Geologists have identified a massive volcanic caldera beneath the Erzurum basin, revealing that the region sits atop a circular volcanic structure approximately 60 kilometers in diameter, the largest known caldera in eastern Türkiye.
A caldera is a large volcanic depression formed when a volcano collapses inward after a massive eruption empties its underlying magma chamber.
Mehmet Salih Bayraktutan, founder of the earthquake research center at Atatürk University, said the discovery fundamentally changes how scientists understand the geological evolution of the basin.
Bayraktutan explained that researchers have long misclassified the Erzurum basin as a tectonic “pull-apart” basin, even though field evidence never fully supported that model.
Instead, the work showed that the basin formed as a compression-related, volcanic caldera, which he and his colleagues have named the Palandöken Caldera.
Field observations first hinted at the caldera’s existence in 1985.
Over the following decades, satellite imagery, remote sensing analyses and detailed field studies consistently revealed a large, circular structure surrounding Erzurum, confirming the caldera’s presence.
Researchers estimate the Palandöken Caldera to be around 6 million years old and dominated by andesitic and basaltic volcanic rocks.
Geological data indicate that early lava flows dipped inward toward the basin center, where a deep lake environment later developed.
Sediments accumulated progressively from the caldera margins toward the center, while fine volcanic materials spread widely across the basin.
Inside the caldera, the sedimentary sequence includes a complex mix of volcanic and sedimentary rocks.
These deposits record a long history of volcanic activity, lake formation and sedimentation.
Bayraktutan noted that arc-shaped segments of the caldera rim remain clearly visible on the southern, eastern, northern and western sides of the basin.
When connected, these segments outline a nearly complete 60-kilometer-wide caldera ring.
Earthquakes destroyed much of the caldera wall in the west and northwest, allowing flood materials to move into lake environments in the region.
These sediments accumulated in stacked fan-delta systems and now form the subsurface foundation of the Daphan Plain.
Despite more than a century of geological research in the region, Bayraktutan emphasized that no previous scientific publication has formally identified or described the Palandöken Caldera.
He stressed that deep drilling at five to six locations across the Erzurum Basin is essential to confirm subsurface structures and fully understand the caldera’s formation.
