Welcome to the Great Wall of China! With this Earthcache, you will learn about the geology around the Mutianyu Section of the Great Wall.
欢迎来到中国长城！通过这个地球宝库，您将了解长城慕田峪段周围的地质情况。
Logging Tasks
At the given coordinates you will find yourself on the Great Wall of China. Please answer the following questions:
- At the posted coordinates, measure the elevation of the Great Wall with your GPS or phone. At the parking area, the elevation is about 350m. How big is the difference in elevation between these two points?
- Describe the shape of the mountain ridge that you can see around the Great Wall near the coordinates.
- With the help of the listing and your on-site observations, please tell me if the profile of the mountain ridge is sharp or rounded. Why do you think the ridge has this profile?
- 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
记录任务
在给定的坐标处，您将发现自己位于中国的长城上。请回答以下问题：
1. 在发布的坐标处，使用 GPS 或手机测量长城的海拔。停车场海拔约350m。这两点之间的高程差异有多大？
2. 描述在坐标附近可以看到的长城周围山脊的形状。
3. 请根据清单和您的现场观察，告诉我山脊的轮廓是尖锐的还是圆形的。您认为山脊为何具有这样的轮廓？
4. 此外，请在坐标附近拍摄您自己、GPS 或属于您的其他物品的照片，并将其附加到您的日志中。
请通过消息中心将问题的答案发送给我。之后，您可以立即记录您的发现。我会尽快回复您。
如果您在回答问题时遇到任何问题，请随时与我联系 - 我很乐意为您提供帮助。 :)
玩得开心！
Geological Background:
The Yan Mountains or Yanshan Mountains, which surround the Great Wall in the Eastern part of China, were formed during the Mesozoic Era (about 100 to 200 million years ago). This period involved intense tectonic activity as the Pacific Plate subducted beneath the Eastern Edge of the Eurasian Plate back then. The resulting compression and faulting uplifted the mountain range and formed the distinctive ridges and peaks visible today.
The bedrock in this area mainly consists of granite and limestone. Over millions of years, natural forces such as wind, water, and ice have slowly shaped the landscape, carving out valleys and gorges between the towering mountain peaks.
Plate tectonics
Plate tectonics is a scientific theory that the Earth's outermost rocky layer consists of several rocky plates that move or "drift" slowly since about 3.4 billion years ago. This outermost rocky layer of the Earth is called litosphere and consists of crust and upper mantle. The litosphere is broken into seven major plates and lots of smaller plates.
The major plates are:
- Eurasian Plate
- African Plate
- North American Plate
- South American Plate
- Australian Plate
- Pacific Plate
- Antarctic Plate
Examples of smaller plates are:
- Nazca Plate
- Somali Plate
- Indian Plate
- Arabian Plate
(Image source: Earth How)
Plate boundaries
There are three different kinds of plate boundaries which are characterized by the way the plates move relatively to each other. On the surface different geological features can be observed for each of the three different plate boundaries.
1. Divergent boundaries: These are where two plates move away from each other. Melted rock comes up to the surface and forms new Earth crust which means new litosphere is created. Examples are the Red Sea or the Great Rift Valley in Africa.
2. Convergent boundaries: These are where two plates move towards each other and collide. There are two different types of convergent boundaries:
- Subduction zone: One plate is moving underneath another plate. If an oceanic and a continental plate collide, the more dense oceanic plate subducts underneath the less dense continental plate. Subduction can form huge ocean trenches, for example the Atacama Trench along the West Coast of South America.
- Collision zone: When two continental plates collide, both plates are pushed up because they have similiar density. The plate edges are compressed, folded and uplifted. Massive mountain ranges can be formed. Famous examples are the Himalaya or the Alps.
3. Transform boundaries: Two plates slide past each other. No litosphere is created or destroyed but instead a fault zone is formed. Most fault zones can be found in Oceanic crust. However, the fault zones on land are usually better known due to the high seismic activity in that area. An example is the San Andreas fault zone in California.
What is granite?
Both the Wall and the surrounding landscape are made of granite. Granite is a kind of igneous rock. Granite is characterized by its coarse-grained texture, which results from the slow cooling of magma deep within the Earth's crust. It typically contains a mix of minerals, with quartz, feldspar, and mica being the most common. If a rock doesn't contain at least 20% of quartz, it is not considered as granite.
What is a mountain ridge?
A mountain ridge is a long, narrow and elevated landform that forms the high point (crest) of a mountain range. It is typically created by tectonic activity, erosion, or volcanic processes, and it runs along the top of a series of connected mountains. Mountain ridges are often characterized by steep slopes on either side. The the ridge itself acts as a division between two valleys or lower-lying areas on both sides of the ridge.
Crest / Ridgecrest: The highest line or edge along the ridge.
Slopes: The (steep) sides that descend from the ridge down to the surrounding terrain.
Sharp or rounded profile: The profile of a ridge can be either sharp (younger mountain ranges) or more rounded (older, eroded mountain ranges). The slopes of a sharp ridge profile are usually quite steep. Rounded ridges have more gentle slopes on each side, so it makes it easier to walk / hike up to these ridges.
Historical Background of the Mutianyu Section of the Great Wall
The Mutianyu section of the Great Wall of China is located about 70 kilometers (43 miles) northeast of Beijing. It is one of the best-preserved and most famous parts of the Great Wall.
The original construction of this section dates back to the Northern Qi Dynasty (550–577 AD). The section that we can see today was largely rebuilt and fortified during the Ming Dynasty (1368–1644 AD) under the supervision of General Xu Da. Xu Da was a famous military commander who served under Emperor Hongwu.
Mutianyu was an important military stronghold. It was designed to protect the capital, Beijing, from invasions by nomadic tribes from the north, particularly the Mongols. At Mutianyu, the terrain provided an ideal location for defensive structures, because the steep slopes and high elevations offered protection against invaders.
The wall was mainly build from granite blocks. The wall has an average height of about 7-8 meters (23-26 feet) and a width of 4-5 meters (13-16 feet). It also features 22 watchtowers spread along this 2.25-kilometer (1.5-mile) stretch, more densely placed than at other sections of the Great Wall.
Mutianyu was restored in the 1980s. In 1987 it was named as a UNESCO World Heritage Site. Today it is easily accessible from Beijing and features several cable cars. It is popular among visitors due to its well-preserved structure and its scenic views and landscape.
地质背景：
围绕慕田峪长城的燕山或燕山山脉形成于中生代（约100至2亿年前）。这一时期发生了强烈的构造活动，当时欧亚板块与附近板块碰撞。由此产生的压缩和断层抬升了山脉，形成了今天可见的独特的山脊和山峰。
该区基岩主要由花岗岩和石灰岩组成。数百万年来，风、水和冰等自然力量慢慢地塑造了地貌，在高耸的山峰之间形成了山谷和峡谷。
地质背景：
中国东部环绕长城的燕山或燕山山脉形成于中生代（约100至2亿年前）。这一时期发生了剧烈的构造活动，当时太平洋板块俯冲到欧亚板块东缘之下。由此产生的压缩和断层抬升了山脉，形成了今天可见的独特的山脊和山峰。
该区基岩主要由花岗岩和石灰岩组成。数百万年来，风、水和冰等自然力量慢慢地塑造了地貌，在高耸的山峰之间形成了山谷和峡谷。
板块构造
板块构造学是一种科学理论，认为地球最外层的岩石层由几个岩石板块组成，这些板块自大约 34 亿年前以来一直在缓慢移动或“漂移”。地球最外层的岩石层称为岩石圈，由地壳和上地幔组成。岩石圈分为七个主要板块和许多较小的板块。
主要板块有：
- 欧亚板块
- 非洲盘
- 北美板块
- 南美板块
- 澳洲盘
- 太平洋板块
- 南极板块
较小板的示例有：
- 纳斯卡板
- 索马里板块
- 印度板
- 阿拉伯盘
板块边界
存在三种不同类型的板块边界，其特征在于板块之间相对移动的方式。在表面上，可以观察到三个不同板块边界中的每一个的不同地质特征。
1.发散边界：这是两个板块相互远离的地方。融化的岩石上升到地表并形成新的地壳，这意味着新的岩石圈被创建。例如红海或非洲大裂谷。
2. 会聚边界：这是两个板块相互移动并碰撞的地方。有两种不同类型的收敛边界：
俯冲带：一个板块正在另一个板块下方移动。如果海洋板块和大陆板块碰撞，密度较大的海洋板块就会俯冲到密度较小的大陆板块下方。俯冲作用可以形成巨大的海沟，例如南美洲西海岸的阿塔卡马海沟。
碰撞区：当两个大陆板块碰撞时，由于密度相似，两个板块都被推升。板块边缘被压缩、折叠和隆起。可以形成巨大的山脉。著名的例子是喜马拉雅山或阿尔卑斯山。
3. 变换边界：两个板相互滑过。没有岩石圈被创造或破坏，而是形成了断层带。大多数断裂带可以在洋壳中找到。然而，由于该地区地震活动频繁，陆地上的断层带通常更为人们所知。加利福尼亚州的圣安德烈亚斯断层带就是一个例子。
什么是花岗岩？
城墙和周围的景观都是由花岗岩制成的。花岗岩是火成岩的一种。花岗岩的特点是其粗粒纹理，这是地壳深处岩浆缓慢冷却的结果。它通常含有多种矿物的混合物，其中最常见的是石英、长石和云母。如果岩石不含至少 20% 的石英，则不被视为花岗岩。
什么是山脊？
山脊是形成山脉最高点（山峰）的狭长高地地貌。它通常是由构造活动、侵蚀或火山过程形成的，沿着一系列相连的山脉的顶部延伸。山脊的特点通常是两侧陡峭的斜坡。山脊本身是两个山谷或山脊两侧的低洼地区之间的分界线。
Crest / Ridgecrest：沿着山脊的最高线或边缘。
斜坡：从山脊下降到周围地形的（陡峭）侧面。
尖锐或圆形的轮廓：山脊的轮廓可以是尖锐的（较年轻的山脉）或更圆的（较古老的、被侵蚀的山脉）。尖锐山脊轮廓的坡度通常相当陡峭。圆形山脊每侧都有更平缓的斜坡，因此更容易步行/徒步到达这些山脊。
慕田峪长城的历史背景
中国长城的慕田峪段位于北京东北约 70 公里（43 英里）处。 它是长城中保存最完好、最著名的部分之一。
该路段的最初建造可以追溯到北齐时期（公元 550-577 年）。我们今天看到的部分大部分是在明朝（公元 1368-1644 年）徐达将军的监督下重建和加固的。徐达是洪武帝麾下著名的军事将领。
慕田峪是重要的军事据点。它的目的是保护首都北京免受北方游牧部落，特别是蒙古人的入侵。 慕田峪的地形为防御建筑提供了理想的位置，因为陡峭的山坡和高海拔可以抵御入侵者。
城墙主要由花岗岩块建造。墙的平均高度约为 7-8 米（23-26 英尺），宽度为 4-5 米（13-16 英尺）。 它还拥有 22 座瞭望塔，分布在这片 2.25 公里（1.5 英里）的长城上，比长城其他路段的分布更为密集。
慕田峪于20世纪80年代修复。 1987年被联合国教科文组织列为世界遗产。如今，从北京可以轻松抵达这里，并设有多条缆车。它因其保存完好的建筑结构和优美的景观而深受游客欢迎。