The origin of large local uplift in extensional regions

Nature ◽  
1990 ◽  
Vol 348 (6303) ◽  
pp. 689-693 ◽  
Author(s):  
Geoffrey King ◽  
Michael Ellis
Keyword(s):  
Local Uplift

scholarly journals Short-term Variations in Strain and Surface Tilt on Storglaciären, Kebnekaise, Northern Sweden

1989 ◽  
Vol 35 (120) ◽  
pp. 201-208 ◽  
Author(s):  
Peter Jansson ◽  
Roger LeB. Hooke
Keyword(s):  
Water Pressure ◽  
High Water ◽  
Ice Thickness ◽  
Gradual Change ◽  
Short Term ◽  
Glacier Surface ◽  
Vertical Movements ◽  
Bed Topography ◽  
The Waves ◽  
Local Uplift

AbstractTiltmeters that can detect changes in slope of a glacier surface as small as 0.1 μ rad have been used on Storglaciären. The records obtained to date have been from the upper part of the ablation area, where the bed of the glacier is overdeepened. A total of 82 d of records has been obtained for various time periods between early June and early September.There is generally a gradual change in inclination of the glacier surface over periods of several days, but these changes do not appear to be systematic. In particular, they are not consistent with vertical movements of stakes located 2–3 ice thicknesses away from the tiltmeters. This suggests that the tiltmeters are sensing disturbances over areas with diameters comparable to the local ice thickness.Superimposed on these trends are diurnal signals suggesting rises and falls of the surface just up-glacier from the riegel that bounds the overdeepening on its down-glacier end. These may be due to waves of high water pressure originating in a crevassed area near the equilibrium line. If this interpretation is correct, the waves apparently move down-glacier at speeds of 20–60 m h−1and become sufficiently focused, either by the bed topography or by conduit constrictions, to result in local uplift of the surface. Also observed are abrupt tilts towards the glacier center line shortly after the beginning of heavy rainstorms. These appear to be due to longitudinal stretching as the part of the glacier below the riegel accelerates faster than that above. Water entering the glacier by way of a series of crevasses over the riegel is believed to be responsible for this differential acceleration. In June 1987, a dramatic event was registered, probably reflecting the initial summer acceleration of the glacier.

scholarly journals The impact of jökulhlaups on basal sliding observed by SAR interferometry on Vatnajökull, Iceland

2007 ◽  
Vol 53 (181) ◽  
pp. 232-240 ◽  
Author(s):  
Eyjólfur Magnússon ◽  
Helmut Rott ◽  
Helgi Björnsson ◽  
Finnur Pálsson
Keyword(s):  
Initial Phase ◽  
Water Pressure ◽  
Drainage System ◽  
Sar Interferometry ◽  
Ice Dynamics ◽  
Velocity Increase ◽  
Basal Sliding ◽  
Tunnel System ◽  
The Impact ◽  
Local Uplift

AbstractWe have analyzed InSAR data from the ERS-1/ERS-2 tandem mission, to study the ice dynamics of Vatnajökull, Iceland, during jökulhlaups from the Skaftá cauldrons and the Grímsvötn geothermal area, which drained under the Tungnaárjökull and Skeiðarárjökull outlets, respectively. During the initial phase of a Grímsvötn jökulhlaup in March 1996, the velocity of Skeiðarárjökull increased up to three-fold (relative to observed velocities in December 1995) over an area up to 8 km wide around the subglacial flood path. Accumulation of water was observed at one location in the flood path. During a small jökulhlaup from the Skaftá cauldrons in October 1995 the velocity on Tungnaárjökull increased up to four-fold over a 9 km wide area. The velocity increase was observed 1.5 days before the floodwater was detected in the river Skaftá. A reduced glacier speed as the flood peaked in Skaftá indicates evolution of the subglacial drainage system from sheet to tunnel flow. The glacier acceleration and local uplift, observed in the early phase of both jökulhlaups, supports the concept that increased water inflow in a narrow tunnel system causes water pressure to rise and forces water into areas outside the channels, thus reducing the coupling of ice with the glacier bed.

Thrust systems of the Southwest Pyrenees and their control over basin subsidence

1990 ◽  
Vol 127 (5) ◽  
pp. 383-392 ◽  
Author(s):  
J. P. Turner ◽  
P. L. Hancock
Keyword(s):  
The South ◽  
Mountain Building ◽  
The West ◽  
Tectonic Regime ◽  
Basin Subsidence ◽  
Extensional Tectonic ◽  
Thin Skin ◽  
Thrust System ◽  
Thick Skin ◽  
Local Uplift

AbstractThere are two thrust systems in the Southwest Pyrenees: a NW-SE trending, thin-skin system exposed in the post-Triassic cover and a larger, thick-skin system of NE-SW thrusts in the Palaeozoic basement. The ‘cover’ thrust system propagated and migrated both southward and westward in response to the non-orthogonal collision of Iberia with Europe during Palaeogene mountain building. The ‘basement’ thrust system is interpreted to be a longer-lived structure, initiated during the extensional tectonic regime in mid Cretaceous time, and inverted during the main episode of Pyrenean collision. A model in which interaction of the two thrust systems controlled the timing and magnitude of thrust-induced, flexural subsidence is presented. The development of the basement thrust system caused regional subsidence along the South Pyrenean foreland margin that was subsequently halted by local uplift associated with the west-migratingcover thrust system.

Seismic response of foundation-mat structure subjected to local uplift

2016 ◽  
Vol 5 (4) ◽  
pp. 285-304
Author(s):  
Nadia El Abbas ◽  
Abdellatif Khamlichi ◽  
Mohammed Bezzazi
Keyword(s):  
Seismic Response ◽  
Local Uplift

scholarly journals A Recent Worldwide Sinking of Ocean-level

1920 ◽  
Vol 57 (6) ◽  
pp. 246-261 ◽  
Author(s):  
Reginald A. Daly
Keyword(s):  
Sea Level ◽  
Sea Water ◽  
Ocean Basin ◽  
Sea Level Changes ◽  
Geological Time ◽  
Sea Floor ◽  
Crustal Movements ◽  
Centre Of Gravity ◽  
Ocean Level ◽  
Local Uplift

LOCAL uplift and local sinking of the earth's surface have been fully demonstrated for past geological epochs. The amounts of these movements have generally been stated with reference to the present sea-level, and for the greater movements the statements of magnitudes are not seriously impaired by the fact that general sea-level itself has been shifting, upwards and downwards, through geological time. Among the causes for general or “eustatic” shifts of sea-level are: appropriate crustal movements whereby the volume of the ocean basin has been changed; delta-building and volcanic eruption on the sea-floor, the displacement of sea-water not being compensated by crustal sinking; volcanic addition of new water to the ocean; subtraction of water which becomes chemically bound during the alteration of rocks; glaciation on land, lowering sea-level by the abstraction of water from the ocean; deglaciation on land, raising sea-level; changes in the earth's centre of gravity and in her speed of rotation.

Mapping and dynamic analysis of faults in the Hengill volcanic area, SW-Iceland 

2021 ◽  
Author(s):  
Hanna Blanck ◽  
Kristín Vogfjörd ◽  
Halldór Geirsson ◽  
Vala Hjörleifsdóttir
Keyword(s):  
Normal Component ◽  
Coulomb Stress ◽  
Volcanic Area ◽  
Coulomb Stress Change ◽  
Tectonic Event ◽  
Coulomb Stress Changes ◽  
Stress Changes ◽  
Best Fitting ◽  
Local Uplift ◽  
Strike Slip Movement

<p>From 1993 to 1998, the Hengill volcanic area in SW-Iceland was subjected to a volcano-tectonic event which caused a local uplift of the crust of 8 cm and triggered over 90.000 earthquakes. Relocating a sub-set of 12.000 earthquakes in the direct vicinity of the uplift centre improved resolution and enabled the mapping of 25, mostly NNE-SSW and ENE-WSW oriented sub-vertical groups of earthquake which are interpreted as faults. Focal mechanisms were calculated, using the best fitting plane through a group of earthquakes as additional constraint. Slip on the interpreted faults could be estimated averaging slip of all earthquakes within that group. Most faults show strike-slip movement with a small normal component. Right-lateral slip prevails. We modelled Coulomb stress changes that the uplift would have caused and compared them to out results. The Coulomb stress changes can only explain the observed movement on some of the faults but on others fault movements is impeded, that is, the Coulomb stress change is negative. Varying the location of the uplift within its error margin increases the number of faults on which the observed movement is promoted but the slip on a number of faults remains unexplained.  </p>

Low-temperature thermochronologic constraints on the tectonic evolution of the Subei and Shibaocheng areas, northern Tibetan Plateau

2020 ◽  
Author(s):  
Jianfeng Li ◽  
Zhicheng Zhang ◽  
Yue Zhao
Keyword(s):  
Tibetan Plateau ◽  
Thermal History ◽  
Tectonic Evolution ◽  
Fission Track ◽  
The Tibetan Plateau ◽  
Apatite Fission Track ◽  
Northern Tibetan Plateau ◽  
Mountain Belt ◽  
Altyn Tagh ◽  
Local Uplift

<p>        The northern Tibetan Plateau, between the Kunlun and the Altyn Tagh faults, contains high relief topography, such as the Eastern Kunlun Range, the Altyn Tagh Range and the Qilian mountain belt, and plays an important role in researching the tectonic evolution and topographic growth of the Tibetan Plateau. We present new apatite fission track (AFT) and <sup>40</sup>Ar/<sup>39</sup>Ar thermochronologic data from the Subei and Shibaocheng areas near the eastern Altyn Tagh fault. Two Cenozoic exhumation phases have been identified from our AFT thermochronology. The AFT cooling ages of ~ 60–40 Ma farther away from the faults represented a slow widespread denudation surface as response to the Indo-Eurasia collision and signified that the Subei and Shibaocheng areas denudated as a whole in the northern Tibetan Plateau. Another phase with AFT cooling ages between about 20.5 Ma to 13.6 Ma on the hanging walls near the faults, located in the Danghenanshan and Daxueshan Mountains, recorded widespread fault activities resulted from local uplift and exhumation in late Miocene (~ 8 Ma) acquired from AFT thermal history modeling. A Cretaceous exhumation (~ 120–70 Ma) acquired from AFT thermal history modeling may have made great contributions to the growth of the pre-Cenozoic northern Tibetan Plateau.</p>

Molasse basins of Europe: a tectonic assessment

1985 ◽  
Vol 76 (4) ◽  
pp. 451-462 ◽  
Author(s):  
P. F. Friend
Keyword(s):  
Sea Level ◽  
Sediment Accumulation ◽  
Sedimentary Basins ◽  
Accumulation Rates ◽  
Thrust Sheet ◽  
Marine Transgression ◽  
Sedimentary Fill ◽  
Orogenic Belts ◽  
Local Uplift

ABSTRACTSedimentary basins are structures that formed either by subsidence of an area relative to its surroundings, or by uplift of the surroundings. The basin is defined by its sedimentary fill, and the vertical kinematics of the fill are reflected by stratal wedging, unconformities and, or, faulting. The following basin mechanisms are distinguished: locally (a) stretch, (b) thrust and piggy-back, (c) local uplift, and regionally (d) stretch-and-cool, (e) load-and-flex and (f) cratonic uplift.Basin patterns are reviewed for the three main Phanerozoic episodes for which molasse-like features of sedimentation or tectonics are claimed. Sediment accumulation rates are used as an index of the vigour of basinal activity.Within the area of the Caledonian orogen, Devonian basinal activity was locally very rigorous, some of it being late orogenic and some post-orogenic, and mostly apparently of ‘stretch-type’. The orogenic area stood high, relative to sea level, throughout Devonian times, but outside the orogenic area, the basins were less vigorous and marine.Within the area of the Hercynian orogen, and outside it, Permian basins were generally not so active, apparently reflecting a different style of orogenesis. However, the whole area was standing high, relative to sea level. The Triassic basins, though post-orogenic, were rather more vigorous, although a marine transgression records the general lowering of the continental surface. Major evaporites accumulated in these settings.In Cenozoic times, the narrow orogenic belts formed the most active basins, and these were of load-and-flex type, reflecting the importance of thrust-sheet movement, itself perhaps a result of the presence of Triassic evaporites. Other non-orogenic basins reflect both ‘stretch’ and ‘stretch-and-cool’ mechanisms. Only the Spanish basins appear to have been standing high, relative to sea level, perhaps in response to cratonic uplift.

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