2016SHSAT_English

51015202530354045Archaeologists first succeeded in usingtree-ring dating while excavating ancientPueblo Indian villages in the southwesternUnited States during the 1920s. At thattime, no one knew when the villages hadbeen occupied, or for how long, but the logsused in the buildings provided a clue. Scientistshad long known that trees add a newgrowth ring to their circumferences duringeach growing season. Drought or early frostresults in little growth and narrow rings.Good growing years result in wide rings.Archaeologists knew that by matchingidentical patterns of wide and narrow ringsin sections of two different logs, they coulddetermine which log was older. For example,a log with a certain pattern of ringsnear its outside edge would indicate aspecific series of good and bad growingseasons. This log would have been cut downbefore a log of comparable size that showsthe identical pattern near its center.But how could these ring patterns helpdetermine the actual dates for the abandonedPueblo villages? Archaeologists hadalready used the ring patterns of trees withoverlapping lifetimes to establish a tree-ringchronology for the southwestern UnitedStates that went back to a.d. 1260. Thatwork had been done in a Hopi village calledOraibi. Oraibi had been continuouslyinhabited since before the arrival of the firstSpanish explorers in 1540.That same team of archaeologists alsodeveloped a relative, or “floating,” chronologyfor the abandoned Pueblo villages bymatching up the ring patterns of the variouslogs used in the buildings. With this “floating”chronology, the archaeologists could tellwhich logs were older and which were morerecent. None could be precisely dated, sinceno log had a pattern of tree rings thatmatched any part of the established chronology.It was clear from this evidence,however, that the buildings must have beenconstructed before a.d. 1260.5101520253035404550556065key beam overlapped the earliest rings inthe established chronology. Furthermore,its inner ring pattern matched the patternformed by the most recent rings of the“floating” chronology. Thus, the chronologyfor the abandoned Pueblo villages could beknown with certainty. Counting backwardfrom the present, the archaeologists estimatedthat the villages had been occupiedbetween a.d. 900 and a.d. 1300.The tree rings also suggested why thevillages had been abandoned. The rings forthe years a.d. 1276 to 1299 were very thin,indicating a severe drought that lasted for23 years. Most likely the villagers had lefttheir homes to search for a more hospitableclimate.39. Which of the following best tells what thispassage is about?A. how variations in weather conditions affecttree growthB. recent breakthroughs in understandingIndian culturesC. why the Pueblo villages were abandonedD. how tree-ring dating can establish the ageof archaeological findingsE. why tree-ring dating is the best method fordetermining dates40. What was the importance of the “key” beamdescribed in the fourth paragraph?F. It proved that trees of the same age wouldhave identical tree-ring patterns.G. It helped to disprove earlier theoriesregarding the abandonment of the villages.H. It helped archaeologists to determine whythe villages had been built at that time.J. It explained why the Pueblo buildings hadbeen constructed at that location.K. It connected the “floating” chronology tothe established chronology.50556065Finally, continued excavations turned up a“key” beam. The outer ring pattern of theFORM B84CONTINUE ON TO THE NEXT PAGE