![]() Discussions focused on the areas where the highest peaks of the mountain chain reach sea-level and shape islands. on geological conservation, representatives from Norway, Iceland, Azores,the United Kingdom, IUCN and UNESCO met to review the geological and biological heritage of the MAR in the North Atlantic. In the context of the “Earth Heritage-World Heritage” conference at the Dorset- and Devon Coast (September 2004, United Kingdom). Brazilian Atlantic Islands: Fernando de Noronha and Atol das Rocas Reserves (Brazil) (2001).Gough and Inaccessible Islands United Kingdom (1995, 2004 ).Landscape of the Pico Island Vineyard Culture Portugal (2004 ).Þingvellir National Park, Iceland (2004 ).The following properties are inscribed on the World Heritage List, but not for their geological values of the sites they were inscribed on the basis of cultural and/or natural criteria: Outstanding Universal Value was recognized for some of the properties located on islands associated with the MAR. Most of the ridge system is under water but forms land as a set of volcanic islands of varying size that run the length of the Atlantic Ocean. These plates are still moving apart, so the Atlantic is growing at the ridge, at a rate of about 2.5 cm per year in an east-west direction. The MAR separates the North American Plate from the Eurasian Plate in the North Atlantic, and the South American Plate from the African Plate in the South Atlantic. Its discovery led to the theory of seafloor spreading and general acceptance of Wegener's theory of continental drift. The MAR is about 3 km in height above the ocean floor and 1000 to 1500 km wide, has numerous transform faults and an axial rift valley along its length. The Mid-Atlantic Ridge (MAR) is a mostly underwater mountain range in the Atlantic Ocean that runs from 87°N -about 333km south of the North Pole- to subantarctic Bourvet island at 54°S. The models have little sensitivity to the wet or dry olivine rheology.The mid ocean ridge systems are the largest geological features on the planet. ![]() The best fitted model suggests a thermal gradient of ~ 54 ☌ km− 1 at depth below where 700 ☌ occurs at the ridge axis. The vertical subsidence rate at the ridge axis increases almost linearly as the half-velocity increases. ![]() At a fixed spreading rate, the deformation field is controlled by the sub-surface thermal state. ![]() We attempt to reproduce the thermal structure of a rift by defining 700 ☌ from 5- to 15-km depth at the rift axis that leads to variation in rheological structure, and to estimate the layer (from surface to a depth of 700 ☌) where the elastic deformation of the lithosphere is the greatest. To understand how the rheology of the lithosphere influences rifting, we applied a thermo-mechanical stretching model that includes thermal states in Iceland using temperature- and stress-dependent wet and dry olivine rheology. About 90% of the deformation occurs in an 80 to 90-km wide zone. Global Positioning System (GPS) data from the Eastern Volcanic Zone (EVZ), Iceland, and crustal deformation of the rift near its southern end at 64°N show a spreading rate of 13.8 ± 1.8 mm yr− 1. Located on the mid-Atlantic ridge, Iceland allows for direct measurement of crustal deformation. ![]()
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