5 - Dating the Seismites

The water level of the Dead Sea has been dropping rapidly for the past 50 years or so. As of 2023, the Dead Sea is dropping well over 1 meter (~3 + feet) per year. As the Dead Sea level drops, what was formerly underwater has been exposed and subject to erosion. Because the Dead Sea bottom sediments are relatively soft, they erode quickly leaving many gullies and sinkholes on the shores. These gullies and sinkholes give Geologists direct access to sediments deposited thousands of years ago. The exposed sediments contain a wealth of information about the earthquake and climate history of the region. Three sites on the western shores of the Dead Sea have been studied in detail - En Feshka, En Gedi, and Nahal Ze’elim. At each site, pieces of burned wood found in the layers were sent to the lab for Carbon dating. Carbon Dating gives us our first understanding of the age of the sediments from the top to the bottom of the outcrop. After doing carbon dating, we find anchor earthquakes. Anchor earthquakes are historically documented earthquakes that deformed the sediments in the Dead Sea. The historical documentation means we know the date when the earthquakes occurred. Two useful anchor earthquakes are the Josephus Quake of 31 BC and the 1293 AD Quake.

The 31 BC Josephus Quake is a useful chronological anchor to help date the Jerusalem Quake. It is observed throughout the Dead Sea including at the three well studied sites of En Feshka, En Gedi, and Nahal Ze’elim. The Jerusalem Quake seismite is also present at these sites. So, the challenge is to use what we know about the date of the Crucifixion (Good Friday between 26 and 36 AD) with what we can read from the sediments to determine if the earthquake in the sediments, the Jerusalem Quake, matches with the story.