Seismic activity at Cadamosto seamount near Fogo Island, Cape Verdes-formation of a new ocean island?

Abstract

S U M M A R YIn global catalogues only a handful of earthquakes occurred at or near the Cape Verde islands. The two most recent events occurring in 1998 and 2004 were observed in the southwest of the Cape Verde archipelago away from aerial volcanic centres. Event relocation suggests that both earthquakes may occur at the Cadamosto seamount, a 3-km-tall submarine volcanic edifice to the southwest of the active volcanic islands of Fogo. Swath mapping efforts revealed numerous small volcanic cones between the volcanic island of Brava and the seamount and between Fogo and Brava. The distribution of volcanic vents may support two plumbing systems, one feeding Fogo and volcanic cones between Fogo and Brava and another system feeding Cadamosto seamount. Using ocean-bottom seismic stations of opportunity, deployed roughly a month after a m b = 4.3 earthquake occurred in 2004 August near or at the Cadamosto seamount, we were able to locate local seismic activity clustering at the seamount. We propose that these events reflect brittle rock failure due to magma redistribution in or near a central magma reservoir or more likely dyke intrusion. The observations reported here suggest that Cadamosto seamount is the seismically most active feature in the archipelago. It might be reasonable to hypothesis that ongoing activity causes the Cadamosto seamount to grow, forming a new oceanic island in the future.

Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

“…10). A strong concentration of epicentres can be seen to the NE of the island, in an area where Masson et al (2008) and Grevemeyer et al (2010) reported submarine volcanic cones. A second, more scattered, concentration of epicentres can be seen to the SE of the island, where Hansteen et al (2013) sampled fresh volcanic products and proposed a recent submarine eruption.…”

“…The locations of Brava seismic stations were chosen taking into account previous seismicity results from temporary networks (Heleno, 2001;Helffrich et al, 2006;Faria, 2010;Grevemeyer et al, 2010), the local geology and the requirement of line of sight to the radio repeaters installed on Fogo (see Fonseca et al, 2013).…”

Pleistocene to Holocene offshore tephrostratigraphy of highly explosive eruptions from the southwestern Cape Verde Archipelago

“…Ramalho et al, 2010aRamalho et al, , 2010b, with the oldest volcanic activity known from Sal (Torres et al, 2002) and the most recent eruption on Fogo in 2014-2015. However, Late Pleistocene to Holocene volcanic activity within the southern group is limited to the islands of Fogo and Brava and the adjacent Cadamosto seamount (Holm et al, 2008;Ramalho et al, 2010a;Ramalho et al, 2010b;Grevemeyer et al, 2010).…”

“…Fogo is the most active subaerial volcano having generated almost 30 eruptions within the last 500 years (Ribeiro, 1960;Torres et al, 1997). Brava island and the adjacent Cadamosto seamount, on the other hand, are the seismically most active volcanoes of the archipelago (Helffrich et al, 2006;Grevemeyer et al, 2010;Faria and Fonseca, 2014). However, no highly explosive eruptions generating widespread ash dispersal have been reported for these three volcanoes (Ribeiro, 1960;Day et al, 1999;Hildner et al, 2011;Hildner et al, 2012;Madeira et al, 2010;Barker et al, 2012).…”

Magmatic evolution of the Cadamosto Seamount, Cape Verde: beyond the spatial extent of EM1

“…The Cadamosto Seamount is located west of the island of Brava, at the western end of the southern island chain, and is the most seismically active seamount in the Cape Verde area ( Fig. 1; Grevemeyer et al 2010). The Cadamosto Seamount, named after Alvise Cadamosto who is credited with the discovery of the Cape Verde islands in 1456, was sampled by dredging in 1985 during an RRS Charles Darwin expedition to Cape Verde (Hill 1985).…”