Why wild Tai Po rocks

Why wild Tai Po rocks

The island is a trove of age-old geological wonders well worth a visit any time

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Photo: Agriculture, Fisheries and Conservation Department, HKSAR
From where it has been standing for the past 280 million years, the Colourful Mudstone in Tai Po has been a witness to plenty of history. It saw two great tectonic plates collide, ancient armoured fish die out and, more recently, humans colonise the territory.

Ma Shi Chau houses Hong Kong's second-oldest sedimentary formations - from before the time of the famous Jurassic era dinosaurs. The 61-hectare island is a protected Special Area and one of China's 182 National Geoparks.

Young Post walked the Ma Shi Chau natural trail in eastern Tai Po with its geological wonders.

Checkpoint 1: Tombolo

One way to get to Ma Shi Chau is by cutting through the fishing village of Sam Mun Chai and over the hill in Yim Tin Tsai. Or just take a 10-minute motorboat ride. Either way, you will land on a tombolo - a bar of sand and rock deposits that links Yim Tin Tsai to the island.

Checkpoint 2: Colourful Mudstone

Along the island's south-eastern shore dotted with seashells and seaweeds, you will come across a mass of grey mudstone rock. It is coloured by patches of reddish brown oxidised iron and lines of white quartz. Mudstone, siltstone and sandstone make up most of the outdoor museum's rock population. These sedimentary rocks are created by compressing sediments, eroded rocks or lava.

Mudstone is known for its smooth surface and soft texture. The day before Young Post's excursion, pouring rain weakened the rock and you could easily rub mud off its face. Fossils, the remnants of animals and plants, are often buried with sediments and converted to rock. Like the fossilised armoured fish found in the Colourful Mudstone, they help scientists tell a rock's age.

Checkpoint 3: Quartz Vein

A stone's throw away stand ghostly weatherbeaten rocks with white raised blood vessels. This rock "blood" is in fact quartz, which once liquefied under high pressure and temperature and flowed through the cracks of volcanic tuff. As years went by, waves and wind wore down the fragile tuff while the stronger quartz veins have remained intact.

Teeny marine gastropods have taken up residence in holes carved into the tuff. This group of some 20 rocks is a fine example as to how different rocks erode at different rates.

Checkpoint 4: Lung Lok Shui

It takes some imagination to make Lung Lok Shui - meaning a dragon diving into the sea - come alive. This jagged rank of rocks is more living proof of how softer stone can be eroded by weather to expose quartz veins inside it. Some of the mudstone has weathered away, leaving more resistant shale and quartz intact. This makes the rock resemble a dragon with spikes on its back.

Checkpoint 5: Abrasion platform

For years, waves have been eroding the cliffs on Ma Shi Chau like a level chainsaw. The cliffs flatten and retreat inland, turning into a field of crumbled red rocks. As sediments build up, a new beach is born.

Checkpoint 6: Fold

Movements in the Earth's crust bend these rocks by almost 90 degrees.

The 1.5-kilometre-long Ma Shi Chau natural trail also features faults, fossils and plants. A round-trip takes about two hours to complete.

The Tai Po Geoheritage Centre offers guided tours: taipoea.org.hk/tpgeopark

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