A transform fault or transform boundary, is a type of fault whose relative motion is predominantly horizontal, in either a sinistral or dextral direction. Furthermore, transform faults end abruptly and are connected on both ends to other faults, ridges, or subduction zones, Transform faults are the only type of strike-slip fault that can be classified as a plate boundary. The new class of faults, called transform faults, produce slip in the 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, the distance remains constant in earthquakes because the ridges are spreading centers. 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 closely related to transcurrent faults, and are commonly confused.
In addition, transform faults have equal deformation across the fault line, while transcurrent faults have greater displacement in the middle of the fault zone. Finally, transform faults can form a plate boundary, while transcurrent faults cannot. The effect of a fault is to strain, which can be caused by compression, extension. Transform faults specifically relieve strain by transporting the strain between ridges or subduction zones, Transform faults act as the plane of weakness allowing for the splitting in rift zones. Transform faults are commonly found linking segments of mid-oceanic ridges or spreading centres and these mid-oceanic ridges are where new seafloor is constantly created through the upwelling of new basaltic magma. With new seafloor being pushed and pulled out, the older seafloor slowly 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 currently active, Transform faults move differently than a strike-slip fault at the mid-oceanic ridge. Evidence of this can be found in paleomagnetic striping on the seafloor, a paper written by 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 period of time with the spreading center or ridge slowly deforming from a straight line to a curved line. Finally, 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 & Crane and gabbro rocks were discovered in the edges of the transform ridges and 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, as previously stated, active transform faults are between two tectonic structures or faults.
Fracture zones represent the active transform fault lines, which have since passed the active transform zone and are being pushed toward the continents
The continental crust is the layer of igneous and metamorphic rocks that forms the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial because its composition is more felsic compared to the oceanic crust. The continental crust consists of layers, with a bulk composition that is intermediate to felsic. The average density of continental crust is about 2.7 g/cm3, less dense than the material that makes up the mantle. Continental crust is less dense than oceanic crust, whose density is about 2.9 g/cm3. At 25 to 70 km, continental crust is thicker than oceanic crust. About 40% of Earths surface is occupied by continental crust. It makes up about 70% of the volume of Earths crust, because the surface of continental crust mainly lies above sea level, its existence allowed land life to evolve from marine life. There is little evidence of continental crust prior to 3.5 Ga, all continental crust ultimately derives from the fractional differentiation of oceanic crust over many eons.
This process has been and continues today primarily as a result of the associated with subduction. In contrast to the persistence of continental crust, the size, different tracts rift apart and recoalesce as part of a grand supercontinent cycle. There are currently about 7 billion cubic kilometers of continental crust, the relative permanence of continental crust contrasts with the short life of oceanic crust. Because continental crust is less dense oceanic crust, when active margins of the two meet in subduction zones, the oceanic crust is typically subducted back into the mantle. Continental crust is rarely subducted.01 Ga, whereas the oldest oceanic crust is from the Jurassic, Continental crust and the rock layers that lie on and within it are thus the best archive of Earths history. The height of mountain ranges is usually related to the thickness of crust and this results from the isostasy associated with orogeny. The crust is thickened by the compressive forces related to subduction or continental collision, the buoyancy of the crust forces it upwards, the forces of the collisional stress balanced by gravity and erosion.
This forms a keel or mountain root beneath the mountain range, the thinnest continental crust is found in rift zones, where the crust is thinned by detachment faulting and eventually severed, replaced by oceanic crust. The edges of continental fragments formed this way are termed passive margins, igneous rock may be underplated to the underside of the crust, i. e. adding to the crust by forming a layer immediately beneath it
Geology of the Alps
The Alps form part of a Cenozoic orogenic belt of mountain chains, called the Alpide belt, that stretches through southern Europe and Asia from the Atlantic all the way to the Himalayas. This belt of mountain chains was formed during the Alpine orogeny, a gap in these mountain chains in central Europe separates the Alps from the Carpathians to the east. Orogeny took place continuously and tectonic subsidence has produced the gaps in between, the Alps arose as a result of the collision of the African and Eurasian tectonic plates, in which the Alpine Tethys, which was formerly in between these continents, disappeared. Most of this occurred during the Oligocene and Miocene epochs, crystalline basement rocks, which are exposed in the higher central regions, are the rocks forming Mont Blanc, the Matterhorn, and high peaks in the Pennine Alps and Hohe Tauern. The formation of the Mediterranean Sea is a recent development. The Alps form a convex arc around their southeastern foreland basin. Quaternary and Neogene sediments in this basin lie discordant over the southernmost thrust units, in the northeast, southward dipping and internally thrusted Cenozoic foreland deposits are found.
This Bavarian and Swiss foreland basin is called the Molasse basin, the foreland basin deposits are overthrusted from the south by the thrustfront of the Alpine nappes. In Switzerland the Molasse Basin is rimmed to the northwest by the Jura mountains, an external fold-and-thrust belt, the western part of the Molasse basin forms the plateau of the Mittelland between the Alps and Jura Mountains. The Jura Mountains location is still a topic for debate, a possible tectonic factor is the north-south extensional Upper Rhine Graben to the north. The Alps continue fairly smoothly into the following related Alpine mountain ranges, the Apennines to the southwest, the Dinarides to the southeast, in the east the Alps are bounded by the Viennese Basin and the Pannonian Basin, where east–west stretching of the crust takes place. The Alps have a geology, but the general structure is the same as for other mountain ranges formed by continental collision. The Alps are often divided into Eastern and Western Alps, the division between the Eastern and Central Alps is approximately the line between St.
Margrethen and Sondrio, the division between the Central and Western Alps is unclear. The main suture in the Alps is called the Periadriatic Seam and this is the boundary between materials from the European and Apulian plates. South of this line are folded and thrusted units of the Southern Alps, north of the Periadriatic seam, rocks from three main palaeogeographic domains are found, the Helvetic or Dauphinois, the Penninic and the Austroalpine domains. Folds and thrusts north of the Periadriatic seam are generally directed to the north, in the Southern Alps the thrusts are to the south so the vergence is dominantly southward. The rocks of the Austroalpine nappes form most of the outcrops in the Eastern Alps, while in the west these nappes are, with the exception of a few places, eroded away. In the Western Alps the Helvetic nappes can be found to the north and west, sometimes still under klippes of the Penninic nappes, as in the Préalpes du Sud south of Lake Geneva
The Periadriatic Seam is a distinct geologic fault in Southern Europe, running S-shaped about 1000 km from the Tyrrhenian Sea through the whole Southern Alps as far as Hungary. It forms the division between the Adriatic plate and the European plate, the term Insubric line is sometimes used to address the whole Periadriatic Seam, but it is more commonly used to mean just a western part of it. Within the Eastern Alps, the marks the border between the Central Eastern Alps and the Southern Limestone Alps. In the Western Alps it forms the division between the southern Apulian foreland and the central zones of the Alps. Continental collision is still going on, with the Apulian and European plates still converging, movement along the Periadriatic Seam is the cause for the earthquake zone between Vienna and Friuli. Meanwhile, the zones of the Alps are rising too. The result is the set of major faultzones collectively named Periadriatic Seam, the uplift caused violent erosion of the young orogen, which led to the formation of the Hohe Tauern window.
At several regions a heavy uplift of the Central Alps by some kilometers took place, Apulian Plate Geology of the Alps
Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate, about 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, most cave systems are through limestone bedrock. The first geologist to distinguish limestone from dolomite was Belsazar Hacquet in 1778, like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids and these organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragment, some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i. e. travertine.
Secondary calcite may be deposited by supersaturated meteoric waters and this produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance, the primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters. Limestones may form in lacustrine and evaporite depositional environments, calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits a characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors, especially with weathered surfaces, Limestone may be crystalline, granular, or massive, depending on the method of formation.
Crystals of calcite, dolomite or barite may line small cavities in the rock, when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams, particularly there are waterfalls. Calcium carbonate is deposited where evaporation of the leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls, coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the building process, limestone recrystallizes into marble
The Molasse basin is a foreland basin north of the Alps which formed during the Oligocene and Miocene epochs. The basin formed as a result of the flexure of the European plate under the weight of the wedge of the Alps that was forming to the south. In geology, the molasse basin is sometimes used in a general sense for a synorogenic foreland basin of the type north of the Alps. The Molasse basin stretches over a length of 1000 kilometers along the axis of the Alps, in France, Germany. The western end is at Lake Geneva, where the outcrop is just 20 km wide. Further to the northeast the basin becomes wider and it forms the subsurface of the Swiss Mittelland and reaches its largest width in the Bavarian foreland of the Alps. From Amstetten to Sankt Pölten the basin forms a narrow band, after that it widens again to the east. North of the Danube River it connects with the Vienna basin, the region where the molasse crops out is divided into two. The Subalpine Molasse zone along the Alps and the Foreland Molasse zone further into the foreland, in the Foreland Molasse zone the molasse sediments are relatively undisturbed, in the Subalpine Molasse zone the beds are often tilted and thrust over each other.
Before the development of the Molasse basin, in the Mesozoic era, the weight of the orogenic wedge made the European plate bend downward, resulting in the formation of a deep marine foredeep. In the Eocene epoch the basin became deeper until it formed a small oceanic trench north of the developing orogen, due to the huge amounts of sediments that were eroded from the forming mountain chain the basin was filled up and got shallower. During the Oligocene and Miocene epochs, undeep marine to continental molasse was deposited in the basin, around 10 to 5 million years ago, tectonic uplift had raised the basin to such a height that netto sedimentation stopped. From the south, the deposits were overthrust about 10 kilometers by the Helvetic nappes. The Jura mountains, a fold and thrust belt along the present Swiss-French border, in some places in the Jura mountains, molasse deposits were folded together with older Mesozoic limestones. Deformation instead localized further north, thus forming the relatively flat Swiss Mittelland between the Alps and the Jura Mountains, the Swiss part of the Molasse basin is now located in between the Alps and the Jura mountains, as a large piggy-back basin.
In the Eastern Alps an external mountain range such as the Jura Mountains never developed, the total thickness of molasse deposits in the basin can be up to 6 kilometers. Lithostratigraphically, this molasse is treated as a group that is divided into four formations and this division is made on whether the sedimentary facies is continental or marine. The lowermost formation is the Lower Marine Molasse and its age is Rupelian and it consists of shallow marine sand and marl
The Adriatic Sea /ˌeɪdriˈætᵻk/ is a body of water separating the Italian Peninsula from the Balkan peninsula and the Apennine Mountains from the Dinaric Alps and adjacent ranges. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto to the northwest, the countries with coasts on the Adriatic are Albania and Herzegovina, Greece, Italy and Slovenia. The Adriatic contains over 1,300 islands, mostly located along its eastern, Croatian and it is divided into three basins, the northern being the shallowest and the southern being the deepest, with a maximum depth of 1,233 metres. The Otranto Sill, a ridge, is located at the border between the Adriatic and Ionian Seas. The prevailing currents flow counterclockwise from the Strait of Otranto, along the eastern coast, tidal movements in the Adriatic are slight, although larger amplitudes are known to occur occasionally. The Adriatics salinity is lower than the Mediterraneans because the Adriatic collects a third of the water flowing into the Mediterranean.
The surface water temperatures range from 30 °C in summer to 12 °C in winter. The Adriatic Sea sits on the Apulian or Adriatic Microplate, which separated from the African Plate in the Mesozoic era, the plates movement contributed to the formation of the surrounding mountain chains and Apennine tectonic uplift after its collision with the Eurasian plate. In the Late Oligocene, the Apennine Peninsula first formed, separating the Adriatic Basin from the rest of the Mediterranean, all types of sediment are found in the Adriatic, with the bulk of the material transported by the Po and other rivers on the western coast. The western coast is alluvial or terraced, while the eastern coast is indented with pronounced karstification. There are dozens of protected areas in the Adriatic, designed to protect the seas karst habitats. The sea is abundant in flora and fauna—more than 7,000 species are identified as native to the Adriatic, many of them endemic and threatened ones. The Adriatics shores are populated by more than 3.5 million people, the earliest settlements on the Adriatic shores were Etruscan and Greek.
By the 2nd century BC, the shores were under Romes control, following Italian unification, the Kingdom of Italy started an eastward expansion that lasted until the 20th century. Following World War I and the collapse of Austria-Hungary and the Ottoman Empire, the former disintegrated during the 1990s, resulting in four new states on the Adriatic coast. Italy and Albania agreed on their maritime boundary in 1992, Fisheries and tourism are significant sources of income all along the Adriatic coast. Adriatic Croatias tourism industry has grown faster economically than the rest of the Adriatic Basins, maritime transport is a significant branch of the areas economy—there are 19 seaports in the Adriatic that each handle more than a million tonnes of cargo per year. The largest Adriatic seaport by annual cargo turnover is the Port of Trieste, in the southeast, the Adriatic Sea connects to the Ionian Sea at the 72-kilometre wide Strait of Otranto
Flysch is a sequence of sedimentary rocks that is deposited in a deep marine facies in the foreland basin of a developing orogen. Flysch is typically deposited during a stage of the orogenesis. When the orogen evolves, the basin becomes shallower and molasse is deposited on top of the flysch. It is therefore called a syn-orogenic sediment, Flysch consists of repeated sedimentary cycles with upwards fining of the sediments. At the bottom of each cycle are sometimes coarse conglomerates or breccias, Flysch typically consists of a sequence of shales rhythmically interbedded with thin, graywacke-like sandstones. Typically the shales do not contain fossils, the coarser sandstones often have fractions of micas. Flysch is formed under deep marine circumstances, in a quiet, the coarser layers are disruptions in these circumstances, caused by pulsewise flows of mass transport from the forming orogenic wedge. In many cases the mass transports are represented in the record by turbidites, Flysch deposits form at convergent plate boundaries at the stage of continental collision, often in remnant ocean basins that are present along the same boundary.
The sedimentary material in the flysch is derived from the forming mountains, the same ocean basin is in the process of subducting under the orogenic wedge. As subduction continues, the sediments are scraped off the down-going oceanic plate and are accreted onto the orogenic wedge. As a result, flysch deposits are often deformed by thrust faulting and folding. The name flysch was introduced in literature by the Swiss geologist Bernhard Studer in 1827. Studer used the term for the typical alternations of sandstone and shale in the foreland of the Alps, the name comes from the German word fliessen, which means to flow, because Studer thought flysch was deposited by rivers. The insight that flysch is actually a deep marine sediment typical for a plate tectonic setting came only much later. The name flysch is currently used in many mountain chains belonging to the Alpine belt, well-known flysch deposits are found in the forelands of the Pyrenees and Carpathians and in tectonically similar regions in Italy, the Balkans and on Cyprus.
In the northern Alps, the Flysch is a lithostratigraphic unit,1999, Earth System History, W. H. Freeman and Company, New York, ISBN 0-7167-2882-6. Einsele, G.2000, Sedimentary Basins, Facies, Flysch in, Encyclopædia Britannica 2010 Online. As accessed on 23 April 2010
The Italian Peninsula or Apennine Peninsula is the central and the smallest of the three large peninsulas of Southern Europe. It extends 1,000 km from the Po Valley in the north to the central Mediterranean Sea in the south, the peninsulas shape gives it the nickname lo Stivale. Three smaller peninsulas contribute to this shape, namely Calabria, Salento. Geographically, the Italian peninsula consists of the south of a line extending from the Magra to the Rubicon rivers. It excludes the Po Valley and the slopes of the Alps. All of the lies within the territory of the Italian Republic except for the microstates of San Marino. Additionally, Sicily and other islands, such as Palagruža, are usually considered as islands off the peninsula. The peninsula lies between the Tyrrhenian Sea on the west, the Ionian Sea on the south, and the Adriatic Sea on the east, the backbone of the Italian peninsula consists of the Apennine Mountains, from which it takes one of its names. Most of its coast is lined with cliffs, the Italian Peninsulas location between the centre of Europe and the Mediterranean Sea made it the target of many conquests.
The peninsula has mainly a Mediterranean climate, though in the parts the climate is much cooler. Its natural vegetation includes macchia along the coasts and deciduous and mixed coniferous forests in the interior. Political divisions of the peninsula sorted by area, Apennine Mountains Roman Republic Roman Italy Insular Italy Media related to Italian Peninsula at Wikimedia Commons
The theoretical model builds on the concept of continental drift developed during the first few decades of the 20th century. The geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s, the lithosphere, which is the rigid outermost shell of a planet, is broken up into tectonic plates. The Earths lithosphere is composed of seven or eight major plates, where the plates meet, their relative motion determines the type of boundary, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The relative movement of the plates typically ranges from zero to 100 mm annually, tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle, the material lost is balanced by the formation of new crust along divergent margins by seafloor spreading.
In this way, the surface of the lithosphere remains the same. This prediction of plate tectonics is referred to as the conveyor belt principle, earlier theories, since disproven, proposed gradual shrinking or gradual expansion of the globe. Tectonic plates are able to move because the Earths lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the ridge and drag, with downward suction. Another explanation lies in the different forces generated by forces of the Sun. The relative importance of each of these factors and their relationship to other is unclear. The outer layers of the Earth are divided into the lithosphere and asthenosphere and this is based on differences in mechanical properties and in the method for the transfer of heat. Mechanically, the lithosphere is cooler and more rigid, while the asthenosphere is hotter, in terms of heat transfer, the lithosphere loses heat by conduction, whereas the asthenosphere transfers heat by convection and has a nearly adiabatic temperature gradient.
The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, Plate motions range up to a typical 10–40 mm/year, to about 160 mm/year. The driving mechanism behind this movement is described below, tectonic lithosphere plates consist of lithospheric mantle overlain by either or both of two types of crustal material, oceanic crust and continental crust. Average oceanic lithosphere is typically 100 km thick, its thickness is a function of its age, as passes, it conductively cools
Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earths surface and within bodies of water. Sedimentation is the name for processes that cause mineral and/or organic particles to settle in place. The particles that form a rock by accumulating are called sediment. Sedimentation may occur as minerals precipitate from solution or shells of aquatic creatures settle out of suspension. The sedimentary rock cover of the continents of the Earths crust is extensive, sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding, sedimentary rocks are important sources of natural resources like coal, fossil fuels, drinking water or ores. The study of the sequence of rock strata is the main source for an understanding of the Earths history, including palaeogeography, paleoclimatology. The scientific discipline that studies the properties and origin of rocks is called sedimentology.
Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as pedology, geochemistry, sedimentary rocks have been found on Mars. Clastic sedimentary rocks are composed of rock fragments that were cemented by silicate minerals. Clastic rocks are composed largely of quartz, rock fragments, clay minerals, and mica, any type of mineral may be present, clastic sedimentary rocks, are subdivided according to the dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions, gravel and mud and this tripartite subdivision is mirrored by the broad categories of rudites and lutites, respectively, in older literature. The subdivision of these three categories is based on differences in clast shape and breccias), composition. Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel, composition of framework grains The relative abundance of sand-sized framework grains determines the first word in a sandstone name.
Naming depends on the dominance of the three most abundant components quartz, feldspar, or the lithic fragments that originated from other rocks, all other minerals are considered accessories and not used in the naming of the rock, regardless of abundance. Clean sandstones with open space are called arenites. Muddy sandstones with abundant muddy matrix are called wackes, six sandstone names are possible using the descriptors for grain composition and the amount of matrix. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles and these relatively fine-grained particles are commonly transported by turbulent flow in water or air, and deposited as the flow calms and the particles settle out of suspension