Building the Cape Verde Islands by Ricardo A. S. Ramalho

By Ricardo A. S. Ramalho

Hotspots are enigmatic floor positive aspects that aren't simply defined within the framework of plate tectonics. Investigating their beginning is the aim of this thesis, utilizing box facts accrued within the Cape Verde Islands, a in demand hotspot archipelago within the japanese Atlantic Ocean. The method taken is to record uplift of the islands relative to sea point and use the uplift gains to check quite a few versions of hotspot improvement. Island uplift is assumed to come up from the expansion of the anomalously shallow seafloor on which the islands relaxation, referred to as the bathymetric swell, that's attribute of hotspots.

The paintings includes a geological precis and precise mapping of paleo sea point markers on Cape Verde. Isotopic courting of the markers exhibits that uplift at the islands during the last 6 Myr is as much as four hundred m, and that the uplift chronology varies between islands. techniques act to elevate the Cape Verde Islands. The dominant technique is one who is neighborhood to person islands. The local, swell-related part is smaller, and doubtless episodic. The observations supply robust constraints on swell improvement and on hotspot models.

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Hodgson, N. (1988). Magma sources of the Cape Verde Archipelago: Isotopic and trace element constraints. Geochimica et Cosmochimica Acta,52, 2979–2992. 46. , & Cliff, R. (1989). A combined chemical and Pb-Sr-Nd isotope study of the Azores and Cape Verde hot spots; the geodynamic implications. Geological Society of London Special Publications, 42(1), 231–255. 47. , & Kurz, M. D. (2003). Pb-Sr-He isotope and trace element geochemistry of the Cape Verde Archipelago. Geochimica et Cosmochimica Acta,67(19), 3717–3733.

Combinations involving Dq significantly larger than 90 kg/m3 yield unrealistic topographies. 3 km height of the swell, suggesting that slightly lower density differences should be used. The suggested solutions involve a flux rate constant (a) that varies from 0 to 1; a = 0 implies instantaneous volumetric release while a = 1 corresponds to constant flux conditions. 3 Lubrication Model Coupled with Isostatic Uplift 35 Fig. 5 Swell topography for each of the selected combination of parameters. qm ¼ 3; 300 kg/m3 , qw ¼ 1; 030 kg/m3 , t ¼ 26 Ma with a volcanic history extending from that time to the present.

An additional constraint is the geoid anomaly (DN) and the geoid to topography ratio (DN=H) associated with the possible numerical solutions. Only solutions that yield 8 DN 12 m and 3:4 DN=H 6:0 m/km are in agreement with the observational constraints. In the following calculations DN is estimated using a reference column composed of: 5:4 km @ 1; 030 kg/m3 þ 7 km @ 2; 800 kg/m3 þ 87:6 km @ 3; 300 kg/m3 Þ |fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl} |fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl} |fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl} sea crust ð3:6Þ mantle The effects on the geoid of the volcanic edifices and the flexural compensation associated with the loading of the edifices were not considered.

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