Petrology
Mohsen Zadsaleh; Fariborz Masoudi; Hamed Pourkhorsandi; Karen Fontijn
Abstract
Damavand is a young volcanic edifice with an elevation of 5610 meters formed in the middle of the central Alborz Mountain range (N Iran) during the Quaternary. Its edifice is composed of trachyte and trachyandesite rocks, pyroclastic fall and flow deposits and lahars, formed during several eruptions ...
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Damavand is a young volcanic edifice with an elevation of 5610 meters formed in the middle of the central Alborz Mountain range (N Iran) during the Quaternary. Its edifice is composed of trachyte and trachyandesite rocks, pyroclastic fall and flow deposits and lahars, formed during several eruptions and under different magmatic conditions. To investigate the crystallization trends in the Damavand magma chamber and its evolution over time, plagioclase internal textures in lava flows, pyroclastic flow and ash deposits were studied. Samples from six different lava flows and pyroclastic fall and density current deposits with different ages were collected. Plagioclase crystals with similar dimensions and sizes but with completely different textures, and plagioclases with different dimensions but similar textural characteristics were observed. Twenty-eight different texture types were observed in plagioclase crystals from lava flows, whereas only three texture types were distinguished in the pyroclastic deposits. A large population of plagioclase in pyroclastic deposits reveal the non-equilibrium crstallization in the Damavand magma chamber(s), while in lava flows, a series of plagioclase cumulates present both equilibrium and non-equilibrium crystallization conditions in the magmat chamber. Plagioclase crystals in the source magmas of lava flows have repeatedly remained in a non-equilibrium state without eruption, letting the crystals to overgrow. Changes in the rate of magma ascent, small- and large-scale convection cells in magma chambers, varying temperature and/or pressure, and different volumes of (non-)eruptible mush/melt, are some of the parameters that are revealed by our textural studies. In the period between about 7-450 ky ago, the magma chamber that led to the buildup of the young Damavand volcano, was in non-equilibrium conditions as demonstrated by individual crystals textures and chemistry. However, these conditions have not always led to volcanic eruptions.
Remote Sensing
A. Eskandari; S. Amini; F. Masoudi
Abstract
Monitoring quiescent volcano such as Damavan is vital. In this research, we investigate the changes of land surface temperature (LST) around the Damavand volcano during 23 years period. The evaluations were done on the thermal anomaly areas related to geothermal activity and results compared with non-anomalously ...
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Monitoring quiescent volcano such as Damavan is vital. In this research, we investigate the changes of land surface temperature (LST) around the Damavand volcano during 23 years period. The evaluations were done on the thermal anomaly areas related to geothermal activity and results compared with non-anomalously thermal areas. The surface thermal anomalies were detected on the basis of processing of Landsat day and night-time images and combination with geological information layers. The average of calculated values for geothermal heat flux (GHF) in the geothermal areas was 42 W/m2 (in the day-time image) and 20 W/m2 (in night-time image). The total radiant GHF in thermal anomaly areas estimated 50 MW (in night-time image) and 119 MW (in the day-time image). The thermal anomaly areas have a close spatial relationship with faults, hot springs, lithology, hydrothermal alterations, active deformation regions and subsurface high heat flow data. After determining thermal anomaly areas related to the geothermal activity, the changes of LST patterns were compared in the six TM and ETM+ images (captured from the same month and overpass time) during 1988- 2011. The highest temperatures were recorded in 2002 and 2007 images, that in line with seismic events and changes in hot springs chemistry. The thermal infrared remote sensing can be used as a cost effective and concise method for monitoring of quiescent and even dormant volcanoes of Iran.
B Rahimzadeh; F Masoudi; Sh Ranjbar
Abstract
Scoria is one of the main pyroclastic units in Damavand volcano, which its main crystals are plagioclase, olivine and pyroxene. In this study, characterization of bubbles and their formation during the eruption considered using Bubble Size Distribution (BSD) method including study of volume, 3D modeling, ...
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Scoria is one of the main pyroclastic units in Damavand volcano, which its main crystals are plagioclase, olivine and pyroxene. In this study, characterization of bubbles and their formation during the eruption considered using Bubble Size Distribution (BSD) method including study of volume, 3D modeling, nucleation and bubble growth. For selected sample, thebubbles investigated in 3 perpendicular dimensions (X-Y-Z) and in total 16830 bubbles (X=7357, Y=5385, Z=4088) were measured and drawn. The Bubbles volumes calculated in 3 dimensions are X=47.21, Y=40.27, Z=40.01 percent. The Bubbles axes were calculated: X=1:1:4, Y=Z=1:1:3.4 and the 3D schematic shape is ellipsoid which the longest axis (L) is about 4 times longer than the other two axes (I, S). The L axis is parallel to the lowest pressure dictated on magma and the bubbles could be grown 4 times more in that direction. The bubbles shape of Damavand scoria is an ellipsoid with an average of 1:1:3.7 for its axes. The presence of 3 peaks in frequency distribution versus bubble size diagram, suggesting polymodal events of bubbles generation and in the Damavand volcano the bubbles nucleation occurred in 3 events(F1, F2, and F3). The nucleation density increased from F1 to F3 but the bubbles growth reduced in the same direction. The first group of bubbles formed in the magma chamber and the second group formed during the magma ascent. The third group of bubbles could form either in the space between earlier groups or in the last stage of magma eruption.
Seyed Mohsen Mortazavi
Abstract
Damavand is a stratovolcano and has power full explosive eruptions during its activity. Pyroclastic products in Damavand volcano has been mostly deposited as pyroclastic fall and flow deposits. Pyroclastic fall deposits in some locality extending up to 20 km from the summit. Damavand pyroclastic deposits ...
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Damavand is a stratovolcano and has power full explosive eruptions during its activity. Pyroclastic products in Damavand volcano has been mostly deposited as pyroclastic fall and flow deposits. Pyroclastic fall deposits in some locality extending up to 20 km from the summit. Damavand pyroclastic deposits cover much of the eastern and southern flanks of the volcano suggested that during the eruption, tephra dispersal axes was toward to the east. There are a major young pumice deposits, named as Karam Poshteh pumices, are identified and consists of a coarse-grained pumice fall deposit with proximal welded facies dispersed to the west, but lacks pyroclastic flow deposits with provisional ages in the interval >7.3 ka and < 25 ka.This young pumice fall deposit is distributed over much of the western and south-western flanks and is located at the foot of the steep Damavand cone at the mouth of a ravine where the proximal welded facies is well exposed on the ravine walls. The deposit can be divided into thin more distal unconsolidated pumice fall deposits and think proximal welded pumice fall deposits. Karam poshteh deposits also consist of welded beds of pale pink pumice with minor cross-layered ash beds. Atmospheric information, in particular wind data, is crucial in order to perform tephra dispersal simulations. Tephra transport and sedimentation is controlled by wind in the atmosphere and is a function of wind velocity and provenance for tropospheric and stratospheric levels. Mehrabad meteorological station is supplied wind data at different altitudes. We apply and intemperate wind data between 1995 to 2010 at Damavand volcano to understand regional distribution of tephra fall. Westerly winds are persistent during winter and summer time at troposphere. The most prominent features in the stratospheric circulation are a westerly jet in the winter hemisphere and low velocity easterly jet in the summer hemisphere. Easterly jet in the summer implies that Westward transport of tephra in Karam poshteh.
E. Moghimi; M. Badri Far; M. Zarei Nejad
Abstract
Morphodynamic characteristics of Damavand volcanic cone have been affected by two factors including internal and external morphodynamics. Major goal of this research is based on external morphodynamics. The morphodynamical landforms of this area are divided in two main groups, the first one is climatic ...
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Morphodynamic characteristics of Damavand volcanic cone have been affected by two factors including internal and external morphodynamics. Major goal of this research is based on external morphodynamics. The morphodynamical landforms of this area are divided in two main groups, the first one is climatic processes and the second one is anthropogenic processes. Climatic processes, including glacial erosion, pre-glacial erosion and alluvial erosion, have changed morphology of slopes and spatial landforms. For the special geographic condition of Damavand volcanic cone, few data is available. Therefore by using satellite images ETM+, ASTER, SPOT, several new data layer have been prepared based on base maps and field checking in GIS environment.
A. Mansourian; M. Zareinejad; E. Moghimi; S. Omidian
Abstract
Damavand volcano is one of the most important geological features in Iran. Although a variety of studies are available about this volcano, there are different problems associated with existing data from Damavand including: they are not stored in a consistent and organized way, they are not directly ...
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Damavand volcano is one of the most important geological features in Iran. Although a variety of studies are available about this volcano, there are different problems associated with existing data from Damavand including: they are not stored in a consistent and organized way, they are not directly applicable in users' information systems (such as GIS), and they are not easily accessible and sometimes not accessible to users. In addition, clear and accurate studies about geomorphological-environmental specifications of Damavand are not still available. Considering these facts, this paper aims to describe design and implementation of Damavand geomorphological-environmental database and then disseminating it using WebGIS. In this research project, firstly, required spatial and attribute data were identified. Then, using available maps, satellite imageries, aerial imageries, and field works, required data were produced, completed and complemented. After that, the proposed database was designed and implemented and finally the mentioned data were stored in the database. By conducting these stages, the Damavand geomorphological-environmental database was established. At the next stage, an interactive WebGIS was designed and implemented in Geological Survey of Iran (GSI). At the last stage, the database was linked to the WebGIS and disseminated via that. At the time of writing this paper, the Damavand WebGIS and hence the geomorphological-environmental database is accessible via GSI intranet. The WebGIS can also be connected to internet in order to make the database accessible for public. Establishing such database for other geological-related datasets and its dissemination using WebGIS can significantly resolve current problems associated with these datasets from storage, accessibility and applicability perspectives.
