101GeoloGical landmarks

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郊野公園之友會Friends of the Country Parks

漁農自然護理署Agriculture, Fisheries and Conservation Department

與別不同的角度，優質的相片，再附以簡單的文字及插圖，將香港101 個地標展現眼前。這是本地第一本以地標為題的優質書籍。

我們向所有地理老師、學生及大自然愛好者強力推薦。

“This book is the first of its kind about Landmarks in the territory. The selection of excellent photographs, providing a vivid

record of the most pertinent landform features in Hong Kong taken at the best vantage points, will be of interest to geography teachers and students as well as nature lovers with an eye for the stunning natural beauty of our unspoilt countryside.”

香港大學 詹志勇教授 香港中文大學 鄒桂昌教授Professor C Y Jim Professor K C Chau

The University of Hong Kong The Chinese University of Hong Kong

天地圖書有限公司Cosmos Books Ltd.

HK $55.00

Published & Printed in Hong Kong

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目錄CoNteNt 目錄CoNteNt

引言 4Introduction

岩石分類 8RockClassification

岩石種類 Rock Types 火成岩IgneousRock 流紋岩 Rhyolite 10 凝灰岩 Tuff 11 火山角礫岩 Pyroclastic breccia 12 花崗岩 Granite 13 偉晶岩 Pegmatite 14 沉積岩SedimentaryRock 角礫岩 Breccia 15 礫岩 Conglomerate 16 砂岩 Sandstone 17 泥岩 Mudstone 18 層凝灰岩 Tuffite 19 變質岩MetamorphicRock 板岩 Slate 20 石英岩 Quartzite 21 磁鐵礦 Magnetite 23

海岸地貌 Coastal Landscapes 侵蝕Erosion 海蝕洞與海蝕隙 Sea Cave and Geo 64 海蝕拱 Sea Arch 69 海蝕柱 Sea Stack 73 海蝕凹地 Wave-cut Notch 75 吹穴 Blowhole 76 海蝕平台 Wave-cut Platform 78 潮上平台 Supratidal Platform 80 堆積Deposition 沙咀 Sand Spit 82 連島沙洲 Tombolo 86 海灣與岬角 Bay & Handland 90 巨礫灘 Boulder Beach 94 沙灘 Sand Beach 97 貝殼灘 Shell Beach 99

丘陵 Hills 高山HighHill 火山岩高山 Volcanic Rock Hill 101 花崗岩高山 Granitic Rock Hill 103 高原Plateau 104 懸崖Cliff 火山岩石崖 Volcanic Rock Cliff 106 沉積岩石崖 Sedimentary Rock Cliff 107 花崗岩石崖 Granitic Rock Cliff 108

河溪地貌 River Landscapes 河谷Valley 109 瀑布Waterfall 112 跌水潭PlungePool 112 壺穴Pothole 115

陸上地貌 Terrestrial Landscapes 風化Weathering 塊狀分裂 Block Disintegration 24 蜂窩狀風化 Honeycomb Weathering 30 球狀風化 Spheroidal Weathering 33 侵蝕Erosion 差異侵蝕 Differential Erosion 36 沖溝 Gully 40 泥石流 Debris Flow 41 劣地 Badland 42 沉積Deposition 內灣沉積 Inner Bay Deposition 44 河口沉積 Delta Deposition 46 氾濫平原 Flood Plain 47

構造形跡 Tectonic Evidence 地殼移動CrustalMovement 斷裂 Faulting 48 褶皺 Folding 51 節理Jointing 六角形柱狀節理 Hexagonal Columnar Jointing 54 X節理 X-shaped Jointing 58 岩漿侵入MagmaIntrusion 岩牆 Dyke 59 熱液循環HydrothermalCirculation 石英脈 Quartz Vein 61

土地利用 Land Uses 淹沒河谷DrownedValley 118 水塘堤壩ReserviorDam 119 石礦場Quarry 120 採泥區BorrowArea 122 填海Reclamation 123

風土人情 Human Heritage 小村莊SmallVillage 124 寺廟Temple 126 曬製海產Productionofdriedseafood 129

地質公園姊妹協議 130SisterAgreementwithGeoparkpartners

遊覽香港地質景點守則 132CodeforVisitingGeositesinHongKong

參考書目 133References

香港地質公園書籍系列 134HongKongGeoparkBookSeries

索引 136Index

p.17 p.24 p.51 p.72 p.106 p.115 p.120 p.127

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引言 iNtroduCtioN 引言 iNtroduCtioN

香港的地質歷史從地質學而言，香港位於華南地塊的東南邊緣，屬於歐亞板塊前緣。在過去4億年的地質歷史裏，香港深受板塊構造活動影響。在侏羅紀中期至白堊紀期間，由於太平洋板塊向歐亞板塊俯衝，中國東南部一帶發生廣泛的火山岩漿活動。香港主要是由火成岩組成，屬於中國東南部中生代大陸火成岩帶。火山岩漿活動結束之後，沉積岩開始在白堊紀和第三紀形成，主要由火山碎屑等沉積物組成。赤洲和鴨洲的沉積岩呈現紅色，顯示直到白堊紀晚期可能仍然存在荒漠的環境；另外，東平洲的沉積岩也顯示第三紀早期香港處於格外乾旱的環境。

香港國家地質公園景點的地質特色中國東部只有數個地質景點擁有世界級的多邊形酸性火山岩柱狀節理，其中香港的岩柱無論在大小、直徑和覆蓋範圍方面都異常壯觀。世上其他地方的岩柱主要由深灰色的玄武岩構成，位於香港西貢、富含二氧化矽及平均直徑達1.2米的淺色酸性流紋質火山岩柱卻同時具有凝灰岩和熔岩的特色，世界罕見。其成因一直是現今地質學家爭論不休的課題。

西貢火山岩園區是白堊紀早期（約 1億4,000萬年前）整個地區（即今日中國東部一帶）的典型火山活動痕迹例子。這裏曾經發生極度劇烈的火山活動，在現時香港東南面形成一個直徑超過20公里的大型火山。連串的猛烈火山爆發噴出大量火山灰和熔岩，其後，騰空的火山崩塌及下陷，成為破火山口。凹坑內大量火山灰及富含二氧化矽的熔岩慢慢冷卻及收縮，形成壯觀的多邊形火山岩柱狀節理。現時岩柱出露的範圍逾 100平方公里，高度超過100米。

橋咀洲位於古破火山口西緣，擁有多種比多邊形岩柱更早形成的典型火山岩，包括凝灰岩、流紋岩和火山角礫岩。沉凝灰岩是在橋咀洲出露的火山沉積岩，是火山休眠期間由火山灰和岩石碎塊在破火山湖底部沉積而成。島上的石英二長岩則因侵入活動而產生。

Geological History of Hong KongGeologically, Hong Kong is situated on the southeastern margin of

the South China Block, at the margin of the Eurasian Plate. In terms

of geological history, Hong Kong has been strongly affected by its

plate-tectonic setting over the past 400 million years. From the

Middle Jurassic to the Cretaceous, widespread volcanism and

plutonism occurred throughout southeastern China, owing to the

subduction of the Pacific Plate beneath the Eurasian Plate. As a

result, the geology of Hong Kong was dictated by igneous actions

forming igneous rocks belonging to an extensive Mesozoic magmatic

province along the continental margin of southeastern China. After

the cessation of igneous activities, sedimentary rocks were formed

from the volcanic detritus during the Cretaceous and Tertiary. The

presence of red sedimentary rocks on Port Island and Ap Chau

indicates that a desert environment probably existed into the Late

Cretaceous. The sedimentary rocks on Tung Ping Chau, however,

also indicate a particularly arid climate in the early Tertiary.

Geology of the Geo-areas in Hong Kong National GeoparkWorld-class polygonal acidic volcanic rocks are found at only a few

geosites in Eastern China. The columns in Hong Kong are

spectacular in terms of their size, diameter and coverage. By any

standard, the silica-rich, acidic rock columns, with an average

diameter of 1.2 metres, in the Sai Kung area of Hong Kong are

rare. While such columns elsewhere in the world are usually made

up of dark grey basalt, the silica-rich, light-coloured rhyolitic

volcanic rocks in Sai Kung have the features of both tuff and lava,

and how they came about has remained controversial among

geologists to the present day.

The Sai Kung Volcanic Rock Region is a typical example of traces of

volcanic activities about 140 million years ago (Early Cretaceous) in

the area that is now eastern China. The area once went through a

period of extremely intense volcanic activities, which resulted in the

formation of a large volcano over 20 kilometres in diameter in what

is now the southeastern part of Hong Kong. A huge amount of

volcanic ash and lava spewed forth during a series of violent volcanic

eruptions. Over time, the hollowed-out volcano collapsed and

subsided, forming a caldera. The large amount of volcanic ash and

silica-rich lava inside the depression slowly cooled and contracted,

forming the spectacular polygonal volcanic rocks reaching heights

of over 100 metres that are now exposed in an area of over 100

square kilometres.

Located on the western edge of the ancient caldera, Sharp Island is

covered by various typical volcanic rocks formed earlier than the

polygonal columns, including tuff, rhyolite and volcanic breccia,

which might be from ancient caldera remains. The rocks outcropped

at Sharp Island also include sedimentary-volcanic rock - tuffite,