導賞點 3
為什麼四處石頭都是紅色的?
Why are all those rocks in red color?
你知道嗎?其實甫踏上今天的旅程,您就已踏足具聯合國教科文組織評級的香港地質公園,既然如此怎能不欣賞一下香港的岩石?
Did you know? The route you are on today is the part of Hong Kong UNESCO Global Geopark. So, how can you not admire Hong Kong’s rock formation?
大家可能會覺得奇怪,怎麼走到三椏涌、三椏村附近,岩石都帶粉紅色的?
Upon reaching near Sam A Chung and Sam A Tsuen, you may find it intriguing that the rocks are pinkish in colour.
苗三古道位於香港地質公園的「新界東北沉積岩園區」內,在三椏灣附近所見的岩石主要是沉積岩,屬八仙嶺組,由礫岩、砂岩及粉砂岩組成。三椏灣亦屬於印洲塘海岸公園的一部分。
Miu Sam Ancient Trail is situated on the Northeast New Territories sedimentary rock region,within the compound of Hong Kong Geopark. The rocks at Sam A Wan are mainly sedimentary rock, (belonging to the same rock formation group as Pat Sin Leng). The rocks consist of conglomerate, sandstone, and siltstone. San A Wan is also part of Yan Chau Tong Marine Park.
有關印洲塘的地質資料:
Geological information about Yan Chau Tong:
「今天所見的印洲塘地貌乃1億8000萬年前中侏羅世多次火山爆發的產物。火山活動摧毀了原來主要由砂岩及粉砂岩組成的沉積岩層,熔岩夾雜着火山灰在地表凝固成岩,產生了厚約2000米的火山岩層,即現時亞椏灣以北至荔枝窩、沙頭角一帶的粗火山灰晶屑凝灰岩,此外還形成往灣洲、娥媚洲及吉澳三島。火山活躍期過後,爆發慢慢消竭,緊接而來的是長約2000萬年的侵蝕風化期,河流從高嶺淙流而下,把沙石沖刷至近岸低地,形成厚約500米的沉積岩層,也就是印洲塘、八仙嶺、赤洲一帶的礫岩、砂岩、粉砂岩及頁岩。」(註1)
“The present landscape of Yan Chau Tong (also known as Double Haven) originates from a series of volcanic eruptions in the Middle Jurassic 180 million years ago. Devastating explosions destroyed the original sedimentary rock which comprised mainly sandstone and siltstone. Great clouds of volcanic ash mixed with lava settled on the ground and formed a volcanic rock stratum about 2,000 metres thick. The coarse ash crystal tuff that extends from the area north of Sam A Wan to Lai Chi Wo and Sha Tau Kok, Double Island, Crescent Island and Crooked Island. As eruptions and volcanic activities gradually stopped, this region underwent about 20 million years of erosion and weathering when rivers washed sand and gravels down the surrounding mountain ranges to settle in the downstream coastal flats. They formed the conglomerate, sandstone, siltstone and shale of Double Haven, Pat Sin Leng and Port Island (Chek Chau). The sedimentary rocks in these parts are about 500 metres thick.” (Footnote 1)
這些沉積岩之所以呈紅色,是因為「沉積物中帶鐵的礦物便轉化為紅色的氧化鐵,它把沉積物如砂粒膠結起來,形成顏色獨特的紅色沉積岩。」(註2) 亦相信是由於形成時期天氣炎熱,令沉積物中的鐵礦物氧化作用特別厲害,造成深淺不一的紅色岩石。
These sedimentary rocks are red because “the ferric minerals within turned into iron oxide and bonded with sand and other sediments to become a unique red sedimentary rock”. (Footnote 2) It is believed that the hot climate caused the iron mineral in the sediment to oxidize intensely, resulting rocks in various shades of red.
香港地質公園於2009 年成為中國國家地質公園,並在2015年更名為「香港聯合國教科文組織世界地質公園」,大家除了可以一睹世界級的地貌景觀外,更可了解更多香港的自然地質歷史。
Hong Kong Geopark became China National Geopark in 2009 and renamed “Hong Kong UNESCO Global Geopark” in 2015. In addition to seeing world-class landscapes, you can also learn more about the natural geology of Hong Kong.
註1及2資料來源 :
Footnotes 1 and 2:
Hong Kong UNESCO Global Park official website
2. 香港地質公園範圍(地圖)