«Sai Kung Geopark Tour Commentary Special Thanks: Agriculture, Fisheries and Conservation Department and San Cheung for their invaluable support The ...»
(The tour would go further up until reaching the top of the island.) Standing on top of Kiu Tau, you can get almost a full view of Sai Kung islands. Referring to maps up here, you can get to know some of the neighboring islands’ names such as Kau Sai Chau (滘西洲) where there is a public Golf Course that everyone can play without membership.
Over there is Jin Island (吊鐘洲), further down is the Ung Kong Group (甕缸群島) and High Island (糧船灣洲). Then down south is the Ninepin group (果洲群島) etc.
Summary Length of trail: Around 2.2 km in length for a round trip.
Highlight of trail: Appreciating stunning Hexagonal Rock columns, Fault & Fissure, Coastal Erosion Landscape, Sea Stack, Twisted Rock Columns and Basaltic Dyke / Basaltic Intrusion.
Recommended time of staying: 1 hour and 30 minutes.
Recommended tour route:
1. The Commemorate Dolosse (the engineering of reservoir and it’s history)
2. The East Dam (looking at Po Pin Chau & the wall mural at far end and left of Dam)
3. The fault line and it’s relationship to the sea cave below the Commemorate Dolosse
4. Hexagonal Rock Column and its formation
5. The grand S-shape Columns (Earth movement forces)
6. Basaltic dyke (magma intrusion)
7. Joints (how it affects the landform)
8. Back up to the Pavilion (free to touch rock specimens and conclusion time)
The tour content:
(The tour starts from the Commemorate Dolosse.) The giant rock here is manmade concrete. It’s in the shape of “Twisted H” and weighted 25 tons each. There are altogether 7000 pieces of this Dolosse Rock made on the spot for the purpose of constructing a Coffer Dam just to protect the Main Dam from being striking continuous by the strong waves coming in from West Pacific Ocean. Especially during the typhoon and the winter monsoon seasons, the roaring wave could be devastating. The landscape around here would be good evidence. When the coffer dam is striking by the strong wave, the twisted H rocks interlock each other to break the wave and absorbed wave Hence, it works so well so far.
Hong Kong was suffering from water rationing in the 60’s. The worst case was only 4 hours water supply to the public in every four days time. Besides working hard with finding space for building reservoirs, Hong Kong had to seek help from China. In 1966, China started to supply water through big water pipes getting water from the Dongjiang in Guang Dong Province.
Unfortunately, China shutdown the supply in 1967 due to the Cultural Revolution. The government then responded with the construction of this High Island Reservoir. It was the second reservoir constructed from the ocean. The first one is Plover Cove Reservoir in Tai Po.
The reservoir was built by constructing two main dams connecting High Island to the Sai Kung Peninsula. With roads laid down on the dams, now High Island is no longer an island any more.
The original ocean channel between the two places was then turned into a closed lake area.
Moreover, the two dams were raised to a level of 100 meter to make it the largest reservoir in Hong Kong by volume. Aqueducts totaling 8 km in length were also constructed to transfer water from streams around Sai Kung Peninsula to the reservoir. The construction took 8 years to complete in 1979. After it’s completion, Hong Kong has been safe with water supply even though today we are still getting regular water supply from China of up to 70 percent of our consumption.
Here’s something interesting to tell you. Can you see the water level inside the dam is much higher than outside at the ocean? Also can you imagine underneath the water, you could find sites of up to ten villages being submerged by the rising water level, and most of their houses are still intact except that they can’t be used any more. The indigenous farming and fishing families were all being removed to live in the Sai Kung Town. Besides each family was compensated by giving them proper living space, they were also given a shop on the ground floor just for them to make a
(Tour to be continued by walking to middle part of the Dam where the information board is located.) There are a few things worth seeing from here. First, you can see lots of big granite rock boulders on the inside of the dam. Please note that these granites are being transported here only, and not originated from here. The way to identify granite from volcanic rock is easy. Can you see granite has relatively large size mineral crystals. Granite was formed by underground magama cooled off over a relatively longer period of time and allowing mineral crystal to grow. Hence, you can identify the 3 major minerals crystal of granite: the quartz (石英), feldspar (長石) and mica (雲母).
Now please come over to the other side and you can have a look on the volcanic rock formed on the ground. Hot volcanic materials, ashes and may be lava came out of crater and into the air with high temperature. It was quickly cooled off by air temperature and solidifies in a short period of time, allowing not much time for minerals to grow into large crystals. Thus, volcanic rocks usually contains no large mineral crystals but only little ones. Those smoky transparent dots are quartz crystal and the pinky ones are feldspar crystals.
Hence you can identify these two types of rocks easily.
Next you should look outside to the ocean at the little island just off the coffer dam. That is the Po Pin Chau. If you look carefully, you can tell it was originally part of the Fa Shan mountain of High Island. It’s a result of the wave erosion alone the fault line over a long period. One of the characteristics of hexagonal columns is that once the lower part being eroded, the hanging upper parts will be easily fall down due to gravity (especially those with horizontal joints exist). The vertical joints of these column help cutting it apart to form this stack island. It’s even more amazing that the cutting wall carrying hundreds of vertical hexagonal rock columns resembling very much like a giant church pipe organ.
Now let’s look at the far end left of the dam where you can see another huge wall mural. Again you can see obvious rock columns and they are literally cover up the entire wall. The horizontal platform layers are to cut short the rock columns in order to avoid long distance falling. Hence the tumbling debris are staying on different levels. But if you look more carefully, there are columns that are bent into curve. Who can bend a piece of rock?
The answer is again the mother-nature. When the magma started to cool off, contracting, and gradually forming the polygonal columns. It still would take sometime before the column rock to get solidified. During such time, there could be other minor earth movement caused by underground collapse due to losing of magma. The jelly form column would then lean over because of its weight until getting its balance. Later on when it got solidified, the rock column then ended up in curve shape.
(Continue to walk down slope until reach the big fissure.) Halfway down the slope, there is an obvious fault line comes into sight. There are lines of weakness existing in most rocks. The fault line in front of us is a major line of weakness. The rock strata / mountain was broken under the enormous generated in earth movement in the past.
The broken parts being compressed and pushed up and down, grinded to each others. In between, rocks were crumbled into fragments or called fault breccia.Fault breccias formed a zone of 2 meter thick and stretch a long way into both ends of the mountain. Look further down across the Page 21 buffer pool. There’s a huge sea cave related to this fault. You can follow the running direction of this fault line and will go exactly where the cave is located, as well as up above the cave. Before the coffer dam was built, crashed rocks along the fault line was eroded easily by the wave to form such a big cave as it was relatively much weaker than the rocks on both sides.
(Continue walking down slope and go all the way to the wall with the big “S”.) On this wall, this is regarded as the master piece of art made by mother-nature. You can tell there are several stages of earth movement happened before. First of all, just before the semi-molten rock columns were getting hardening, there were two forces coming from opposite side pushing the rock slowly to bend in the shape of a big “S”. Gradually, the columns were solidified and getting harder, but the forces were still there. Then the columns were cracked and going apart leaving a big gap in the center. Some years later, there were other minor earth movements that the Basaltic lava found its way gushed up to fill up the gap. After cooling, it became a line of Basalt Dyke (玄武岩岩脈) which appeared in black colour and easy to identify. Lava that formed basalt is much lower in acidic content and thinner in viscosity that it could make its intrusion easier.
(End of commentary. From here everyone will have free time to take pictures and should slowly walk back uphill to the bus.) The Sai Kung Visitor Centre Before or after going through the gate of restriction on vehicles at Pak Tam Chung, there sits an excellent option for visitors going to High Island East Dam – The Sai Kung Visitor Centre. You can flip through information and background on the followings in a short while to make your trip more fruitful.
Traditional rituals of villages in Sai Kung: The local inhabitants were mostly Hakka farmers coming here for more than two centuries. They farmed for their own daily necessities. They collected shells and corals for making lime powder together with excavation of granite stones as building materials. They believed in several gods and have special festivals with serious rituals.
Ecological and geological interest in the area: The ecosystem in this area is rich in variety due to diversity of habitats - a wide variety of landform, mountain, valleys, streams, ponds and coast etc.
Hence animals and human alike is found in large number. The geological features are also rich enough to provide leisure fun and educational purposes for visitors. Pictures and models are displayed to indulge visitors’ desire for seeing more.
Recreation and Scenic areas in Sai Kung Country Parks: The landscape of Sai Kung is unrivaling in Hong Kong. It has high mountains and valleys that suits hiking and picnicking.
Beautiful beaches and islands cater water sporting lovers wonderful pastimes. Nature lovers will find Sai Kung like heaven to them.
Page 22Boat Tour Route
Boat Tour of Sai Kung Islands (The tour takes 4 hours to appreciate the various coastal landforms and the spectacular Hexagonal Rock Columns from the sea. As most offshore islands in Sai Kung are remote, boat tour provides access for visitors to appreciate the scenic beauty and see the diverse morphology of coastal erosion landscapes such as sea caves, sea stacks and sea arches, as well as some depositional landforms such as beaches and tombolos.) The tour travels around: Sharp Island, Port Shelter, Jin Island, Bluff Island, Basalt Island, Wang Chau, Po Pin Chau, East Dam and High Island Interesting background of the Sai Kung Islands Hong Kong was originally a coastal plain extending much further down south of its present position. Throughout the three million years of violent volcanic eruptions during the late Jurassic to early Cretaceous (143 mya - ~140mya), the whole region was uplifted (when the continental plate being pushed by the Philippine plate) and the landscape was being re-shaped to have many peaks and ridges. Then these parent rocks were subject to weathering and erosion for over 100 millions of years transforming all peaks and ridges into fantastic shapes. Most amazingly, the last Ice-age was ended some 8000 years ago that the melted ice had raised up the sea-level by 130 meters, literally drowning the majority part of the mountain ranges leaving only those high peaks and ridges standing in water as islands. These islands and those thin ridges after being striking by the relentless West Pacific waves for the last thousands of years, amazing sea arches, precipitous cliffs and numerous sea caves are now present in this beautiful Sai Kung harbour area. Let’s now start out our sea voyage immediately.
(As boat leaves the pier of Sai Kung, start briefing on tour route and giving outline of surrounding area.) Sai Kung is getting more popular than before after the enlisting of Global Geopark. People come here could really find multiple pleasure. There are famous hiking trails accessible from here. A few famous white sandy beaches also available if they want. Lots of water recreation and sports can be arranged right at the pier. Of course boating around the Port Shelter like what we are going to do would be one of the best options from Sai Kung.
Port Shelter is basically an inland sea which is well protected from the ocean wave by many islands and islets. It is one of the largest inshore water-body in Hong Kong stretching almost 100 sq km in area. There are many inshore and offshore islands and most of them are carried very special characters and moods of their own making the entire area charming to all visitors. Some are inhabited with indigenous Hakka Farmers or Tanka Fishermen for a long time. But most islands here are uninhabited especially those offshore islands. Without being touched by human, these islands are remaining with their natural beauty making boating around becoming the best recreation in Hong Kong.
Our boating route today will allow us to see the most famous geological scenic spots in Sai Kung.
We will take turn to visit the Sharp Island, Kau Sai Chau, Jin Island, Bluff Island, Basalt Island, Wang Chau, Town Island, Po Pin Chau, East Dam and High Island respectively.
It will take about 4 hours to complete the whole journey.
Interesting background Once when the boat leaves Port Shelter, we will be entering into the area of an ancient volcano.