Entrance fee 有入場費用
The earthcache is located in the national park with entrance fee. 地質寶位於收入場維護費的國家公園區域。
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Cape Eluanbi is the most southern point of the main island of Taiwan and it is in the tropical area. At the posted coordination, there is a rocky seashore in front. You can face the Luzon Strait to the south and the Pacific Ocean to the east. Rocks near the posted coordination are mostly limestone and the seashore has some uniqueness under lines.
Normally, coastal erosion produces straight lines of surge channels at rocky seashores. However, lines in grids are there at this rocky seaside, even resembling artificial limestone pavement.
This earthcache will lead you observe the rocky seashore and explore the "underline" geology.
Logging tasks are at the bottom of page. Entrance is from the parking lot with access fee.
Limestone pavement
Limestone pavement is a karst landform and usually would be formed under the condition of glaciers. The surface of limestone pavement is flat on the top. And those cracks, dissolved by water, cut off limestones in grids, resembling a aritificial pavement. Look the demonstration pics below.
Take deep look on the formation of limestone pavement. Under the condition of glacier, the bedding of limestone were eroded and formed flat top. When the ice melting, the water flow into joints and cracks, producing rock slabs and fissures around through chemical solution weathering.
Limestone Characteristics
Limestone is a soluble carbonate rock and it is easily affected by acid. When rainwaters, especially acid rain, run through the joints and cracks on the limestone, it produces clints(rock slab) isolated by grykes(rock fissures).
The chemical weathering at the rocks of Cape Eluanbi involves carbonate dissolution/solution weathering and biological weathering.
The chemistry process in carbonate dissolution involves calcium carbonate(CaCo3) in the limestone. Carbonate minerals are more soluble in the presence of higher carbon dioxide. That means the rain water reacts with CO2 in soil to create acid water, then triggering the dissolving process. Biological weathering here involves organic acid dissolving some composition of the rocks. The organic acid can be derived from bacteria, fungi, tree plants, or the body of ocean creatures.
Rocky seashore of Cape Eluanbi is located in the tidal area. Hence, the limestones here are also affected by the coastal erosion bringing away those softened rock composition.
Surge Channel
Surge channel is a narrow inlet, which is an entrance for sea water, on the rocky seashore.
The weathering process involves coastal wave action, a type of physical weathering. Coastal waves crash toward rocks at the seaside, affecting weak lines of rocks. The wave action produces cracks, then expanding the crack into narrow channels for powerful currents.
Coastal erosion is also involved in the process. The currents cause violent hydrodynamic mixing confined in the channel, eroding rocks in the wall and base of the channel. And there is relatively less exchange of water between channels.
鵝鑾鼻位於台灣本島最南端，屬於熱帶區域。 公布點是一處岩岸，南方為呂宋海峽、東方為太平洋。公布點附近的岩石大多為石灰岩，這片海岸有些獨特的線條。
一般來說，海岸侵蝕作用會在岩岸產生筆直的海蝕溝，不過，這片岩岸卻可以觀察格狀線條，甚至形如人為的石灰岩鋪石路面。
這個地質寶會帶你觀察岩岸、探索潛藏線條中的地質。
石灰岩特性
石灰岩鋪石面是喀斯特地形，通常是形成於冰川條件的區域。
石灰岩可溶於水且容易受到酸性物質影響，當雨水、酸雨經過石灰岩的節理、裂縫時，會產生獨立石塊(clint, rock slab)與溝壑(gryke, rock fissure)。
作用於鵝鑾鼻岩石的化學風化作用包含溶蝕作用、生物風化。
溶蝕作用主要跟石灰岩中的碳酸鈣有關，碳酸鈣在二氧化碳濃度較高時比較溶於水，所以當雨水作用於土中的二氧化碳，會產生酸性水、接著促發溶解作用。 生物風化則與有機酸溶解岩石成分有關，有機酸的來源為細菌、蕈類、植物、或海洋生物殘骸。
鵝鑾鼻岩岸位在潮間帶，所以，風化作用之下而軟化的岩石組成，也會被海岸侵蝕作用影響而流失。
海蝕溝
海蝕溝是岩岸中狹長的進水口，主要涉及的物理風化作用為水力作用。海浪衝擊海邊岩石、影響岩石的脆弱線，海浪衝擊的力量會形成裂縫，在狹長水道中水流作用下逐漸擴大。
這個過程也受到海岸侵蝕作用的影響，海流在海蝕溝水道之中前後混合，形成強力的水流動力，也會侵蝕掉水道兩側與底部的岩石。通常，海蝕溝水道間鮮少有水流互換的情形。
登錄任務 注意：請不要離開觀景平台。
1. 你有發現格狀結構嗎？請指出是在下方圖片中哪個位置。
2. 你認為這個格狀結構是 石灰岩鋪面 、 海蝕溝 、或 兩者都不是？請解釋你的想法。
3. 比較Ａ區、Ｃ區的溝壑深度。哪個區域的溝壑比較淺？有什麼因素影響？請解釋這些因素如何作用。
4. 請與溶蝕過的石灰岩拍照，照片包含溶蝕過的石灰岩與你、你的代表物、或你的GPS裝置。
除了登錄任務4，請不要在log中公布你的答案。線上登錄這個地質寶，請寄到Geocaching.com的信箱。希望你喜歡這個地質寶，歡迎給予FP，有任何問題請寄送訊息。
Logging Tasks. Attention: Stay on the observation deck, please.
1. Do you discover rocks in forms of grids? Indicate which area in the picture below.
2. Do you agree the grid is limestone pavement, surge channel, or neither? Explain your thoughts.
3. Compare the depth of the fissures of area A and C. Which area’s fissures are shallower? What influencing forces are involved and how they interact?
4. Photo the outcome of dissolved limestone with you, your identifying object, or your GPS device.
Log this cache "Found it" and send me your suggested answers. Don't post answers in the log except logging task 4, please. Hope you like this earthcache and favorite points appreciated.