Vulcanicity of historic times in the Middle Atlantic Islands

Mitchell-Thomé, Raoul C.

doi:10.1007/bf02598189

Cited by 9 publications

(7 citation statements)

References 16 publications

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“…This flow reached both the northern coast (at Rabo de Peixe town) and the southern coast near the town of Lagoa. The two historical flows are described in chronicles by Mitchell-Thomè (1981) and Booth et al (1978). For older flows, boundaries were delimited on the geological map of Moore (1990) based on field evidences.…”

Section: Geological Setting and Studied Lava Flowsmentioning

confidence: 99%

Paleointensity determination from São Miguel (Azores Archipelago) over the last 3ka

Chiara

Tauxe

Speranza

2014

Physics of the Earth and Planetary Interiors

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Paleointensity data from the Atlantic Ocean are rare. We present new paleointensity data from São Miguel (Azores Islands, Portugal) based on 20 paleomagnetic sites from 13 lava flows emplaced over the last 3000 years. Ten lava flows are radiocarbon dated, whereas three flows were paleomagnetically dated and one site was dated using stratigraphic relations. All the samples, previously investigated to recover paleodirections, were subjected to IZZI experiments. Importantly, the new data are internally consistent, agree with Moroccan and European datasets, and offer new constraints for global geomagnetic field models. Some of the ages of the paleomagnetically dated lava flows have been revised based on the intensity data presented here. The inferred Virtual Axial Dipole Moments (VADMs) range from 68.2 to 163.5 ZAm 2. A peak in field strength with an estimated age of around 600 BC is well supported by two sites from the same flow (Furna), and is comparable to the high intensity values found in Portugal for the same age and the earlier field peak at about 1000 BC in the Levant. A gradient in VADM values with latitude from northwestern Africa and across Europe between 100 and 1000 AD is confirmed as well as its absence from between 0 to 100 AD.

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Section: Geological Setting and Studied Lava Flowsmentioning

confidence: 99%

Paleointensity determination from São Miguel (Azores Archipelago) over the last 3ka

Chiara

Tauxe

Speranza

2014

Physics of the Earth and Planetary Interiors

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“…Native vegetation is under pressure due to the grazing of cows, donkeys and goats (GEF/UNEP, 2015). Brava's neighbouring islands, Santiago and Fogo, were the first to be significantly settled by Europeans (c. 1460 and 1470 CE, respectively), but it is estimated that Brava remained only marginally inhabited until c. 1680 CE, when ‘many families’ from Fogo fled to take refuge in Brava after an earthquake and a major volcanic eruption (Correia, 2000; Mitchell‐Thomè, 1981; Ribeiro, 1960) (Table S1). Here, we present multiple palaeoecological analyses to show how ecosystems and soils in Brava changed over the last 9700 yr in response to global‐to‐local and potentially co‐occurring environmental changes, including regional drying, within‐archipelago volcanism and inter‐island human migration.…”

Section: Introductionmentioning

confidence: 99%

Effects of Holocene climate change, volcanism and mass migration on the ecosystem of a small, dry island (Brava, Cabo Verde)

Castilla‐Beltrán

Nascimento

Fernández‐Palacios

et al. 2021

Journal of Biogeography

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“…In this paper we report 33 new paleomagnetic directions obtained from 16 different lava flows of the last 3 ka exposed at São Miguel, the largest island in the Azores (Figure 1). Two of the studied lava flows were emplaced in the last five centuries and are described in historical chronicles [ Mitchell‐Thomè , 1981; Booth et al , 1978], while the ages of eleven flows are tightly constrained by radiocarbon ages of charcoals or paleosols lying below the flows themselves. Our data, along with six paleomagnetic directions previously gathered from the same lavas by Johnson et al [1998], allow reconstruction of the evolution of geomagnetic field directions for the Azores during the last 3 ka.…”

Section: Introductionmentioning

confidence: 99%

Paleomagnetic secular variation at the Azores during the last 3 ka

Chiara¹,

Speranza²,

Porreca³

2012

J. Geophys. Res.

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We report on 33 new paleomagnetic directions obtained from 16 lava flows emplaced in the last 3 ka on São Miguel, the largest island of the Azores. The data provide 27 well‐dated directions from historical or 14C dated flows which, together with 6 directions previously gathered from the same flows by Johnson et al. (1998), yield the first paleomagnetic directional record of the last 3 ka from the Atlantic Ocean. Within‐flow directions are consistent, suggesting that inclination swings from 60° to 25° and declination changes between −10° to 20° reflect variations in the geomagnetic field over the last 3 ka. To a first approximation, the declination record is consistent with predictions from CALS3k.4 and gufm1 global field models. Conversely, inclination values are lower than model predictions at two different ages: 1) four sites from the 1652 AD flow yield I = 48° instead of I = 63° predicted by gufm1; 2) data from several flows nicely mimic the inclination minimum of 800–1400 AD, but inclination values are lower by ∼10° than CALS3k.4 model predictions. By interpolating a cubic spline fit on declination / inclination versus age data, we tentatively infer the directional evolution of the geomagnetic field at the Azores from 1000 BC to 1600 AD. The obtained curve shows three tracks in virtual overlap during the 1000–800 BC, 800–500 BC, and 400–700 AD time spans.

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Vulcanicity of historic times in the Middle Atlantic Islands

Cited by 9 publications

References 16 publications

Paleointensity determination from São Miguel (Azores Archipelago) over the last 3ka

Paleointensity determination from São Miguel (Azores Archipelago) over the last 3ka

Effects of Holocene climate change, volcanism and mass migration on the ecosystem of a small, dry island (Brava, Cabo Verde)

Paleomagnetic secular variation at the Azores during the last 3 ka

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