ArabianEmpires&Caliphates
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The story of the famous volcano in Saudi Arabia near the Prophet’s (saws) Mosque
- Thread starter Saif al-Arab
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ArabianEmpires&Caliphates
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Amazing.
ArabianEmpires&Caliphates
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GATES TO HELL? Hundreds of ancient structures found on edge of VOLCANOES in Saudi Arabia
STUNNED researchers have discovered 400 mysterious stone structures in Saudi Arabia which date back thousands of years, it has been revealed.
Experts are still unsure as to the purpose of the structures, but some of them were found to be draped over lava domes – a mound shaped area where lava has dried near volcanoes.
The stone walls, which have been called “gates” as they resemble field gates when viewed aerially, were found in a region in west-central Saudi Arabia called Harrat Khaybar.
David Kennedy, a professor at the University of Western Australia, who helped to discover the gates through satellite imagery, said they "are stone-built, the walls roughly made and low.”
He adds that they "appear to be the oldest man-made structures in the landscape,” and that "no obvious explanation of their purpose can be discerned”.
GOOGLE MAPS
The 'gates' found in Saudi Arabia
WIKIMEDIA COMMONS
Harrat Khaybar from space
The size of the gates varies massively, with the smallest being 43 feet and the largest stretching to 1,699 feet.
Prof Kennedy adds: "Gates are found almost exclusively in bleak, inhospitable lava fields with scant water or vegetation, places seemingly amongst the most unwelcoming to our species.”
Mr Kennedy says that more field work is needed to be done on the gates to determine the and purpose of them.
Before these gates were discovered, volcanologists Vic Camp and John Roobol mapped an area of the Harrat Khaybar region which also had gates and stone structures.
These gates, Mr Camp estimated, were built some 7,000 years ago.
However, it is likely that Mr Camp’s gates are older than the recently discovered ones as some of them are covered in lava flow.
Mr Camp told Live Science: "We see several areas where the younger lavas are devoid of such [stone] structures, although surrounded by several [stone structures].”
Stunning volcanic views of Harrat Khaybar
Harrat Khaybar is a volcanic field located north of Medina in Saudi Arabia
1 / 7
The presence of tuff cones, formed by eruption of lava in the presence of water
2 / 7
Map of where Harrat Khaybar is located
3 / 7
According to scientists, the volcanic field was formed by eruptions
4 / 7
The most recent recorded eruption took place between 600-700 A.D
5 / 7
The local climate was much wetter during some periods of volcanic activity
6 / 7
7 / 7
https://www.express.co.uk/news/scie...-volcano-eruption-saudi-arabia-Harrat-Khaybar
STUNNED researchers have discovered 400 mysterious stone structures in Saudi Arabia which date back thousands of years, it has been revealed.
Experts are still unsure as to the purpose of the structures, but some of them were found to be draped over lava domes – a mound shaped area where lava has dried near volcanoes.
The stone walls, which have been called “gates” as they resemble field gates when viewed aerially, were found in a region in west-central Saudi Arabia called Harrat Khaybar.
David Kennedy, a professor at the University of Western Australia, who helped to discover the gates through satellite imagery, said they "are stone-built, the walls roughly made and low.”
He adds that they "appear to be the oldest man-made structures in the landscape,” and that "no obvious explanation of their purpose can be discerned”.
The 'gates' found in Saudi Arabia
Harrat Khaybar from space
The size of the gates varies massively, with the smallest being 43 feet and the largest stretching to 1,699 feet.
Prof Kennedy adds: "Gates are found almost exclusively in bleak, inhospitable lava fields with scant water or vegetation, places seemingly amongst the most unwelcoming to our species.”
Mr Kennedy says that more field work is needed to be done on the gates to determine the and purpose of them.
Before these gates were discovered, volcanologists Vic Camp and John Roobol mapped an area of the Harrat Khaybar region which also had gates and stone structures.
These gates, Mr Camp estimated, were built some 7,000 years ago.
However, it is likely that Mr Camp’s gates are older than the recently discovered ones as some of them are covered in lava flow.
Mr Camp told Live Science: "We see several areas where the younger lavas are devoid of such [stone] structures, although surrounded by several [stone structures].”
Stunning volcanic views of Harrat Khaybar
Harrat Khaybar is a volcanic field located north of Medina in Saudi Arabia
1 / 7
The presence of tuff cones, formed by eruption of lava in the presence of water
2 / 7
Map of where Harrat Khaybar is located
3 / 7
According to scientists, the volcanic field was formed by eruptions
4 / 7
The most recent recorded eruption took place between 600-700 A.D
5 / 7
The local climate was much wetter during some periods of volcanic activity
6 / 7
7 / 7
https://www.express.co.uk/news/scie...-volcano-eruption-saudi-arabia-Harrat-Khaybar
ArabianEmpires&Caliphates
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ArabianEmpires&Caliphates
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National Center for Earthquakes and Volcanoes
At the present day it is known that the Arabian tectonic plate is migrating away from the African Plate at a rate of around 2 cm per year. In north-western and central western Arabia crustal extension is also occurring, and has resulted in significant Cenozoic volcanism. The two most common types of volcanic emission (more than 80 percent) in Saudi Arabia are shield volcanoes, with fairly flat slope (2o to 6o), due to thin fluid basalt lava flows and with a clearly-marked crater, and cinder (scoria) and spatter cones making degassing points along fissures. Ash cones may also occur, such as in Harrats Lunayyir and Kishb.
The first phase of the volcanism took place 20 to 30 million years ago, and was associated with the opening of the Red Sea. These older lava fields are so eroded that no morphological volcanoes remain on the surface. The more recent basaltic lava fields and volcanoes date from 10 million years ago up to the historic eruptions. They lie along a 900 km line within the shield that extends south from the Great Nafud Desert, through the cities of Al Madinah and Makkah, and then as far south along the coastal plain as Al Qunfudah. The northernmost 600 km length of this trend takes the form of a north-south graben structure about 600 km long through which the main Cenozoic basaltic lava fields (harrats) have been erupted. This zone has been named the Makkah-Madinah-Nafud (MMN) Volcanic line, and includes Harrats Rahat, Khaybar and Ithnayn. Harrat Rahat, which extends between Makkah and Madinah, covers about 20,000 km2, and has 644 scoria cones, 36 shield volcanoes and 24 domes. The MMN volcanic line is a weakly propagating rift zone where crustal extension has averaged about 0.054 mm per year over the past 10 million years, and is distinct from the main Red Sea rift zone. It forms the axis of uplift in western Saudi Arabia, and geothermal phenomena are observed along this trend.
It has been suggested that most of the volcanism in western Saudi Arabia occurs due to a northward flow or channel in the asthenosphere (the hot plastic layer under the more rigid upper mantle and crust) that extends from the Afar triple junction at the southern end of the Red Sea, where the East African rift joins the spreading centres of the Red Sea and the Gulf of Aden. The Afar junction is probably underlain by an upwelling mantle plume, a convection phenomenon that arises from deep within the Earth’s mantle. The channelled northward flow under western Saudi Arabia then provides the material that generates the observed surface volcanism by upwelling along the MMN axis and incipient rifts related to seafloor spreading and regional tension within the Arabian plate. Low level geothermal activity and seismicity indicate that the MMN trend remains active. The areas of Cenozoic volcanism and the MMN volcanic line are shown in the map of the harrats.
A: The main Cenozoic lava fields (harrats) in western Saudi Arabia showing the MMN volcanic line.
B: The three-armed rift of the Red Sea – Gulf of Aden – East African Rift zone. The inferred mantle plume is below the Afar triangle.
Cenozoic volcanic cones in northern Harrat Rahat
One of the more spectacular volcanic features in the shield is the Wahbar crater, which lies in Harrat Kishb about 200 km to the northeast of Makkah. This crater, which is about 200 m deep and 2 km wide, resulted from a phreatic explosion caused by the near-instantaneous generation of steam at the contact between rising magma and ground water.
Historic volcanic activity
The areas of Tertiary volcanism in western Saudi Arabia appear to be largely inactive at present. However, the Cenozoic volcanic lava field of Harrat Rahat, which is about 310 km long and lies between Makkah and Al Madinah, has experienced volcanism in historic times. The total volume of lava in this harrat is about 2000 km3, and volcanism commenced about 10 million years ago, with the more recent flows toward the northern end of the harrat. The oldest lavas near Madinah are geologically very young, only about 2 million years old. In this area the youngest “Post-Neolithic” lavas (less than 6000 years old) resulted from 11 eruptions, with 2 historic eruptions in AD 641 and AD 1256. The 641 AD eruption resulted in a small line of cinder cones to the southwest of the city. The last well-documented eruption in Saudi Arabia occurred in the northern end of Harrat Rahat near Al Madinah in 1256 AD/ 654 AH, and was preceded by significant earthquake activity for several days. Fountains of basalt lava were then seen 19 km to the southeast of the city, and lava advanced toward the city. The eruption continued for 52 days, and the lava flow reached to within 12 km of the city before activity ceased. About half a cubic kilometer of alkali olivine basalt was extruded from a 2.25 km-long fissure during this eruption. Three large scoria cones and three low spatter cones were produced at the vent zone, and the lava flowed a maximum distance of 23 km. The area continues to be of some concern, especially since the city is now expanding into the area of the flow, and SGS maintains a local seismograph network around this end of the harrat and the city to warn of any impending risk from an eruption, although there is a very low probability of this happening.
NASA World Wind Geocover2000 false color image of northern Harrat Rahat, derived from 2 infrared and 1 visible green spectral bands. The city of Al Madinah occupies the left side of the image, and the harrat lava flows are the black regions, with the most recent flows showing as the darkest areas. The volcanic cones or eruption centers are red/orange in this image. It can be seen that the flows from the 1256 AD eruption reached almost to the city, and are close to the present airport, part of which can be seen near the top edge of the image. Note that development is now taking place within the area of this historic lava flow, which increases the risk in the very unlikely event of any further volcanic activity in the area.
Volcanic cone from the historic (1256 AD) eruption in northern Harrat Rahat
Volcanic cones and historic lava field in northern Harrat Rahat near Al Madinah
Volcanologist Dr. M.J. Roobol explains the origins of a ground fissure and volcanic cones in northern Harrat Rahat
A large ground fissure associated with volcanism in northern Harrat Rahat near Al Madinah
Lava tube, volcanic cones in northern Harrat Rahat, near the area of the historic lava flow
Harrat Lunayyir (Al-Shaqah)
From late 2007 onwards a swarm of more than 30,000 earthquakes has occurred beneath Harrat Lunayyir (locally referred to as Harrat Al-Shaqah) in western Saudi Arabia, a late Cenozoic to Holocene basaltic lava field to the north of Yanbu, where the older volcanism occurred in the southern part of the harrat. This harrat is about 150 km to the west of the main MMN volcanic line and less than 100 km from the coast. On 19 May, 2009, 19 earthquakes of M4.0 or greater took place, including a M5.4 event at 17:35 UTC, which caused minor damage to structures in the town of Al Ays (40 km to the SE). An 8-km-long surface rupture across the northern part of the volcanic field occurred during this event. Modelling of Interferometric Synthetic Aperture Radar (InSAR) data indicates that close to 40 cm of regional uplift and well over 1 meter of east-west extension occurred. The earthquakes and ground deformation resulted from tensional faulting that is consistent with intrusion of a 2 m thick magmatic dike of about 0.13 km3 volume, with its top at less than 2 km depth. The faulting is consistent with previous observations that the Quaternary volcanism is concentrated along an orientation about N35oW.
Although the magma did not reach the surface, and recent earthquake activity has only continued at a low level in the area, SGS is continuing to monitor the area for any signs of renewed activity and possible surface eruptions of lava from the dike. In some of the potentially active harrats plumes of steam have occasionally been noted, especially during colder weather when the steam becomes more visible. Hence in Harrat Lunayyir remotely operated cameras using telemetry have recently been established at several locations to determine if there are any visible indications of shallow volcanism, such as venting of steam or gases.
Part of the May 19, 2009, ground fissure in soft sediments in Harrat Lunayyir, with a Cenozoic volcano and lava flow in the background.
Aerial view along the main May 19, 2009, fissure in soft sediments in Harrat Lunayyir with a Cenozoic volcanic cone in the background.
Part of the fissure associated with the May 19, 2009, earthquake in Harrat Lunayyir. The ground cracks seen in this photograph are due to differential slumping or collapse in soft sediments that are up to 60 m thick at this location, whereas the maximum actual dip-slip offset on the fault in the hard rock in the nearby hills is about 90 cm.
Cenozoic lava flows filling valleys (wadis) between the hills (Precambrian basement) in Harrat Lunayyir
Hot springs and fumaroles
The MMN line and areas further south along the Red Sea coast show geothermal phenomena. These take the form of shallow water wells with elevated temperatures, fumaroles and hot springs. A fumarole is defined as a vent, usually volcanic, from which gases and vapours are emitted, and it is characteristic of a late stage of volcanic activity. Elevated temperatures may occur in fissures cutting the lava flows, and also in some places in the Precambrian basement between the harrats and on the Red Sea coastal plain. In some places along the harrats steam emerges naturally from the ground, such as in Harrats Ithnayn and Khaybar. Where the steam temperature is less than 50oC these are called “cold fumaroles”, and they can only be observed in the morning during the colder months when the warmer steam can rise.
Steam fumarole in an eroded lava flow in Harrat Khaybar to the north of Al Madinah. The photograph was taken on February 8, 1992, with an air temperature of 6oC and a steam temperature of 25oC (after Roobol et al., 2007, SGS-TR-2007-6).
The areas of geothermal activity in western Saudi Arabia are shown in the map reproduced here from a 1981 report on the geothermal resources in the Kingdom (Berthier et al., Open-File Report BRGM-OF-01-24). The main geothermal springs are in the foothills of the Precambrian shield adjacent to the Red Sea. Above the escarpment near the western margin of the shield (where the crust is about 40 km thick) water temperatures up to 53oC have been observed, and on the Red Sea coastal plain (where the crust decreases in thickness to around 15 km) temperatures of the order of 100oC have been reported for a hot spring at Al Lith, about 150 km to the southeast of Jeddah, with even higher temperatures, 120oC to 150oC, at springs near Jazan in the far south of the Kingdom. These thermal springs result from heating of meteoric or rain water that has infiltrated through faults or cracks in the ground. Ground water in wells in and around the cities of Al Madinah and Makkah also show slightly elevated temperatures. Commercial hot mineral baths have been developed in the past in at least four sites along the main north-south volcanic line. At this stage it is not known if the geothermal resources in Saudi Arabia are of any economic importance as far as their energy content is concerned, but the temperatures at the hot springs in the Al Lith and Jazan areas suggest that further studies there are required.
Areas of potential geothermal interest in western Arabia (after Berthier et al., 1981, BRGM-OF-01-24)
Geothermal monitoring
The temperature of water wells in several of the harrats is checked periodically by SGS to see if there are any significant changes that may be associated with incipient volcanic activity. The patterns of water well temperatures may also indicate the areas that have elevated heat flow or temperature gradients due to deep-seated magma. In the 1980’s monitoring of the Al Madinah area identified a 3.2 km long line of weak fumaroles adjacent to the 1256 AD lava flow, close to the modern city. Recording by the local seismograph network also located clusters of epicentres of low-magnitude earthquakes along this line at this time, but the geothermal and micro-seismic activity appears to have decreased in recent years. Studies of water wells in the area show that temperatures as high as 53oC have occurred, although these are variable. Isotopic studies of groundwater near Al Madinah and from hot springs on the coastal plain show only a meteoric component (rain water source) with no indication of a magmatic source for the water.
Volcano alert system
A volcanic activity alert system is in place, in which the volcanic hazard in an area is rated in four levels according to the table below. This assists the authorities in planning for natural hazards that may be associated with possibly imminent or ongoing volcanic activity, such as the recent volcano-tectonic crisis in Harrat Lunayyir.
https://www.sgs.org.sa/English/Earthquakes/Pages/Volcanoes.aspx
At the present day it is known that the Arabian tectonic plate is migrating away from the African Plate at a rate of around 2 cm per year. In north-western and central western Arabia crustal extension is also occurring, and has resulted in significant Cenozoic volcanism. The two most common types of volcanic emission (more than 80 percent) in Saudi Arabia are shield volcanoes, with fairly flat slope (2o to 6o), due to thin fluid basalt lava flows and with a clearly-marked crater, and cinder (scoria) and spatter cones making degassing points along fissures. Ash cones may also occur, such as in Harrats Lunayyir and Kishb.
The first phase of the volcanism took place 20 to 30 million years ago, and was associated with the opening of the Red Sea. These older lava fields are so eroded that no morphological volcanoes remain on the surface. The more recent basaltic lava fields and volcanoes date from 10 million years ago up to the historic eruptions. They lie along a 900 km line within the shield that extends south from the Great Nafud Desert, through the cities of Al Madinah and Makkah, and then as far south along the coastal plain as Al Qunfudah. The northernmost 600 km length of this trend takes the form of a north-south graben structure about 600 km long through which the main Cenozoic basaltic lava fields (harrats) have been erupted. This zone has been named the Makkah-Madinah-Nafud (MMN) Volcanic line, and includes Harrats Rahat, Khaybar and Ithnayn. Harrat Rahat, which extends between Makkah and Madinah, covers about 20,000 km2, and has 644 scoria cones, 36 shield volcanoes and 24 domes. The MMN volcanic line is a weakly propagating rift zone where crustal extension has averaged about 0.054 mm per year over the past 10 million years, and is distinct from the main Red Sea rift zone. It forms the axis of uplift in western Saudi Arabia, and geothermal phenomena are observed along this trend.
It has been suggested that most of the volcanism in western Saudi Arabia occurs due to a northward flow or channel in the asthenosphere (the hot plastic layer under the more rigid upper mantle and crust) that extends from the Afar triple junction at the southern end of the Red Sea, where the East African rift joins the spreading centres of the Red Sea and the Gulf of Aden. The Afar junction is probably underlain by an upwelling mantle plume, a convection phenomenon that arises from deep within the Earth’s mantle. The channelled northward flow under western Saudi Arabia then provides the material that generates the observed surface volcanism by upwelling along the MMN axis and incipient rifts related to seafloor spreading and regional tension within the Arabian plate. Low level geothermal activity and seismicity indicate that the MMN trend remains active. The areas of Cenozoic volcanism and the MMN volcanic line are shown in the map of the harrats.
A: The main Cenozoic lava fields (harrats) in western Saudi Arabia showing the MMN volcanic line.
B: The three-armed rift of the Red Sea – Gulf of Aden – East African Rift zone. The inferred mantle plume is below the Afar triangle.
Cenozoic volcanic cones in northern Harrat Rahat
One of the more spectacular volcanic features in the shield is the Wahbar crater, which lies in Harrat Kishb about 200 km to the northeast of Makkah. This crater, which is about 200 m deep and 2 km wide, resulted from a phreatic explosion caused by the near-instantaneous generation of steam at the contact between rising magma and ground water.
Historic volcanic activity
The areas of Tertiary volcanism in western Saudi Arabia appear to be largely inactive at present. However, the Cenozoic volcanic lava field of Harrat Rahat, which is about 310 km long and lies between Makkah and Al Madinah, has experienced volcanism in historic times. The total volume of lava in this harrat is about 2000 km3, and volcanism commenced about 10 million years ago, with the more recent flows toward the northern end of the harrat. The oldest lavas near Madinah are geologically very young, only about 2 million years old. In this area the youngest “Post-Neolithic” lavas (less than 6000 years old) resulted from 11 eruptions, with 2 historic eruptions in AD 641 and AD 1256. The 641 AD eruption resulted in a small line of cinder cones to the southwest of the city. The last well-documented eruption in Saudi Arabia occurred in the northern end of Harrat Rahat near Al Madinah in 1256 AD/ 654 AH, and was preceded by significant earthquake activity for several days. Fountains of basalt lava were then seen 19 km to the southeast of the city, and lava advanced toward the city. The eruption continued for 52 days, and the lava flow reached to within 12 km of the city before activity ceased. About half a cubic kilometer of alkali olivine basalt was extruded from a 2.25 km-long fissure during this eruption. Three large scoria cones and three low spatter cones were produced at the vent zone, and the lava flowed a maximum distance of 23 km. The area continues to be of some concern, especially since the city is now expanding into the area of the flow, and SGS maintains a local seismograph network around this end of the harrat and the city to warn of any impending risk from an eruption, although there is a very low probability of this happening.
NASA World Wind Geocover2000 false color image of northern Harrat Rahat, derived from 2 infrared and 1 visible green spectral bands. The city of Al Madinah occupies the left side of the image, and the harrat lava flows are the black regions, with the most recent flows showing as the darkest areas. The volcanic cones or eruption centers are red/orange in this image. It can be seen that the flows from the 1256 AD eruption reached almost to the city, and are close to the present airport, part of which can be seen near the top edge of the image. Note that development is now taking place within the area of this historic lava flow, which increases the risk in the very unlikely event of any further volcanic activity in the area.
Volcanic cone from the historic (1256 AD) eruption in northern Harrat Rahat
Volcanic cones and historic lava field in northern Harrat Rahat near Al Madinah
Volcanologist Dr. M.J. Roobol explains the origins of a ground fissure and volcanic cones in northern Harrat Rahat
A large ground fissure associated with volcanism in northern Harrat Rahat near Al Madinah
Lava tube, volcanic cones in northern Harrat Rahat, near the area of the historic lava flow
Harrat Lunayyir (Al-Shaqah)
From late 2007 onwards a swarm of more than 30,000 earthquakes has occurred beneath Harrat Lunayyir (locally referred to as Harrat Al-Shaqah) in western Saudi Arabia, a late Cenozoic to Holocene basaltic lava field to the north of Yanbu, where the older volcanism occurred in the southern part of the harrat. This harrat is about 150 km to the west of the main MMN volcanic line and less than 100 km from the coast. On 19 May, 2009, 19 earthquakes of M4.0 or greater took place, including a M5.4 event at 17:35 UTC, which caused minor damage to structures in the town of Al Ays (40 km to the SE). An 8-km-long surface rupture across the northern part of the volcanic field occurred during this event. Modelling of Interferometric Synthetic Aperture Radar (InSAR) data indicates that close to 40 cm of regional uplift and well over 1 meter of east-west extension occurred. The earthquakes and ground deformation resulted from tensional faulting that is consistent with intrusion of a 2 m thick magmatic dike of about 0.13 km3 volume, with its top at less than 2 km depth. The faulting is consistent with previous observations that the Quaternary volcanism is concentrated along an orientation about N35oW.
Although the magma did not reach the surface, and recent earthquake activity has only continued at a low level in the area, SGS is continuing to monitor the area for any signs of renewed activity and possible surface eruptions of lava from the dike. In some of the potentially active harrats plumes of steam have occasionally been noted, especially during colder weather when the steam becomes more visible. Hence in Harrat Lunayyir remotely operated cameras using telemetry have recently been established at several locations to determine if there are any visible indications of shallow volcanism, such as venting of steam or gases.
Part of the May 19, 2009, ground fissure in soft sediments in Harrat Lunayyir, with a Cenozoic volcano and lava flow in the background.
Aerial view along the main May 19, 2009, fissure in soft sediments in Harrat Lunayyir with a Cenozoic volcanic cone in the background.
Part of the fissure associated with the May 19, 2009, earthquake in Harrat Lunayyir. The ground cracks seen in this photograph are due to differential slumping or collapse in soft sediments that are up to 60 m thick at this location, whereas the maximum actual dip-slip offset on the fault in the hard rock in the nearby hills is about 90 cm.
Cenozoic lava flows filling valleys (wadis) between the hills (Precambrian basement) in Harrat Lunayyir
Hot springs and fumaroles
The MMN line and areas further south along the Red Sea coast show geothermal phenomena. These take the form of shallow water wells with elevated temperatures, fumaroles and hot springs. A fumarole is defined as a vent, usually volcanic, from which gases and vapours are emitted, and it is characteristic of a late stage of volcanic activity. Elevated temperatures may occur in fissures cutting the lava flows, and also in some places in the Precambrian basement between the harrats and on the Red Sea coastal plain. In some places along the harrats steam emerges naturally from the ground, such as in Harrats Ithnayn and Khaybar. Where the steam temperature is less than 50oC these are called “cold fumaroles”, and they can only be observed in the morning during the colder months when the warmer steam can rise.
Steam fumarole in an eroded lava flow in Harrat Khaybar to the north of Al Madinah. The photograph was taken on February 8, 1992, with an air temperature of 6oC and a steam temperature of 25oC (after Roobol et al., 2007, SGS-TR-2007-6).
The areas of geothermal activity in western Saudi Arabia are shown in the map reproduced here from a 1981 report on the geothermal resources in the Kingdom (Berthier et al., Open-File Report BRGM-OF-01-24). The main geothermal springs are in the foothills of the Precambrian shield adjacent to the Red Sea. Above the escarpment near the western margin of the shield (where the crust is about 40 km thick) water temperatures up to 53oC have been observed, and on the Red Sea coastal plain (where the crust decreases in thickness to around 15 km) temperatures of the order of 100oC have been reported for a hot spring at Al Lith, about 150 km to the southeast of Jeddah, with even higher temperatures, 120oC to 150oC, at springs near Jazan in the far south of the Kingdom. These thermal springs result from heating of meteoric or rain water that has infiltrated through faults or cracks in the ground. Ground water in wells in and around the cities of Al Madinah and Makkah also show slightly elevated temperatures. Commercial hot mineral baths have been developed in the past in at least four sites along the main north-south volcanic line. At this stage it is not known if the geothermal resources in Saudi Arabia are of any economic importance as far as their energy content is concerned, but the temperatures at the hot springs in the Al Lith and Jazan areas suggest that further studies there are required.
Areas of potential geothermal interest in western Arabia (after Berthier et al., 1981, BRGM-OF-01-24)
Geothermal monitoring
The temperature of water wells in several of the harrats is checked periodically by SGS to see if there are any significant changes that may be associated with incipient volcanic activity. The patterns of water well temperatures may also indicate the areas that have elevated heat flow or temperature gradients due to deep-seated magma. In the 1980’s monitoring of the Al Madinah area identified a 3.2 km long line of weak fumaroles adjacent to the 1256 AD lava flow, close to the modern city. Recording by the local seismograph network also located clusters of epicentres of low-magnitude earthquakes along this line at this time, but the geothermal and micro-seismic activity appears to have decreased in recent years. Studies of water wells in the area show that temperatures as high as 53oC have occurred, although these are variable. Isotopic studies of groundwater near Al Madinah and from hot springs on the coastal plain show only a meteoric component (rain water source) with no indication of a magmatic source for the water.
Volcano alert system
A volcanic activity alert system is in place, in which the volcanic hazard in an area is rated in four levels according to the table below. This assists the authorities in planning for natural hazards that may be associated with possibly imminent or ongoing volcanic activity, such as the recent volcano-tectonic crisis in Harrat Lunayyir.
https://www.sgs.org.sa/English/Earthquakes/Pages/Volcanoes.aspx
ArabianEmpires&Caliphates
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KSA has the largest number of volcanoes in the MENA region by far. Luckily all of them are extinct with the last one erupting 750 years ago and the lava flow reaching the gates of Madinah.
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ArabianEmpires&Caliphates
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The White Volcanoes of Harrat Khaybar
by Kaushik
Of the millions of pilgrims that visit the holy city of Medina, in Saudi Arabia, every year to pray in the Prophet’s Mosque, few people are aware that the city is build upon the basalt flows of a past volcano, with the now dormant volcano lying very close to the city. This volcanic field, known as Harrat Khaybar, contains some of the rarest examples of white volcanoes, so called because of their light colored rocks caused by the presence of a kind of alkali and silica-rich light blue-gray igneous rock called comendite.
An aerial view of the Jebel Bayda, a white volcano made by silica-rich lava (comendite) in Harrat Khaybar. Photo credit: Luigi Vigliotti
wide range of volcanic rock types and spectacular landforms, as represented in the photograph below. The image was taken by the Expedition 16 crew aboard the International Space Station in March 2008.
The symmetric structures are tuff cones, formed by eruption of lava in the presence of water. The combination produces wet, sticky pyroclastic deposits that can build a steep cone structure, particularly if the deposits consolidate quickly. The presence of these tuff cones indicate that the local climate was much wetter during some periods of volcanic activity. Today, this region is as dry as bone with little to no yearly precipitation leading to an almost total lack of vegetation.
https://www.amusingplanet.com/2019/10/white-volcanoes-of-harrat-khaybar.html
by Kaushik
Of the millions of pilgrims that visit the holy city of Medina, in Saudi Arabia, every year to pray in the Prophet’s Mosque, few people are aware that the city is build upon the basalt flows of a past volcano, with the now dormant volcano lying very close to the city. This volcanic field, known as Harrat Khaybar, contains some of the rarest examples of white volcanoes, so called because of their light colored rocks caused by the presence of a kind of alkali and silica-rich light blue-gray igneous rock called comendite.
An aerial view of the Jebel Bayda, a white volcano made by silica-rich lava (comendite) in Harrat Khaybar. Photo credit: Luigi Vigliotti
wide range of volcanic rock types and spectacular landforms, as represented in the photograph below. The image was taken by the Expedition 16 crew aboard the International Space Station in March 2008.
The symmetric structures are tuff cones, formed by eruption of lava in the presence of water. The combination produces wet, sticky pyroclastic deposits that can build a steep cone structure, particularly if the deposits consolidate quickly. The presence of these tuff cones indicate that the local climate was much wetter during some periods of volcanic activity. Today, this region is as dry as bone with little to no yearly precipitation leading to an almost total lack of vegetation.
https://www.amusingplanet.com/2019/10/white-volcanoes-of-harrat-khaybar.html
ArabianEmpires&Caliphates
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ArabianEmpires&Caliphates
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