Zoo Entrance Gate #Chemicalweathering
登錄任務
1. 觀察動物園大門、找看看板岩和花崗岩，哪一種比較多？
2. 從這些岩石上觀察到哪些化學風化？試著指出那一種化學風化的位置，根據網頁的知識與你的觀察，解釋你為什麼覺得是這種類型的化學風化。
3. 指出動物園大門哪些區域受到風化的影響比較大、哪些區域比較小？你覺得可能原因是什麼？解釋你的答案。
4. 與「重返伊甸園」拍照，照片請包含有化學風化的岩石與你、你的GPS裝置、或你的代表物。
線上登錄這個地質寶，請寄到Geocaching.com的信箱，歡迎給予FP。
Logging Task
1. Observe the gate and Recognize rocks. Which type of rock is more in the gate?
2. Which types of chemical weathering do you recognize with these rocks? Indicate the positions and the types of the chemical weathering. Based on the knowledge on the page and the observation, explain why you think it is the specific type of chemical weathering?
3. Indicate which area was weathered more and which area was weathered less on the Gate. Reason the distribution of the area based on your observations.
4. Take a photo of weathered rocks in the “Return to the Eden Garden” with you, your GPS device, or your identifying item.
Log this cache "Found it" and send me your suggested answers either via my profile, or via geocaching.com Message Center. Favorite Point Appreciated.
大自然中的風化作用不只有影響郊外的岩石，地球表面上所有的東西都受到風化或侵蝕的影響，城市中的建築物同樣也不例外。在地質寶點有一座大門，動物園大門使用臺灣自然常見的岩石作為建材，多年來暴露於大氣、陽光、雨水，這座大門上有野外岩石風化的縮影，靠近一點就可以觀察到不同的風化作用如何影響這座大門。
這個地質寶要做什麼？
觀察台灣常見的岩石，認識風化作用的結果，辨識不同的化學風化作用。
台北市立動物園大門的岩石
動物園大門建於2006年，建物提名為「重返伊甸園」，主要建材為板岩與花崗岩。活躍的造山運動後，在台灣島很容易發現這兩種岩石。
板岩屬於變質岩，從黏土或火山灰組成的頁岩，這類具有細緻顆粒的沈積岩經過區域變質而來，板岩主要由石英、白雲母、和綠泥石組成，可高達板岩中百分之95的主要成分，最主要的副成分礦物是氧化鐵、硫化鐵、和碳酸類礦物。板岩的顏色因礦物成份而不同，主要是灰色，有些是綠色、甚至是紫色。
花崗岩屬於侵入性火成岩，有比較粗糙的表面，主要組成礦物為石英、鹼性長石、和斜長石。分餾結晶作用會增加鐵、鈉、鉀、鋁、和矽等礦物的含量，再次分餾後降低鐵、鈣、和鈦等礦物的含量，讓花崗岩有大量的石英與鹼性長石。花崗岩的顏色取決於不同的礦物，主要是白色、粉紅色、或是灰色。
風化作用
風化作用為岩石、土壤及其礦物等與地球大氣層接觸而分解。風化作用發生在原地，並不涉及岩石或礦物的移動，所以不能和侵蝕作用互相混淆。風化作用可以分為物理性與化學性。物理性的風化產生壓力讓岩石崩解，可能透過熱力、水、冰或是其他介質來產生物理性壓力。化學性的風化作用則涉及與水、氧氣、生物製造的化學物質產生化學反應，最終令岩石、土壤、及礦物碎裂開來。無論物理性或化學性風化，水都是相當常見與重要的媒介。
化學風化
溶解作用(Solution)：岩石中的礦物完全溶解於水，沒有產生新的物質，這類岩石含有鈣、鎂等礦物的岩石。
水解作用(Hydrolysis)：岩石中的礦物一部分和水作用，產生可溶性鹽類，另一部分則產生新的物質，像是黏土類礦物。
水合作用(Hydration)：岩石中的礦物與水結合，形成含有氫、氫氧離子的化合物，像是赤鐵礦與水結合成為褐鐵礦。
氧化作用(Oxidation)：岩石中的礦物與氧作用，多種礦物都會和氧發生化學作用，常見的像是二價鐵氧化成為三價鐵，讓岩石顏色變為紅褐色。
生物風化(Biological weathering)：細菌、蕈類、地衣等微生物可能會讓岩石中的礦物發生化學變化，透過產生溶於水的有機酸引發化學變化。
我們已經瞭解岩石、風化、特別是化學風化的知識，現在回到動物園大門，這些岩石受到不同程度的風化，你能從不同的顏色與外貌，輕易地找到風化作用的結果。不過，有些區域似乎風化得比較嚴重。一起來觀察和推測看看發生了什麼事。
Weathering affects not only the rocks in nature but also building materials. All materials on the earth would be under the force of weathering, erosion, and deposition, W.E.D. Buildings in the city are not an exception. Taipei City Zoo’s Gate is located at the posted coordination. The gate was built with some common rocks from Taiwan. It has been exposed to air, sunshine, and rain water for years. There is a miniature of wild nature with those weathered rocks. Come closer to the gate. You can observe the consequence of different weathering forces.
What to do with this earthcache?
Observe different common types of rocks from Taiwan. Recognize the consequence of the weathering process. Indicate and differentiate chemical weathering.
Rocks used in the Taipei City Zoo Gate
The gate, titled “Return to the Garden of Eden”, was built in 2006 with rock materials of slate and granite. These two types of rocks are commonly discovered due to active orogeny in Taiwan island.
Slate is metamorphic rocks derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. Slate is mainly composed of the minerals quartz, illite, and chlorite, which account for up to 95% of the composition of the slate. The most important accessory minerals are iron oxides, iron sulfides, and carbonate minerals. The color of slate may be different with minerals, most commonly in gray, some in green or even purple.
Granite is intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. Fractional crystallization may enrich the melt in some minerals such as iron, sodium, potassium, aluminum, and silicon. Further fractionation may reduce the content of iron, calcium, and titanium, forming the high content of quartz and alkali feldspar. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy.
Weathering
Weathering breaks down rocks, soil, and minerals through contact with air, water, and biological organisms. Weathering occurs on site, and it should not be confused with erosion which involves the transport of rocks and minerals. Weathering process can be divided into physical and chemical. Physical weathering involves the breakdown process with mechanical effects of heat, water ice, and other agents. Chemical weathering involves the chemical reactions to water, oxygen, and chemical compounds produced by biological organisms. Water is the principal agent behind physical and chemical weathering.
Chemical Weathering
Solution：The process in which a mineral dissolves completely without producing any new solid substance.
Hydrolysis：Only part of a mineral is taken into solution. The rest of the mineral is transformed into a new solid material, such as a clay mineral.
Hydration：The process involves the rigid attachment of water molecules or H+ and OH- ions to the atoms and molecules of a mineral. iron oxides are converted to iron hydroxides.
Oxidation：The process in which a mineral reacts to oxygen. The most common one is the oxidation of Fe2+ by oxygen and water to form Fe3+ , giving the rock a reddish-brown color.
Biological Weathering：Microorganisms,like bacteria, fungi, or lichen, may initiate the chemical process of minerals by producing carbon dioxide and organic acid dissolving in water.
We have read some knowledge about the rock, and weathering, especially chemical weathering. Now, back to the gate, rocks used in the gate were weathered at different levels. You can easily recognize the weathering process with different colors and appearances. However, some areas seemed weathered more than the others. Let’s do some observations and speculations.