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Hotspots and volcanic uplift

An EU team unravelled the Cape Verde islands' uplift history due to volcanism. The study found evidence of the largest megatsunami known to science, caused by a flank-collapse, also highlighting the contemporary risk of such events.
Hotspots and volcanic uplift
The Cape Verde Archipelago is a group of 10 volcanic islands located 600 km off the tropical west-African coast. The group has been uplifted during the last 2.5 million years, yet it is unclear whether the cause was local or regional geological processes.

The EU-funded ISLAND FREEBORD (What can island isostasy tell us about hotspot dynamics) project dated the islands' uplift features using several methods.

First, the team searched for dateable material, including preserved wave-cut surfaces, young lava deltas and pristine corals. Results indicated that two northwestern islands (Santo Antao and Sao Vicente) lack uplift features above 20 m. Other islands showed various kinds of evidence for Quaternary uplift, up to 130 m.

Dating of surface materials yielded mixed results. Most samples showed a complex mix of exposure ages, or ages younger than expected. U-Th radioisotope dating of corals allowed dating of certain lower terraces (<20 m). However, the complexity of exposure ages in the higher terraces did not allow discrimination between competing theoretical models. Thus the team introduced additional geochronology to increase the dating resolution.

The study concluded that competing volcanic and intrusive processes govern island growth. Islands can emerge above sea level by uplift rather than summit eruptions.

Researchers also found unprecedented evidence of megatsunamis caused by island flank collapses. One such megatsunami affected the archipelago, caused by the catastrophic flank collapse of the Fogo volcano 73 000 years ago. The work ended a long debate on the tsunami potential of island-flank collapses, with Fogo constituting the largest megatsunami known from the geological record. The study also pioneered the use of 3He geochronology for such deposits.

The project's work benefitted the scientific community and hazard-monitoring agencies. As a result, such agencies, with civil protection bodies, may be more informed of the tsunami threat posed by Cape Verde volcanoes.

Related information


Cape Verde Archipelago, ISLAND FREEBORD, uplift, isostasy, hotspot, dynamics
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