RE S EAR CH | R E P O R T S SCIENCE sciencemag.org phene, also allows one to selectively inject carriers propagating in the same direction and to probe pseudospin-polarized quasi-particles. In principle, the technique can be extended to tunneling devices in which surface states of topological insulators are used as electrodes; then, all-electrical injection of spin-polarized current (28) with noninvasive tunneling contacts could reveal a number of exciting phenomena (29–31). 24. 25. 26. 27. RE FERENCES AND NOTES AC KNOWLED GME NTS 1. K. S. Novoselov et al., Nature 438, 197–200 (2005). 2. Y. Zhang, Y. W. Tan, H. L. Stormer, P. Kim, Nature 438, 201–204 (2005). 3. A. H. Castro Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov, A. K. Geim, Rev. Mod. Phys. 81, 109–162 (2009). 4. M. I. Katsnelson, K. S. Novoselov, A. K. Geim, Nat. Phys. 2, 620–625 (2006). 5. M. I. Katsnelson, Eur. Phys. J. B 51, 157–160 (2006). 6. A. F. Young, P. Kim, Nat. Phys. 5, 222–226 (2009). 7. F. V. Tikhonenko, D. W. 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SUPPLEMENTARY MATERIALS www.sciencemag.org/content/353/6299/575/suppl/DC1 Materials and Methods Supplementary Text Figs. S1 to S9 References (32–49) 11 February 2016; accepted 13 July 2016 10.1126/science.aaf4621 ARCHAEOLOGY Outburst flood at 1920 BCE supports historicity of China’s Great Flood and the Xia dynasty Qinglong Wu,1,2,3*† Zhijun Zhao,2,13 Li Liu,4‡ Darryl E. Granger,5 Hui Wang,6 David J. Cohen,7‡ Xiaohong Wu,1 Maolin Ye,6 Ofer Bar-Yosef,8 Bin Lu,9 Jin Zhang,10 Peizhen Zhang,3,14§ Daoyang Yuan,11 Wuyun Qi,6 Linhai Cai,12 Shibiao Bai2,13 China’s historiographical traditions tell of the successful control of a Great Flood leading to the establishment of the Xia dynasty and the beginning of civilization. However, the historicity of the flood and Xia remain controversial. Here, we reconstruct an earthquakeinduced landslide dam outburst flood on the Yellow River about 1920 BCE that ranks as one of the largest freshwater floods of the Holocene and could account for the Great Flood. This would place the beginning of Xia at ~1900 BCE, several centuries later than traditionally thought. This date coincides with the major transition from the Neolithic to Bronze Age in the Yellow River valley and supports hypotheses that the primary state-level society of the Erlitou culture is an archaeological manifestation of the Xia dynasty. C hina’s earliest historiographies, including Shujing (Book of Documents) and Shiji (Records of the Grand Historian, by Sima Qian), tell of the Great Flood, a lengthy, devastating flood of the Yellow River. The culture hero Yu eventually tamed this flood by dredging, earning him the divine mandate to establish the Xia dynasty, the first in Chinese history, and marking the beginning of Chinese civilization. Because these accounts laid 5 AUGUST 2016 • VOL 353 ISSUE 6299 579 Downloaded from http://science.sciencemag.org/ on August 4, 2016 The projected states are composed of two sublattice components in the emitter and collector. As a result, momentum-dependent constructive (φe(c) = 0) or destructive (φe(c) = p) interference between sublattice components is governed by jyA þ yB j2 º1 þ cosφe(c), for the states both in emitter (φe) and collector (φc) and manifests itself in the tunneling characteristics I(Vb). Because the magnetic field selects the pairs of particular plane wave states probed by tunneling at a particular gate or bias voltage (Fig. 4, A and B), the measured asymmetry provides a direct visualization of the pseudospin polarization of the Dirac fermions. In the presence of the magnetic field, each resonance peak represents tunneling from a particular corner of the BZ. This allows one to inject electrons with a particular valley polarization, and from a selected corner of the BZ. We use the experimental parameters to calculate the amount of polarization achieved in our experiment (Fig. 3, J and M), and estimate that the valley polarization, P ¼ ðIK − IK ′ Þ=ðIK þ IK ′ Þ [where IK (IK ′ ) is the current injected into the K(K′) valley] can be as high as 30% (40%) for the particular Gr/3hBN/ Gr (Gr/5hBN/BGr) devices. The main limit to the degree of polarization is the energy broadening of states at the Fermi levels caused by inelastic tunneling processes. However, even for the current level of disorder, with the resonances at around Vb ≈ 0 V (e.g., resonances marked by yellow dashed lines on Fig. 2D at Vg > 50 V), which maximizes the number of states participating in tunneling and sensitive to magnetic field, a polarization close to 75% could be achieved (19). By using devices with smaller misalignment between the graphene electrodes [on the order of 0.2°, now within the reach of the current technology (19)], valley polarization close to 100% is possible (19). The same mechanism can also be used to select electrons with a particular pseudospin polarization. In Fig. 4, C to R, we present results of a calculation of the contribution of different electronic states in k-space to the tunnel current for the Gr/3hBN/Gr (Fig. 4, C to I) and Gr/5hBN/ BGr (Fig. 4, J to R) devices. We choose the position of the Fermi levels in the emitter and collector to be very close to a resonance at B = 0 T. Then, for certain directions of B, the resonant conditions are achieved only in one valley and for only a very narrow distribution in k-space (Fig. 4, G to I). Tunneling of the electrons from other parts of k-space is prohibited either because they are off-resonance or because of the pseudospin selection rule. Alternatively, for the Gr/5hBN/ BGr device and exploiting the difference in curvature of monolayer and bilayer electronic bands, we can choose the overlap between the bands in such a way that the magnetic field reduces the overlap in one valley and increases it for the other (Fig. 4, M to R). In this case, momentum conservation at B = 0 T is fulfilled for the states marked by white dashed lines (Fig. 4O). However, only one of those lines contributes to tunneling, owing to pseudospin interference (Fig. 4, M and N). Our technique, which enables tunneling of valleypolarized electrons in monolayer and bilayer gra- the ideological foundations for the Confucian rulership system, they had been taken as truth for more than 2500 years until challenged by the “Doubting Antiquity School” in the 1920s. Within a decade, archaeological excavations demonstrated the historicity of the second dynasty, Shang, and the search for similar evidence for Xia began (1, 2). Archaeological fieldwork since the 1950s on the Early Bronze Age Erlitou culture (~1900 to 1500 BCE) has led many scholars to associate it with the Xia (1–6) because it overlaps with the spatial and temporal framework of the Xia dynasty. Traditionally, historians have dated the start of Xia to ~2200 BCE, whereas the government-sponsored Xia-Shang-Zhou Chronology Project adopted the date as 2070 BCE (5), leaving a chronological gap in associating Erlitou with Xia (7–9). Other scholars see Xia purely as a myth fabricated to justify political succession (10, 11). Scholars also have long sought a scientific explanation of the Great Flood (12–14), with even Lyell mentioning it (15), yet no evidence for it has been discovered. Here, we present geological evidence for a catastrophic flood in the early second millennium BCE and suggest that it may be the basis of the Great Flood, thereby lending support to the historicity of the Xia dynasty. The evidence found in our investigations along the Yellow River in Qinghai Province includes remains of a landslide dam, dammed lake sediments (DLS) upstream, and outburst flood sediments (OFS) downstream (Fig. 1 and figs. S1 to S5) that allow us to reconstruct the size of the lake and flood (16). Field observations (fig. S2B) show that the ancient landslide dam deposits reach an elevation of 240 m above present river level (arl) and stretch for 1300 m (fig. S2A) along Jishi Gorge (Figs. 1A and 3A). We estimate that the saddle of the dam would have been 30 to 55 m lower than the highest preserved remnants, so the lake would have filled to an elevation of 185 to 210 arl [2000 to 2025 m above sea level (asl)] (fig. S2B), impounding 12 to 17 km3 of water (16) (table S1). Based on typical river discharge values, the dam would have completely blocked the Yellow River for 6 to 9 months before overtopping (16). DLS distributed widely upstream of the dam are up to 30 m thick and have a highest elevation of ~1890 m asl (Fig. 1B and figs. S1 and S3A). We interpret this as indicating that the catastrophic breach dropped the water level 110 to 135 m (Fig. 1B), releasing ~11.3 to 16 km3 of water (16) (table S1), tens of times that estimated by a previous study (17). After the breach, DLS infilled a residual lake behind the lowest part of the dam that remained. Outburst flood sediments are found downstream at elevations from 7 to 50 m arl in the lower Jishi Gorge and in Guanting Basin (Fig. 1 and figs. S1 and S4). They are characterized by high-concentration suspension deposition and consist exclusively of angular clasts of greenschist and purple-brown mudrock sourced from Jishi Gorge (table S2). At the mouth of the gorge, where the Yellow River enters Guanting Basin, the sediments reach 20 m thickness and include boulders up to 2 m in diameter (Fig. 1B and figs. S1 and S4, C and D). We also identified the OFS at the earthquake-destroyed prehistoric Lajia site (fig. S5), a settlement of the Qijia culture (18, 19) known for its early noodle remains (20), 25 km downstream from the dam. OFS at Lajia covered the settlement’s last Qijia culture occupation and filled in collapsed cave dwellings (fig. S5, A and B), pottery vessels (fig. S5B), and earthquake fissures (fig. S5C), mixing with pottery sherds (fig. S5D) and other Qijia cultural materials, with heights of up to 38 m arl. Stratigraphic relationships of the OFS, remnant dam, DLS, loess, and other deposits in Jishi Gorge and neighboring basins, along with destruction features at the Lajia site (fig. S1), allow us to reconstruct and date a sequence of events ending in the outburst flood. First, they show that the damming and outburst flood event occurred during the archaeological Qijia culture period (~2300 to 1500 BCE) after the collapse of the Lajia cave-houses. Ground fissures caused by the earthquake at the Lajia site were entirely filled with OFS (fig. S5C) before silts from surface runoff during the annual rains could enter them, indicating that the outbreak flood must have occurred less than 1 year after the earthquake and collapse of the houses. It is likely that the same earthquake that destroyed Lajia also triggered the landslide that dammed the river, along with widespread contemporaneous rock avalanches whose deposits lay directly beneath the DLS (fig. S3A). 1 School of Archaeology and Museology, Peking University, Beijing 100871, China. 2School of Geography Science, Nanjing Normal University, Nanjing 210023, China. 3State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China. 4Department of East Asian Languages and Cultures, Stanford University, Stanford, CA 94305, USA. 5Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA. 6Institute of Archaeology, Chinese Academy of Social Sciences, Beijing 100710, China. 7Department of Anthropology, National Taiwan University, Taipei 10617, Taiwan (R.O.C). 8Department of Anthropology, Harvard University, Cambridge, MA 02138, USA. 9CCTEG Xi’an Research Institute, Xi’an 710077, China. 10 Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China. 11Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, China. 12Qinghai Provincial Institute of Cultural Relics and Archaeology, Xining 810007, China. 13Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, Jiangsu 210023, China. 14School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China. *Corresponding author. Email: wuqinglong@pku.edu.cn †Present address: School of Geography Science, Nanjing Normal University, Nanjing 210023, China. ‡These authors contributed equally to this work. §Present address: School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China. 580 5 AUGUST 2016 • VOL 353 ISSUE 6299 Fig. 1. Evidence of the exceptional outburst flood in the upper valley of the Yellow River. (A) Distributions of OFS, DLS, and landslide dam. Light purple and dark green shaded areas indicate purple-brown mudrock and greenschist, respectively. Line AB across the Lajia site shows the location of the reconstructed cross section in fig. S6C. (B) The vertical distribution of the OFS, landslide dam, DLS, Lajia site and reconstructed lake levels relative to the longitudinal profile of the present Yellow River. DLS are classified into lacustrine sediments (LS) and fan delta deposits (FD). sciencemag.org SCIENCE Downloaded from http://science.sciencemag.org/ on August 4, 2016 R ES E A RC H | R E PO R TS To date the outburst flood, we collected carbon samples for accelerator mass spectrometry (AMS) 14C dating (16). Seventeen charcoal samples from the OFS and the only charcoal sample from a layer overlying the OFS (fig. S1) indicate that the age for the flood is between 2129 and 1770 cal. BCE [95% confidence interval (CI)] (Fig. 2A and table S5) (16). Charcoal samples from DLS upstream of the dam (fig. S1) yield calibrated 14C results (95% CI) spanning 2020 to 1506 BCE (Fig. 2A and table S5), demonstrating that the DLS is coeval with or younger than the outburst flood and confirming that it is fill from the remnant lake. The best dating for the flood comes from the Lajia site (16), because it was destroyed within 1 year before the outburst flood. Radiocarbon determinations of bone samples from three human victims, aged 6 to 13 years old, in collapsed Lajia dwellings (Fig. 2B) agree to within uncertainty (Fig. 2A and table S5), consistent with that of two victims reported previously (21) as well. Because the radiocarbon calibration curve is linear in this region and the bones are the same age, we use the inverse variance weighted mean of the three measurements. This yields a calibrated age with a median of 1922 ± 28 BCE (1 SD) and a 95% CI of 1976 to 1882 BCE (Fig. 2C). To simplify this range, we use 1920 BCE to indicate the approximate date of the flood. We estimate the peak discharge of the flood in two ways. Empirical formulas considering the volume of the lake and the height of the dam lead to estimates ranging from 0.08 to 0.51 × 106 m3 s−1, with large uncertainties (16) (table S3). We also reconstruct the flood channel cross section from detailed surveys in Guanting Basin and use Manning’s equation to estimate a peak discharge of 0.36 to 0.48 × 106 m3 s−1 (16) (fig. S6 and table S4), consistent with the dam break estimations (16) (table S3). The calculated peak discharge of ~0.4 × 106 m3 s−1 is more than 500 times the average discharge of the Yellow River at Jishi Gorge. This ranks globally among the largest freshwater floods of the Holocene (22). We do not explicitly model the inundation and effect of this outburst flood in the lower reaches of the river, but analogous events demonstrate that outburst floods from landslide dams can propagate long distances. In 1967, an outburst flood with a volume of just ~0.64 km3 propagated at least 1000 km along the YalongYangtze Rivers (23), so the Jishi prehistoric outburst flood, with a volume of ~11 to 16 km3, could have easily travelled more than 2000 km downstream. The Jishi flood would have breached the natural levees of the Yellow River, resulting in rare, extensive flooding. It is possible that this outburst flood was also the cause of a major avulsion of the lower Yellow River (Fig. 3A) inferred from archaeological data, with a previously estimated date of ~2000 BCE (24, 25). Widespread destruction of levees and deposition of tributary mouth bars may have destabilized the main river channel, leading to repeated flooding until a new river channel was established. Extensive flooding on the lower Yellow River plain would have had a great effect on societies there. We argue that this event and its aftermath likely would have sur- vived in the collective memories of these societies for generations, eventually becoming formalized in the received accounts of the Great Flood in the first millennium BCE. In fact, early texts such as the Shujing and Shiji even record that a place called Jishi (the same characters as the gorge where the outburst flood began) was where Yu began his dredging of the Yellow River; whether this is a coincidence will require further historical geographical research. The ~1920 BCE flood shares the main characteristics of the Great Flood described in ancient texts. Apart from its huge peak discharge, the secondary flooding on the lower plains may have been long-lasting, just as the Great Flood remained uncontrolled for 22 years until it was managed by dredging (rather than by blocking breaches in natural levees). There is also the issue of whether the Great Flood could have been caused by exceptional meteorological flooding, but a speleothem record shows a generally weakened Asian summer monsoon from 8000 to 500 years before the present (26), and proxies from lake and loess records also indicate that a cool, dry climate regime begins 2000 BCE along the lower Yellow River (27), so this would be unlikely. Furthermore, the early textual records make no mention of frequent, extreme storms related to the Great Flood. The discovery and reconstruction here of the massive outburst flood originating in Jishi Gorge provide scientific support that the ancient Chinese textual accounts of the Great Flood may well be rooted in a historic natural event. They also shed light on the potential Fig. 2. Radiocarbon chronology of the prehistoric outburst flood on the Yellow River. (A) Calibrated age probabilistic histograms of radiocarbon data. The outliers of the ages inconsistent with stratigraphic sequences and indicating reworking are denoted with asterisks. Samples best constraining the age of the outburst flood are boxed in red. See fig. S1 for sample locations. (B) The radiocarbon dated skeletons in cave dwelling F4 at the Lajia site. The skeletons were identified by reference (30). (C) The calibration of the inverse variance weighted mean for three bone samples on calibration curve IntCal13 (31). All radiocarbon dates were calibrated individually with IntCal13 (31) and OxCal 4.2 (32). SCIENCE sciencemag.org 5 AUGUST 2016 • VOL 353 ISSUE 6299 581 Downloaded from http://science.sciencemag.org/ on August 4, 2016 RE S EAR CH | R E P O R T S Fig. 3. Major transition of archaeological cultures in the Yellow River valley around 1900 BCE. C, culture; LS C, Longshan culture. (A) Distribution of the late Neolithic and early Bronze Age cultures in the Yellow River valley. 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Press, New York, 1999), pp. 30–36. 26. Y. Wang et al., Science 308, 854–857 (2005). 27. A. M. Rosen et al., Holocene 25, 1640–1650 (2015). 28. D. S. Nivison, K. D. Pang, Early China 15, 87–95 (1990). 29. J. Y. Han, The Environment and Cultural Development in PreQin Northwestern China (Wenwu Press, Beijing, 2008), pp. 40–468. 30. M. H. Wang, Kaogu 2002, 1081–1084 (2002). 31. P. J. Reimer et al., Radiocarbon 55, 1869–1887 (2013). 32. University of Oxford, OxCal/ORAU; https://c14.arch.ox.ac.uk/ oxcal/OxCal.html. ACKN OW LEDG MEN TS historicity of the Xia dynasty itself, as Yu’s founding of the dynasty is directly tied to his achievements in controlling the Great Flood. According to the Shiji, Yu’s father labored unsuccessfully for 9 years to tame the flood before Yu took over for 13 more years. Yu’s success led to his mandate to become founding king of the Xia 22 years after the flood started. If the Jishi Gorge outburst flood of ~1920 BCE is the natural cataclysm that came to be known as the Great Flood, then we can propose a new beginning date for the Xia dynasty, ~1900 BCE. This date, some 2 to 3 centuries later than previous reckonings (1, 2, 5), is compatible with the 1914 BCE date proposed by Nivison based on astro-historiographical evidence (28). This 1900 BCE date for the founding of the Xia coincides with the beginning of the Erlitou culture (6), so this finding also supports the arguments that the Erlitou culture is the archaeological manifestation of the Xia and that the Erlitou site was a Xia dynastic capital (1–3). This outburst flood is 582 5 AUGUST 2016 • VOL 353 ISSUE 6299 also coincident with the major sociopolitical transition from Neolithic to Bronze Age in the Yellow River valley (2, 6, 29) (Fig. 3, A and B), suggesting that the concurrence of these major natural and sociopolitical events known through the geological, historiographical, and archaeological records may not simply be coincidence but rather an illustration of a profound and complicated cultural response to an extreme natural disaster that connected many groups living along the Yellow River. RE FERENCES AND NOTES 1. X. P. Yuan, W. M. Yan, C. X. Zhang, Y. L. Lou, Eds., The History of Chinese Civilization, vol. 1 (Cambridge Univ. Press, New York, 2012). 2. K. C. Chang, The Archaeology of Ancient China, 4th ed. (Yale Univ. Press, New Haven and London, 1986). 3. H. Zou, Henan Wenbo Tongxun 1, 34–35 (1978). 4. R. L. Thorp, Early China 16, 1–33 (1991). 5. The Xia-Shang-Zhou Chronology Project Group, The Xia-Shang-Zhou Chronology Project Report for the years 1996–2000 (abridged) (World Book Publishing Company, Beijing, 2000). This research was supported by the National Science Foundation of China (nos. 40801010 and 41271017), Fundamental Research Grant of China (no. F-IGCEA-0607-1-10), Chinese Geological Survey Project (no. 121201102000150009-16), the Priority Academic Program Development of Jiangsu Higher Education Institutions, and National Science and Technology Support Program (no. 2013BAK08B01). P. Dong, H. P. Zhang, and W. Qin partly contributed to the fieldwork; X. Su and P. M. Zhang provided important financial support; Y. Chen and J. Liu-Zeng provided partial financial support; and J. K. Lu gave suggestions on the discharge estimation. Three anonymous reviewers provided valuable comments on the manuscript. We especially thank and commemorate H. B. Wang, who passed away in an accident in November 2011, for his passionate and laborious work in reconstruction of the cross section in June 2010. All data are available in the main manuscript and supplementary materials. SUPPLEMENTARY MATERIALS www.sciencemag.org/content/353/6299/579/suppl/DC1 Materials and Methods Figs. S1 to S7 Tables S1 to S5 References (33–47) 20 December 2015; accepted 14 June 2016 10.1126/science.aaf0842 sciencemag.org SCIENCE Downloaded from http://science.sciencemag.org/ on August 4, 2016 R ES E A RC H | R E PO R TS Outburst flood at 1920 BCE supports historicity of China's Great Flood and the Xia dynasty Qinglong Wu, Zhijun Zhao, Li Liu, Darryl E. Granger, Hui Wang, David J. Cohen, Xiaohong Wu, Maolin Ye, Ofer Bar-Yosef, Bin Lu, Jin Zhang, Peizhen Zhang, Daoyang Yuan, Wuyun Qi, Linhai Cai and Shibiao Bai (August 4, 2016) Science 353 (6299), 579-582. [doi: 10.1126/science.aaf0842] Flood control initiates Chinese civilization Around four millennia ago, Emperor Yu the Great succeeded in controlling a huge flood in the Yellow River basin. This is considered to have led to the establishment of the Xia dynasty and the start of Chinese civilization. However, the dates of the events and the links between them have remained uncertain and controversial. Using stratigraphic data and radiocarbon dating, Wu et al. verify that the flood occurred and place the start of the Xia dynasty at about 1900 BC, thus reconciling the historical and archaeological chronologies (see the Perspective by Montgomery). Science, this issue p. 579; see also p. 538 This copy is for your personal, non-commercial use only. 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Downloaded from http://science.sciencemag.org/ on August 4, 2016 Editor's Summary Evidence Found for China's Ancient Origin Story - Eos 8/4/16, 5:19 PM Evidence Found for China’s Ancient Origin Story New geological findings suggest that an ancient flood in a popular legend about the birth of China's civilization might have actually occurred, but some 150 years later than historians thought. This photo shows Jishi Gorge upstream from the landslide dam. Gray silt deposits reveal an ancient, massive lake held by the dam. Credit: Wu Qinglong By JoAnna Wendel ! 3 hours ago In Chinese mythology, the tale of a great flood marks the beginning of the ancient civilization and the debut of China’s first-ever, but possibly fictional, dynasty—the Xia Dynasty. Today, researchers published a paper in Science (http://science.sciencemag.org/cgi/doi/10.1126/science.aaf0842) laying out geological evidence for a huge flood on the Yellow River almost 4000 years ago that may have inspired the origin story. “The scientific evidence of this flood would lend support to parts of the legendary history,” said Li Liu, an archaeologist at Stanford University in https://eos.org/articles/evidence-found-for-chinas-ancient-origin-story Page 1 of 4 Evidence Found for China's Ancient Origin Story - Eos 8/4/16, 5:19 PM California and coauthor on the new paper. Specifically, the findings could lend credibility to arguments that the Xia Dynasty actually existed (http://www.chinahighlights.com/travelguide/china-history/the-xia-dynasty.htm). Yu the Great The story of the Xia Dynasty (http://www.ancient.eu/Xia_Dynasty/) starts with a flood that supposedly lasted 20 years. In ancient times, a man called Yu recruited villagers in the Yellow River valley to divert the waters that had been raging untamed for almost a decade. Over another decade, Yu and the villagers dug channels and tributaries that led the water to the sea. Grateful countrymen crowned Yu the Great (http://www.chinaknowledge.de/History/Myth/personsyu.html) as their ruler. He started the dynastic tradition when he eventually passed his throne to his son. Modern scholars suggest that Yu’s reign started in 2070 B.C.E (http://www.self.gutenberg.org/articles/xia%E2%80%93shang%E2%80%93zhou_chronology_project).—if it existed at all. Because Chinese texts made no mention of this story for the next millennium, some scholars reject the existence of the dynasty itself, said Wu Qinglong, a geologist at Peking University in Beijing and lead author of the paper. History in Rock Starting nearly a decade ago, Wu found evidence of a landslide along the slopes bordering the Yellow River in the Jishi Gorge. Sediments from this landslide contained a jumbled mix of green schist and purple mudstone grains, which he also found 25 kilometers away in sediment that filled earthquake fissures at the Lajia archaeological site, an earthquake-damaged site famous for preserving the oldest intact noodles (http://news.nationalgeographic.com/news/2005/10/1012_051012_chinese_noodles.html). How did these sediments get so far downstream? To Wu, one answer seemed the most logical—a huge flood must have burst through the landslide dam, washing down sediment from higher elevations. Although he realized a flood must have carried these sediments, Wu didn’t discover its epic size until he and his team investigated more closely. The Size of the Dam The researchers started by calculating the size of the dam itself. They already knew about parts of the dam, but further inspection using satellite imagery revealed its breadth—the ancient landslide completely blocked the river, spanning 700–800 meters across, rose 240 meters above the river’s water level, and stretched downriver for more than a kilometer. Lake sediments found upstream of the ancient dam indicate that a massive lake grew and grew, holding as much as 17 cubic kilometers of water. The raging waters would have carried 300,000–500,000 cubic meters of water per second. At the mouth of Jishi Gorge, where it opens into the downstream Guanting Valley, the researchers found boulders scattered around as if they’d been carried by a violent flood, said Darryl Granger, a geologist at Purdue University in West Lafayette, Ind. They also found beds where smaller grains lay beneath larger ones. Usually, floods deposit sediment in the opposite way—the largest and heaviest rocks carried by a flood sink first, then smaller and smaller grains rain out of the passing waters. This inversely graded bed indicates that the mass of water began moving slowly— as it overtopped the dam—and then rapidly sped up when the dam collapsed, Granger said. Using sediments found downstream of the gorge, the researchers estimated that the ancient flood would have climbed as high as 38 meters above the current river’s level. With flood discharge calculations—using the amount of water thought to have been present in the massive lake and the gorge’s geometry—they estimated that the raging waters would have carried 300,000–500,000 cubic meters of water per second, making it one of the largest freshwater floods on Earth in the last 10,000 years, Granger said. “This cataclysmic flood would have been devastating for anyone living on the Yellow River downstream,” Granger continued. Radiocarbon dating of charcoal found in ancient flood deposits on both sides of the river’s path through the Jishi Gorge revealed that the flooding occurred around 1920 B.C.E. Piecing Together the Tale https://eos.org/articles/evidence-found-for-chinas-ancient-origin-story Page 2 of 4 Evidence Found for China's Ancient Origin Story - Eos 8/4/16, 5:19 PM Wu and his colleagues then compared their calculated radiocarbon dates of the flood to those from skeletal remains of children killed at the Lajia site during the same earthquake. The dates were a close match, indicating that the earthquake may have triggered the landslide in the first place. Through research and models, a story came together: In 1920 B.C.E., an earthquake caused a landslide to tumble into the Yellow River, blocking it completely. Water accumulated behind this dam for 6–9 months, after which it started to pour over the top. Eventually, the 130-meter-high dam partially collapsed, unleashing a wall of water down through the Jishi Gorge and into the valley below. The flood could have lasted some tens of hours or even days, possibly creating new tributaries and channels as the water cascaded through the valley, Granger said. Annual flooding of those tributaries could have disrupted the agricultural landscape with each rainy season, Granger continued—a possible inspiration for the myth of a 20-year-long flood. Culture Shock Around 1900 B.C.E., legend says, the Xia Dynasty began after Yu the Great calmed the flooding waters. This date closely coincides with a radical cultural shift, said David Cohen, an archaeologist at the National Taiwan University in Taipei and a coauthor on the study. China’s Bronze Age (http://afe.easia.columbia.edu/special/china_4000bce_bronze.htm) started around 1900 B.C.E., he said, when urban centers and bronze centers started to rise. “I think many will be excited to see ‘scientific evidence’ of some truth behind this founding legend.” One collection of urban ruins identified as the Erlitou culture (http://www.chinadaily.com.cn/en/doc/2003-11/11/content_280475.htm), which some historians have associated with the Xia Dynasty, also dates to about 1900 B.C.E. That is too late to overlap with the dynasty if Yu truly came to power in 2070 B.C.E. However, if the newly documented flood is the flood of myth, its timing strengthens the possibility the Erlitou culture and hypothetical Xia Dynasty were linked, Cohen said. “The [Great Flood] tale is central to Chinese identity and is known by everyone in China, just as Westerners know the story of Creation in the Bible or Noah’s flood,” Cohen told Eos. “I think many will be excited to see ‘scientific evidence’ of some truth behind this founding legend.” https://eos.org/articles/evidence-found-for-chinas-ancient-origin-story Page 3 of 4 Evidence Found for China's Ancient Origin Story - Eos 8/4/16, 5:19 PM Historians have debated timelines for the beginning of the Xia Dynasty for decades. New research argues that on the basis of geological evidence of a great flood, the Xia Dynasty began almost a century later than originally proposed and coincides with archeological evidence of the beginning of China’s Bronze Age. Credit: —JoAnna Wendel, Staff Writer Citation: Wendel, J. (2016), Evidence found for China’s ancient origin story, Eos, 97, doi:10.1029/2016EO057269. Published on 04 August 2016. © 2016. The authors. CC BY-NC-ND 3.0 https://eos.org/articles/evidence-found-for-chinas-ancient-origin-story Page 4 of 4 • • • • • Write two pages in APA format Please avoid plagiarism Please make it as simple as you can Here’s more info about the topic and the requirements There will be more attachments for the article You will then write a short essay, 1-2 pages in length, detailing the parts of the scientific method discussed in your article and comparing that information to what was reported in the news story. Each entry will be written in a logical and professional manner using the APA template attached to the post. The entire entry must be written IN YOUR OWN WORDS. Direct quotes of the articles are not allowed. However, when you summarize or paraphrase something from one of the articles you will need to provide an in-text APA reference. The guide to APA referencing is attached to this post. The essay must be written entirely in third person. DO NOT USE FIRST OR SECOND PERSON. This means you cannot use the words “I”, “we”, or “you”. What is turned in to the instructor? Entry Content You will be graded on the following content that combines information you obtain from both the news story and the scientific article: Introduction (1 paragraph) This section identify which of the two articles was the scientific study and the subject of the scientific study. You will also identify the problem or observation that spurred the research. DO NOT LIST THE RESULTS OF THE STUDY ITSELF HERE. You will identify the hypothesis the scientists were testing. Remember that a hypothesis is a testable educated guess. Thus, it is not appropriate to pose a question here. However, while reading your articles, it can be helpful to ask yourself what explanation scientists tried to use to explain their initial observation. You will then transition into the body of the journal. Body (~1 paragraph each) Here, you will identify the test or experiment that was performed to address the hypothesis. You should be detailed here. It may be helpful to pull from other sources, if you do not fully understand how the experiment was conducted. After detailing how the experiment was done compared to how it reported in the media, you will transition into a discussion of the results. In this section of your entry you will identify the experimental results that the scientists obtained. What did the scientists find after doing their experiment? Again, you can be detailed here. After detailing the results, you will transition into the conclusion sections. The last paragraph of the body should explain the conclusion of the study. You should address whether the hypothesis was supported or rejected, and how the results led to that finding. Also provide a possible new avenue of research the scientists might pursue based on what was discovered in this study. Evaluation (1 paragraph) Here you will signal the end of your entry. In this section you will identify the new study about the scientific study and discuss whether or not the news story was a representative reporting of the scientific study. Did the news change anything or leave out something important from the scientific study? Summarize the important content from your entry, then you will end with a definitive final statement.
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