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The Sabbatical Year Quakes were a pair of earthquakes which appear to have struck less than 16 hours apart starting on the night of the 16th, 17th, or 18th of January in 749 CE.
  • The Holy Desert Quake struck first - at night. It devastated villages around the Sea of Galilee, Bet She'an, sites east of the Jordan River Valley and the Israeli Coastal Plain. It was felt in the Nile Delta but does not appear to have caused permanent damage or led to significant casualties there. In Jerusalem, Al Aqsa Mosque was damaged and there are reports that monasteries east of Jerusalem collapsed. A tsunami appears to have struck Caesarea due to offshore shelf collapse.
  • The Talking Mule Quake struck in the middle of the morning of the following day and affected Northern Syria and Jazira. There are reports of a church collapse, casualties, and wall collapses in Menbij (aka Mabbug) in northern Syria, a translational landslide in an unspecified location, and earth fissures and sand boils in Jazira.
The key to understanding these two earthquakes lies with Pseudo-Dionysius of Tell-Mahre, our only local and contemporaneous source, who was living close to where the Talking Mule Quake struck He wrote about both earthquakes in a morality tale about a Priest and his flock of parishioners. In Menbij, a distant earthquake induced rumble was felt and heard in the night. The rumble came from the far off Holy Desert Quake. A village priest, thinking earthquakes were caused by man's sins, told his parishioners to show up the next morning to march to a church to pray for forgiveness. It took some time to march to the church which is described as being outside of town. Once there, a service was initiated and, during the service, the Talking Mule Quake struck and the church collapsed. This happened around ten in the morning. The Priest and everyone inside the church died. Michael the Syrian and the anonymous author of Chronicon 1234, writing ~550 years after the earthquake, added that there was widespread destruction in Menbij with many casualties, other church collapses, and fallen walls. Neither of these two later authors specified their source but their information likely came from Theophilus of Edessa and his lost Chronicle. Theophilus was in his 50's and probably living in the area where the Talking Mule Quake struck.

Theophilus was probably also the primary source for the Byzantine accounts written in Greek and Latin. Collectively, the Byzantine authors wrote about both earthquakes but transposed the timing of the Talking Mule Quake into the Holy Desert Quake. Rather than stating that the Holy Desert Quake struck at night, they said it struck in the morning - around 10 am. Evidence that it struck at night comes from several sources. Severus Ibn al-Muqaffa translated into Arabic a Coptic language biography which was written in the first person and told of a nighttime earthquake which was felt in the Nile delta and caused widespread death and destruction from Gaza to Persia. Mujir ad-Din accessed three accounts, two written in the first person, telling how the Al Aqsa mosque in Jerusalem was damaged at night by what appears to be the Holy Desert Quake. In Pella, skeletons of humans and animals were found in a house where all seemed to be in for the night - sleeping - when an earthquake struck, collapsed their home and led to a devastating fire. All three of these locations could have experienced such shaking from the Holy Desert Quake - centered more or less in the Sea of Galilee. They could not have experienced such shaking from an earthquake with an epicenter in Northern Syria (e.g. around Menbij). The Holy Desert Quake struck at night.

How the Byzantine sources transposed their accounts will be explained in a bit but first I am going to introduce a few more clues which help establish the year that the Holy Desert struck - 749 CE - and the approximate date - 17 January.
  • As reported by Tsafrir and Foerster (1992b), when the Holy Desert Quake struck Bet She'an, it collapsed a number of small shops including one with a hoard of gold dinars. The youngest coin in the hoard was minted in A.H. 131 (31 August 748 -19 August 749) and was in near mint condition indicating that it had barely circulated. Thus, the Holy Desert Earthquake must have struck in A.H. 131 or later - probably in A.H. 131.
  • A book of Jewish prayers found in the Cairo Geniza spoke of a fast day on the 23rd of Shevat commemorating a day when many cities collapsed and people died. The Jewish Piyyut Ra‘ash Shvi’it appears to describe the same earthquake while mentioning destruction in Tiberias and flooding in the plain of Sharon. These locations indicate that both texts refer to the Holy Desert Quake.
  • Theophanes, one of the earliest Byzantine sources, wrote about two earthquakes. He specified that the first one - the Holy Desert Quake - struck on the 18th of January.
  • 23 Shevat and 18 January only coincide during 749 CE. During other years (e.g. 746-762 CE), they do not fall on the same day. This indicates that the Holy Desert Quake struck in 749 CE - in January - a date which is compatible with the coin evidence from Bet She'an.
  • Since the Jewish day starts at sundown, the 23 Shevat nighttime Holy Desert Quake could have struck on the night of 17 January or early in the morning on 18 January of 749 CE.
At this point, it probably should be mentioned that our Coptic source Al-Muqaffa reports that the Holy Desert earthquake struck a day earlier - on 16 January. Although this means that everything will not tie up into a neat little bag, we should not lose sight of the fact that three independent sources and traditions have triangulated the Holy Desert Quake to 17 January 749 CE plus or minus a day and two eyewitness accounts, one contemporaneous account, and archaeoseismic evidence from Pella all tell us that it struck at night.

Collectively, the Byzantine authors wrote about two earthquakes separated by three years. But their year for the Holy Desert Quake is too low. They say it struck in January 746 CE. However, we know from that gold dinar in Bet She'an it could not have struck before A.H. 131 (31 August 748 -19 August 749). They also specified the wrong time. They say it struck at 10 am when all the other evidence says that it struck at night. Pseudo-Dionysius of Tell-Mahre captured the correct timing. After the Holy Desert Quake struck at night and gave Menbij a little shake, the Talking Mule Quake struck the next morning around at ~10 am. So, why did they make such mistakes ? The answer is that it is likely that their source made the mistake.

None of the Byzantine authors lived in the region. They wrote from Italy or Constantinople. This means that they must have relied on a local source. Textual scholars often refer to this source as the Eastern source. This hypothesized source is used to explain how Theophanes, the most prominent among them, got his information about events in muslim controlled lands. Because none of the Byzantine authors wrote or read Syriac and they all read Greek, their source had to be written in Greek. This meant that their source was likely Melkite - a Christian faction of the time. The Melkites wrote in Greek and Syriac and after civil unrest led to the dissolution of Melkite monasteries in Palestine and Syria, a number of Melkite Monks ended up in Constantinople in 813 CE while Theophanes was writing his Chronicle (Brooks, 1906:587). The eastern source was probably penned in a Melkite monastery. It probably also had more than one author, it was likely edited, and it was probably also redacted - i.e. the editor rewrote passages from his sources as he saw fit.

Literary criticism of Theophanes' work suggests that the eastern source was completed shortly after 780 CE and covered events up to this date. Two authors whose works are now lost have been proposed as promising candidates in providing source material - John son of Samuel of whom nothing is known beyond that he lived in Western Syria and Theophilus of Edessa. John’s Chronicle is thought to have ended in 746 CE ( supposedly). It is not known when Theophilus wrote his Lost Chronicle but it was surely before he died in 785 CE.

A possible way the Byzantine accounts transposed the time of the Talking Mule Quake into the time of the Holy Desert Quake will be explained using a hypothetical scenario below:
  • The first author of the ‘eastern source’ was a Monk living in the vicinity of Palestine. He wrote about the Holy Desert Quake. Then he died.
  • Many years later, another monk took this book, added events to it for ~30 years after the first Monk died, and edited the original text. He added an earthquake account from Theophilus of Edessa. This left two earthquake accounts in the book – the Holy Desert Quake originally written by the ~Palestinian author and the Talking Mule Quake written by Theophilus.
  • Theophilus, like everyone else at the time, thought that there was one big earthquake. Since Theophilus experienced the Talking Mule Quake in the north he reported that the earthquake struck at 10 am.
  • Because Theophilus included reports of seismic damage in Palestine, the editor of the ‘eastern source’ rewrote the original passage of the Holy Desert Quake to say that it struck on January 18 at 10 am. He may have also created confusion in his editing.
A final summary is detailed below:
  • A massive nighttime earthquake was reported by Coptic sources from the Nile Delta. Damage was reported from Gaza to Persia. One of the Coptic sources is written in the first person and purports to present eyewitness testimony.
  • The Dead Sea Transform is segmented and cannot produce such a large earthquake from one fault break alone. There had to have been more than one earthquake.
  • The Byzantine accounts are a chronological mess. They relied on a report from the region which historical and textual scholars call the 'eastern source'. This hypothetical document is used to explain how the Byzantine authors sourced their information.
  • The Byzantines accounts speak of two earthquakes. They are given names below
    • The Holy Desert Quake in the south
    • The Talking Mule Quake in the north
  • A coin found beneath seismic rubble in Bet She’an dates the Holy Desert Quake to A.H. 131 (31 August 748 - 19 August 749 CE) or later – probably in A.H. 131. The coin was in near mint condition indicating that it had barely circulated.
  • There are other chronological clues in the texts – e.g., dates
    • 16 January from Coptic accounts
    • 17/18 January from Jewish accounts - but only for the year 749 CE
    • 18 January from the Byzantine accounts
  • The Byzantine accounts also say that the Holy Desert Quake struck at 10 am
  • The date from the Jewish sources and the coin from Bet She’an tell us that the Holy Desert Quake struck in 749 CE.
  • Pseudo-Dionysius of Tell-Mahre, our only contemporaneous source, records that two earthquakes were experienced in Menbig in Northern Syria – a nighttime earthquake which was so far away it did no damage (the Holy Desert Quake) and a mid-morning earthquake that collapsed buildings and killed people (the Talking Mule Quake).
  • Although the Byzantine accounts said that the Holy Desert Quake struck at 10 am, it struck at night. We know this from our Coptic sources in Egypt and a Muslim source (Mujir ad-Din) which presents what is purported to be eyewitness testimony from Jerusalem. It is the Talking Mule Quake which struck at 10 am.
  • In summary, the Holy Desert Quake struck first - at night. The Talking Mule Quake struck the next morning. In Egypt they thought it was one big nighttime earthquake. In Northern Syria, they (e.g., Theophilus) thought it was one big day time earthquake.
  • Later accounts in Michael the Syrian and Chronicon Ad Annum 1234 got much of their information from Theophilus and wrote about one big earthquake. They did not specify whether it struck in the daytime or the nighttime.
  • Muslim sources wrote about earthquakes which struck Jerusalem and Damascus in A.H. 130 or A.H. 131. A.H. 131 is the correct date. The A.H. 130 date may reflect a less well reported earthquake in this sequence. After all, Elias of Nisibis and Cedrenus both said it was a time of many earthquakes.