Welcome to the Forbidden City in Beijing! With this Earthcache you will learn about weathering.
歡迎來到聯合國教科文組織世界遺產北京故宮！透過這個 Earthcache，您將了解風化作用。
Logging Tasks
At the given coordinates you will find a huge artwork between the stairs (see picture). Both the stairs and the artwork are made of alabaster.
- What signs of weathering can you see at this alabaster artwork and / or the stairs?
- With the help of the listing, name at least two types of weathering that might have caused this.
- Do you think it was a good idea to use alabaster at this location? How will the state of this alabaster artwork develop in the future?
- Additionally, please take a picture of yourself, your GPS or something else that belongs to you near the coordinates and attach it to your log.
Please send me the answers to the questions via the Message Center. After that you can log your find immediately. I will try to answer you as soon as possible.
If you have any problems answering the questions, don't hesitate to contact me - I am glad to help. :)
Have fun!
Joskaranch
記錄任務
在給定的座標處，您會在樓梯之間發現一幅巨大的藝術品。樓梯和藝術品都是由雪花石膏製成的。
1. 您可以在這件雪花石膏藝術品和/或樓梯上看到哪些風化跡象？
2. 在清單的幫助下，至少列出兩種可能導致這種情況的風化。
3. 您認為在這個位置使用雪花石膏是個好主意嗎？未來這件雪花石膏藝術品的狀態會如何發展？
4. 此外，請在座標附近拍攝自己、GPS 或屬於您的其他物品的照片，並將其附加到您的日誌中。
請透過訊息中心將問題的答案寄給我。之後，您可以立即記錄您的發現。我會盡快回覆您。
如果您在回答問題時遇到任何問題，請隨時與我聯繫 - 我很樂意為您提供協助。 :)
玩得開心！
約斯卡蘭奇
The Forbbiden City - Imperial Palace of China
The Forbidden City is located in the centre of Beijing, China's capital, and is a huge imperial palace complex. It served as the political and ceremonial center of Chinese emperors for over 500 years. The Forbidden City was built between 1406 and 1420 during the Ming Dynasty and it housed 24 emperors of the Ming and Qing dynasties. It is enclosed by towering walls and a wide moat. The Forbidden City was strictly off-limits to common people, symbolizing the emperor's supreme power. Today, it is a UNESCO World Heritage Site and one of China's most iconic cultural landmarks. Millions of visitors are coming to the Forbidden City every year.
Mao Zedong's portrait prominently hangs on the Tiananmen Gate which is the main entrance to the Forbidden City. It is overlooking Tiananmen Square in Beijing. The large portrait has been a symbolic feature since 1949, when the People's Republic of China was established under Mao's leadership. The portrait serves as a reminder of Mao's significant role in modern Chinese history and the founding of the communist state.
Historically, the Tiananmen Gate was highly restricted. Only the emperor had the exclusive right to pass through its central arch. High-ranking officials and members of the imperial family could use the side gates, but common citizens were forbidden from crossing through the gate. It served as a ceremonial gateway to the Forbidden City, symbolizing imperial authority and power. However today, Tiananmen Gate is accessible to the public and every visitor can walk through the central arch!
What is weathering?
Weathering is the process by which rocks, minerals, and soils are broken down into smaller particles through physical, chemical, and biological mechanisms. This process occurs at or near the Earth's surface and plays a crucial role in the formation of soil and the alteration of landscapes over time. There are three main types of weathering: Mechanical, chemical and biological weathering.
Mechanical Weathering
Mechanical (or physical) weathering involves the physical breakdown of rocks without changing their chemical composition. Common processes include freeze-unfreeze cycles due to temperature changes, thermal expansion of rocks and abrasion from wind and water. Forms of mechanical weathering are:
Thermal Stress: A form of weathering resulting from thermal expansion and contraction of rock due to temperature change. It is most effective in areas were there is a big temperature difference between day and night, for example in deserts. There are two types of thermal stress weathering:
- 1. Thermal Shock: This occurs when a material experiences a sudden and significant change in temperature, causing rapid expansion or contraction. If the material cannot evenly distribute the stress caused by this sudden temperature change, it can crack or shatter.
- 2. Thermal Fatigue: This refers to the progressive weakening of a material due to repeated cycles of heating and cooling. Over time, these cycles cause the material to expand and contract repeatedly, leading to the formation of microcracks and eventual failure.
Abrasion: Rocks and particles carried by wind, water, or ice scrape against each other, wearing down surfaces and breaking rocks into smaller pieces.
Exfoliation (Pressure Release): As overlying material is removed through erosion, the pressure on underlying rocks decreases, causing them to expand and crack into layers or sheets.
Salt Crystal Growth: Saltwater seeps into the pores or cracks of rocks. When the water evaporates, salt crystals form and expand, exerting pressure on the rock, which can lead to fragmentation.
Biological Activity: Organisms such as plant roots grow into cracks in rocks, exerting pressure and causing the rock to break apart.
Frost weathering: One of the most important forms of mechanical weathering. Water flows into existing cracks of rocks. When later freezing, the water extends the cracks in the rocks and causes them to break further.
Chemical Weathering
Chemical weathering is the process by which rocks and minerals are broken down and altered through chemical reactions with environmental agents such as water, oxygen, carbon dioxide, and acids. This process changes the chemical composition and physical properties of the rocks, leading to their decomposition and contributing to soil formation and landscape evolution. Chemical weathering can result in the formation of new minerals and the dissolution of existing ones. Forms of chemical weathering are:
Hydrolysis: Water reacts with minerals, especially feldspar in granite, to form clay minerals and soluble ions. This process transforms the original minerals into different minerals and dissolves some of the rock material.
Oxidation: Oxygen reacts with minerals, particularly those containing iron, leading to the formation of oxides or hydroxides. This process often results in the rusting of rocks and the weakening of their structure.
Dissolution: Soluble minerals, such as salt or gypsum, dissolve in water, leading to the removal of material from the rock. Acidic solutions, including those formed from carbon dioxide in rainwater, can enhance this process.
Carbonation: Carbon dioxide in the atmosphere reacts with water to form carbonic acid, which then reacts with minerals like calcium carbonate in limestone or marble, leading to their dissolution.
Acid Rain: Acidic precipitation, caused by pollutants like sulfur dioxide and nitrogen oxides, reacts with minerals in rocks, leading to their chemical breakdown and alteration.
Biological Weathering
Biological weathering involves the actions of living organisms, such as plants, animals, and microorganisms, contributing to the breakdown of rocks and minerals. Examples of biological weathering are:
Lichen and Moss Growth: Lichens and mosses growing on rock surfaces produce acids that chemically weather the rock by dissolving minerals and promoting further physical breakdown.
Burrowing Animals: Animals like earthworms, rodents, and insects dig into the ground, exposing new rock surfaces to weathering processes and helping to dislodge fragments.
Microbial Activity: Microorganisms, such as bacteria and fungi, can produce acids as metabolic byproducts that chemically weather minerals in rocks, contributing to their breakdown.
紫禁城 - 中國故宮
紫禁城位於中國首都北京的中心，是一座巨大的皇宮建築群。 500多年來，它一直是中國皇帝的政治和禮儀中心。紫禁城建於明朝 1406 年至 1420 年間，曾居住明清兩代 24 位皇帝。它被高聳的城牆和寬闊的護城河包圍。紫禁城嚴格禁止平民進入，象徵皇帝的至高權力。如今，它已被聯合國教科文組織列為世界遺產，也是中國最具代表性的文化地標之一。每年都有數百萬的遊客來到紫禁城。
毛澤東的肖像顯著地懸掛在紫禁城正門天安門城樓上。俯瞰北京天安門廣場。自1949年中華人民共和國在毛澤東領導下成立以來，這幅巨幅肖像畫一直是個象徵性的特徵。這幅肖像畫提醒人們毛澤東在中國現代歷史和共產主義國家的建立中所扮演的重要角色。
歷史上，天安門城樓受到嚴格限制。只有皇帝才有透過其中央拱門的專有權利。高級官員和皇室成員可以使用側門，但普通公民禁止穿過大門。它是紫禁城的禮儀性門戶，象徵皇權和權力。然而今天，天安門城樓向公眾開放，每個遊客都可以穿過中央拱門！
什麼是風化？
風化是岩石、礦物和土壤透過物理、化學和生物機制分解成更小的顆粒的過程。這個過程發生在地球表面或附近，並且在土壤的形成和地形隨時間的變化中發揮著至關重要的作用。風化作用主要有三種：機械風化、化學風化和生物風化。
機械風化
機械（或物理）風化涉及岩石的物理分解而不改變其化學成分。常見的過程包括由於溫度變化、岩石熱膨脹以及風和水的磨損而導致的凍結-解凍循環。機械風化的形式有：
熱應力：由於溫度變化導致岩石熱膨脹和收縮而產生的一種風化形式。它在晝夜溫差較大的地區（例如沙漠）最有效。熱應力風化有兩種：
- 1. 熱衝擊：當材料經歷突然且顯著的溫度變化，導致快速膨脹或收縮時，就會發生這種情況。如果材料不能均勻分佈突然的溫度變化引起的應力，它可能會破裂或破碎。
- 2. 熱疲勞：這是指材料因反覆的加熱和冷卻循環而逐漸減弱。隨著時間的推移，這些循環會導致材料反覆膨脹和收縮，導致微裂紋的形成並最終失效。
磨損：風、水或冰攜帶的岩石和顆粒相互刮擦，磨損表面並將岩石破碎成更小的碎片。
剝落（壓力釋放）：當上覆物質透過侵蝕被去除時，下伏岩石上的壓力降低，導致它們膨脹並破裂成層或片。
鹽晶體生長：鹽水滲入岩石的孔隙或裂縫中。當水蒸發時，鹽晶體形成並膨脹，對岩石施加壓力，導致碎裂。
生物活性：植物根等生物體生長到岩石裂縫中，施加壓力並導致岩石破裂。
霜凍風化：機械風化最重要的形式之一。水流入現有的岩石裂縫中。當後來結冰時，水會擴大岩石的裂縫並導致它們進一步破裂。
化學風化
化學風化是岩石和礦物透過與水、氧氣、二氧化碳和酸等環境因素發生化學反應而分解和改變的過程。這個過程改變了岩石的化學成分和物理性質，導致岩石分解並促進土壤形成和景觀演化。化學風化會導致新礦物的形成和現有礦物的溶解。化學風化的形式有：
水解：水與礦物質，特別是花崗岩中的長石反應，形成黏土礦物和可溶性離子。這個過程將原始礦物質轉化為不同的礦物質並溶解一些岩石材料。
氧化：氧氣與礦物質，特別是含有鐵的礦物質反應，導致形成氧化物或氫氧化物。這個過程通常會導致岩石生鏽並削弱其結構。
溶解：可溶性礦物質，如鹽或石膏，溶解在水中，導致岩石中的物質被去除。酸性溶液，包括由雨水中的二氧化碳形成的溶液，可以增強此過程。
碳酸化：大氣中的二氧化碳與水反應形成碳酸，然後與石灰石或大理石中的碳酸鈣等礦物質反應，導致其溶解。
酸雨：由二氧化硫和氮氧化物等污染物引起的酸性沉澱與岩石中的礦物質發生反應，導致其化學分解和改變。
生物風化
生物風化涉及植物、動物和微生物等生物體的活動，導致岩石和礦物的分解。生物風化的例子有：
地衣和苔蘚生長：生長在岩石表面的地衣和苔蘚會產生酸，透過溶解礦物質並促進進一步的物理分解，對岩石進行化學風化。
穴居動物：蚯蚓、囓齒動物和昆蟲等動物會挖入地下，使新的岩石表面暴露在風化過程中，並幫助移動碎片。
微生物活動：細菌和真菌等微生物可以產生酸作為代謝副產物，對岩石中的礦物質進行化學風化，促進其分解。