On Venus as on Earth !

دسته مقالات جنبی
گروه سازمان زمین شناسی و اکتشافات معدنی کشور
مکان برگزاری بیست و چهارمین گردهمایی علوم زمین
نویسنده Pedram Aftabi
تاريخ برگزاری ۰۹ اسفند ۱۳۸۴

A diapir can be defined as a ductile mass that has penetrated or appears to have penetrated its overburden by gentle or strong eruptions.

Measurements suggest that the climatic and tectonic signal interact to shape of viscous diapirs on Earth. The surface of Venus is covered by salt (sulfates) which flow at different rates with Earth ,but in similar ways.The plutonic diapirs(granite) are viscous materials similar to salt diapirs and  PDMS diapirs(in analogue modeling).

The combination of radial symmetry, a steeply sloping perimeter, and strong relief exhibited by domes at Venus suggests that they may have formed from viscous lava that erupted uniformly from a central vent. The models suggest they may result in the final stages of a multioverhanging system, when the magma source is not very powerful. In this case the Pseudo droplets change to pseudo fountains and later the pancakes changed to pseudo droplet-fountain. The fractures in Venus domes may imply that the surface temperature for a spreading cone or diapirs with multioverhangs are important for the change of  a viscous to semi viscous ,semi brittle and brittle material during time. The flat surface volcanic and plutonic diapirs on the surface of Venus showed that the intrusions spread laterally over a rim less than 15 degrees. These droplet shape diapirs showed that rate of rise was very less than rate of spreading .The hottest temperature on Earth measured 56.7 degrees C(120 F) and 475(900 F) on Venus.

The high temperature of atmosphere (Venus) 475 degrees decreased the primary rim and spread a volcano to larger spread mountain. Both the diapirs and country rock spread during high temperatures, and formed overhangs in the models probably under extension. With increasing 47 degrees to the air temperature, PDMS spread 0.25 times faster than primary state with 9 degrees in temperature. The mountain same size at 8 and 22 minutes in the same 24 degrees atmosphere. The daily measurements(by simple tape and thermometer) in salt diapir Central Iran, and calculation of micro strains suggest that the high activity area of The InSAR image(salt) and related faults are mainly affected by climatic changes. The Pancake diapirs of Venus and low angle tapers imply to understanding atmospheric, lithosphere temperature and pressure for the shaping of  diapirs.The spreading sheets of PDMS under different temperature and pressure(on Venus) results same structures(folds) and strain markers with normal positions(Earth) but in different tightness. The analogue models suggests that the shape of other plutonic diapirs on Venus is similar to Earth.

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