The following passage is adapted from an essay on polar paleoclimatology and tephrochronology.
In the ice sheets of Antarctica and Greenland, layers of accumulated snow preserve an uninterrupted physical archive of Earth's atmospheric history spanning hundreds of thousands of years. While paleoclimatologists frequently measure stable isotope ratios of oxygen and hydrogen to reconstruct ancient temperatures, another subdiscipline—tephrochronology—focuses on microscopic layers of volcanic ash, known as tephra, embedded within the ice core strata. When a volcano erupts with sufficient explosive intensity, fine volcanic glass particles and ash are injected high into the stratosphere. Winds distribute these microscopic shards globally or regionally before they settle onto the ice sheet surface, becoming sealed beneath subsequent snowfalls.
In 1998, a research team analyzing the Siple Dome ice core in West Antarctica uncovered a distinct 0.5-millimeter tephra horizon situated at a depth of 620 meters. Initial visual inspection under optical microscopes identified glassy shards with a refractive index characteristic of highly silicic magma. To pinpoint the precise volcanic source, geochemists subjected individual glass shards to electron microprobe analysis, measuring concentrations of major elements including silicon, aluminum, iron, and sodium. The resulting chemical signature matched precisely with the eruptive products of Mount Tethys, a remote submarine volcanic complex in the South Sandwich Arc.
The identification of Mount Tethys tephra in the Siple Dome core served two critical functions for ice core chronology. First, because the eruption of Mount Tethys had previously been dated using argon-argon () radiometric techniques on terrestrial lava flows to years before present, the Siple Dome tephra horizon provided a definitive absolute chronological marker, known as an isochron. Prior to this discovery, glaciologists had relied primarily on annual layer counting, which becomes increasingly subject to cumulative uncertainty at depths exceeding 500 meters due to severe ice compaction and thinning.
Second, the geochemical profile revealed that despite being separated by over 2,200 kilometers of open ocean and ice sheet, atmospheric transport had conveyed the tephra plume south-southwest across the Ross Ice Shelf within a window estimated at less than seventy-two hours. This rapid atmospheric transport was deduced from the unblemished, angular geometry of the glass shards, which exhibited virtually no physical abrasion or micro-fracturing—features that would inevitably have developed had the particles undergone extended re-entrainment or saltation near the surface.
Based on the passage, evaluate the following statement:
Glaciologists found annual layer counting to be increasingly subject to cumulative uncertainty at ice core depths exceeding 500 meters because of severe ice compaction and thinning.
Answer: Answer