BIBLE HISTORY DAILY

Measuring Time Through Trees

Archaeologists learn to read the language of tree rings

Charred wood remains found in an Iron Age building in the City of David excavations in Jerusalem. Courtesy Israel Antiquities Authority.

Most people know that you can count a tree’s rings to determine its age. Many also know that the rings indicate the climate in any one of the years of the tree’s life: a larger ring indicates a wet year while smaller rings indicate dryness. A tree’s rings form a pattern, kind of like a bar code, that scientists can “read,” allowing them to: 1) know when a tree grew and was cut; and 2) build unbroken chronologies by matching sequences of rings from different trees from the same region through time.

In other words, trees are chroniclers, and they speak in the language of rings. Their stories can reach back thousands of years, offering a history written not by people—who invented writing only around 3000 BCE—but by nature. The science of reading this natural archive is called dendrochronology.

We can once again marvel at dendrochronology thanks to large wooden beams recently found during the City of David excavations in Jerusalem. A joint dig between Tel Aviv University and the Israel Antiquities Authority (IAA) anticipates using this method to date exceptionally large samples of ancient tree rings.

The beams once formed part of a roof over an inner courtyard of a building. The building caught fire, causing the roof to collapse and the beams to fall to the floor. Excavation director Efrat Bocher suggests that the building’s plaster walls were exposed to such intense heat that the plaster detached or partially melted before collapsing over the burnt beams. This layer of plaster and rubble sealed the wooden remains for over 2,600 years.

Wood is very rare in the archaeology of ancient Israel. Warm conditions, microorganisms, insects, and the repeated reuse of timber have all worked against its survival.

Remains of the charred beams, with plastered wall pictured at left. Courtesy Israel Antiquities Authority.

The beams are of exceptional scientific value due to their size and the number of tree rings preserved. Stratigraphic evidence suggests the beams date to the Babylonian destruction of Jerusalem in 586 BCE, a date the team now plans to test via dendrochronology. They also hope the beams’ tree rings will allow them to refine regional chronologies, as additional timbers accumulate from other sites.

To date ancient remains, archaeologists typically combine several lines of evidence. For Jerusalem during the Iron Age (c. 1200–586 BCE), the most common  include stratigraphy, changes in pottery, architectural style, and radiocarbon dating. Together, these methods usually narrow events to decades or centuries.

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Johanna Regev, an archaeological and scientific researcher with the IAA, reports, “Until recently, we could date finds from this time within a range of hundreds of years. Now, as we separate and collect the rings one by one in the field, we can attain much greater precision, potentially narrowing the dating range down to as little as ten years.” By contributing so much data (so many tree rings), the beams give researchers a better chance of matching the wood to the existing regional chronology. Further, these rings may provide valuable new data to strengthen or extend that archive for future studies.

There is something astonishing about the path from a tree’s growth in antiquity, to the reconstruction of ancient climate, and, ultimately, to the creation of an absolute chronology. Dendrochonology inspires a deep sense of awe, both of the natural world, which has preserved this record, and of the human ingenuity that discovered how to read it.

Lauren K. McCormick is an assistant editor at Biblical Archaeology Review and a specialist in ancient Near Eastern religions, visual culture, and the Bible. She holds degrees in religion from Syracuse University, Duke University, New York University, and Rutgers University, and completed a postdoctoral fellowship on religion and the public conversation at Princeton University.

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