For Absolute Dating of Archeological Artifacts, the Radiocarbon Method Emerged

Reading Passage Question

For absolute dating of archeological artifacts, the radiocarbon method emerged during the latter half of the twentieth century as the most reliable and precise method. The results of obsidian (volcanic glass) dating, a method based on the belief that newly exposed obsidian surfaces absorb moisture from the surrounding atmosphere at a constant rate, proved uneven. It was initially thought that the thickness of the hydration layer would provide a means of calculating the time elapsed since the fresh surface was made. But this method failed to account for the chemical variability in the physical and chemical mechanism of obsidian hydration. Moreover, each geographic source presented unique chemical characteristics, necessitating a trace element analysis for each such source. Yet, despite its limitations, obsidian dating helped archeologists identify the sources of many obsidian artifacts and to identify in turn ancient exchange networks for the flow of goods. Nor were ceramic studies and fluoride analysis supplanted entirely by the radiocarbon method, which in use allows for field labeling and laboratory errors, as well as sample contamination. In addition, in the 1970s dendrochronological (tree-ring) studies on the bristlecone pine showed that deviation from radiocarbon values increases as one moves back in time. Eventually calibration curves were developed to account for this phenomenon; but in the archeological literature we still find dual references to radiocarbon and sidereal, or calendar, time.

“For absolute dating of archeological artifacts, the radiocarbon method emerged” - is a GMAT reading comprehension passage with answers. Candidates need a strong knowledge of English GMAT reading comprehension.

This GMAT Reading Comprehension consists of 3 comprehension questions. The GMAT Reading Comprehension questions are designed for the purpose of testing candidates’ abilities in understanding, analyzing, and applying information or concepts. Candidates can actively prepare with the help of GMAT Reading Comprehension Practice Questions.

Solution and Explanation

1. Based on the information in the passage, which of the following is LEAST likely to have been a means of dating archeological artifacts?

(A) Ceramics studies
(B) Radiocarbon dating
(C) Dendrochronological studies
(D) Fluoride analysis
(E) Obsidian hydration-layer analysis

2. In the passage, the author mentions all of the following as problems with radiocarbon dating EXCEPT:

(A) disparities with the calendar dating system.
(B) deterioration of samples.
(C) identification errors by archeological field workers.
(D) contamination of artifacts.
(E) mistakes by laboratory workers.

3. With which of the following statements would the passage’s author most likely agree?

(A) The greater the time that has elapsed since exposure of the obsidian surface to moisture the less reliable the results of obsidian dating.
(B) The hydration layer accumulating through obsidian moisture absorption varies in thickness depending on the amount of surface area exposed to moisture.
(C) The unpredictability of the obsidian hydration process renders the obsidian dating method problematic as a means of determining historical trade routes.
(D) The results of obsidian dating are as reliable and precise as those of fluoride analysis only if trace element analysis is performed for the geographic source of the obsidian.
(E) An obsidian artifact can be reliably dated using the obsidian method only if certain environmental conditions where the artifact was found are considered.

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