2,629 research outputs found
A 70,000 year multiproxy record of climatic and environmental change from Rano Aroi peatland (Easter Island)
No full textThe Rano Aroi mire on Easter Island (also known as Rapa Nui; 27°09′S, 109°27′W, 430 m above sea level) provides a unique non-marine record in the central South Pacific Ocean for reconstructing Late Pleistocene environmental changes. The results of amultiproxy study on twocores fromthe center and margin of the Rano Aroi mire,including peat stratigraphy, facies analysis, elemental and isotope geochemistry on bulk organic matter, X-ray fluorescence (XRF) core scanning and macrofossil analysis, were used to infer past water levels and vegetation changes. The chronology was based on 18 14C AMS dates for the upper 8.7 m. The extrapolated age for the base of the sequence is 70 kyr, which implies that this record is the oldest paleolimnological record on Easter Island.The recovered Rano Aroi sequence consists of a radicel peat formed primarily from the remains of sedges,grasses and Polygonaceae that have accumulated since Marine Isotopic Stage (MIS) 4 (70 kyr BP) to the present. From 60 to 40 kyr BP (MIS 3), high precipitation/runoff events were recorded as organic mud facies with lighter δ13C, low C/N values and high Ti content, indicating higher detritic input to the mire. A gradual shift in δ13C bulk organic matter from −14% to −26%, recorded between 50 and 45 cal kyr BP, suggests a progressive change in local peat-forming vegetation from C4 to C3 plant types. Post-depositional Ca and Fe enrichment during sub-aerial peat exposure and very low sedimentation rates indicate lower water tables during Late MIS 3 (39-31 cal kyr BP). During MIS 2 (27.8-19 cal kyr BP), peat production rates were very low, most likely due to cold temperatures, as reconstructed from other Easter Island records during the Last Glacial Maximum (LGM).Geochemical and macrofossil evidence shows that peat accumulation reactivates at approximately 17.5 cal kyr BP, reaching the highest accumulation rates at 14 cal kyr BP. Peat accretion decreased from 5.0 to 2.5 cal kyr BP, coinciding with a regional Holocene aridity phase. The main hydrological and environmental changes in Rano Aroi reflect variations in the South Pacific Convergence Zone (SPCZ), Southern Westerlies (SW) storm track, and South Pacific Anticyclone (SPA) locations
The mosses of Easter Island
No full textThe bryophyte flora of Easter Island has been poorly known primarily because few botanists have collected there. In order to increase the knowledge of the flora the two authors collected bryophytes from 12 localities on the island from April 28-May 3, 2000. The small island, which is south of the Tropic of Capricorn, is of volcanic origin and the volcanic soil as well as the destruction of most of the native flora have undoubtedly contributed to the paucity of bryophytes. The present study revealed that the bryophyte flora consists of only a few species, including one unidentifiable member of the Anthocerotaceae, 11 hepatics and 30 mosses. Eighteen mosses are new to the island. Three mosses, Chenia leptophylla (Müll. Hal.) R. H. Zander, Dicranella hawaiica (Müll. Hal.) Broth. and Tortella humilis (Hedw.) Jennings, are new for Chile, while three, Fissidens pascuanus Broth. in Skottsb., Ptychomitrium subcylindricum Thér. and Trematodon pascuanus Thér., are presently known to be endemic to Easter Island. Two of the three endemics, Fissidens pascuanus and Ptychomitrium subcylindricum, were rediscovered on the island. Fissidens pascuanus was found with sporophytes for the first time and a revised description of the species is provided
Rapa Nui (Easter Island)’s Stone Worlds
No full textThis article explores the spatial, architectural and conceptual relationships between landscape places, stone quarrying, and stone moving and building during Rapa Nui’s statue-building period. These are central themes of the ‘Rapa Nui Landscapes of Construction Project’ and are discussed using aspects of the findings of our recent fieldwork. The different scales of expression, from the detail of the domestic sphere to the monumental working of quarries, are considered. It is suggested that the impressiveness of Rapa Nui’s stone architecture is its conceptual coherence at the small scale as much as at the large scale. </div
Easter Island’s Collapse : A Tale of a Population Race
No full textThe Easter Island tragedy has become an allegory for ecological catastrophe and a warning for the future. In the economic literature the collapse is usually attributed to irrational or myopic behaviors in the context of a fragile ecosystem. In this paper we propose an alternative story involving non-cooperative bargaining between clans to share the crop. Each clan’s bargaining power depends on its threat level when fighting a war. The biggest group has the highest probability of winning. A clan’s fertility is determined ex ante by each group. In the quest for greater bargaining power, each clan’s optimal size depends on that of the other clan, and a population race follows. This race may exhaust the natural resources and lead to the ultimate collapse of the society. In addition to well-known natural factors, the likelihood of a collapse turns out to be greater when the cost of war is low, the probability of succeeding in war is highly responsive to the number of fighters, and the marginal return to labor is not too low. We analyze whether these factors can account for the difference between Easter and Tikopia Islands. The paper also makes a methodological contribution in that it is the first fertility model to include strategic complementarities between groups’ fertility decisionsFertility, War, Bargaining Power, Collapse, Natural Resources
Easter Island’s collapse: A tale of a population race
No full textWe study different extended formulations for the set (formule) in order to tackle the feasibility problem for the set (formule). Here the goal is not to find an improved polyhedral relaxation of conv(X+), but rather to reformulate in such a way that the new variables introduced provide good branching directions, and in certain circumstances permit one to deduce rapidly that the instance is infeasible. For the case that A has one row a we analyze the reformulations in more detail. In particular, we determine the integer width of the extended formulations in the direction of the last coordinate, and derive a lower bound on the Frobenius number of a. We also suggest how a decomposition of the vector a can be obtained that will provide a useful extended formulation. Our theoretical results are accompanied by a small computational study.fertility, war, bargaining power, collapse, natural resources.
B. J. Pfohl and Austin Burke at practice for the Easter Sunrise Service, 1947.
No full textB. J. Pfohl and Austin Burke at practice for the Easter Sunrise Service, 1947. Mr. Pfohl was the Moravian Band director for many years, and was succeeded by Austin Burke
B. J. Pfohl and Austin Burke at practice for the Easter Sunrise Service, 1947.
No full textB. J. Pfohl and Austin Burke at practice for the Easter Sunrise Service, 1947. Mr. Pfohl was the Moravian Band director for many years, and was succeeded by Austin Burke
Models of stress at mid-ocean ridges and their offsets
No full textThis thesis aims to investigate the stresses at mid-ocean ridge offsets, and particularly at the particular class of offsets represented by oceanic microplates. Amongthese, the Easter microplate is one of the best surveyed. This thesis first studies the stress field associated with mid-ocean ridges and simple types of ridge offsets, and then uses the stress field observed at Easter to constrain the driving mechanism of microplates. Two-dimensional finite element modelling is used to predict the lithospheric stress indicators, which are then compared with observations. Extensional structures at high angles (> 35 ) to ridge trends are often observed at ridge-transform intersections and non-tranform offsets, but remained unexplained until now. This study proposes that the topographic loading created by the elevation of mid-ocean ridges relative to old seafloor is a source of ridge parallel tensile stresses, and shows they can be explained by the rotation of ridge parallel tensile stresses at locked offsets. The elasto-plastic rheology is used to investigate the evolution of normal faults near mid-ocean ridges. It is shown that variations in the lithospheric strength, caused entirely by variations in the brittle layer thickness, can account for the observed variations in fault character with spreading rate and along-axis position. Plasticity is shown to prevent the achievement of large fault throws in thin brittle layers. Consequently, it may be important at fast spreading ridges. A new dynamic model is proposed for Easter microplate. It mainly consists of: 1) driving forces along the East and West Rifts, resulting from the combination of a regional tensile stress with an increasing ridge strength towards rift tips, 2) mantle basal drag resisting the microplate rotation, and contributing with less than 20% to the total resisting torque, and 3) resisting forces along the northern and southern boundaries. To explain both the earthquake focal mechanism evidence and theexistence of compressional ridges in the Nazca plate, the boundary conditions alongthe northern boundary are required to change with time, from completely locked tolocked in the normal direction only. This study does not invalidate the microplate kinematic model proposed by Schouten et al. (1993), but shows that normal resisting forces along the northern and southern boundaries of Easter microplate must exist in order to explain the stress observations. Also, it suggests that ridge strength variations play an important role in the dyamics of mid-ocean ridge overlap regions
Maxfield Lodge, Easter 1922
No full textBlack and white photograph of people outside Maxfield Lodge in Big Cottonwood Canyon, probably during the Wasatch Mountain Club gathering at Maxfield Lodge at Easter in 1922
Easter Sunrise Service at God's Acre in Salem, 1938.
No full textEaster Sunrise Service at God's Acre in Salem, 1938. The men are Bishop Paul B. Kern and Bishop J. Kenneth Pfohl
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