: Is the midpoint of the limb. The axial surface is defined as a plane connecting all the hinge lines of stacked folded surfaces. If the axial surface is planar, it is called an axial plane and can be described in terms of strike and dip . Folds can have a fold axis . A fold axis "is the closest approximation to a straight line that when moved parallel to itself, generates the form of the fold". (Ramsay 1967). A fold that can be generated by

1134-520: The Atlantic Ocean , both northward and southward. The Rock of Gibraltar is a monolithic promontory . The Main Ridge has a sharp crest with peaks over 400 metres (1,300 ft) above sea level, formed by Early Jurassic limestones and dolomites. It is a deeply eroded and highly faulted limb of an overturned fold . The sedimentary strata composing the Rock of Gibraltar are overturned, with

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1188-614: The Iberian Peninsula . The rock serves as an impregnable fortress and contains a labyrinthine network of man-made tunnels known as the Tunnels of Gibraltar . Most of the Rock's upper area comprises a nature reserve which is home to about 300 Barbary macaques . It is a major tourist attraction. The Rock of Gibraltar, the northern of the two historic Pillars of Hercules , was known to the Romans as Mons Calpe ("Mount Calpe"),

1242-422: The Rock comprises steep cliffs and scree slopes descending to the sea, allowing little space for human habitation. In modern times a road (Sir Herbert Miles Road, named after Lieutenant General Sir Herbert Miles , Governor of Gibraltar 1913-1918) has been cut into the shore, its southernmost part being through a tunnel ( Dudley Ward Way , named after Sir Alfred Dudley Ward , Governor of Gibraltar 1962-1965) in

1296-440: The Rock of Gibraltar. Geologists have found various poorly preserved and badly eroded and rolled marine fossils within it. The fossils found in the Gibraltar limestone include various brachiopods , corals , echinoid fragments, gastropods , pelecypods , and stromatolites . These fossils indicate an Early Jurassic age (Lower Lias) for the deposition of the Gibraltar limestone. The Little Bay and Dockyard shale formations form

1350-441: The accommodation of strains between neighboring faults. Fault-bend folds are caused by displacement along a non-planar fault. In non-vertical faults, the hanging-wall deforms to accommodate the mismatch across the fault as displacement progresses. Fault bend folds occur in both extensional and thrust faulting. In extension, listric faults form rollover anticlines in their hanging walls. In thrusting, ramp anticlines form whenever

1404-493: The axis of the fold. Those with limbs of relatively equal length are termed symmetrical , and those with highly unequal limbs are asymmetrical . Asymmetrical folds generally have an axis at an angle to the original unfolded surface they formed on. Vergence is calculated in a direction perpendicular to the fold axis. Folds that maintain uniform layer thickness are classed as concentric folds. Those that do not are called similar folds . Similar folds tend to display thinning of

1458-560: The base of the Rock. The western face, where the City of Gibraltar is located, is comparatively less steep. Calcite , the mineral that makes up limestone , dissolves slowly in rainwater. Over time, this process can form caves. For this reason the Rock of Gibraltar contains over 100 caves. St. Michael's Cave , located halfway up the western slope of the Rock, is the most prominent and is a popular tourist attraction. Fossils of Neanderthals have been found at several sites in Gibraltar. In 1848,

1512-412: The closures of the major folds lie, and their cleavage indicates the attitude of the axial planes of the major folds and their direction of overturning A fold can be shaped like a chevron , with planar limbs meeting at an angular axis, as cuspate with curved limbs, as circular with a curved axis, or as elliptical with unequal wavelength . Fold tightness is defined by the size of the angle between

1566-760: The coaster was moved to the Alabama State Fairgrounds where it operated for several years. The Cyclone coaster which operated at the Century of Progress exposition between 1933 and 1934 in Chicago is also thought to be the same coaster. While at the Century of Progress, the coaster was first built near what is now Burnham Park , then later moved to a pier just south of the Adler Planetarium . A number of sources suggest that this coaster

1620-728: The early part of the Jurassic Period some 175–200 million years ago, their current appearance is due to far more recent events of about 5 million years ago. When the African tectonic plate collided tightly with the Eurasian Plate , the Mediterranean became a lake that, over the course of time, dried up during the Messinian salinity crisis . The Atlantic Ocean then broke through the Strait of Gibraltar , and

1674-409: The effects of a high-level igneous intrusion e.g. above a laccolith . The fold hinge is the line joining points of maximum curvature on a folded surface. This line may be either straight or curved. The term hinge line has also been used for this feature. A fold surface seen perpendicular to its shortening direction can be divided into hinge and limb portions; the limbs are the flanks of

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1728-450: The fold's limbs (as measured tangential to the folded surface at the inflection line of each limb), called the interlimb angle. Gentle folds have an interlimb angle of between 180° and 120°, open folds range from 120° to 70°, close folds from 70° to 30°, and tight folds from 30° to 0°. Isoclines , or isoclinal folds , have an interlimb angle of between 10° and zero, with essentially parallel limbs. Not all folds are equal on both sides of

1782-409: The fold, and the limbs converge at the hinge zone. Within the hinge zone lies the hinge point, which is the point of minimum radius of curvature (maximum curvature) of the fold. The crest of the fold represents the highest point of the fold surface whereas the trough is the lowest point. The inflection point of a fold is the point on a limb at which the concavity reverses; on regular folds, this

1836-439: The folding deformation cannot be accommodated by a flexural slip or volume-change shortening (buckling), the rocks are generally removed from the path of the stress. This is achieved by pressure dissolution , a form of metamorphic process, in which rocks shorten by dissolving constituents in areas of high strain and redepositing them in areas of lower strain. Folds generated in this way include examples in migmatites and areas with

1890-471: The full spectrum of metamorphic rocks , and even as primary flow structures in some igneous rocks . A set of folds distributed on a regional scale constitutes a fold belt , a common feature of orogenic zones . Folds are commonly formed by shortening of existing layers, but may also be formed as a result of displacement on a non-planar fault ( fault bend fold ), at the tip of a propagating fault ( fault propagation fold ), by differential compaction or due to

1944-697: The garrison throughout the siege , was anxious to bring flanking fire on the Spanish batteries in the plain below the North face of the Rock. On the suggestion of Sergeant-Major Henry Ince of the Royal Engineers, he had a tunnel bored from a point above Willis's Battery to communicate with the Notch, a natural projection from the North face. The plan was to mount a battery there. There was no intention at first of making embrasures in this tunnel, but an opening

1998-548: The limbs and thickening of the hinge zone. Concentric folds are caused by warping from active buckling of the layers, whereas similar folds usually form by some form of shear flow where the layers are not mechanically active. Ramsay has proposed a classification scheme for folds that often is used to describe folds in profile based upon the curvature of the inner and outer lines of a fold and the behavior of dip isogons . that is, lines connecting points of equal dip on adjacent folded surfaces: (A homocline involves strata dipping in

2052-609: The mechanical layering and the contrast in properties between the layers. If the layering does begin to fold, the fold style is also dependent on these properties. Isolated thick competent layers in a less competent matrix control the folding and typically generate classic rounded buckle folds accommodated by deformation in the matrix. In the case of regular alternations of layers of contrasting properties, such as sandstone-shale sequences, kink-bands, box-folds and chevron folds are normally produced. Many folds are directly related to faults, associated with their propagation, displacement and

2106-1093: The oldest strata overlying the youngest strata. These strata are the Catalan Bay Shale Formation (youngest), Gibraltar Limestone , Little Bay Shale Formation (oldest), and Dockyard Shale Formation (age unknown). These strata are noticeably faulted and deformed. Predominantly of shale , the Catalan Bay Shale Formation also contains thick units composed of either brown calcareous sandstone , soft shaly sandstone interbedded with bluish-black limestone , and interlayered greenish-gray marls and dark gray cherts . The Catalan Bay Shale Formation contains unidentifiable echinoid spines and belemnite fragments and infrequent Early Jurassic (Middle Lias ) ammonites . The Gibraltar limestone consists of greyish-white or pale-gray compact, and sometime finely crystalline, medium to thick bedded limestones and dolomites that locally contain chert seams. This formation comprises about three quarters of

2160-540: The orientation of pre-shearing layering or formed due to instability within the shear flow. Recently deposited sediments are normally mechanically weak and prone to remobilization before they become lithified, leading to folding. To distinguish them from folds of tectonic origin, such structures are called synsedimentary (formed during sedimentation). Slump folding: When slumps form in poorly consolidated sediments, they commonly undergo folding, particularly at their leading edges, during their emplacement. The asymmetry of

2214-721: The other southern pillar on the African side of the Strait of Gibraltar being Mons Abila , identified today as either Monte Hacho or Jebel Musa , with a distance of about 27 km between the two "pillars". According to ancient legend fostered by the Greeks and the Phoenicians , and later adopted by the Romans, the two pillars marked the western limit of the known world, although the Phoenicians had sailed beyond this point into

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2268-492: The passage periods. The vegetation on the Rock, unique in southern Iberia , provides a temporary home for many species of migratory birds that stop to rest and feed before continuing migration for their crossing over the sea and desert. In spring, they return to replenish before continuing their journeys to Western Europe , journeys which may take them as far as Greenland or Russia . The Rock has been identified as an Important Bird Area by BirdLife International , because it

2322-635: The rapidly undulating "Jazz Track" which was characteristic of earlier Jazz Railways and the later Giant Cyclones. The coaster grossed over $ 28,000 during the course of the Sesquicentennial Exposition while running at or near full capacity. It grossed over $ 75,000 at the Century of Progress in Chicago. Rock of Gibralter The Rock of Gibraltar (from the Arabic name Jabal Ṭāriq جبل طارق , meaning "Mountain of Tariq" )

2376-520: The resultant flooding created the Mediterranean Sea . The Rock forms part of the Betic Cordillera , a mountain range that dominates southeastern Iberia. The local geology of the region has been uplifting the rock at roughly 0.05 mm (0.0020 in) per year for the past 200,000 years (or a total uplift of around 10 metres (33 ft)), and for at least 50,000 years before that had been uplifted by 0.33 mm (0.013 in) per year for

2430-589: The rock. Towards the south-east end of the Rock close to sea-level is located Gorham's Cave , a UNESCO World Heritage Site . The Moorish Castle is a relic of Moorish rule over Gibraltar, which lasted for 710 years. It was built in the year AD 711, when the Berber chieftain Tariq ibn-Ziyad first landed on the rock that still bears his name. The 17th-century Muslim historian Al-Maqqari wrote that upon landing, Tariq burned his ships. The principal building that remains

2484-400: The same direction, though not necessarily any folding.) Folds appear on all scales, in all rock types , at all levels in the crust . They arise from a variety of causes. When a sequence of layered rocks is shortened parallel to its layering, this deformation may be accommodated in a number of ways, homogeneous shortening, reverse faulting or folding. The response depends on the thickness of

2538-420: The slump folds can be used to determine paleoslope directions in sequences of sedimentary rocks. Dewatering: Rapid dewatering of sandy sediments, possibly triggered by seismic activity, can cause convolute bedding. Compaction: Folds can be generated in a younger sequence by differential compaction over older structures such as fault blocks and reefs . The emplacement of igneous intrusions tends to deform

2592-472: The south end above the strait at O'Hara's Battery . The Rock's central peak, Signal Hill and the top station of the Gibraltar Cable Car , stands at an elevation of 387 m (1,270 ft). The near-cliffs along the eastern side of the Rock drop down to a series of wind-blown sand slopes that date to the glaciations when sea levels were lower than today, and a sandy plain extended east from

2646-482: The surrounding country rock . In the case of high-level intrusions, near the Earth's surface, this deformation is concentrated above the intrusion and often takes the form of folding, as with the upper surface of a laccolith . The compliance of rock layers is referred to as competence : a competent layer or bed of rock can withstand an applied load without collapsing and is relatively strong, while an incompetent layer

2700-615: The train bodies was said to be one used in aeronautical engineering. Construction of the Cyclone took approximately half the time of a comparable wooden roller coaster. After the Sesquicentennial Exposition, the Cyclone was removed from the fairgrounds. Some sources report that it was put into storage for several years at the Traver Engineer Company's factory in Beaver Falls, Pennsylvania , whereas others report that

2754-476: The tunnel system and made the Rock a keystone in the defence of shipping routes to the Mediterranean. In February 1997, it was revealed the British had a secret plan called Operation Tracer to conceal servicemen in tunnels beneath the Rock in case the Germans captured it. The team in the rock would have radio equipment with which to report enemy movements. A six-man team waited undercover at Gibraltar for two and

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2808-678: Was declared a nature reserve in 1993. The flora and fauna of the Gibraltar Nature Reserve are of conservation interest and are protected by law . Within it is a range of animals and plants, but the highlights are the Barbary macaques (the famous Rock apes ), the Barbary partridges , and flowers such as Gibraltar's own chickweed , thyme and the Gibraltar candytuft . The Barbary macaques may have originated from an escape of North African animals transported to Spain; it

2862-444: Was found necessary for ventilation; as soon as it had been made a gun was mounted in it. By the end of the siege, the British had constructed six such embrasures, and mounted four guns. The Galleries, which tourists may visit, were a later development of the same idea and were finished in 1797. They consist of a whole system of halls, embrasures , and passages, of a total length of nearly 304 m (997 ft). From them, one may see

2916-586: Was the first to ever bear the name "Cyclone", though other sources argue it was the Revere Beach Cyclone or another coaster. As with the later Giant Cyclone Safety Coasters, there was very little straight track in the Sesquicentennial Cyclone. The coaster was shorter and more compact than the "Terrifying Triplets" however. It was 60 feet (18 m) tall and operated in a footprint of 90 by 290 feet (27 by 88 m). It included

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