Historic volcanic activity around Al Madinah

 
Oldest lavas near Al Madinah

2 Million years

1st Historic eruption

641 AD (20 AH)

2nd Historic eruption continued  for 52 days

1256 AD (654 AH)

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
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  • Volcanic cones and historic lava field in northern Harrat Rahat near Al Madinah
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  • Volcanologist Dr. M.J. Roobol explains the origins of a ground fissure and volcanic cones in northern Harrat Rahat
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  • A large ground fissure associated with volcanism in northern Harrat Rahat near Al Madinah
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  • Lava tube, volcanic cones in northern Harrat Rahat, near the area of the historic lava flow
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 Source: Saudi Geological Survey

 

  Harrat Khaybar

 The Madinah Erruption

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.
Source: Aramco Worl

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Harrat Khaybar, Saudi Arabia lies in the western half of the Arabian peninsula and contains not only large expanses of sand and gravel, but also extensive lava fields known as haraat (harrat for a named field). According to scientists, the volcanic field was formed by eruptions along a long north-south linear vent system over the past 5 million years; the most recent recorded eruption took place between 600-700 A.D.

 

The presence of tuff cones - formed by eruption of lava in the presence of water together with other volcanic features indicative of water - in the Harrat Khaybar suggest that the local climate was much wetter during some periods of volcanic activity. Today, however, the regional climate is hyperarid - little to no yearly precipitation - leading to an almost total lack of vegetation.

 

The image was taken by the Expedition 16 crew aboard the Inernational Space Station in March 2008.

 

Image Credit: NASA