Roca Remolinos

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, but its top can occasionally be seen during extremely low tides. It is located at the narrowest part of the channel, about 700 m from the nearest shore (the southern one). Its northern slope reaches 16° while its southern one reaches 14°. 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. The uppermost 40 m is a caprock layer made of medium to fine sandstone and is tuffite. Below this layer comes 35 m of medium sandstone which in parts has low cementation levels. Below this there are 30 m of well-cemented silt. Under the well-cemented silt there is at least 20 m of densely compacted medium sand which is partly cemented.

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. 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. Before the final decision, Roca Remolinos was investigated for its capability to support a tower. As of 2023 the central tower is being built on top of Roca Remolinos.