Basalt's Frozen Gas #vesiclepipe
Basalt in Nei-an is unique with vesicle pipes (gas bubbles). 內垵玄武岩有獨特的地方，玄武岩中有氣孔柱。
Nei-an is covered with basalts and sedimentary deposits of different ages. Along the trail to the Nei-an beach, the fossil of Penghusuchus (an extinct type of crocodile) was discovered in sedimentary rocks rounded with basalts. 內垵地層中有不同時期的玄武岩與沈積物，沿著步道至內垵海灘，澎湖潘氏鱷魚的化石就是在內垵海灘附近的玄武岩、沈積岩中被發現。
At posted coordination (picture below), Siliceous basalt and Alkali basalt from different intrusion or explosion can be discovered. Alkali basalt has darker colors and Siliceous basalt has light grey colors with more gas bubble. 公布點(下圖)處可以觀察到不同時期入侵的矽質玄武岩與鹼性玄武岩，鹼性玄武岩顏色較深，矽質玄武岩顏色淺灰且多有氣孔。
Vesicular basalt is a unique form of Siliceous basalt. This type of basalt captures many gases in the magma or lava while fast cooling dawn in forming rocks. 多孔狀玄武岩是一種獨特形式的矽質玄武岩，形成玄武岩的岩漿冷卻過程中捕捉到大量氣體而成岩。
Vesicle pipes are gas frozen in basalt. If the gas didn’t get large enough to pop, it would be frozen in lava as a buoyant rise of the gas bubble. Vesicle pipes are widely discovered on the surface of lava due to buoyancy. They might also squeeze into cracks forming horizontal pipes if there was no way out to the atmosphere. 氣孔柱則是凍在玄武岩中的空氣。當氣體不夠大、沒有足夠的浮力，可以讓氣體從岩漿中噴出，就會被凍結在玄武岩中。因為氣體浮力的關係，氣孔柱通常分布在岩漿表面。不過，當沒有進入大氣的出口時，這些氣體也可能擠進岩石裂縫中形成水平的氣孔柱。
Logging tasks 登錄任務
1. Where can you discover vesicular basalt? (picture below: A/B/C) 哪個位置可以發現多孔狀玄武岩(A/B/C)？
2. Based on your observation, which part (A/B/C) has bigger vesicle pipes and why is that? 根據實地觀察，哪個位置有較大的氣孔柱？為什麼會是這樣分布？
3. Photo a vesicle pipe in the basalt with you, your identifying item, or your GPS device. 請與玄武岩氣孔柱拍照，包含氣孔柱與你、你的代表物、或你的GPS裝置。
除了登錄任務3，請不要線上公布你的答案。請直接線上登錄這個地質寶，將答案寄到Geocaching.com的信箱，若有什麼問題會再回覆。希望你喜歡這個地質寶，歡迎給予FP，感謝。Log this cache "Found it" and send me your suggested answers via geocaching.com messaging. Please, do not post your answers in the log, except task 3. Hope you like this earthcache. Favorite Point Appreciated.
Reference
Geologic Time Pics Marli Miller Photography
澎湖海洋地質公園 含氣孔柱玄武岩