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ATLANTIS & the Atlantic Ocean


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Author Topic: ATLANTIS & the Atlantic Ocean  (Read 22110 times)
dhill757
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« Reply #345 on: March 30, 2009, 12:05:19 am »



   Sete Cidades


A small peninsula juts into Lagoa Azul ("Blue Lake"), one of two lakes partially filling the summit caldera on Sete Cidades volcano at the western end of Sao Miguel Island. The 5-km-wide caldera was formed about 22,000 years ago, and at least 22 post-caldera eruptions have occurred. This view looks to the NW from the rim of a post-caldera cone, Caldiera Grande. Two other post-caldera cones, Caldiera do Alfreres and Seara Cerrado da Ladeira, lie across the lake, behind and to the right of the town of Sete Cidades.

Photo by R.V. Fisher, 1980 (University of California Santa Barbara).



 Country: Portugal
Subregion Name: Azores and Madeira
Volcano Number: 1802-08=
Volcano Type: Stratovolcano
Volcano Status: Historical
Last Known Eruption: 1880   
Summit Elevation: 856 m 2,808 feet
Latitude: 37.87°N  37°52'0"N
Longitude: 25.78°W 25°47'0"W
Sete Cidades volcano at the western end of Sao Miguel Island contains a 5-km-wide summit caldera, occupied by two caldera lakes, that is one of the scenic highlights of the Azores. The steep-walled, 500-m-deep caldera was formed about 22,000 years ago, and at least 22 post-caldera eruptions have occurred. A large group of Pleistocene post-caldera trachytic lava domes, lava flows, and pyroclastic-flow deposits is found on the western-to-northern flanks. A nearly circular ring of six Holocene pyroclastic cones occupies the caldera floor. These have been the source of a dozen trachytic pumice-fall deposits erupted during the past 5000 years. Sete Cidades is one of the most active Azorean volcanoes. Historical eruptions date back to the 15th century and have occurred from within the caldera and from submarine vents off the west coast. 
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