The story of the famous volcano in Saudi Arabia near the Prophet’s (saws) Mosque

[The SC]

First time I have seen so many volcanos in the same place..and aligned like this on top of it..really amasing..but not too surprised that this is in a country proven to be the center of earth..

 

[xenon54 out]

First time I have seen so many volcanos in the same place..and aligned like this on top of it..really amasing..but not too surprised that this is in a country proven to be the center of earth..

Quite common actually.

https://en.wikipedia.org/wiki/Hotspot_(geology)

 

[Fledgingwings]

A very information rich post.Thanks mate !

 

[Saif al-Arab]

Ancient volcanic field reawakens in Saudi Arabia

In 2009, more than 30,000 earthquakes struck an ancient lava field, opening up a five-mile long crevice. Sensors shoow that magma has risen to roughly a mile below the surface of the Earth, and eruptions remain possible.

By Charles Q. Choi, Our AmazingPlanet Contributor SEPTEMBER 26, 2010

AFP/Newscom

A swarm of thousands of earthquakes that struck the corner of Saudi Arabia nearest to Egypt in 2009 helped reveal that the area is unexpectedly volcanically active, scientists now report.

The seismic readings that researchers managed to collect from these quakes could help predict when volcanoes might erupt in the future, investigators added.

Scientists had largely thought northwest Saudi Arabia was quiet, geologically speaking. Few earthquakes and few volcanic eruptions have been recorded there in the past millennium.

However, between April and June 2009, more than 30,000 earthquakes struck an ancient lava field there named Harrat Lunayyir, with 19 earthquakes of magnitude 4 or greater striking at the swarm's peak on May 19, including a magnitude 5.4 quake that fractured walls in the town of Al Ays. Sensors even suggested that a volcanic eruption was possible. Alarmed, the Saudi Arabian government then evacuated 40,000 people from the region.

Part of Red Sea Parting

The lava field of Harrat Lunayyir is part of a "lava province" roughly 70,000 square miles (180,000 square kilometers) in size that began forming 30 million years ago when Arabia split from Africa, rifting that helped create the Red Sea. Harrat Lunayyir was previously considered inactive because of its location on the margins of the continental rift, nearly 120 miles (200 kilometers) away from the active center of spreading beneath the Red Sea.

Still, "the Red Sea rift is a very active place to start with, with a chain of volcanoes down the middle of it that we're rarely aware of because they are underwater," said researcher John Pallister, a volcanologist and chief of the U.S. Geological Survey's volcano disaster assistance program. "When continents are being pulled apart as you have there, you'll often see intrusions of magma on the shoulders of the rift."

The researchers discovered a roughly 2-mile-long (3-km-long) rupture had opened up in the area and widened to 5 miles (8 km) long during the most powerful quake. Satellite radar images suggested the most likely cause of this fault was magma intruding upward over a 6-mile-long (10-km-long) stretch.

Based on these findings, on June 19, 2009, the researchers forecast a moderate chance of a volcanic eruption and a low probability of magnitude 5 or greater earthquakes in the two months following. A decline of seismic activity by August 2009 led the scientists to conclude the crisis had ended, allowing evacuees to return to their homes and daily lives.

Magma rises

Still, now that magma has risen to shallow levels roughly a mile (2 kilometers) below the surface of the Earth, eruptions remain possible, and the authorities have to remain vigilant, the researchers said.

"It is more likely that we'll get additional intrusions of magma and potentially even an eruption in this area — the pathway is prepared," Pallister told Our Amazing Planet.

The highly detailed readings the Saudi Geological Survey collected from these quakes might be able to help scientists forecast volcanic eruptions in the future, Pallister added.

Volcanic quakes often generate a mix of high- and low-frequency seismic waves that could yield clues as to when an eruption might occur. These signals are often dulled by the nature of the earth they pass through, but when it came to the Arabian quakes, they were detected through the crystalline rocks of the area quite clearly. The low-frequency seismic waves detected during the quakes seemed to show magma flowing under the earth, while the high-frequency waves indicated fracturing of crystalline rocks as magma crept toward the surface.

"Understanding what these signals mean could prove instrumental to forecasting what can be deadly events worldwide," Pallister said.

The scientists detailed their findings online Sept. 26 in the journal Nature Geoscience.

http://www.csmonitor.com/Science/2010/0926/Ancient-volcanic-field-reawakens-in-Saudi-Arabia

The volcanic miracle of Arabia
There is a place in the Kingdom of Saudi Arabia which is like no other in the world. Whereas it is not well-known Saudi Arabia has volcanoes, even plenty of volcanoes including active ones. Volcanic activity is related to hot spot activity on the Arabian Plate which was uplifted on the eastern side of the Red Sea rift.
The basaltic lava fields in the western part of the country are called harrat. They cover about 180 000 square km and extend from Turkey to Yemen in the south.

One of the largest volcanic fields is known as Harrat Khaybar, named after the city which lays on its western side. Its ancient and recent lava flows spread between the provinces of Madinah and Ha’il, on the northwest of the city of Madinah, and cover more than 14 000 square kilometers. It contains a 100-kilometer-long north-south oriented line of volcanic vents including scoria cones, lava domes, maars, basalt lava flows, and the only stratovolcano (built up by many layers (strata) of hardened lava) in the Harrat of western Arabia, the Jebel Qidr.

Center of the Harrat Khaybar (Google earth image)

Volcanoes at the center of the Harrat Khaybar (photo: Florent Egal)

https://imgur.com/a/6rpY1

Recent lava flow of Jebel Qidr (photo: Florent Egal)

The Harrat Khaybar is still active as testified at least eight eruptions that took place during Islamic era (less than 1500 years old). These include the prominent 55-kilometer-long Habir lava flow and flows from Jabal Qidr which present lava flows that have till today a fluid aspect. However, only one eruption is recorded in historic memory from early Islamic times during the 7th century CE (1st century H).

But the jewel of the Harrat Khaybar is to be found in its center where lay a very rare kind of volcanoes made of silica-rich called comendite which give them a whitish color. The two largest are the Jebel Abiadh and the Jebel Bayda whose grandiose majesty revealed by satellite images is even more stunning once on site.

Jebel Abiadh (photo: Florent Egal)

Jebel Abiadh (literally “white mount”) is the highest crater of the harra with 2093 meters of altitude and the Jebel Bayda (in Arabic the feminine of “white mount”) is the largest with 1,5 kilometers of diameter.

Mixes of colors in the center of the Harrat Khaybar (photo: Elizabeth Henrich)

As shown on the satellite images the center of the Harrat Khaybar is not only about the clear colors of the white volcanoes as other volcanic formations brought with many shades of other types of lava, ranging from creamy ocher of Jebel Bayda, to shades of red and brown of Jebel Al-'Aqir, until the deep dark lava flows of Jebel Qidr. The subsequent mixing lava flows created fantastic patterns of shades on the ground in between the craters.

The contrast is the most striking where the whitish creamy lava of the Jebel Bayda meets the deep dark one of the Jebel Qidr. A track leads to the edge of both lava flows where it is possible to stand on this volcanic border having one foot on each type of lava.

https://imgur.com/a/D3sq0

Sharp contrast of colors between the white lava of Jebel Bayda and the dark one of Jebel Qidr (photo: Florent Egal)

Jebel Qidr (photo: Elizabeth Henrich)

1,5 km wide crater of Jebel Bayda (photo: Florent Egal)

The creativity of nature is not limited to a wide range of colors but also marvelously attested by the incredible variety of volcanoes shapes that can be found in the Harrat Khaybar. From a high viewpoint it is possible to admire the elegantly spread silhouette of Jebel Bayda, the Fujiyama-like volcanic cone of Jebel Qidr, and the fancy hat-shaped of Jebel Al-'Aqir.

Hat-shaped Jebel Al-'Aqir (photo: Florent Egal)

It is possible to reach safely some of the craters by foot in order to take the most of the out-of-this-world sights this place offers. Local Bedouins drive up the sides of the Jebel Bayda with theirs pickups but it is rather advisable to go for a short hike uphill instead.

Crater of Jebel Bayda (photo: Florent Egal)

The sides of Jebel Abiadh are definitely to steep for car but the southern slope of the volcanic cone is just about gentle enough to allow a relatively safe (although slippery) climb up to the crater.

Crater of Jebel Abiadh (photo: Florent Egal)

And the viewpoint from the summit of Jebel Abiadh is absolutely worth the effort. This volcano being the highest one peaking up at 2093 meters of altitude its offers stunning sights on the surrounding landscapes that seem to be from another world.

View on the center of the Harrat Khaybar from Jebel Abiadh (photo: Florent Egal)

It is very important to note that reaching the white volcanoes by car implies driving through 50 kilometers of lava fields where Bedouins have dig deep tracks that are the only option since the ground in between tracks is covered with sharp basalt rocks that would shred any tire after few kilometers or even damage the bottom of the car. Moreover, many tracks led to dead-ends so proper and accurate planning has to be done before any trip there and guidance from locals have to be taken into account seriously.

Given the difficulties to reach the center of the Harrat Khaybar the while volcanoes used to be a desert place for long but nowadays some Bedouins leave there and visitors are not uncommon. As a reminder of this no-longer-so-far human presence, camels are even found all around the area.

Camels at the bottom of Jebel Abiadh (photo: Florent Egal)

The volcanic miracle of Arabia (author: Florent Egal)

About the Author

My name is Florent Egal, I am a French national living in Riyadh since January 2010. After six years of exploration of Saudi Arabia I have decided to show with this website that KSA has much more to offer than the stereotype landscape of empty extends of sand dunes. I hope that after reading through these pages people will feel the same willingness and amazement than I have to discover this fascinating country

http://www.saudiarabiatourismguide.com/white-volcanoes/

 

[hacibin]

What the hell? White volcanos and black camels

 

[Trango Towers]

What the hell? White volcanos and black camels

Allah creates a wondrous variety

 

[Saif al-Arab]

Allah creates a wondrous variety

Indeed and sometimes even us locals are not aware of the tons of hidden and fairly unknown treasures that KSA (KSA is the size of Western Europe) has to offer. The few areas of KSA that this thread talks about are a heaven for geologists and hopefully geologists from across the world will have a bigger access to this jewel one day.

 

[Saif al-Arab]

Volcanoes of Saudi Arabia
Albert / 07/03/2016

Jurassic escarpment in central Saudi Arabia. Source: http://www.geo.tu-darmstadt.de/fg/hydrogeol/hydro_personen/khuffjilhminjurstudy.en.jsp

The rocky desert stretches as far as the eye can see: a fascinating vista, forbidding and seemingly unending. Distant hills shimmer in the heat and glare of the Sun. There is beauty here but it is on an inhuman and unearthly scale. The land has been baked bone-dry by many years of sun, heat and but little rain. Beneath, there is liquid to be found, but it is not water. Much of the oil which keeps our world moving was found here. There is another liquid down there too: molten rock.

Saudi Arabia is a land of contrasts, caught between different seas. To the west, the Red Sea. This side of Saudi Arabia is build on the ancient Arabian Shield, pre-Cambrian with some rocks over 3 billion years old although most is less than 1 billion years. There is old flood basalt here too, evidence of a tortured past. Along the Red Sea is the youngest part of the country: a low-lying strip of land less than 100 kilometer wide, a young scar in an old land. To the east, the Persian Gulf. Here the land becomes younger; this region is called the Arabian Platform, to distinguish it from the old shield. The oil is found at the eastern edge of Saudi Arabia. The Ghawar field, on the Persian Gulf, is the largest oil field in the world. Once, the tropical Tethys ocean was here. At times the Thetys became oxygen-depleted: the anoxic events lead to widespread die-off, forming thick layers of black mud. Over millions of year the mud turned to oil. The Tethys disappeared 10 million years ago but the oil remained: riches of the past. It is hard to believe that this unyielding desert was once a tropical ocean, teaming with life. How times change.

Two mountain ranges are stretched out along the Red Sea. The Hajiz mountains begin near the Gulf of Aqaba, and reach over 2 kilometers high; the range peters out near Jeddah. To the south are the Asir mountains, a higher range with peaks near 3 kilometers tall: the range reaches into Yemen where it becomes even higher. The mountains form the western edge of the Arabian Shield. To the west, they drop precipitously to the plain along the Red Sea (‘Hajiz’ meaning ‘barrier’), forming an escarpment. To the east, in-land, the drop is much more gradual. The Asir mountains are the wettest part of the Arabian peninsula, and some high areas receive an annual rainfall which would not be out of place in the UK. The rains have decreased over time. 5000 years ago, there was a major river flowing from the Hajiz towards Kuwait. Now, only a trace remains: the Wadi Bisha. Climate change -for the worse- is not new. There is a third mountain range, on the Indian ocean side, but located in Oman rather than Saudi Arabia. Near the centre of Saudi Arabia, east of the Hajiz mountains, are the remains of an ancient continental microplate. The microplate contains a memory of the formation and break-up of Pangea, and of the Rodinia supercontinent which came before. Continents tend to break up along old sutures, re-opening old wounds and leaving slivers in their wake.

A combination of Landsat images and ocean topography. From William Bosworth et al, Journal of African Earth Sciences 43 (2005) 334–378: The Red Sea and Gulf of Aden Basins

And now a new wound has formed; the Earth has stirred and the Arabian Shield has split. Half is stranded in Eritrea and Ethiopia, where it is called the Nubian Shield. The Red Sea has invaded the wound. Arabia became a peninsula, surrounded by the Red Sea, the Gulf of Aden, the Arabian Sea (part of the Indian Ocean), the Gulf of Oman, the shallow Persian Gulf (also known as the Arabian Gulf), and the Gulf of Aqaba. The split has formed the Arabian plate, the youngest of the main continental plates. The plate is slowly rotating anti-clock wise, pushing into and fracturing the Golan heights.

The Afar triple junction. From http://www.see.leeds.ac.uk/afar/new-afar/geology-afar/structure-tech-pages/red-sea-aden-tech.html

The stirrings started in (aptly named) Afar, where the Red Sea, the Gulf of Aden and the Ethiopian (or East African) rift meet. Afar is a perfect example of a triple junction, distinguished by the typical 120 degree angles between the three rifts. The Afar triple junction is not actually located in the Red Sea, but on land in Africa, at the westernmost point of Djibouti. The three rifts have fragmented old Africa into three plates: the Arabian plate, Nubia (Africa), and the Somalian plate.

To see more evidence of this process, one has to look under water, an appealing thought in this dry land. The seafloor topography (see the Landsat image above) shows the Carlsberg Ridge within the Indian Ocean: this is the spreading centre that long ago split India from Africa and pushed it into Asia. Near Arabia the Carlsberg Ridge jumps north along a fault (the Owen Fracture Zone); it continues on the other side into the Arabian Sea, but than changes direction and enters into the Gulf of Aden. Near the Afar triple junction it disappears. A little beyond, in the middle of the Red Sea another spreading ridge can be seen. Back in the Indian Ocean, there is a subduction zone along the coast of Pakistan and Iran (the Makran trench, location of an M8.1 earthquake in 1945) but it is comparatively small.

The Owen Fracture Zone is a 1000-km long strike-slip fault. This is the meeting place between the Arabian and Indian plate. It is considered a transform fault (i.e. with sideways motion), with a relative motion of about 3 mm per year, which would make Arabia a remarkably slow-moving continent. In reality, the velocity of the Arabian plate is a more respectable, albeit still slow, 1-2 cm per year, but the Indian and Arabian plate have almost the same velocity and cancel each other out. Along the Owen Fracture Zone, on the Arabian side, is the Owen ridge, reaching up to 2 km above the sea floor. It is a sizable mountain chain, but fully hidden underneath the ocean.

The Red ocean?

The Afar plume, which initiated the break-up of this part of Africa, was active 27 million year ago. The Red Sea began as a continental rift which formed over a short period 24 million years ago. The sea first entered the basin about 20 million years ago. Sea-floor spreading along the southern Red Sea dates to about 5 million year ago, but only in the past million year has it started in the northern Red Sea.

The Red Sea is currently 2 kilometers deep: it is becoming a proper deep-sea basin, and is considered a proto-oceanic basin. But it took a long time to develop a sea-floor spreading ridge. The Gulf of Aden rifted at approximately the same time, but sea floor spreading started here already 16 million year ago: the Red Sea took twice as long. The Ethiopian rift is even slower: so far a few lakes have formed, but nothing more: it is widening at no more than 2.5 mm per year and the faults along its edges are now inactive. Before sea floor spreading can start, the rift has to drop below sea level. This is still a long way from happening in the Ethiopian rift.

The Red Sea has taken 24 million years to grow to 350 kilometer width. That is not particularly fast: it has grown at about 1.5 cm per year. The Gulf of Aden has a similar problem: although it had a 10-million-year head start in ocean-forming, it is still only 500 kilometer wide. The geological advertisements promised more than has been delivered. Why this reluctance to become an ocean?

The spreading rate of the Red Sea is four times slower than the Atlantic Ocean which is one of the slower mid-oceanic spreading ridges. The North Atlantic also had a very slow start, similar to the Red Sea, but it did in the end become oceanic. There is hope. The location of the Red Sea spreading centre is a difficult one. The spreading centre is trying to push Arabia north, but this runs into immovable Asia. Iran is giving it some space by moving north (pushing up its own mountain chain in the process), and the Red Sea has been able to fill the space vacated by Iran. It also tries to push Africa south, but Africa is a very big and very deep continent and is hard to shift. The Red Sea is thus meeting stiff resistance. It is truly a titanic battle between an irresistable force and not one but two immovable continents. The going is tough.

This may in fact be an excellent example of the ‘pull’ versus ‘push’ controversy: is continental drift caused by spreading centres pushing new crust out, or by subduction zones pulling old crust in? The Red Sea has plenty of northward push, but there is little or no pull acting on Arabia, and it isn’t working well. Arabia is becoming compressed. The Ethiopian rift is working in an east-west direction, trying to push Somalia out to sea, but this is going even slower. Continents apparently drift little without help from subduction zones. For continents, push doesn’t come to shove: push without pull won’t do.

The images below depict the evolution of the rifting, starting with a reconstruction of the continental arrangement of 30 million year ago, just before the Afar plume made its appearance. It shows how the plate separated and how the spreading ridges progressed into the rifts. The final panel shows what may happen in the future, at a time when the Persian Gulf has disappeared.

Reconstruction of the Arabian plate evolution, by Bosworth et al., Journal of African Earth Sciences 43 (2005) 334–378: The Red Sea and Gulf of Aden Basins. The final panel shows the expected layout 10 million years from now. This is subject to change!

Volcanoes

During the time of the Afar plume, 26-28 million years ago, volcanic eruptions badly affected Saudi Arabia. The outpourings of flood basalts left lava fields covering large areas, which can still be seen in the landscapes inland from the Red Sea coast. Lava fields are called ‘harraat’ (singular: ‘harrah’), or ‘harrat’ if used as part of a name. This word occurs in many localities. The old ones dating from the Afar plume appearance are appropriately called the Older Harrats. Around this time the western and southern margins of the Arabian Plate were uplifted, creating what is now the Red Sea Escarpment and the mountains beyond. Volcanic activity diminished after this.

Volcanoes re-emerged 13 million years ago, perhaps in response to the collision between Iran and Asia. A series of haraats were deposited: Uwayrid, Khaybar, and Rahat, 10-12 million years ago. These are, for obvious reasons, called the Younger Harrats.The Younger Harrats are typically less than 300 meter thick. Eruptions continued along the newly formed continental edge until the present day, albeit weaker than before.

The main harraats in Saudi Arabia.
From M.Moufti et al. Journal of Asian Earth Sciences, 62, 253 (2013)

The most recent documented eruption of a volcano in Saudi Arabia was in 1256, near Medinah (known as Madinah in Arabic, which is also how it is pronounced). It came from a fissure within the extensive Harrat Rahat. The event started on June 5th with an earthquake swarm. The strongest earthquake hit 4 days later and it was followed by fountaining from a rift, only 19 kilometer southeast of Medinah. Eye witnesses, albeit paraphrased and reported 300 years later, give a vivid account of the events (from Camp et al., 1987, Bull Volcanology, 49, 489 ):
For days the volcanic eruption was preceded by many great earthquakes which occured in Madinah at the beginning of Jumad-Al-Thani (Monday 1st June 1256). At first the movements were slight and not all of the residents of Madinah town felt them. On Tuesday, the second day of Jumad Al-Thani, the earthquakes became stronger. On Wednesday, in the third part of the night, the greatest earthquake occured, which frightened the residents. The earth tremors continued throughout the rest of the night. On Friday, a major event occured, when the ground and ceiling of houses were shaken. Eighteen earthquakes were recorded during this day. […] After the main earthquake was felt in Medinah at midday, fire appeared associated with black smoke clouds which accumulated in the atmosphere. The greatest fire covered the horizon to the east of Madinah. […] The lava flow carried along its way gravel, stones and trees. It was like a red-blue boiling river, with thundering noises. The lava flow moved toward the north of Wadi Eheline. The light of the fire was seen in Makkah, Busrah, and Taima. The historians wrote that the fire continued for three months […] The lava flow descended on the rocky ground and was as high as a long spear above the ground level […] When the lava flow came to a complete stop […] it created a dam that formed a great lake in the rainy seasons (Lake Al Habas).

(The ‘third part of the night’ means the hours before sunrise, the night being divided into three parts. ‘High as a long spear’ indicates that the lava flow was a couple of meters thick.)

The eruption formed six (unnamed) scoria cones along a 2.25-kilometer rift. Over the next 52 days several lava flows extended 10 kilometers from the rift, and one much longer flow came to within 7 kilometer of the old city, within the area of the current suburbs, turning north just in time and sparing the city. About 0.5 km3 of lava was erupted. The lava is a mixture of two components, one of which had fractionated in the mantle and came up rapidly, and one which had been stored in a higher-lying magma chamber in the crust and included some crustal melt. The presence of both a magma chamber in the mantle and one in the crust is an interesting complexity.

Medinah and its 1256 lava. Source: Google earth

The 1256 flow field is located near the northern edge of the Harrat Rahat: this lava field, of which the 1256 eruption was the latest twitch, stretches from Medinah to Makkah, measuring 300 kilometers tip-to-tip, with an average width of 60 kilometers. It contains 644 scoria cones, 36 shield volcanoes and 24 domes. At times the lava flowed over the escarpment onto the coastal plain. The activity migrated north with time, and the main forcus is now south of Medinah. Future eruptions from the Harrat Rahat will probably occur in this region, and eruptions close to or within the city cannot be excluded. In fact another minor eruption occured in 641 producing several aligned cinder cones southwest of the city, lighting up the night sky.

Near the western margin of Harrat Kishb, 100 km southeast of Medinah, is the 2-km wide Wahba crater which was probably formed in a phreatic explosion. It is the largest crater of its kind in Saudi Arabia. The date is not well known but it has been estimated as 10,000 year ago, with a minimum age of 4,500 year. The crater provides a spectacular sight, but being a hole in the ground, is only visible from close-up.

Geothermal activity is also present. Hot springs with temperatures ranging from 50 to over 100 degrees occur on and off the escarpment, mainly south of Jeddah. Fumaroles are present, e.g. on Harrat Ithnayn and Harrat Khaybar, but the steam may only become visible during the coldest time of the year. More worryingly, weak fumaroles are present along a 3 kilometer line close to Medinah, coincident with occasional earthquake activity. This area is closely monitored; there is currently no indication of increasing activity.

Bedouin sources indicate that there was an eruption from one of the cones of Harrat ‘Uwayrid volcano, midway between Medinah and the Sinai, around the year 640. It is not known precisely which cone erupted and the eruption appears to have been a minor one.

Location of the 2009 swarm. Earthquakes are indicated by the yellow dots. From Koulakpov et al, Solid Earth, 5, 873–882 (2014)

In April to June 2009, in a previously seismically quiet area in Harrat Al-Shaqah(also known as Harrat Lunayyir) 150 kilometer northwest of Medina, an earthquake swarm occured similar to that in 2014 in Bardarbunga. The figure shows the distribution of the quakes, along the linear dyke: it was 20 kilometer long, and came up from more than 20 km depth at the southern end to less than 7 km at the northern end. An 8-km-long surface rupture occurred during this event, with a vertical offset of 90 cm between both sides. The 2 meter thick dyke was filled with an estimated 0.13 km3 of magma. The magma managed to get to within 2 kilometer of the surface but the last bit of crust was too rigid and it failed to break through. For a while an eruption was considered possible, and as a precaution 20,000 people were evacuated. The event happened underneath an existing lava field which may have been erupted around the year 1000.

Jabal Abyad, Jabal Bayda and Jabal Qidr form a vivid contrast

A natural marvel is the area known as the Black and White Volcanoes. It lies within Harrat Khaybar, due north of Medina. Two volcanoes here have erupted a cream-white lava, a felsic silicate called comendite. Nearby is Jabal Qidr, a dome of pitch-black basalt, a hawaiite. The division between the two lavas is stark. There are neolithic stone walls on the black volcanic slopes, and some of them have been overtopped with lava. There may have been as many as seven eruptions since people started building the walls, and Jabal Qidr may have erupted as recently as the year 1800. The two white mountains, Jabal Abyad, at 2,093 meters and Jabal Bayda at 1,913 meters, are the two highest volcanoes of Saudi Arabia. (Both words mean ‘white mountain’, one with the female and one with the male adjective.) The pairing would have been a wonder of the world, but it is in an isolated and desolate region, difficult to reach. The contrasting lavas have come from a single magma chamber in the crust underneath, which is extremely stratified.

No less wondrous are the gems found in the area. Beautiful peridots, a form of olivine, are embedded in the basaltic harraats. The peridots from this region are of a pure green, a precious colour in the desert: the peridots are highly valued. The most recent find was in Harrat Kishb.

The rift itself, now deep below the sea, is also volcanically active. A number of volcanic islands have formed within the Red Sea, near the Afar triple point. On 30 Sept 2007 there was an eruption midway between both Red Sea coasts, on the small island of Jabal al-Tair. In 2011 and 2013 there were Surtseyan-type, submarine eruptions in the Zubair group of islands, further south along the coast of Yemen towards Djibouti, where new islands emerged from the sea. Volcanic activity further north along the younger Red Sea spreading centre is much less, although there are deep hydrothermal vents. There is no sign that the extensive flood basalt activity prior to the opening of the Red Sea will one day resume. Lesser, intermittent activity remains common, however.

Underground

The potentially active volcanoes within Saudi Arabia are offset from the Red Sea spreading centre by about 100-150 kilometers. One can speculate why this is. Around Medinah, the oldest lava fields are 2 million years old, but these are in almost the same location as the new activity. Over that time, the Arabian plate has moved by perhaps 50 kilometer due to the widening of the Red Sea. The volcanoes have moved with the plate. This means that the magma is located in the continental plate and does not come from the oceanic Red Sea spreading centre. The felsic lavas confirm that the magma has been stored in the crust and is not currently coming directly from the mantle, but the predominant lava is still basaltic, i.e. originally derived from the mantle.

The magmatic activity may be due to local crustal extension. Alternatively, the magma may have been emplaced at the start of the seafloor spreading, but this begs the question what kept it from cooling. A sub-crustal flow of magma from the triple point has also been suggested, but the level of activity does not seem to decline with distance from Afar which argues against it. Crustal extension therefore seems most plausible. Especially the northern-most Red Sea does not yet have an active spreading centre, and without new oceanic crust being formed, the movement of the Arabian Plate has to be accommodated by the crust, leaving a line of weakness around Medina.

An interesting suggestion is that the line of the Younger Harrats, which is under a slightly different angle to that of the Red Sea, is a separate rifting event. There seems little direct support for this, but if this is correct we may end up with two parallel oceans, separated by a sliver of Arabia.

State of the nation

At the current time, volcanic eruptions in Saudi Arabia tend to be minor to medium in size. Several eruptions were reported about a millennium ago but there has been little activity since 1256. In the empty desert, more recent eruptions may have been missed. An eruption in the near future is not unlikely. Although it would probably not be a large event, Saudi Arabia could still be supplementing its oil with liquid rock. Just remember the word ‘harrat’.

/ Albert
With thanks to Samira Alharbi

http://www.volcanocafe.org/volcanoes-of-saudi-arabia/

So in a few million years Arabia and the Iranian plateau will border each other directly and there will be no Gulf!

When impacting each other (the two landmasses) this will likely create significant mountain ranges.

At least the Red Sea will become bigger and wider!

 

[Saif al-Arab]

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.

http://www.sgs.org.sa/English/Earthquakes/Pages/Volcanoes.aspx

@Full Moon @Saudi Typhoon @Bubblegum Crisis @Frosty @KTOOOOM @الأعرابي @The SC @Alithemoor1 etc.

 

[Saif al-Arab]

PHOTOS: A volcanic mountain in the middle of Red Sea in Saudi Arabia

The island is visited by many tourists who have to take a boat to reach it. (Supplied)

Mohamed al-Harby, Al Arabiya.net
Monday, 8 January 2018


An island alongide an island in the middle of the Red Sea on the Saudi Arabian side exists within the blue waves of the ocean right across from al-Qahmah beach in the Asir region, southwest of Saudi Arabia.

The island is visited by many tourists who have to take a boat to reach it. It is also considered a volcanic mountainous island which is covered in sand and rocks with little greenery, and a 360-degree view of the ocean.

The island attracts hunting enthusiasts, who hunt birds including pigeons and eagles which can be found around the island.

It is also believed that 11 ancient cemeteries were built there.

These pictures were taken by photographer Adel Asiri who documented different areas of the island and the surrounding sea.

Last Update: Monday, 8 January 2018 KSA 15:07 - GMT 12:07

http://english.alarabiya.net/en/lif...ntain-amidst-the-Red-Sea-in-Saudi-Arabia.html

 

[Fledgingwings]

I never thought the arabian lands filled with so many wonders.A very good job you,re doing posting such stuff.helping me learn alot more about this part of the world I wish to see atleast once more.

 

[Saif al-Arab]

Incredible video.

I never thought the arabian lands filled with so many wonders.A very good job you,re doing posting such stuff.helping me learn alot more about this part of the world I wish to see atleast once more.

I wish that I could say that I have covered more than 1% of the wonder that is Arabia but I would be dishonest if I claimed so. God was very generous.

My pleasure brother and you will always be welcome back again.

 

[Fledgingwings]

I wish that I could say that I have covered more than 1% of the wonder that is Arabia but I would be dishonest if I claimed so. God was very generous.

My pleasure brother and you will always be welcome back again.

You,re right ! Infact Allah Almighty chose this land I am sure for a very good reason which he knows best.And thanks I hope that day will come soon.

 

[ArabianEmpires&Caliphates]

Amazing.

 

[HAIDER]

Written and photographed by Peter Harrigan

Above: The harrah near Madinah has been active for more than two million years, explains Mohammed-Rashad Moufti, a consultant to the Saudi Geological Survey (SGS). Below: This small dam was broken by an earthquake along one of the several faults that run through the harraat.

“During my stay, I remember to have once made the observation to my cicerone, in going with him to Jebel Ohod, that the country appeared as if all burnt by fire; but I received an unmeaning reply; no hint or observation afterwards in the town which could lead me to suppose that I was near so interesting a phenomenon of nature.” It was not until his arrival in Cairo that Burckhardt discovered a written account referring to the eruption.

With the exception of Charles Doughty’s description (see “‘A Titanic Desolation’” below), European references to volcanic Arabia are few and far between. Even since the founding of Saudi Arabia in 1932, the focus on oil in the sedimentary Eastern Province and the stereotype of sand-and-gravel deserts have left largely neglected the volcanic aspects of the Arabian Shield, the geological name for much of the western Arabian Peninsula. It was not until recent years that the scientific and economic significance of this geology began to be recognized and understood.

Western Saudi Arabia is in fact covered not only with sand, but also with vast fields of lava. In Arabic, these lava fields are known as harraat. (The singular is harrah; before a name, it is harrat.) Some dozen named harraat in Saudi Arabia together form one of Earth’s largest alkali basalt regions, covering some 180,000 square kilometers (nearly 70,000 sq mi), an area greater than the state of Missouri.

After the evening prayer, according to one account quoted by Johann Ludwig Burck hardt, “a fire burst out in the direction of al-Hijaz; it resembled a vast city with a turreted and battlemented fort, in which men appeared drawing the flame about, as it were, whilst it roared, burned and melted like a sea everything that came in its way. Presently a red and bluish stream, bursting from it, ran close to al-Madinah, and at the same time the city was fanned by a cooling zephyr from the same direction.”

The eruption lasted for 52 days. At its fiery zenith those further afield also witnessed strange sights, with reports of the light of the eruption visible in Makkah and Tayma’, six days’ journey from Madinah. Historians relate that the depth of the lava flow was a long spear’s length, around three meters (10'), and that it flowed like a red-blue boiling river, carrying in its way gravels, stones and trees, with thundering noises. Al-Qastalani asserts that the fire was so fierce that no one could approach within two arrow flights, and that at night “the brilliant light of the volcano made the face of the country as bright as day; and the interior of the harim (the sacred area of the city) was as if the sun shone upon it.” The governor and citizens prayed for the safety of the city, and as the lava inexorably approached, many, including women and children, wept and prayed around the Prophet’s tomb. Then, the lava current turned north, and the city was spared.



Mohammed-Rashad Moufti holds Saudi Arabia’s first—and so far only—doctoral degree in volcanology. He has devoted 20 years to studying and promoting awareness of the lava field near Madinah, which is known as Harrat Rahat.

“The eruption that threatened the Holy City happened very recently in geological time, and it overlaid previous lava flows. It’s known as the historic lava flow because we have recorded accounts. Volcanism first occurred on this part of the harrah two million years ago and has remained active,” explains Moufti to a group of German and Saudi visitors who stand on the fissure site. They have come as guests of the Saudi Geological Survey (SGS), which has mapped the volcanic features and pioneered geo-tours to the volcanic fields.

Moufti explains that Harrat Rahat is twice the area of Lebanon. Its pond of 2000 cubic kilometers (480 cu mi) of basalt lava stretches 310 kilometers (190 mi) from the southern outskirts of Madinah to the suburbs of Jiddah, where there are other flows that date back 10 million years. The main body of the flow measures 75 kilometers (46 mi) east to west, and lava tongues run a further 75 kilometers westward where molten basalt flowed along wadis, or valleys, broke through the 1500-meter-high (nearly 5000') mountains of the Red Sea escarpment and fanned out in dendritic tentacles across the Peninsula’s coastal plain.

Satellite and aerial photographs reveal the extent of this single harrah and the variety of volcanic features strewn across its desolate, often trackless landscape of variegated flows. Satellite images from nearly 500 kilometers’ (300 mi) altitude reveal the different colors of magma extruded in past epochs: Jet-black indicates the most recent flows, while rust-red indicates surface exposure and erosion over millions of years. White areas—with one remarkable exception—reveal by-product features known as qi‘aan (singular: qa‘)—flat expanses of silt and salt and other residue laid down after lava flows blocked watercourses to form seasonal lakes. Other sand and silt areas, deposited in craters, appear as white dots and speckles from a satellite or, from lower altitudes, as more artful shapes set within often perfectly circular crater rims. A dark crater floor lacking silt or sand may be the result of more recent, even historic, volcanic activity.

A Neolithic relic that hunters may have used to guide prey across the harrah and into a corral.

Spread across the harraat is a host of textbook geological features: scoria (cinder), spatter and tuff cones; smooth and ropy pahoehoe, sharp and broken a’a and pyroclastic flows; shield volcanoes; fumaroles; trachyte and comendite domes; eroded feeder necks; craters; fissures; vesiculated lapilli and other forms of basalt bombs; whaleback lava flows; maar craters and one stratovolcano. Some, like the maar craters—circular landforms created by explosive ash eruptions—are huge: A massive steam explosion, generated by the meeting of molten basaltic magma with subterranean water, created the spectacular maar crater of al-Wahbah on the western margins of Harrat Kashib. Some of the most distinctive volcanic scenery and geology in all of Arabia is on Harrat Khaybar, where the circular white cones of Jabal Bayda’ and Jabal Abyad look from the air like snow-capped mountains. (Both names mean “white,” one in the feminine form, the other in the masculine.)

Thamer al-Khiary is a former geological engineer with the SGS who now, with the support of the agency, leads private tours into the volcanic areas. “It’s a thrill to take visitors over an apparently flat landscape and see their faces when they climb a gentle slope that breaks unexpectedly into a vast explosion crater beneath, or lead families up a scoria cone to discover at the summit a perfect rim and crater below. Our greatest thrill is to spend the night in a crater and see the inner walls sparkle with minerals in the moonlight,” says al-Khiary. At 31, wearing a polo shirt with desert-motif logo, trekking shoes and slacks and wraparound sunglasses, he looks every bit the adventure-tour guide. “What’s remarkable is that so many people have no idea that these features exist, even though they live nearby and drive past some of them on the highway.”

MAPPING SPECIALISTS

Moufti recalls hiking into remote areas of Harrat Rahat 20 years ago with his visiting professor. “Like other geologists, he was astonished at the complexity and extent of volcanic Arabia. I remember climbing a volcanic cone, my professor wearing a battered hat and smoking a pipe. When we reached the rim and looked down to the flat crater floor, there was a Bedouin girl grazing livestock there. I don’t know who was the most surprised!”

Such idyllic scenes belie a charged, daunting and even threatened environment, for Madinah’s was not the only eruption in historic times in Arabia. In the 1970’s, the search for non-petroleum mineral resources became an impetus for surveys of harraat. The current president of the SGS, Mohammed Assad Tawfiq, was then chief geologist of the Directorate General of Mineral Resources (DGMR). Tawfiq remembered stories of the harraat from his school days in Madinah, and he deployed his team to the lava fields as part of a mapping initiative that involved hundreds of international geologists and a fleet of helicopters and other aircraft.



Top: A scoria (cinder) cone in the Hayil region rises from the desert floor. Bottom: Al-Wahbah crater, nearly two kilmoeters (1.2 mi) wide, is a maar crater, formed not by volcanic eruption but by the collision of rising volcanic material with an underground body of water, resulting in a colossal release of steam—an event geologists call a phreatic explosion.

His studies of the Madinah eruption revealed evidence of magma mixing with simultaneous extrusions of three types of basaltic lava, which demonstrated the complexity of the harrah’s subterranean “plumbing” systems. The findings, published in 1987, threw intriguing light on the relationship of tectonic forces to the harraat, for the control mechanisms at work, it turned out, are not—as most people assumed —directly related to the continental rift valleys of the Red Sea.

Above: Maher Idris, assistant president of the SGS, holds loose volcanic cinders. Along with monitoring of "geohazards"—earthquakes are riskier than volcanos, he points out—the job of the SHS is to "effectively balance exploitation with the need for geo-conservation." Below: A crater inside a large scoria cone.

The most recent eruptions on the Arabian Peninsula occurred in 1937, on a harrah near the town of Dhamar, in the north of Yemen. Before that, in 1846 an eruption took place on the volcanic Red Sea island of Saddle in the Zubair Islands, 90 kilometers (55 mi) northwest of the Yemeni port of Hodaida. Casting farther back—into the Neolithic period on the Arabian Peninsula—there is evidence of eruptions and lava flows that date to roughly 4500 BC. On Harrat Khaybar, satellite imagery has revealed at least seven post-Neolithic eruption sites and eight historic eruptions, the most spectacular from Jabal Qidr. That daunting black basaltic cone rises 322 meters (more than 1000') above a 1700-meter-high (5525') central platform; its sides sweep symmetrically up to 30-degree slopes that top out at a red-oxidized crater 400 meters (1300') in diameter. A field of ash roughly a meter (39") thick fans out more than 20 kilometers (12 mi) eastward from the crater, revealing that westerly winds predominated during the eruption. (Vague historic reports point to the likelihood that Jabal Qidr erupted as recently as about 1800, but such is the remoteness of the region, the paucity of records and the uncertainty regarding previously used local names that there is no definitive account.)

In the same area, a historic pahoehoe lava flow partially buries kite-shaped Neolithic stone fences that were probably constructed as animal traps. There is also abundant archeological evidence of Neolithic communities over the harraat of Rahat and Khaybar, where thousands of tumuli and stone fences, keyhole-shaped, kite-shaped and circular, cover extensive areas. By counting the number of vents and eruptions that have occurred on northern Harrat Rahat, volcanologists estimate that, during the past 4500 years, there have been 13 major eruptions—one every 346 years, on average.

Farther still into the past, on Harrat al-Birk, south of Jiddah on the Tihama plain near the Red Sea, lava covers gravel terraces in which archeologists have found Acheulian stone tools that date the eruption back some half-million years to Lower Paleolithic times. Much older than this, the earliest harraat of all date as early as 13 million years ago, isotopic dating suggests.

When it comes to English descriptions of the volcanic features of the Arabian Peninsula, none are more evocative than those of Charles Montague Doughty, whose finely observed account of his 22-month journey through central and northwestern Arabia, Travels in Arabia Deserta, was first published in 1888. Setting out in November 1876, Doughty skirted and crisscrossed the harraat of Kura, al-‘Uwayrid, Khaybar, Ithnayn and Rahat, and in doing so became one of the few Europeans to have ventured onto them.“In the train of the Harras we see a spectacle of the old volcanic violence that tormented this border of the Arabian peninsula,” wrote Doughty. “I have followed these Harras almost to Makkah; that is through nearly seven degrees of latitude.” Doughty came well-equipped, for he had studied geology at Cambridge, and he was fascinated with the emerging earth sciences of the day. In 1872 he had stood before the eruption of Vesuvius at perilously close quarters. Aptly, he places this description of the Italian eruption in the midst of his account of traversing the cinder-cone and lava wilderness of Harrat al-‘Uwayrid.

It was in Harrat al-‘Uwayrid that Doughty spent the summer of 1877 living with the Moahib Bedouin, and his account of his sojourn with them on the elemental lava fields in “high tempered air” is among the most memorable passages in the book: “This Titanic desolation, seeming in our eyes as if it could not bear life, is good Beduin ground and heritage of the bold Moahib Abu Shamah,” he wrote. “In this difficult volcanic country, their small cattle can be seldom robbed; and milk of the flocks is in less scarcity among them, which is the health and wealth of the poor nomads.”

Travel across the harraat, “more often a vast bed and banks of rusty and basaltic bluish blocks,” was a formidable task: “Because of this cumber of stones and sharp cutting lavas, the Harra country is hard to pass, out of the paths, for any other than Harra-bred camels. The heavy poised stones sliding and toppling to the tread, the herdsmen’s feet are oftentimes sorely bruised; of which, and because the stones are as glowing coals in the summer sun, the Beduin hinds in the Harra commonly sit all day upon the croups of their browsing camels.”

In addition to mapping and describing topographic and geological formations, Doughty observed Bedouin life and natural features and their relationship with the volcanic landscape. He described sulphurous warm springs issuing from basalt near Khaybar and herds of gazelle “robust and nearly of the colour of basalt,” unlike the lighter-colored varieties of the desert plains.

>“We removed again, and when we encamped, I looked round from a rising ground, and numbered forty crater hills within our horizon; I went out to visit the nighest of them. To go a mile’s way is weariness, over the sharp lava field and beds of wild vulcanic blocks and stones. I passed in haste, before any friendly person could recall me; so I came to a cone and crater of the smallest here seen, 300 feet in height, of erupted matter, pumice and light rusty cinders, with many sharp ledges of lava. The hill-side was guttered down by the few yearly showers in long ages. I climbed and entered the crater. Within were sharp walls of slaggy lava, the further part broken down—that was before the bore of out-flowing lavas—and encrusted by the fiery blast of the eruption. Upon the flanks of that hill, I found a block of red granite, cast up from the head of some Plutonic vein, in the deep of the mountain.”

Travels in Arabia Deserta, however, failed to impress England’s scientific establishment. The chairman of the Royal Geographical Society, Sir Henry Rawlinson, dismissed Doughty as competent with neither pen nor hammer. But The Times of London (April 6, 1888) was more generous: “Mr. Doughty’s contribution to the geology of Arabia and its wonderful volcanic remains is in itself of great value.” Today, his 600,000-word tome is a classic. The National Geographical Society lists it as one of the 100 great adventure books of all time, and scholarly journals still cite his observations.
CHARLES M. DOUGHTY TRAVELS IN ARABIA DESERTA (BONI & LIVERIGHT, 1921)

Given the Peninsula’s violent geological history, Maher Idris, assistant president of the Saudi Geological Survey, is responsible for identifying “geohazards.” Earthquakes, not volcanoes, are the most significant geohazard in Saudi Arabia, Idris explains. Until recently, seismic monitoring was carried out by several governmental bodies, but in 2004 all monitoring was consolidated under the SGS.

“There is a long history in Arabia of volcanoes and earthquakes, but no real comprehensive record of activity, so we have really just started,” says Idris. Although most seismic monitoring stations are located on the Arabian Shield, the country will soon be operating nearly 150 stations and pooling data and expertise with Yemen and Egypt.

Idris explains that, apart from submarine activity below the Red Sea, there are also active rifting regions in the northwest of the Peninsula, around the city of Tabuk and the Gulf of Aqaba, and in the southwest near the border with Yemen. (The Aqaba earthquake of 1995, which caused widespread destruction, measured 7.3 on the Richter scale).

“The Madinah area has a volcanic history, with hundreds of related shallow shocks occurring daily, ranging from magnitude one to three, and occasionally four, on the Richter scale,” he says. “We have established a network of seismic monitoring stations around the city,” and the SGS runs educational programs for communities and trains civil-defense teams in preparedness for both earthquakes and volcanic eruptions.

Opportunities interest Idris as much as hazards, and while talking of the harraat regions he’s also keen on geo-conservation, scientific investigations and the economic development of natural-resource prospects. “This is a world-class geological stage for Saudi and foreign visitors and scientists, and we want them to come and see these treasures,” he says, adding that identification of geo-sites parallels an international geo-parks program, sponsored by the United Nations Educational, Scientific and Cultural Organization, in which the SGS participates.

“We’ve already identified seven sites in the Madinah area,” says Idris. “The local people are often surprised and amazed to realize the complexity and nature of the volcanic features they live so near. We have over 400 vents and craters in the Madinah area and more than 2000 scoria cones on our harraat.”

Scoria cones, made of porous, cinder-like lava, now attract not only visitors and scientists, but also investors eying the abundant, easily extractable lightweight aggregate. It turns out that the cones’ pyroclastic material, aside from being easily accessible on the surface, has excellent thermal and acoustic insulating properties, making it well-suited for the manufacture of lightweight blocks for construction of high-rise and—ironically—earthquake-proof buildings. Volcanic materials also provide ingredients for high-quality basaltic “wool,” lightweight cement and bricks. The SGS estimates the commercial value of the aggregate on just one scoria cone might exceed $250 million over 30 years.

The ash crater of Jabal Bayda' ("White Mountain") contrasts so starkly with the surrounding landscape that from a distance it has been mistaken for a snow-capped peak. It has a smaller but taller neighbor, Jabal Abyad (not shown), that is also bright white.
SAUDI GEOLOGICAL SURVERY
The cinders have consumer uses as well: Glowing a pleasant red at 1000 degrees centigrade, volcanic cinders are ideal for lining gas barbecues. As firewood becomes more scarce in the region, kebab restaurants and grills increasingly turn to volcanic stone placed over gas fires. (Curiously, because most people are unaware of the almost unlimited local availability of this material, the stone most commonly used in Saudi Arabian grills is imported from Iceland—giving rise to a local saw equivalent to “carrying coals to Newcastle.”) Medium-sized granules of lava, with good porosity and water-retaining properties, also provide useful horticultural material ideal for arid regions. The SGS office and laboratory complex in Jiddah has healthy trees bedded in cinders that retain water. Yet this knowledge, too, is new: Most Saudi garden suppliers still import the material from Italy. Idris notes also that while the SGS coordinates exploration for mining, it also monitors undesirable environmental side effects. Open excavation of one scoria cone facing the highway linking Makkah and Madinah has already left an unsightly scar; elsewhere, illegal mining and quarrying are creating other eyesores. “Our challenge is to effectively balance exploitation with the need for geo-conservation,” says Idris.

Exploitation of resources on the harraat stems from the surveys of the 1970’s. With technical assistance from the United States Geological Survey (USGS) and the French Bureau de Recherches Géologiques et Minières, the early focus was on the country’s high-value mineral prospects—particularly gold, silver, zinc and lead.

John Roobol is a volcanologist and an advisor to the SGS who has worked in Saudi Arabia since those days, and he has helped survey and map many harraat regions. “This initial phase of extensive geological mapping brought together one of the largest-ever assemblies of geologists in one territory, involving specialists from France, Japan, Germany, Great Britain, Austria, Canada and the United States,” he says. “This was one of the last great challenges left: a pristine chunk of planet Earth with superb exposure, unknown and unmapped. It was a real opportunity and privilege to be part of the effort: This was total geology.”

Top left: Mapping the harraat was "one of the last great challenges left on earth," says volcanologist and SGS advisor John Roobol. "This was total geology." Here, he shows a basalt "bomb" that was ejected during an eruption. Bottom left: This and other lava-tube openings may have counterparts on Mars that could shelter future explorers and give insight into Martian geology. Right: Fissures make walking on harraat difficult and hazardous.
SAUDI GEOLOGICAL SURVEY

The harraat mapping project, under Mohammed Tawfiq of the DGMR, lasted from 1983 to 1991, and for it Roobol and US volcanologist Victor Camp flew hundreds of helicopter hours, surveying from the air and landing on otherwise inaccessible lava fields to take samples. They also made photogeologic interpretations of aerial photographs and satellite imagery. The result was a series of detailed (1:250,000) geological maps and explanatory notes, as well as papers in the international scientific literature covering three of the largest Cenozoic lava fields: Harrat Rahat, Harrat Kashib and the coalesced harraat of Khaybar, Ithnayn and Kura.

“The mapping of the harraat was a surprising success,” recalls Roobol. “Until then they were largely places where no one wanted to go, and at the international level people simply did not know there were such extensive lava fields here. We attended a conference in New Zealand and scientists were surprised. They asked what these poorly known lava fields were doing there, as they were not expected according to new plate-tectonic theories.”

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