Small-scale mantle convection system and stress field under the Pacific plate

We outline the methodology of our numerical studies aimed at increasing the understanding of the relation between dynamics and stress field of the lithosphere with particular reference to oceanic lithosphere. The ridge-push force is modelled as a pressure gradient integrated over all contributing parts of the lithosphere. The slab-pull force is modelled as being dependent on the age of the subducting lithosphere. We parametrize the resistive forces and determine the unknown parameters by requiring the total torque of all forces acting on the plate to vanish. We illustrate the approach by the presentation and discussion of new modelling results for the Pacific plate.

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PLATE BOUNDARY PROCESSES AND SMALL-SCALE MANTLE CONVECTION BENEATH THE REYKJANES RIDGE

10.1130/abs/2017am-304570 ◽

2017 ◽

Author(s):

Fernando Martinez ◽

◽

Richard Hey

Keyword(s):

Mantle Convection ◽

Plate Boundary ◽

Small Scale ◽

Reykjanes Ridge

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Multilingualism in Vanuatu: Four case studies

International Journal of Bilingualism ◽

10.1177/13670069211023132 ◽

2021 ◽

pp. 136700692110231

Author(s):

Mary Walworth ◽

Amy Dewar ◽

Thomas Ennever ◽

Lana Takau ◽

Iveth Rodriguez

Keyword(s):

Case Studies ◽

Primary Data ◽

Small Scale ◽

Language History ◽

Speech Communities ◽

The Pacific ◽

Historical Processes ◽

The Social ◽

Original Contribution ◽

B Mobility

Each of the 65 inhabited islands of Vanuatu hosts its own unique linguistic environment in which varying degrees of multilingualism are found. This paper defines various types of small-scale multilingual settings in Vanuatu and explores what sociohistorical factors have led to them. This paper is based on first-hand observations and primary data collected by the authors in four locations in the Pacific Island nation of Vanuatu since 2016: two neighboring villages of Emae Island (Makatu and Tongamea), North Malekula, and on Maewo Island. The assessments of multilingualism in these examples from Vanuatu were qualitative, based on observations of sociolinguistic practices in each of these areas, as well as data from language history and language use surveys carried out in each place. Through defining and comparing the types of multilingualism present in the four case studies, we identify patterns in the social and historical processes that lead to various kinds of multilingualism: (a) interaction of linguistic and sociocultural identities and (b) mobility of both individuals and entire speech communities. The examples described in this paper are used to highlight the diversity of multilingualism found in Vanuatu and to explore how their differing linguistic environments and histories have contributed to their varying degrees of multilingualism. This paper makes an original contribution to knowledge about the small-scale multilingual situations in Vanuatu, offering descriptions of previously undocumented and endangered multilingual environments. Through an examination of the sociocultural motivations for multilingualism, alongside historical migrations of speaker groups and marked sociolinguistic identities, this paper contributes to research on why and how small-scale multilingualism can develop. Furthermore, this paper provides the foundation for future, more rigorous investigations into the small-scale multilingual situations of this highly understudied region.

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Planform of mantle convection beneath the Pacific Ocean

Nature ◽

10.1038/288442a0 ◽

1980 ◽

Vol 288 (5790) ◽

pp. 442-446 ◽

Cited By ~ 130

Author(s):

Dan McKenzie ◽

Anthony Watts ◽

Barry Parsons ◽

Micheline Roufosse

Keyword(s):

Pacific Ocean ◽

Mantle Convection ◽

The Pacific ◽

The Pacific Ocean

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Unusual earthquakes in the Gulf of Alaska and fragmentation of the Pacific Plate

Geophysical Research Letters ◽

10.1029/gl015i013p01483 ◽

1988 ◽

Vol 15 (13) ◽

pp. 1483-1486 ◽

Cited By ~ 44

Author(s):

J. C. Lahr ◽

R. A. Page ◽

C. D. Stephens ◽

D. H. Christensen

Keyword(s):

Gulf Of Alaska ◽

Pacific Plate ◽

The Pacific

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On the enigmatic birth of the Pacific Plate within the Panthalassa Ocean

Science Advances ◽

10.1126/sciadv.1600022 ◽

2016 ◽

Vol 2 (7) ◽

pp. e1600022 ◽

Cited By ~ 16

Author(s):

Lydian M. Boschman ◽

Douwe J. J. van Hinsbergen

Keyword(s):

Triple Junction ◽

Tectonic Evolution ◽

Plate Boundary ◽

Pacific Plate ◽

Plate Tectonic ◽

Point Location ◽

Marine Magnetic Anomalies ◽

The Pacific ◽

History Of ◽

Ridge System

The oceanic Pacific Plate started forming in Early Jurassic time within the vast Panthalassa Ocean that surrounded the supercontinent Pangea, and contains the oldest lithosphere that can directly constrain the geodynamic history of the circum-Pangean Earth. We show that the geometry of the oldest marine magnetic anomalies of the Pacific Plate attests to a unique plate kinematic event that sparked the plate’s birth at virtually a point location, surrounded by the Izanagi, Farallon, and Phoenix Plates. We reconstruct the unstable triple junction that caused the plate reorganization, which led to the birth of the Pacific Plate, and present a model of the plate tectonic configuration that preconditioned this event. We show that a stable but migrating triple junction involving the gradual cessation of intraoceanic Panthalassa subduction culminated in the formation of an unstable transform-transform-transform triple junction. The consequent plate boundary reorganization resulted in the formation of a stable triangular three-ridge system from which the nascent Pacific Plate expanded. We link the birth of the Pacific Plate to the regional termination of intra-Panthalassa subduction. Remnants thereof have been identified in the deep lower mantle of which the locations may provide paleolongitudinal control on the absolute location of the early Pacific Plate. Our results constitute an essential step in unraveling the plate tectonic evolution of “Thalassa Incognita” that comprises the comprehensive Panthalassa Ocean surrounding Pangea.

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