scholarly journals Magnetic Fly Ash as a Chronological Marker in Post-Settlement Alluvial and Lacustrine Sediment: Examples from North Carolina and Illinois

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 476
Author(s):  
David A. Grimley ◽  
Ashley S. Lynn ◽  
Colby W. Brown ◽  
Neal E. Blair
Keyword(s):  
North Carolina ◽  
Fly Ash ◽  
20Th Century ◽  
Agricultural Land ◽  
Lacustrine Sediment ◽  
Annual Rainfall ◽  
Late 20Th Century ◽  
Alluvial Deposits ◽  
Particulate Pollution ◽  
Decadal Scale

Fly ash consists of mainly silt-size spherules that form during high-temperature coal combustion, such as in steam locomotives and coal-burning power plants. In the eastern USA, fly ash was distributed across the landscape atmospherically beginning in the late 19th century, peaking in the mid-20th century, and decreasing sharply with implementation of late 20th century particulate pollution controls. Although atmospheric deposition is limited today, fly ash particles continue to be resedimented into alluvial and lacustrine deposits from upland soil erosion and failure of fly ash storage ponds. Magnetic fly ash is easily extracted and identified microscopically, allowing for a simple and reproducible method for identifying post-1850 CE (Common Era) alluvium and lacustrine sediment. In the North Carolina Piedmont, magnetic fly ash was identified within the upper 50 cm at each of eight alluvial sites and one former milldam site. Extracted fly ash spherules have a magnetite or maghemite composition, with substitutions of Al, Si, Ca, and Ti, and range from 3–125 µm in diameter (mainly 10–45 µm). Based on the presence of fly ash, post-1850 alluvial deposits are 15–45 cm thick in central North Carolina river valleys (<0.5 km wide), ~60% thinner than in central Illinois valleys of similar width. Slower sedimentation rates in North Carolina watersheds are likely a result of a less agricultural land and less erodible (more clayey) soils. Artificial reservoirs (Lake Decatur, IL) and milldams (Betty’s Mill, NC), provide chronological tests for the fly ash method and high-resolution records of anthropogenic change. In cores of Lake Decatur sediments, changes in fly ash content appear related to decadal-scale variations in annual rainfall (and runoff), calcite precipitation, land-use changes, and/or lake history, superimposed on longer-term trends in particulate pollution.

A 1000-Year Record of Temperature and Precipitation in the Sierra Nevada

1993 ◽  
Vol 39 (2) ◽  
pp. 249-255 ◽  
Author(s):  
Lisa J. Graumlich
Keyword(s):  
20Th Century ◽  
Sierra Nevada ◽  
Response Surfaces ◽  
Summer Temperature ◽  
Ice Age ◽  
Late 20Th Century ◽  
Temperature And Precipitation ◽  
Decadal Scale ◽  
Tree Ring Data ◽  
Precipitation Variation

AbstractTree-ring data from subalpine conifers in the southern Sierra Nevada were used to reconstruct temperature and precipitation back to A.D. 800. Tree growth of foxtail pine (Pinus balfouriana) and western juniper (Juniperus occidentalis ssp. australis) is influenced by nonlinear interactions between summer temperature and winter precipitation. Reconstruction of the separate histories of temperature and precipitation is feasible by explicitly modeling species and site differences in climatic response using response surfaces. The summer temperature reconstruction shows fluctuations on centennial and longer time scales including a period with temperatures exceeding late 20th-century values from ca. 1100 to 1375 A.D., corresponding to the Medieval Warm Period identified in other proxy data sources, and a period of cold temperatures from ca. 1450 to 1850, corresponding to the Little Ice Age. Precipitation variation is dominated by shorter period, decadal-scale oscillations. The long-term record presented here indicates that the 20th century is anomalous with respect to precipitation variation. A tabulation of 20- and 50-yr means indicates that precipitation equaling or exceeding 20th-century levels occurred infrequently in the 1000+-yr record.

“Band Wagon and Gravy Train”: uses and abuses along the Silk Road

Afghanistan ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 171-194
Author(s):  
Warwick Ball
Keyword(s):  
20Th Century ◽  
21St Century ◽  
Silk Road ◽  
Late 20Th Century ◽  
Ancient Trade ◽  
International Image ◽  
Academic Discussion ◽  
The Silk Road

The Silk Road as an image is a relatively new one for Afghanistan. It appeals to both the pre-Islamic and the perceived Islamic past, thus offering an Islamic balance to previous identities linked to Bamiyan or to the Kushans. It also appeals to a broader and more international image, one that has been taken up by many other countries. This paper traces the rise of the image of the Silk Road and its use as a metaphor for ancient trade to encompass all contacts throughout Eurasia, prehistoric, ancient and modern, but also how the image has been adopted and expanded into many other areas: politics, tourism and academia. It is argued here that the origin and popularity of the term lies in late 20th century (and increasingly 21st century) politics rather than any reality of ancient trade. Its consequent validity as a metaphor in academic discussion is questioned

scholarly journals Run to the hills: Forest growth responsiveness to drought increased at higher elevation during the late 20th century

2021 ◽  
Vol 772 ◽  
pp. 145286
Author(s):  
Marín Pompa-García ◽  
Marcos González-Cásares ◽  
Antonio Gazol ◽  
J. Julio Camarero
Keyword(s):  
20Th Century ◽  
Forest Growth ◽  
Late 20Th Century

scholarly journals Urban Policies and Large Projects in Central City Areas: The Example of Madrid (Spain)

Urban Science ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 42
Author(s):  
Dolores Brandis García
Keyword(s):  
Urban Planning ◽  
20Th Century ◽  
Large Scale ◽  
Central City ◽  
Global Market ◽  
Late 20Th Century ◽  
Public And Private ◽  
Urban Policies ◽  
Starting Point ◽  
The City

Since the late 20th century major, European cities have exhibited large projects driven by neoliberal urban planning policies whose aim is to enhance their position on the global market. By locating these projects in central city areas, they also heighten and reinforce their privileged situation within the city as a whole, thus contributing to deepening the centre–periphery rift. The starting point for this study is the significance and scope of large projects in metropolitan cities’ urban planning agendas since the final decade of the 20th century. The aim of this article is to demonstrate the correlation between the various opposing conservative and progressive urban policies, and the projects put forward, for the city of Madrid. A study of documentary sources and the strategies deployed by public and private agents are interpreted in the light of a process during which the city has had a succession of alternating governments defending opposing urban development models. This analysis allows us to conclude that the predominant large-scale projects proposed under conservative policies have contributed to deepening the centre–periphery rift appreciated in the city.

scholarly journals Place matters: geographical context, place belonging and the production of locality in Mediterranean Noirs

GeoJournal ◽  
2021 ◽  
Author(s):  
Nicola Gabellieri
Keyword(s):  
20Th Century ◽  
Crime Fiction ◽  
The Novel ◽  
Late 20Th Century ◽  
Literary Works ◽  
Geographical Discourse ◽  
Detective Stories ◽  
Narrative Medium ◽  
Geographical Context

AbstractScholars have been investigating detective stories and crime fiction mostly as literary works reflecting the societies that produced them and the movement from modernism to postmodernism. However, these genres have generally been neglected by literary geographers. In the attempt to fill such an epistemological vacuum, this paper examines and compare the function and importance of geography in both classic and late 20th century detective stories. Arthur Conan Doyle’s and Agatha Christie’s detective stories are compared to Mediterranean noir books by Manuel Montalbán, Andrea Camilleri and Jean Claude Izzo. While space is shown to be at the center of the investigations in the former two authors, the latter rather focus on place, that is space invested by the authors with meaning and feelings of identity and belonging. From this perspective, the article argues that detective investigations have become a narrative medium allowing the readership to explore the writer’s representation/construction of his own territorial context, or place-setting, which functions as a co-protagonist of the novel. In conclusion, the paper suggests that the emerging role of place in some of the later popular crime fiction can be interpreted as the result of writer’s sentiment of belonging and, according to Appadurai’s theory, as a literary and geographical discourse aimed at the production of locality.

Focusing on India’s Look East Policy: India–China relationship from 1947 to 2020

2021 ◽  
pp. 223386592110183
Author(s):  
Kaushik Roy
Keyword(s):  
20Th Century ◽  
Industrial Revolution ◽  
International System ◽  
China Policy ◽  
Economic Competition ◽  
Intimate Contact ◽  
Late 20Th Century ◽  
Republic Of China ◽  
China And India ◽  
The World

Before the onset of the industrial revolution, China and India were the two biggest powers in Eurasia. Their total population comprised almost half of the world’s population. And the GNP of premodern China was half of the combined GNP of the world. Before circa 1600 CE, most of the textiles and iron in the world were manufactured in these two countries. China and India suffered a temporary eclipse during the age of colonialism. However, with the rise of the economic and military power of China and India from the late 20th century, it seems that these two countries are bound to reclaim their traditional positions as big powers in the international system. However, there is a caveat. In the premodern era, the Himalayas prevented any intimate contact between the ‘dragon’ and the ‘elephant’. But, from the mid-20th century, advances in technology, economic competition and the annexation of Tibet by the People’s Republic of China (PRC) among other factors resulted in China and India coming into direct contact with each other. The result has been cooperation–competition–conflict. And this has had consequences not only for these two countries but for the whole world. The present article attempts to trace the troubled trajectory of India’s China policy from the late 1940s (when these two countries became independent) up to the present day.

Did We Finally Slay the Evil Dragon of Cigarette Smoking in the Late 20th Century?

CHEST Journal ◽  
2014 ◽  
Vol 146 (6) ◽  
pp. 1438-1443 ◽  
Author(s):  
Richard D. Hurt ◽  
Joseph G. Murphy ◽  
William F. Dunn
Keyword(s):  
Cigarette Smoking ◽  
20Th Century ◽  
Late 20Th Century

scholarly journals Micro: An International Open Access Journal for All of Microscale and Nanoscale Science

Micro ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 1-2
Author(s):  
Eiichi Tamiya
Keyword(s):  
Open Access ◽  
20Th Century ◽  
Special Interest ◽  
Biological Properties ◽  
Open Access Journal ◽  
Length Scale ◽  
Late 20Th Century ◽  
Physical Chemical ◽  
Nanoscale Science

Since the late 20th century, there has been a special interest in the microscale and nanoscale research investigating and exploiting the physical, chemical, and biological properties of these length-scale systems [...]

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