Roca Remolinos

This article is about the submarine rock in Chile. For the submarine rock in the Falkland Islands, see Roca Remolinos, Falkland Islands.
Platform built on top of the Roca Remolinos during the ongoing construction of Chacao Channel bridge. Picture from January 2019.

Roca Remolinos (lit. "Eddies Rock") is a submarine hill in Chacao Channel, Chile, notorious for being a major hazard for traffic along the channel. With its highest point at 20 m below sea level, Roca Remolinos does not break the surface during ordinary low tides,[1] but its top can occasionally be seen during extremely low tides.[2] It is located at the narrowest part of the channel, about 700 m from the nearest shore (the southern one).[1] Its northern slope reaches 16° while its southern one reaches 14°.[1] The rock composition varies: four different horizontal layers have been identified, all of which are made of combinations of sand and silt cemented by ferric oxide.[3] The uppermost 40 m is a caprock layer made of medium to fine sandstone and is tuffite.[3] Below this layer comes 35 m of medium sandstone which in parts has low cementation levels.[3] Below this there are 30 m of well-cemented silt.[3] Under the well-cemented silt there is at least 20 m of densely compacted medium sand which is partly cemented.[3]

When there are strong tidal currents in Chacao Channel the rock creates eddies, drawing objects to it.

Roca Remolinos was studied by Chilean Navy officer Francisco Hudson in the 19th century.[4] In early planning Chacao Channel bridge was not planned to have a central tower, but it was redesigned to make use of Roca Remolinos for installing a central tower and cut thus the span in half.[3] Before the final decision, Roca Remolinos was investigated for its capability to support a tower.[3] As of 2023 the central tower is being built on top of Roca Remolinos.[5][6]

Sketch of Chacao Channel Bridge according to Diario Concepción.[7]
  1. ^ a b c Cáceres, Mario; Valle-Levinson, Arnoldo; Atkinson, Larry (2003). "Observations of cross-channel structure of flow in an energetic tidal channel". Journal of Geophysical Research: Oceans. 108 (C4): 3114. Bibcode:2003JGRC..108.3114C. doi:10.1029/2001JC000968.
  2. ^ SHOA (1995). Derrotero de la costa de Chile, Pub. 3001, 8th ed., vol. I and II, Hydrographic and Oceanographic Service of the Chilean Navy (SHOA), Valparaíso, Chile.
  3. ^ a b c d e f g Syngros, K.; Dobry, R.; Leventis, G.E. Chacao Channel Bridge–the Design Challenges. In Proceedings of the International Conference on Case Histories in Geotechnical Engineering—Sixth International Conference on Case Histories in Geotechnical Engineering, Arlington, VA, USA, 11–16 August 2008.
  4. ^ Sepúlveda Ortíz, Jorge (1998), "Francisco Hudson, un destacado marino poco conocido en nuestra historia" (PDF), Revista de Marina (in Spanish): 1–20
  5. ^ "Comenzó construcción definitiva del Puente Chacao". Aqua (in Spanish). 2018-02-28. Retrieved 2022-04-09.
  6. ^ Martinez, Francisco; Winckler, Patricio; Zamorano, Luis; Landeta, Fernando (2023). "Bridge Pier Scour in Complex Environments: The Case of Chacao Channel in Chile". Water. 15 (2). MDPI: 296. doi:10.3390/w15020296.
  7. ^ Felipe Plascencia, Puente colgante de Chacao se levanta con acero de la Región del Bío Bío, Diario Concepción, 8 de diciembre de 2019.