Baipijie Mountain Sea Area

Baipijie Mountain Sea Area

The Baipijie Mountain Sea Area is located at the edge of the continent, extending into the coastal water system facing the open sea. The seabed gradually slopes from west to east. The western part mainly consists of soft mud and muddy-sandy sediments, while the eastern half is dominated by sandy-mud and gravel. The entire sea area lies within the mixing zone of two major water systems: the continental freshwater discharge and the offshore waters of the East China Sea, resulting in a mixed water mass formed by the blending and transformation of these two systems. The water transparency is around 2 meters, with a water color index of 17–19. The tides in this sea area are regular semi-diurnal tides. The tidal level is higher in summer and lower in winter, with two high tides and two low tides occurring each day. Each tidal cycle takes approximately 12 hours. The water depth ranges from 15 to 52 meters. The flood current flows northwest, while the ebb current flows southeast, with the current direction reversing around three hours before and after the high tide at Lvhuashan, at a speed of 3–4 knots. The sea area includes islands such as Baipijie Mountain, Yingke Mountain, Yingzhao Reef, Ping Reef, Xiaobaipijie Mountain, Baipijie Long Reef, Hongshan, Nanshan, Banbianshan, Yuyan Yu, Xiaobanbianshan, Banbian Dajiao, and Tianluo Reef. The total land area of these islands is approximately 1.188 square kilometers, with the larger ones being Baipijie Mountain and Banbianshan. The sea area stretches about 10 kilometers in length and 6 kilometers in width, covering an area of about 60 square kilometers.

Baipijie Island is an irregular right-angled triangle with a winding coastline. The western shore is 1,300 meters long, forming a right angle with the 750-meter-long northern shore. The southeastern shore is the hypotenuse, measuring 1,600 meters in length. Both the northern and southeastern shores have bays, and the southern end is only 250 meters wide, with an area of 0.5 square kilometers. The highest elevation in the center is 120.7 meters. The exposed rocks are acidic welded tuffs from the Upper Jurassic system. The surrounding water depths are 3.3–7.6 meters to the northeast and 17 meters to the southwest. The island is lush with vegetation, including black pine and willow trees, and the shoreline produces shellfish. Banbianshan is 1,400 meters long and 200–300 meters wide, stretching in a northwest–southeast direction in an irregular elongated shape, with an area of 0.24 square kilometers. Its highest point is 79.4 meters above sea level. The exposed rocks are intermediate-acidic volcanic rocks and rhyolite from the Upper Jurassic system. The surrounding water depths range from 12.8 to 38 meters. The island is covered with grass, reeds, and kudzu vines, with scattered small black pine trees planted. The Baipijie Mountain Lighthouse is located on the mountain.

The Baipijie Mountain Lighthouse is an international-grade lighthouse and one of the main navigation aids in the Baipijie Strait. The total building area is 180.95 square meters, with the lantern room covering 9.07 square meters. The tower is constructed of reinforced concrete, cylindrical in shape, with red and white horizontal stripes. It stands 14.3 meters tall, with the light source elevated 75 meters above sea level. Originally fueled by kerosene, the light source has since been converted to diesel-generated electricity. The lantern uses a bull’s-eye lens, housing a flashing light that alternates between red and white every minute, with a brightness of 500 watts, a range of 22 nautical miles, and a candlepower of 8,000. In the second year of the Xuantong era (1910), this was increased to 32,000 candlepower, and by 1929, it reached 75,000 candlepower. The lantern room originally had two fog cannons, which fired every two minutes during foggy conditions, but these were dismantled by the Japanese invaders in 1937. There is also a standby white fixed light with a range of 8 nautical miles.