Soru

In the early decades of the twentieth century, astronomer A. E. Douglass originally developed dendrochronology—the science of tree-ring dating—not to serve archaeology, but to investigate cyclic solar activity through its presumed influence on terrestrial climate patterns. Douglass posited that annual precipitation variations, reflected in the fluctuating widths of tree rings in long-lived coniferous species of the American Southwest, would mirror sunspot cycles. Although his attempts to establish a direct, predictive link between solar output and regional precipitation yielded inconclusive results, the rigorous cross-dating methodology Douglass created revolutionized archaeological chronology. By overlapping ring patterns from living trees with those from timber preserved in Ancestral Puebloan structures, Douglass constructed an unbroken annual calendar spanning several centuries. Decades later, when Willard Libby introduced radiocarbon dating in the late 1940s, researchers initially assumed that atmospheric concentration of carbon-14 had remained strictly constant over millennia. However, when radiocarbon dates from ancient wood samples were systematically compared against Douglass’s dendrochronological sequences, significant discrepancies emerged. Tree-ring samples of known absolute age consistently exhibited higher radiocarbon ages than expected for dates prior to 1000 BCE. This discrepancy revealed that historical variations in Earth's magnetic field and solar activity had systematically altered cosmic ray flux and thus atmospheric carbon-14 production, necessitating the creation of dendrochronologically calibrated radiocarbon calibration curves.

Based on the passage, which of the following can be inferred regarding Douglass’s research on tree-ring patterns? Consider each of the choices separately and select all that apply.