The Luzon Strait is approximately 250 kilometers (160 mi) wide containing a number of islands belonging to the Philippines that are grouped into two: the islands comprising the province of Batanes and the Babuyan Islands, which are part of the province of Cagayan. The strait is divided into a number of smaller channels. The Babuyan Channel separates Luzon from the Babuyan Islands, which is separated from Batanes by the Balintang Channel [tl]. Batanes is separated from Taiwan by the Bashi Channel.[citation needed]
Some of the largest ocean waves in the world, at times over 170 meters in height and stemming from tides and ocean currents, are found in the north of the strait. These waves or currents are underwater and rarely break the surface, thus posing no danger to shipping but are sometimes visible to satellites. The oscillation is largely prompted by a long north–south ridge which covers almost all of the strait, then amplified in the northern section by a second parallel ridge.[4] The depth of the strait reaches the 3,500 m and 4,000 contours in north–south trenches in the middle and south-western edge.[citation needed]