How a wet tropical rainforest copes with repeated volcanic destruction

The Holocene Period for the province of West New Britain, Papua New Guinea, is characterised by periodic catastrophic volcanism. The region is mantled in dense wet tropical rainforest, and has been occupied by people since the Pleistocene. Analyses of peat from two nearby sites within a lowland rainforest environment provide us with a macro-level landscape account of the periodic destruction and recovery of the coastal forests during seven periods of volcanic activity in the latter part (2900 yr ago to present) of the Holocene. Radiocarbon dating shows the very close correlation of the peat and tephra layers at both sites, yet the pollen analysis reveals different vegetation communities. These initial results allow us to begin identifying the processes of recovery, and to recognise different ecological pressures placed on vegetation at these neighbouring sites. Evidence of hydrological changes are observed beginning with a marine incursion recorded at Garu Site 3 1360 ¹⁴C yr B.P. The distinct differences in the vegetation re-establishment and community regeneration rates suggest the greater level of disturbance at Garu Site 1 could be related to the depth of the ashfall, although the proximity of a known human settlement may also be a contributing factor. Of note, palynologically, we found that the fern spore flora is particularly rich and believe it will be useful for ecological interpretation.     

23,000 yr of vegetation history of the Upper Lerma, a tropical high-altitude basin in Central Mexico

Pollen analysis on a 9.54-m sediment core from lake Chignahuapan in the upper Lerma basin, the highest intermontane basin in Central Mexico (2570 m asl), documents vegetation and limnological changes over the past ∼23,000 ¹⁴C yr. The core was drilled near the archaeological site of Santa Cruz Atizapán, a site with a long history of human occupation, abandoned at the end of the Epiclassic period (ca. 900 AD). Six radiocarbon AMS dates and two well-dated volcanic events, the Upper Toluca Pumice with an age of 11,600 ¹⁴C yr B.P. and the Tres Cruces Tephra of 8500 ¹⁴C yr B.P., provide the chronological framework for the lacustrine sequence. From ca. 23,000 ¹⁴C yr B.P. to ca. 11,600 ¹⁴C yr B.P. the plant communities were woodlands and grasslands based on the pollen data. The glacial advances MII-1 and MII-2 correlate with abundant non-arboreal pollen, mainly grasses, from ca. 21,000 to 16,000 ¹⁴C yr B.P., and at ca. 12,600 ¹⁴C yr B.P. During the late Pleistocene, lake Chignahuapan was a shallow freshwater lake with a phase of lower level between 19,000 and 16,000 ¹⁴C yr B.P. After 10,000 ¹⁴C yr B.P., tree cover in the area increased, and a more variable lake level is documented. Late Holocene (ca. 3100 ¹⁴C yr B.P.) deforestation was concurrent with human population expansion at the beginning of the Formative period (1500 B.C.). Agriculture and manipulation of the lacustrine environment by human lakeshore populations appear at 1200 ¹⁴C yr B.P. (550 A.D.) with the appearance of Zea mays pollen and abundant charcoal particles.     

Liquefaction potential evaluations by energy-based method and stress-based method for various ground motions

An energy-based liquefaction potential evaluation method (EBM) previously developed was applied to a uniform sand model shaken by seismic motions recorded at different sites during different magnitude earthquakes. It was also applied to actual liquefaction case histories in Urayasu city during the 2011 M9.0 Tohoku earthquake and in Tanno-cho during the 2003 M8.0 Tokachi-oki earthquake. In all these evaluations, the results were compared with those by the currently used stress-based method (SBM) under exactly the same seismic and geotechnical conditions. It was found that EBM yields similar results with SBM for several ground motions of recent earthquakes but has easier applicability without considering associated parameters. In Urayasu city, the two methods yielded nearly consistent results by using an appropriate coefficient in SBM for the M9.0 earthquake, though both overestimated the actual liquefaction performance, probably because effects of plasticity and aging on in situ liquefaction strength were not taken into account. In Tanno-cho, EBM could evaluate actual liquefaction performance due to a small-acceleration motion during a far-field large magnitude earthquake while SBM could not.     

Vegetation history of the penultimate glacial period (Marine isotope stage 6) at Ioannina,north‐west Greece

The vegetational history of the penultimate glacial period, Marine Isotope Stage (MIS) 6 (c. 185–135 ka), has remained relatively unexplored. Here we present a new record from the Ioannina basin, north‐west Greece, which constitutes the highest‐resolution terrestrial pollen record for this interval produced to date. It shows that the vegetation history of MIS 6 in this region can be divided into two parts: an early period (185–155 ka) with pronounced oscillations in tree population extent, and a later period (155–135 ka) with much smaller tree populations and subdued oscillations. This pattern is analogous to the MIS 3/MIS 2 division during the last glacial in the same sequence, although the early part of MIS 6 had larger Pinus populations and fewer temperate trees relative to the equivalent interval in MIS 3. This implies cooler and wetter conditions, which is somewhat counterintuitive given the high summer insolation during MIS 6e, but is in line with other palaeoclimatic evidence from the Mediterranean. Comparison with North Atlantic records suggests that despite the absence of pronounced iceberg discharges during MIS 6, North Atlantic millennial‐scale variability had a significant downstream impact on tree populations in north‐west Greece. Copyright © 2011 John Wiley & Sons, Ltd.     

John Turnbull Thomson,Fellow of the Royal Geographical Society: An early New Zealand geographer

John Turnbull Thomson is more known in New Zealand for his work as Chief Surveyor of Otago Province (1856–1876) and first Surveyor General of New Zealand (1877–1879). He was also a Fellow of the Royal Geographical Society of London from 1848 until his death in 1884. Thomson was an important and early self‐declared ‘does’ of geographer in New Zealand, prior to the establishment of university geography in 1937. Thomson's contribution included survey and mapping but he also gave public lectures on geography and contributed to debates about glaciation.     

Where Are the Women? Accounting for Discrepancies in Female Doctorates in U.S. Geography

Although there have been noticeable improvements in recent years, geography continues to be a predominantly male discipline. The percentage of women receiving PhDs in geography has tracked lower than the U.S. average of female PhDs. Previous studies of women's contribution to geography have focused on personal accounts or on the study of some of the most prominent practitioners, with a few studies using basic data on PhDs awarded and Association of American Geographers membership to determine trends. This article provides a comprehensive overview of doctoral degrees in geography by gender, over time, and across all universities in the United States by examining an alternative database, that of doctoral dissertations. The analysis yields three separate types of results. First, historical and contemporary variations among U.S. universities are examined. Second, data indicate that male and female doctoral students differ in the sex of their advisor. Third, a simple regression model explains some of the discrepancies in the proportion of female doctoral students by department. In sum, this article provides a comprehensive empirical study of the factors that might contribute to the continued disparities in female doctoral students in geography.     

The Legacy of Jedidiah Morse in Early American Geography Education: Forgotten and/or Forgettable Geographer?

Despite numerous and significant writings by historians of geography and biographers from other disciplines, and his authorship of the first geography textbooks written in and for the new American republic, most geographers are largely unaware of the contributions of Jedidiah Morse in academic geography. Writings about Morse suggest that he had alienated himself from many of his contemporaries early in his career through his authoritarian brand of Calvinistic republicanism, a perceived contradiction of that style with his entrepreneurial ambitions, his role in the controversial Bavarian Illuminati, and a dispute with a noted New England historian. But subsequent, broader intellectual movements sealed Morse's fate as a forgotten geographer (to most), including the end of the Second Great Awakening, Transcendentalism, Darwinism, and the “new,” process‐based geographical thinking inspired by Carl Ritter, Alexander von Humboldt, and Arnold Guyot. Regardless of the reasons for Morse's lost legacy, his contributions to geographical education are important and should be remembered.     

Tectono–Thermal Evolution, Hydrocarbon Filling and Accumulation Phases of the Hari Sag, in the Yingen–Ejinaqi Basin, Inner Mongolia, Northern China

This work restored the erosion thickness of the top surface of each Cretaceous formations penetrated by the typical well in the Hari sag, and simulated the subsidence burial history of this well with software BasinMod. It is firstly pointed out that the tectonic subsidence evolution of the Hari sag since the Cretaceous can be divided into four phases: initial subsidence phase, rapid subsidence phase,uplift and erosion phase, and stable slow subsidence phase. A detailed reconstruction of the tectonothermal evolution and hydrocarbon generation histories of typical well was undertaken using the EASY R_0% model, which is constrained by vitrinite reflectance(R_0) and homogenization temperatures of fluid inclusions. In the rapid subsidence phase, the peak period of hydrocarbon generation was reached at c.a.105.59 Ma with the increasing thermal evolution degree. A concomitant rapid increase in paleotemperatures occurred and reached a maximum geothermal gradient of about 43-45℃/km. The main hydrocarbon generation period ensued around 105.59-80.00 Ma and the greatest buried depth of the Hari sag was reached at c.a. 80.00 Ma, when the maximum paleo-temperature was over 180℃.Subsequently, the sag entered an uplift and erosion phase followed by a stable slow subsidence phase during which the temperature gradient, thermal evolution, and hydrocarbon generation decreased gradually. The hydrocarbon accumulation period was discussed based on homogenization temperatures of inclusions and it is believed that two periods of rapid hydrocarbon accumulation events occurred during the Cretaceous rapid subsidence phase. The first accumulation period observed in the Bayingebi Formation(K_1 b) occurred primarily around 105.59-103.50 Ma with temperatures of 125-150℃. The second accumulation period observed in the Suhongtu Formation(K_1 s) occurred primarily around84.00-80.00 Ma with temperatures of 120-130℃. The second is the major accumulation period, and the accumulation mainly occurred in the Late Cretaceous. The hydrocarbon accumulation process was comprehensively controlled by tectono-thermal evolution and hydrocarbon generation history. During the rapid subsidence phase, the paleo temperature and geothermal gradient increased rapidly and resulted in increasing thermal evolution extending into the peak period of hydrocarbon generation,which is the key reason for hydrocarbon filling and accumulation.     

阿尔金断裂带对青藏高原北部生长、隆升的制约

大量的同位素年代学证据表明(古)阿尔金断裂带可能形成于三叠纪,后又经历了侏罗纪、白垩纪的强烈左旋走滑活动,自印度板块与欧亚大陆碰撞后阿尔金断裂再次活动。主要的走滑活动发生在:(1)245~220Ma;(2)180~140Ma;(3)120~100Ma;(4)90~80Ma;(5)60~45Ma;(6)渐新世至中新世;(7)上新世至更新世以及(8)全新世。沿阿尔金断裂带,伴随左旋走滑活动形成一系列的逆冲断裂和正断裂,反映走滑过程中伴随隆升作用的存在,并且形成自北向南包括祁连山、大雪山、党河南山、柴北缘山、祁漫塔格山和昆仑山,表明阿尔金断裂带制约着青藏高原北部的生长和隆升。阿尔金断裂带东、西两端的白垩纪和新生代火山活动是断裂走滑活动的响应。     

Parametric study on performance of bridge retrofitted by unseating prevention devices

1 Introduction Structural retro?t techniques (Roberts, 2005), such as restrainers, concrete shear keys, steel jackets, CFRPshells, base isolators, or dampers have been widely studied and implemented in actual structures based on the experiences learned from past earthquakes. In the Chi-Chi earthquake (EERI, 2001), the damage to simply-supported PCI girder bridges provided a different view from which to examine the function of a rubber bearing system for simply- supported bridges (NCREE,…