We present the first regional map of CO₂ Earth degassing from a large area (most of central and south Italy) derived from the carbon of deep provenance dissolved in the main springs of the region. The investigation shows that a globally significant amount of deeply derived CO₂ (10% of the estimated global CO₂ emitted from subaerial volcanoes) is released by two large areas located in western Italy. The anomalous flux of CO₂ suddenly disappears in the Apennine in correspondence to a narrow band where most of seismicity concentrates. Here, at depth, the gas accumulates in crustal traps generating CO₂ overpressurized reservoirs which induce seismicity.