The Pillars of the Earth - 大地的支柱 EarthCache

This Earthcache does not include a physical container at the posted coordinates.

This cache takes you on a journey to the Sacred Heart Cathedral, recognized as one of the largest Roman Catholic cathedrals in China, also known as the "Stone Chamber" due to its complete construction from granite, encompassing walls, pillars, and twin spires.

To claim your find for this cache, your task is to enter the cathedral. Please note that the cathedral is accessible from 9:00 to 17:00 and closed on Mondays.

History and Architecture

The construction of the Sacred Heart Cathedral commenced in 1863 and concluded in 1888. The oversight of this monumental project fell under the leadership of Philippe François Zéphirin Guillemin, the bishop of the Paris Foreign Missions Society. Contributing to the design were three French architects: Léon Vautrin, Charles Hyacinthe Humbert, and Antoine Hermitte. The construction process engaged hundreds of local masons, spanning a duration of 25 years. The foundation stone was ceremoniously laid on June 18, 1863, coinciding with the Feast of the Sacred Heart, from which the cathedral derives its name. Embodying the essence of the Gothic Revival style, both the façade and interior decoration of the cathedral reflect this architectural tradition.

Disagreements arose between the bishop and the architect regarding the selection of building materials. During the mid-19th century, Guangzhou lacked the technology for reinforced concrete. At that time, only fragile green bricks were manufactured locally, while the production of sturdy red bricks and other industrial materials remained underdeveloped. Architect Hermetic advocated for the use of red bricks due to their cost-effectiveness and suitability for local conditions. However, Bishop Guillemin ultimately rejected this proposal, insisting instead on constructing the cathedral entirely from granite.

To secure a consistent supply of granite for the project, Bishop Guillemin corresponded with the Viceroy of Liangguang, requesting quarries under French control. Consequently, permission was granted for French quarrying operations in the hills of Ngau Tau Kok and Cha Kwo Ling on the Kowloon Peninsula. These quarries were utilized from 1863 to 1872, spanning nearly a decade, and provided all the necessary granite for the cathedral's construction.

What is granite?

Granite is a light-coloured igneous rock with grains large enough to be discernible to the naked eye. It forms through the gradual crystallization of magma beneath the Earth's surface.

Comprising primarily quartz and feldspar, along with minor quantities of mica, amphiboles, and other minerals, granite typically displays hues of red, pink, grey, or white, interspersed with dark mineral grains.

Abundant in the continental crust, granite is prominently exposed in mountain range cores, expansive formations known as 'batholiths,' and the central regions of continents referred to as 'shields.'

The substantial mineral crystals found in granite serve as evidence of slow cooling from molten rock material. Such gradual cooling occurred beneath the Earth's surface over an extended period. The exposure of these granites at the surface necessitates their uplift and the subsequent erosion of overlying rock layers.

Across much of the Earth's continents, sediments or sedimentary rocks cloak the surface, while granites, metamorphosed granites, or closely related rocks lie beneath—a collective often termed "basement rocks."

Granite is the primary material quarried for "dimension stone," naturally occurring rock material cut into blocks or slabs of specific dimensions. Renowned for its durability against abrasion, strength to bear heavy loads, resistance to weathering, and polishability to a high sheen, granite is highly sought after and serves a multitude of purposes.

Utilized both indoors and outdoors for millennia, rough-cut and polished granite finds application in buildings, bridges, pavements, monuments, and various outdoor constructions. Indoors, polished granite slabs and tiles serve as countertops, flooring, stair treads, and numerous practical and decorative elements.

On the Kowloon Peninsula, where the quarries supplying stone for the cathedral were situated, two distinct types of granite were extracted: Kowloon granite and Mount Butler granite, each distinguished by its petrographic characteristics. Further details on both varieties are provided below.

^{(View of the Hong Kong and Kowloon basin showing the outcrop of the Kowloon and Mount Butler granites)}

Kowloon Granite

The Kowloon Granite forms a subcircular biotite monzogranite pluton centred on Kowloon and Hong Kong Island. Its northern boundary aligns with the southern foothills between the Kowloon and Sha Tin districts. To the east and south, volcanic roof rocks mark the pluton's perimeter, though volcanic formations are generally absent along the western boundary, except for Stonecutters Island.

Characterized by remarkable uniformity in texture and composition, the Kowloon Granite typically manifests as an equigranular, medium-grained biotite monzogranite. Plagioclase exhibits strong concentric zoning, while microcline serves as the dominant alkali feldspar, often accompanied by subordinate microperthite. Biotite, ranging from green to brown, occurs as individual flakes (1–3 mm), with accessory minerals including allanite, apatite, zircon, and Fe-oxide.

Minor textural variations include porphyritic fine-grained granite in Kings Park, fine-grained granite along the pluton's northern boundary and near Ma On Shan, and occasional outcrops of coarse-grained granite near Kwun Yam Shan. These variations typically feature quartz and plagioclase megacrysts embedded within a matrix of quartz, alkali feldspar, plagioclase, and abundant biotite. Notably large titanite and allanite crystals are present. Petrographic characteristics of the Kowloon Granite, such as strongly zoned plagioclase, bear resemblance to those of the Lantau Granite, albeit lacking amphibole and feldspar megacrysts.

Geochronological analysis has determined the age of the Kowloon Granite to be 138 ± 1 Ma through a seven-point Rb–Sr whole-rock isochron. Additionally, a U–Pb single zircon dating of the King's Park textural variant yielded an age of 140.4 ± 0.2 Ma.

^{(Equigranular, medium-grained Kowloon Granite)}

Mount Butler Granite

The Mount Butler Granite comprises small, subcircular leucocratic monzogranite intrusions situated on the southeast and east peripheries of the Kowloon Granite on Hong Kong Island and in eastern Kowloon. Predominantly equigranular and fine-grained, it occasionally varies to a finer to medium-grained texture. Intruding the Kowloon Granite, as well as the Ap Lei Chau and Mount Davis formations, the Mount Butler Granite exhibits local greisenization near Kwun Tong, resulting in saccharoidal-textured equigranular rock intersected by narrow (0.1–1.5 m) west-northwest-trending quartz veins. These veins often contain minor quantities of fluorite, chalcopyrite, molybdenite, wolframite, and beryl. Pegmatite patches and miarolitic cavities are prevalent, especially in close proximity to the granite-volcanic interface.

In thin sections, the granular texture reveals subhedral poikilitic alkali feldspar (orthoclase), albite, and quartz, interspersed with sporadic single flakes of greenish-brown biotite. Plagioclase occasionally exhibits weak zoning, with accessory minerals including zircon, apatite, and Fe-oxide. The presence of miarolitic cavities and pegmatite serves as evidence of shallow emplacement and subsequent post-magmatic hydrothermal activity.

An Rb–Sr whole-rock isochron age of 136 ± 1 Ma has been determined for the Mount Butler Granite. However, it is worth noting that the Rb–Sr system may have been influenced by interactions with water during post-emplacement hydrothermal activity.

^{(Equigranular, fine-grained Mount Butler Granite)}

Logging Requirements

To complete this cache, kindly provide the answers to the following inquiries:

1. As previously mentioned, granite quarried on the Kowloon Peninsula supplied the stone for the Sacred Heart Cathedral. The cathedral was constructed using either Kowloon granite or Mount Butler granite, each distinguished by unique petrographic characteristics. Examine the architectural features of the cathedral closely to determine which type of granite constitutes its building material.

2. The cathedral endured severe damage during the Cultural Revolution, with scriptures and pews piled and burned within its confines. The intense heat generated during this event caused the granite walls and pillars to crack. Despite subsequent restoration efforts, the fissures remain visible, alongside burn marks that persist to this day. Identify these traces of damage and elucidate why prolonged exposure to elevated temperatures compromises the strength of the stone.

3. Share a photograph of yourself (or an identifiable personal object) taken at the specified coordinates or in close proximity, with the granite structure serving as a discernible backdrop.

（以下提供部分内容的中文翻译）

建筑历史

圣心大教堂是中国现存最大的石结构哥特式天主教堂，因以花岗岩石砌造，俗称“石室”。大教堂始建于1863年，落成于1888年，由巴黎外方传教会广东教区主教明稽章主持，在两广总督行署原址上修建。来自法国的莱昂·沃特兰、夏尔·安贝尔、安东尼·赫美德三位建筑师先后参与设计工作，数百名石匠参与施工，历时25年建成。教堂于1863年6月18日圣心瞻礼日奠基，故名圣心大教堂。教堂坐北朝南，平面为拉丁十字形，立面特征和装饰细节均是典型的哥特复兴式风格。

在建筑材料的选择上，主教明稽章与建筑师赫美德曾有过一些讨论。在19世纪中叶的广州，钢筋混凝土技术尚未发展成熟，当时广州只生产较脆的青砖，而红砖烧制技术落后，也缺乏其他工业材料。建筑师赫美德建议使用更便宜也更易于融入本土环境的烧制红砖，但主教明稽章最终没有采纳，而坚持用花岗岩来建造整栋建筑。为保障花岗岩供运稳定，明稽章甚至上书两广总督请求为建设教堂而开辟独立的采石场。九龙半岛的牛头角、茶果岭两山最终被划给法方开采。从1863到1872年，这两处采石场前后开采了近十年，为圣心大教堂提供了施工所需的全部石料。

广东历史上建筑石材的选用主要跟地理和技术因素有关，一般为了开采和运输的便利而就近选择，常用石材的种类随着技术进步有着清晰的演变脉络：宋末、元、明初多用红砂岩、斑岩（广东俗称鸭屎石），明中到清初多用红砂岩，而清中到民初多用花岗岩——硬度逐渐提高，孔隙率和吸水率逐渐降低。广州近代建筑中最常用的石材是硬度较高的花岗岩，兼用红砂岩、青石、大理石等。

花岗岩

花岗岩是一种浅色的火成岩，由地球表面下的岩浆缓慢结晶形成。

花岗岩的主要矿物组成是结晶状的石英和长石，也含有少量云母、角闪石、辉石等。这些矿物成分通常使花岗岩呈现红色、粉红色、灰色或白色，整块岩石中可见深色矿物颗粒。因表面可见不同矿物质形成的麻点，广东地区俗称麻石。

花岗岩是从熔融的岩石中形成，在地表下进行冷却需要漫长的时间。当上层岩石被侵蚀后，花岗岩被抬起，就暴露在地表上。地球大陆的大部分地区都被沉积物或沉积岩所覆盖，底层岩石通常是花岗岩、变质的花岗岩或其他密切相关的岩石，这些深层花岗岩通常被称为 "基底岩"。

由于花岗岩质地坚实，抗压强度高，物理性能好，耐酸碱性能良好，成为应用最广的一种石材，广泛用于基础、墙体、台阶、铺地、梁柱以及饰面等构造部位，也是石砌体的主要材料。同时因为具有良好的节理和构造，也是石雕构件加工的理想材料。花岗岩品种多样，根据蕴含矿物质呈现不同的颜色及性状。广州近代应用最广的花岗岩为灰白色花岗岩，也称白麻石。

藏点任务

请把以下问题的答案发送给我，并拍摄照片，以完成这个地质藏点的任务：

1. 九龙半岛出产两种花岗岩——九龙花岗岩和毕拿山花岗岩，它们的岩相特征各不相同。圣心大教堂是用其中一种花岗岩建造的。请仔细观察大教堂的建筑细节，得知石室的建筑材料是哪种花岗岩。

2. 文化大革命期间，石室受到严重破坏，经书和讲道用的长椅被堆成小山在教堂里焚烧，石壁、石柱部分被烧至开裂，虽经数次修复但至今仍见烧焦痕迹。请您找到这些痕迹，并解释为什么温度上升会削弱岩石的强度。

3. 在大教堂拍照，照片中包含您自己或您的个人物品，以花岗岩建筑构件为背景，在日志中附带这张照片。