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Geology of Hong Kong

Geology of Hong Kong is dominated by igneous rocks formed during a major volcanic eruption period in Mesozoic. It made up 85% of Hong Kong's land surface. The remaining 15% are mostly sedimentary rocks formed by deposition of sediments located in northeast New Territories of Hong Kong. There are also a very small percentage (less than 1%) of metamorphic rocks found in New Territories. These are formed by deformation of pre-existing sedimentary rocks which changed the mineral assemblages in the rock.

Geological history of Hong Kong started as early as Devonian period (~420 million years old) which was determined by the discovery of Placoderm fossils in northeast Hong Kong. The youngest rock is from Paleogene (~50 million years old) which is exposed in Tung Ping Chau, an island in the northeastern corner of Hong Kong.

The three type of rocks: igneous, sedimentary, and metamorphic rocks all formed spectecular geological landscapes in Hong Kong. Igneous rocks fromed the famous hexagonal columns in Sai Kung and the most of the hills in Hong Kong. Sediementary rocks fromed erosion platforms and sea stacks in Tung Ping Chau. Metamorphic rocks fromed the iron ore in Ma On Shan which was an active mining site before. Each of these will be introduced in later sections.

In terms of sturctural geology, there are two main faults running from the northeast, through Tolo channel, to the southwest of Hong Kong. Deformation features can be found along the fault,