"Fringing reef A fringing reef is one of the four main types of coral reef recognized by most coral reef scientists. It is distinguished from the other main types (barrier reefs, platform reefs and atolls) in that it has either an entirely shallow backreef zone (lagoon) or none at all. If a fringing reef grows directly from the shoreline (see photo, right) the reef flat extends right to the beach and there is no backreef. In other cases (e.g., most of the Bahamas), fringing reefs may grow hundreds of yards from shore and contain extensive backreef areas with numerous seagrass"
"Natural arch A natural arch, natural bridge, or (less commonly) rock arch is a natural rock formation where an arch has formed with an opening underneath. Natural arches commonly form where inland cliffs, coastal cliffs, fins or stacks are subject to erosion from the sea, rivers or weathering (subaerial processes). Most natural arches are formed from narrow fins and sea stacks composed of sandstone or limestone with steep, often vertical, cliff faces. The formations become narrower due to erosion over geologic time scales. The softer rock stratum erodes away creating rock shelters, or alcoves, on opposite sides of the formation"
"as well as atolls. A fringing reef is a reef that is attached to an island. A barrier reef forms a calcareous barrier around an island resulting in a lagoon between the shore and the reef. An atoll is a ring reef with no land present. The reef front (ocean side) is a high energy locale whereas the internal lagoon will be at a lower energy with fine grained sediments. Ancient reefs buried within stratigraphic sections are of considerable interest to geologists because they provide paleo-environmental information about the location in Earth's history. In addition, reef structures within a sequence"
"Natural barrier A natural barrier refers to a physical feature that protects or hinders travel through or over. Mountains, swamps, deserts and ice fields are among the clearest examples of natural barriers. Rivers are a more ambiguous example, as they may obstruct large-scale movement across them (especially by armies) but may facilitate smaller-scale movement along them in boats, once some of the people in the region have developed the relevant technologies. Seas have likewise been an obstacle at first, then a convenient medium for transport along coastlines, and finally a medium for intercontinental transport. Natural barriers have been important factors"
"of the various types and sizes of barrier islands depend on the wave energy, tidal range, basement controls, and sea level trends. The islands create multiple unique environments of wetland systems including marshes, estuaries, and lagoons. Steep, cliff-backing abrasion coastline The coastline along the western part of the nation consists of very steep, cliffed rock formations generally with vegetative slopes descending down and a fringing beach below. The various sedimentary, metamorphic, and volcanic rock formations assembled along a tectonically disturbed environment, all with altering resistances running perpendicular, cause the ridged, extensive stretch of uplifted cliffs that form the peninsulas, lagoons,"
"Cuspate foreland Cuspate forelands, also known as cuspate barriers or nesses in Britain, are geographical features found on coastlines and lakeshores that are created primarily by longshore drift. Formed by accretion and progradation of sand and shingle, they extend outwards from the shoreline in a triangular shape. Some cuspate forelands may be stabilised by vegetation, while others may migrate down the shoreline. Because some cuspate forelands provide an important habitat for many flora and fauna, effective management is required to reduce the impacts from both human activities and physical factors such as climate change and sea level rise. The debate"
"in human history, by obstructing migration and invasion. For example, Jared Diamond argues that West European nations have been the dominant powers of the last 500 years because Europe's many natural barriers divided it into competing nation-states and this competition forced the European nations to encourage innovation and avoid technological stagnation. Some examples of natural barriers are the Himalayas isolating the Indian subcontinent from the rest of Asia, the Grand Canyon, the Dead sea, and the Mississippi river. Natural barrier A natural barrier refers to a physical feature that protects or hinders travel through or over. Mountains, swamps, deserts and"
"Yardang A yardang is a streamlined protuberance carved from bedrock or any consolidated or semiconsolidated material by the dual action of wind abrasion by dust and sand, and deflation which is the removal of loose material by wind turbulence. Yardangs become elongated features typically three or more times longer than wide, and when viewed from above, resemble the hull of a boat. Facing the wind is a steep, blunt face that gradually gets lower and narrower toward the lee end. Yardangs are formed by wind erosion, typically of an originally flat surface formed from areas of harder and softer material."
"barrier arising externally to a species. These extrinsic barriers often arise from various geologic-caused, topographic changes such as: the formation of mountains (orogeny); the formation of rivers or bodies of water; glaciation; the formation or elimination of land bridges; the movement of continents over time (by tectonic plates); or island formation, including sky islands. These can change the distribution of species populations. The emergence of suitable or unsuitable habitat configurations may arise from these changes and can originate by changes in climate or even large scale human activities (for example, agricultural, civil engineering developments, and habitat fragmentation). Among others, these"
"Barrier island Barrier islands are coastal landforms and a type of dune system that are exceptionally flat or lumpy areas of sand that form by wave and tidal action parallel to the mainland coast. They usually occur in chains, consisting of anything from a few islands to more than a dozen. They are subject to change during storms and other action, but absorb energy and protect the coastlines and create areas of protected waters where wetlands may flourish. A barrier chain may extend uninterrupted for over a hundred kilometers, excepting the tidal inlets that separate the islands, the longest and"
"weather phenomena such as hurricanes are emergent structures. The development and growth of complex, orderly crystals, as driven by the random motion of water molecules within a conducive natural environment, is another example of an emergent process, where randomness can give rise to complex and deeply attractive, orderly structures. It is useful to distinguish three forms of emergent structures. A ""first-order"" emergent structure occurs as a result of shape interactions (for example, hydrogen bonds in water molecules lead to surface tension). A ""second-order"" emergent structure involves shape interactions played out sequentially over time (for example, changing atmospheric conditions as a"
"was to be removed their barriers would be eroded away and bays would form in the lagoons place with inundation. Washdyke Lagoon was created by the formation of a mixed sand and gravel (MSG) beach barrier (Figure 2) allowing fluvial water from Washdyke Creek to accumulate behind it, with some tidal infiltration through the barrier. The MSG barrier type is relatively rare and has its own unique set of processes and morphology. MSG barriers form mostly on paraglacial coasts where there is a large amount of coarse grained sediments available and storm wave conditions during which more sediment load is"
"Random Formation The Random Formation is a near-shore rock unit dating to the early Cambrian period, dominated by tidal quartz arenites, but also incorporating intertidal and open-shelf deposits, including glauconitic and mud-cracked mudstones (now shales), and red channel sandstones. It was deposited quickly and is approximately 175 m thick. The Blue Pinion Formation was originally recognized as a separate formation, but is now interpreted as an expression of the Random Formation. Its white arenitic sandstones are very distinctive, recognizable from their herringbone cross-stratification that denotes the influence of storm systems. Interbedded green-grey sands and silts speak to an intertidal setting."
"to be effectively managed. Cuspate foreland Cuspate forelands, also known as cuspate barriers or nesses in Britain, are geographical features found on coastlines and lakeshores that are created primarily by longshore drift. Formed by accretion and progradation of sand and shingle, they extend outwards from the shoreline in a triangular shape. Some cuspate forelands may be stabilised by vegetation, while others may migrate down the shoreline. Because some cuspate forelands provide an important habitat for many flora and fauna, effective management is required to reduce the impacts from both human activities and physical factors such as climate change and sea"
"in open water rather than next to a shoreline. Like an atoll, it is thought that these reefs are formed either as the seabed lowered or sea level rose. Formation takes considerably longer than for a fringing reef, thus barrier reefs are much rarer. The best known and largest example of a barrier reef is the Australian Great Barrier Reef. Other major examples are the Belize Barrier Reef and the New Caledonian Barrier Reef. Barrier reefs are also found on the coasts of Providencia, Mayotte, the Gambier Islands, on the southeast coast coast of Kalimantan, on parts of the coast"
"but calm waters behind the spit there will form a salt marshland. Spits often form around the breakwater of artificial harbours requiring dredging. Occasionally, if there is no estuary then it is possible for the spit to grow across to the other side of the bay and form what is called a bar, or barrier. Barriers come in several varieties, but all form in a manner similar to spits. They usually enclose a bay to form a lagoon. They can join two headlands or join a headland to the mainland. When an island is joined to the mainland with a"
"from Lima, Peru crosses the Rio Yauli on a natural bridge near kilometer 214.2 as it approaches the city of La Oroya, Peru. Natural arch A natural arch, natural bridge, or (less commonly) rock arch is a natural rock formation where an arch has formed with an opening underneath. Natural arches commonly form where inland cliffs, coastal cliffs, fins or stacks are subject to erosion from the sea, rivers or weathering (subaerial processes). Most natural arches are formed from narrow fins and sea stacks composed of sandstone or limestone with steep, often vertical, cliff faces. The formations become narrower due"
"A fringing reef forms around an extinct volcanic island as the island and ocean floor subsides. As the subsidence continues, the fringing reef becomes a barrier reef and ultimately an atoll reef. Darwin predicted that underneath each lagoon would be a bedrock base, the remains of the original volcano. Subsequent research supported this hypothesis. Darwin's theory followed from his understanding that coral polyps thrive in the tropics where the water is agitated, but can only live within a limited depth range, starting just below low tide. Where the level of the underlying earth allows, the corals grow around the coast"
"considered an intermediary stage of many other erosional geologic features like windows, arches, and hoodoos. The formation of such features is a simplified four-step process. The first step is uplift that results in deep parallel, vertical fractures within the plateau. The second step is weathering and erosion that enlarges the fractures, producing fins. The third step is erosion attacking fins from below, causing windows and arches. The fourth step is continuing weathering that enlarges holes, causing arches and holes to collapse, creating spires or hoodoos. Fins will form typically in sedimentary rocks, mainly sandstone. Sandstone is bedded, which provides zones"
"other formations were created, and continue to be shaped, by the natural processes of weathering and erosion. Some of the rock layers are composed of a harder caprock material which resists the effects of weathering and erosion. Those caprock layers will remain intact much longer than other less resistant layers which weather and erode away below and around them leaving behind the current arches and hoodoos. Cycles of heat and cold, precipitation, ice, wind and gravity all play a part in the creation of the formations. Daily extreme temperature variations create fractures by repeated expansion and contraction of the rock"
"form in the path of streams that wear away and penetrate the rock. Pothole arches form by chemical weathering as water collects in natural depressions and eventually cuts through to the layer below. Natural Bridges National Monument in Utah protects the area surrounding three large natural bridges, all of which were formed by streams running through canyons, the largest of which is named Sipapu Bridge with a span of . The Rainbow Bridge National Monument's namesake was also formed by flowing water which created the largest known natural bridge in the Western Hemisphere with a span of , based on"
"creates grooves or small depressions. Ventifacts are rocks which have been cut, and sometimes polished, by the abrasive action of wind. Sculpted landforms, called yardangs, are up to tens of meters high and kilometers long and are forms that have been streamlined by desert winds. The famous Great Sphinx of Giza in Egypt may be a modified yardang. Major global aeolian dust movements thought to influence and/or be influenced by weather and climate variation: Particles are transported by winds through suspension, saltation (skipping or bouncing) and creeping (rolling or sliding) along the ground. Small particles may be held in the"
"skeletal framework. Coral reefs are an excellent example of this kind. Corals and calcareous algae grow on top of one another and form a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework (""see"" stromatolite). Mounds are built by microorganisms or by organisms that don't grow a skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria. Excellent examples of biostromes formed by cyanobacteria occur in the Great Salt Lake in Utah, and in Shark Bay on the coast of Western Australia. Cyanobacteria do"
"that it is composed of weakly cemented particles, and was most likely formed by the deposition of wind-blown dust or volcanic ash. Yardangs are parts of rock that have been sand blasted into long, skinny ridges by bouncing sand particles blowing in the wind. Layers are seen in parts of the formation. A resistant caprock on the top of yardangs has been observed in Viking, Mars Global Surveyor, and HiRISE photos. Images from spacecraft show that they have different degrees of hardness probably because of significant variations in the physical properties, composition, particle size, and/or cementation. Very few impact craters"
"transported ashore. They also form steep slopes in high wave energy environments and have very high levels of seepage of freshwater into the ocean, due to the large grain size range increasing permeability. Another characteristic is the zonation of sediments on the barrier. Coarse, flat sediments form the crest, whilst large, spherical and rod shape sediments form the outer part and the barrier infill is made up of finer sediment sizes. Washdyke Lagoon is a useful example of a barrier that displays all of these characteristics. The lagoon is situated at the southern end of the Canterbury Bight. This coastline"
"Ridge and swale Ridge and swale, or in dunal areas dune and swale, is a landform consisting of regular, parallel ridges alternating with marshy depressions. Ridge-and-swale landscapes are most commonly formed by the gradual movement of a beach, for example as a result of gradually fluctuating water levels, or the shifting meanders of a river. In the river context, ridge-and-swale landscapes are commonly formed by scroll bars. They are also found along ocean coasts, for example on the Outer Banks of North Carolina. Freshwater ridge-and-swale ecosystems are globally rare and found only in parts of the Great Lakes of North"
"includes most of the provinces included in the original LIP classifications. It is composed of continental flood basalts, oceanic flood basalts, and diffuse provinces. Volcanic rifted margins are found on the boundary of large igneous provinces. Volcanic margins form when rifting is accompanied by significant mantle melting, with volcanism occurring before and/or during continental breakup. Volcanic rifted margins are characterized by: a transitional crust composed of basaltic igneous rocks, including lava flows, sills, dikes, and gabbros, high volume basalt flows, seaward-dipping reflector sequences (SDRS) of basalt flows that were rotated during the early stages of breakup, limited passive-margin subsidence during"
"to build shallow moats around the bottom. They are more commonly created from softer rock types like siltstone, sandstone, shale and limestone, but have also been observed in crystalline rocks such as schist and gneiss. Other names for them are ""mud-lions [citing desert explorer Ralph Bagnold, 1939], mushroom rocks, sphinx-like hills, koukour (Tunisia) and kalut [ridge] (Iran)."" The massive features of mega-yardangs are called ""crêtes et couloirs"" (ridges and corridors) in the French geological literature. Yardang A yardang is a streamlined protuberance carved from bedrock or any consolidated or semiconsolidated material by the dual action of wind abrasion by dust"
"layers form concentrically from the outside in, defined by breaks in viscosity and temperature. This forms laminar flow, which separates several domains of the magma chamber which can begin to differentiate separately. Flow banding is the result of a process of fractional crystallization which occurs by convection, if the crystals which are caught in the flow-banded margins are removed from the melt. The friction and viscosity of the magma causes phenocrysts and xenoliths within the magma or lava to slow down near the interface and become trapped in a viscous layer. This can change the composition of the melt in"
"About 5% of the park's landforms (mostly in its eastern margin near Mount Dana) are metamorphosed volcanic and sedimentary rocks. These rocks are called ""roof pendants"" because they were once the roof of the underlying granitic rock. Erosion acting upon different types of uplift-created joint and fracture systems is responsible for creating the valleys, canyons, domes, and other features we see today. These joints and fracture systems do not move, and are therefore not faults. Spacing between joints is controlled by the amount of silica in the granite and granodiorite rocks; more silica tends to create a more resistant rock,"
"gradually erode into separate hills that take on the unique shape of a yardang. This process yields a field of yardangs of roughly the same size, commonly referred to as a fleet due to their resemblance to the bottoms of ships. Alternatively, one can be formed by the migration of a dune that leaves behind a cemented core. As the process of formation continues, typically a trough will form around the base of the yardang. Most yardang fields are in sand-poor areas, but the associated troughs, especially in grooved terrain, may be invaded by sand. Sometimes this sand will accumulate"
"the 'First Line of Defense' for beach systems. Front dune ridges may be followed by a secondary line of dunes more inland. Plants that grow naturally on dunes stabilize the dunes by their roots preventing potential damage caused by water and wind. Behind the dunes are areas called barrier flats. Barrier flats, also known as over wash or mud flats that are developed by sand sediments forced through dune systems by strong winds caused by storms. Last, salt marshes fall behind Barrier flats that tend to be low-lying areas that border the sound side of the island. Tides flood salt"
"(such as slumping, gravity-flow, and olistostromal action), or some combination of these. Some larger blocks of rock may be as much as across. Smaller-scale localized mélanges may also occur in shear or fault zones, where coherent rock has been disrupted and mixed by shearing forces. Examples include the Franciscan Formation along the Coast Ranges of central and northern California and the Bay of Islands ophiolite complex in Newfoundland. The Gwna Mélange in the UK extends through Anglesey and the Llŷn Peninsula onto Bardsey Island in North Wales. The Northern Palawan melange is distributed in the Philippines' , west coast of"