Danxia wonder at sea － Port Island (Chek Chau)

Danxia wonder at sea － Port Island (Chek Chau)
Background Information
Sitting at the mouth of Tolo Harbour in Tai Po, Port Island overlooks the southern Tap Mun Island. This uninhabited island may seem lone and barren, but it is the gateway of Tolo Harbour for it guards the strategic pass of Tolo Channel. As the Chinese name Chek Chau implies, Port Island is a place of red earth. The ground on the entire island is rust-coloured conglomerate and siltstone. From Wong Chuk Kok Hoi to Hung Shek Mun, past Tsat Shue Wan, Cheung Tsui to Hung Pai, it is a grandiose domain of red peaks, rusty soil, red earth and green trees. This extraordinary scene is known as “Danxia Wonder at Sea”.
Red earth landscapes are called “Danxia” wonders in China. Examples are Danxia Shan in Guangdong, Wuyi Shan in Fujian and Lungfu Shan in Jiangxi. Port Island is the number one representative of Hong Kong. Other danxia sites are Kung Chau, Ap Chau and the Hong Kong Red Sea. Dazzling red terrain is the biggest fascination of Port Island. The hills are completely covered with reddish-brown conglomerate and siltstone, making it a true “red island”. What brought about such unusual sights? Geologically, the answer lies in the ancient times. After more than 6 million years of robust lava and volcanic activities, most regions of Hong Kong became igneous rock terrains. When volcanic activities subsided, extended dry climate set in. Great temperature difference between day and night caused avalanches. Weathered rocks toppled down from the uplands and were quickly transported and deposited. Gravel, sand and silt arising from weathering were washed down by seasonal rainstorms to the alluvial plains where they settled. There, the ferric minerals within turned into iron oxide and bonded sand and other sediments to become a unique red sedimentary rock. Hot climate and the scorching sun aided release of iron in the sand and gravel. For this reason they were tinted red or rust in various intensities. Sediments of the alluvial plains and river channels eventually formed the red or coloured terrestrial clastic sedimentary rocks seen on Port Island today. Main components are conglomerate, sandstone and siltstone. These rocks are known as Port Island Formation.