問題：Questions:

1. 分類佛手洞(選擇題) Classify the cave of Buddha’s hand. (Options below)

A. 溶洞Solusional cave B. Corrasional Cave C. 海蝕洞Littoral cave D. Primary cave E. Talus cave

2. 進入佛手洞感受一下裡面的岩石，這些是什麼類型的岩石？Go inside the cave and feel the rocks inside. What type is the rock inside?

3. 在裡面有找到鐘乳石、石筍、或是石柱嗎？請解釋為什麼有、或為什麼沒有。Do you find stalactites, stalagmites, or columns inside? Explain why or why not.

4. 依循waypoint 1 的地圖，進入佛手洞找到佛手。描述佛手的大小。Follow the guide map at the entrance. Go inside to discover the Buddha’s hand. Describe how big it is.

5. 佛手表面有沒有任何顏色？哪一種風化作用是這些顏色主要的影響因素？請解釋原因。Do you find any color on the surface of Buddha’s hand? Which kind of weathering is the main influencing factor? Explain why (the color is that).

6. 附上你在現場的照片、GPS位置圖、或是你的旅行蟲，感激不盡。A photo of the Buddha's hand with you, your GPS or your TB at WP.

線上登錄這個地質寶，上方答案請寄到Geocaching.com的信箱，若有什麼問題，會再回覆給你，歡迎給予FP，感謝。Log this cache "Found it" and send me your suggested answers either via my profile, or via geocaching.com (Message Center) messaging, and I will contact you if there is a problem. Hope you like this earthcache. Favorite Foint Appreciated.

Buddha over your head

There is a Chinese proverb in Taiwan folk culture, “raise your head three feet there is God. (舉頭三尺有神明)” The proverb implies that God/Fairy/Buddha is watching you and observing your behavior by conscience. Here comes a spot, the Buddha Hand Cave, at the posted coordination literally demonstrates the proverb. Placed an earthcache paying tribute to the spot. Hope you like this earthcache.

What to do with this earth cache?

Go to the posted coordination. Figure out what type is the Buddha Hand Cave. Observe the unique rock formation, Buddha’s hand. Figure out which kind of weathering is the main influencing factor. The question is at the end.

Geological properties of Keelung

This earthcache is located at Keelung. Introducing some geological properties of Keelung. The main Formation under Keelung is Taliao Formation (1130) and Shiti Formation (1270). These two Formations belong to Miocene (24 Ma to 4.8 Ma). The main Keelung city is a seaport. There are many areas belong to modern sedimentary formation. Main type of rocks in Keelung is sedimentary rock, mainly composed of sandstone, few shale and siltstone. Discovered fossils showed that the area is under the sea while it was formed. The plate arose up becoming to land due to tectonic activities of collision between Philippine Sea Plate and Eurasian Plate.

Cave

Definition of cave is a large hole in the side of a hill, or mountain, or one that is underground. The spot at the posted coordination is called the Buddha Hand Cave. There are many caves in Keelung and North Coast of Taiwan. The cave is a classic type of cave in Keelung. Introducing some different types of cave to get known with caves. And through these geological information to figure out what type is the Buddha Hand Cave.

Different types of cave

Solusional Cave

Solusional caves, also called Karst cave, are the most frequent occurring caves. This kind of cave forms in rocks that are soluble. Most likely rocks in this kind of caves may be limestones. Sometimes it may be other types of rocks which are also soluble with natural acid in the groundwater. Limestone caves are full with calcium carbonate formations produced through slow precipitation. These include stalactites, stalagmites, or columns. A very deferential feature belongs to solusional cave.

Corrasional Cave

Corrasional caves or erosional caves are those caves formed through flowing streams. The art work of flowing streams can be with any kind of rocks. There should be a weakness zone to guide the water flowing through. The weakness zone might be a fault or a joint. Sometimes, it’s hard to classify and differentiate solusioanl caves and corrasional caves. Some caves might be influenced by solutional process at first, and then undergo ongoing process of erosional enlargement where river or stream flows. It could be a hybrid cave.

Littoral Cave

Littoral caves or Sea caves are those caves can be found along coast around the world. The cave may be formed by wave action on the weakness zone in a sea cliff. These weakness zone may be a fault or dike on metamorphic and igneous rocks. Also the weakness zone may be a dike or contact between layers of different hardness on sedimentary rocks. Sea cave varies with length and depth depending on the host rock and the power of erosion. This kind of sea caves may be full of sea water by the tides of ocean. Some sea caves are easy to visit with foot. Some Sea caves needs special transport to get in, such as boat or kayak. Some sea caves are located above sea level. It may be the result of tectonic activity and uplifting of the land.

Primary Cave

Primary caves are those cave formed at the same time as the surrounding rocks. Lava tube formed by lava activity is the main type of the primary caves. Lava on the surface cools down and solidifies. Hot liquid lave still flows under the cool-down lava and most of them flow out. A hollow tube is formed.

Talus Cave

Talus caves are openings formed by large boulders piled up on the mountain slope. These large piling up are boulders that have fallen down into a random heap. If the heaps are unstable, it may be subject to rockfalls and landslides.

Rock formation

Mother earth is a brilliant artist. Amazing rock formations are the art works of earth. Forming rocks is a very delicate phenomenon. Such phenomenon happens due to weathering, lava cooling, water current or erosion, and earthquake, etc. These stunning rock formations are located at coast, beaches, hills, mountains, islands, deserts, and in the middle of ocean.

Rock Formation in the Buddha Hand Cave

 (Photo discoloration)

A very special rock formation is inside the Buddha Hand Cave. Along the North Coast of Taiwan, lot of stunning rock formation stands outdoor under the sunshine. There is also a stunning rock formation inside the  Buddha Hand Cave. Moreover, weathering inside the Buddha Hand Cave made the unique rock formation like a human hand on the ceiling. There are some influencing factors associated with this unique rock formation.

Joint

Joint is the very first feature of this rock formation. Tectonic activities push layer of rocks from different direction. Layer of rocks are forced by pressure to be curved or broken along the pressure. Hence joint and fault may be the result of these tectonic activities. If the connecting layers of rocks move away becoming a crack or a visible gap, that would become a fault. A joint is similar to a fault. But the difference is the connecting layer of rocks still connected with each other, not involving into shear displacement. Though you can see a straight or grid lines on the rocks. Joint might be the reason of the unique structure of Buddha’s hand. See the picture below to know the difference between fault and joint.

Weathering

Weathering is a very important process making a rock formation unique. Rocks are like raw diamonds and weathering is like the carving tool.

Weathering can be classified into two categories, physical and chemical.

Physical weathering involves the breakdown of rocks through direct contact with atmosphere conditions, like heat, water, ice and pressure. On the other side, chemical weathering involves effect of chemical reactions influenced by four main agents, including water with different dissolved substances, oxygen and carbon dioxide, substances produced by living beings, and temperature.

Physical weathering is strong at where the climate is very cold and dry. Chemical weathering is strong at where the climate is hot and wet. Two different type of weathering can occur together and tend to accelerate the other.

The rock formation, Buddha’s hand, might be affected by joint, mild erosion, physical weathering and chemical weathering. The process takes a long time evolving into the shape nowadays.

Buddha over your head

俗語說「舉頭三尺有神明」，意味著你的舉止行動都有神明在觀察著，隱含著行為是否符合心中良知的表現。此處的地質完整字面上呈現了這句俗語，設置一個地質寶來向這個地點致敬，希望你喜歡這個地質寶。

這個地質寶要做什麼?

前往公布座標，釐清佛手洞是什麼類型的洞穴，觀察佛手獨特的石頭造型，釐清受到哪一種風化作用的影響。問題在最下方。

基隆地質特性

此地質寶設置在基隆，來認識一下基隆的地質特性，基隆區域主要的地層為大寮層(1130)與石底層(1270)，兩個地層都屬於2400萬年前至480萬年前的中新世。基隆市區港口，地質分布上也有許多現代沖積層，基隆區域主要的岩石類型為沉積岩，主要是砂岩，少部分為頁岩與粉砂岩。透過化石調查知悉基隆地層成形時為海相環境，菲律賓海板塊與歐亞板塊碰撞，地殼運動而上升成陸地。

洞穴

洞穴的定義為山丘一側、山脈、或是地底的大洞。公布座標位置的地點名稱為佛手洞，在基隆與北海岸有許多洞穴，這個洞穴是基隆地區的典型洞穴之一，接下來介紹一些不同類型的洞穴，透過學習洞穴的地質知識來釐清佛手洞屬於什麼類型的洞穴。

不同種類的洞穴

溶洞

溶洞又可稱為喀斯特洞，是最常形成的洞穴。這種洞穴中的岩石可溶於水的特性，最可能的石頭為石灰石，有時也可能是其他種類可溶於水中酸性物質的岩石。石灰岩洞穴中透過緩慢的沉澱會出現碳酸鈣形成物，相是鐘乳石、石筍、石柱…等等，這也是石灰岩溶洞的顯著特徵。

Corrasional Cave

Corrasional Cave又可稱為erosional cave，這類洞穴是透過流動的水流逐步侵蝕而成，這種作用可形成於各種不同類型的岩石，不過在岩石上需要有一個脆弱區域可引導水流，像是斷層或是節理。有時候，不易區辨分類溶洞與Corrasional Cave，有些洞穴起初可能像是溶洞一樣出現溶解過程，後來則是透過流動的水流侵蝕之下而變大，這類型的洞穴可能屬於複合型洞穴。

Littoral Cave

Littoral cave又稱為海蝕洞，這類型洞穴分布於全世界海岸線。該種洞穴形成過程與侵蝕作用相關，由波浪打在海岸懸崖的脆弱區域，變質岩與火成岩的脆弱區域可能為斷層或是岩脈，沉積岩的脆弱區域則可能為岩脈或是不同硬度沉積岩塊接觸區域。海蝕洞的大小可能會不同，取決於岩盤性質與侵蝕作用的強度，這類洞穴在潮汐變化時可能會灌滿海水，有些海蝕洞可以步行抵達，有些則需要乘船或是獨木舟才能進入。而有些海蝕洞位在海平線之上，這種類型的海蝕洞則可能受到地殼上升運動的影響。

Primary cave

Primary cave是一種週遭岩石成形時就完成的洞穴。岩漿活動所留下的岩漿管道是這種洞穴的主要類型，岩漿活動表面冷卻後成岩，表面下的岩漿液體依然在流動，這些液體大部分流光之後，空心的管道就成形了。

Talus Cave

Talus cave是堆積在山腰的石堆之開口，這些大型堆積石塊掉落下來隨機地堆疊，若是這些堆積石塊不穩固，可能之後會形成土石流或是地層滑落。

岩體

大地母親是傑出的藝術家，令人驚豔的岩體便是大地的傑作。形成岩石是非常細緻的現象，形成這種現象的原因包含風化作用、岩漿冷卻、水流或侵蝕作用、以及地震等等因素。這類巧奪天工的岩體分布在海岸線、海灘、山丘、山脈、島嶼、沙漠或是海洋中央。

佛手洞中的岩體

在佛手洞中有一個非常特別的岩體。沿著台灣北海岸，許多巧奪天工的岩體佇立在陽光下，在佛手洞中同樣有一個巧奪天工的岩體，更特別的是，佛手洞中的岩體受到自然風化作用，讓這個位在石洞天花板上的獨特岩體巧妙地出現手掌的形狀。形成這個獨特岩體的影響因素可能有節理與風化作用。

 (照片變色處理)

節理

節理是這塊岩體非常顯著的特徵。地殼活動從不同方向擠壓岩層，岩層受力後皺摺或是沿著壓力破碎。節理和斷層就是地殼活動的結果之一。若是相連的岩層位移並出現明顯的裂痕，這便是斷層；節理跟斷層很相似，不過差別在於岩層依然相連，沒有出現石塊位移，雖然你還是可以在岩層上看到明顯的線條或是方格痕跡。節理可能就是佛手洞中獨特岩體形狀的主要原因。

下圖解說斷層與節理的不同。

風化作用

風化作用是讓岩體獨特的重要過程。岩石像是裸鑽，風化作用則是雕刻工具。

風化作用大致可以區分成兩個類別：物理風化與化學風化。

物理風化作用在岩石接觸大氣環境的表面，直接受到熱、水、冰或是壓力的影響：另一方面，化學風化則涉及化學作用的影響，可能受到四種因素的作用，水的影響（像是水解、水和）、氧氣與二氧化碳、生物製造的溶解性物質、溫度。

物理風化在大氣環境非常冷、非常乾燥的條件下作用旺盛，化學風化則在大氣環境非常熱、非常濕的條件下作用旺盛。兩種風化作用可以一起發生，且還會加速另外一種風化作用。

佛手洞中的獨特岩體受到節理、輕微侵蝕作用、物理風化與化學風化作用的影響，在這些條件之下持續發展至現在的形狀結構。

Reference

https://en.wikipedia.org/wiki/Cave

https://en.wikipedia.org/wiki/Weathering

https://en.wikipedia.org/wiki/Joint_(geology)

https://gis3.moeacgs.gov.tw/gwh/gsb97-1/sys8/t3/index1.cfm

http://library.taiwanschoolnet.org/cyberfair2005/anlo3/2/kl.htm

感謝管理單位 基隆市中山區公所

Thanks goofiemumkanokailer, Joychang, and dirtybrando for the investigation together.