地理位置
居庸关云台，又称“云台石阁”， 位于北京市昌平区南口镇北的居庸关关城内，是元代过街塔的基座，始建于元至正二年（1342年），至正五年（1345年）落成。
云台位于居庸关景区内，你只需要购买居庸关门票即可。门票人民币40元。
居庸关云台的老照片
建筑材料
居庸关云台主体结构是颜色洁白的纯质细粒大理石，质地坚硬，是上等的建筑和雕刻材料。主要成分是碳酸钙，化学式是CaCO3，其他成分还有MgCO3和SiO2等。主要特征是颗粒状的纹理、中等大小的粒度和较高的硬度，基本上不溶于水。它可存在于以下形态：霰石、方解石、白垩、石灰岩等。这些特点，保证了云台在历经700多年的风吹、日晒、雨淋，虽然颜色改变了，但依旧能矗立在此。
岩石类型：大理石（变质岩）
粒度： 0.5至2毫米
质地：固体
成分：碳酸钙
颜色：乳白色，浅灰色，淡黄
形态：霰石，方解石
大理石的种类：
1）纯质碳酸盐大理石，主要是方解石、白云石。
2）硅质碳酸盐大理石，主要是滑石、石英、透辉石、粒硅钙石等。
3）泥质碳酸盐大理石，主要是蛇纹石、绿泥石、方柱石、正长石等。
建筑结构
云台呈长方形，通高9.5米，基座下部东西长26.84米，南北长17.57米，基座顶部东西长25.21米，南北长12.9米。台顶四周为雕花石栏及排水龙头，台子正中南北方向辟有一卷洞，形状如半个八角形，属于中国古代砖石拱中一种较为特殊的构造。卷洞宽6.32米，高7.27米，长17.57米，车马可在内通行。
雕刻特点
居庸关云台券门内外的浮雕和装饰均为藏式风格。浮雕对人物的刻画细致入微，动静结合，刚柔相济，堪称元代雕刻艺术的精品之作。
云台券门内壁的顶部雕刻有5个曼陀罗图案，斜顶部雕刻有十方佛图案，曼陀罗和十方佛之间雕刻有千佛。两侧垂直的内壁雕刻有四大天王造像，东西两壁各有两尊。在四大天王造像之间的两面均有石刻文字，其中一侧为藏文、梵文、汉文、八思巴文、维吾尔文和西夏文拼写的《陀罗尼经咒》；另一侧为藏文、汉文、八思巴文、维吾尔文和西夏文记载的《造塔功德记》。南北券门外侧的两边雕刻有四个圆形交杆浮雕，其正中为大鹏金翅鸟。左右对称雕刻有鲸鱼、龙子、童男骑怪兽和二象等“六拏具”图案。
云台券门内壁的五曼荼罗的主尊佛像，由北往南依次为：释迦牟尼佛（如来佛）、阿弥陀佛（菩萨形）、阿佛（菩萨形）、金刚手菩萨、普明菩萨。其中除释迦牟尼为佛祖之外，其他四菩萨在此显现，则有四方教主的意思。五曼荼罗连同其他佛像，共197尊。十方佛的每方佛周围还分别刻有小佛102座，共计小佛1020座，取共千佛之意。这些小佛，是明朝正统年间，修建泰安寺时补刻的。连同十方佛下的菩萨、比丘，券顶两侧共有刻像1060尊。
你的任务
要登录这个Earthcache，您必须认真阅读文档，在现场仔细观察云台的构造和大理石的特征。在登录前，必须以发送信息的方式回答以下问题。
如果没有没有电子邮件或网站短信发送答案、答案不完整或答案明显错误，或者发送的日志中没有图片或图片显示的是云台本身，日志将被删除。
问题
1、构建云台的大理石是什么类型的（纯质、硅质、泥质大理石）？
2、从你的观察来看，构建云台的大理石是光滑的还是粗糙的？
3、你认为大理石现在是什么颜色？为什么会这样？
4、云台券洞内两侧地面有什么特点？它是怎么产生的？
5、这三张图片，分别是什么文字和什么图案？
6、请在登录地点提供一张照片，但不包括云台本身。建议可以与居庸关景区内的其他景点合影。当然，这都是自愿的行为。
English
Location
Yuntai Terrace in Juyongguan Pass , also known as "Yuntai Stone Pavilion"( Below I call it Yuntai) ，is located in the Juyongguan Pass City in the north of Nankou Town, Changping District, Beijing. It is the base of the street tower of the Yuan Dynasty, which was built in the 1342 and completed in the 1345.
Yuntai is located in Juyongguan scenic area, you only need to buy Juyongguan tickets. The entrance fee is RMB 40.
View Yuntai
Building material
The main structure of Yuntai is pure fine grained marble with white color and hard texture, which is a first-class building and carving material. The main component is calcium carbonate, the chemical formula is CaCO3, and other components are MgCO3 and SiO2. The main characteristics are granular texture, medium size particle size and high hardness, basically insoluble in water. It can exist in the following forms: aragonite, calcite, chalk, limestone, etc. These characteristics ensure that the cloud head after more than 700 years of wind, sun, rain, although the color has changed, but still can stand here.
Type: Marble (metamorphic rock)
Size: 0.5 to 2 mm
Texture: solid
Composition: Calcium carbonate
Color: Milky white, light gray, light yellow
Form: aragonite, calcite
Types of marble:
1) Pure carbonate marble, mainly calcite, dolomite.
2) siliceous carbonate marble, mainly talc, quartz, diopside, granular calcite and so on.
3) Argillaceous carbonate marble, mainly serpentine, chlorite, quartzite, orthoclase and so on.
Building structure
The Yuntai is rectangular, with a height of 9.5 meters, the lower part of the base is 26.84 meters from east to west, 17.57 meters from north to south, and the top of the base is 25.21 meters from east to west, 12.9 meters from north to south. The top is surrounded by carved stone columns and drainage taps, and there is a roll of holes in the middle of the platform in the north and south direction, shaped like a half octagon, which belongs to a special structure in ancient Chinese brick and stone arches. The cave is 6.32 meters wide, 7.27 meters high, and 17.57 meters long.
Carving characteristics
The relief and decoration inside and outside the Yuntai are Tibetan style. The characters of the relief are depicted in detail, the combination of static and dynamic, rigid and soft, which can be called the fine sculpture art of the Yuan Dynasty.
There are five mandala patterns carved on the top of the inner wall of the gate, ten square Buddha patterns carved on the oblique top, and thousands of Buddhas carved between the mandala and the ten square Buddha. The vertical inner walls on both sides are carved with four heavenly Kings, and there are two statues on each of the east and west walls. There are stone inscriptions on two sides between the four heavenly king statues, one of which is the "Dharani Sutra Mantra" spelled in Tibetan, Sanskrit, Chinese, Bhasba, Uyghur and Tangut. On the other side is the book of Making Pagoda Merit recorded in Tibetan, Chinese, Bhasaba, Uyghur and Tangut. The two sides of the outside gate of the north and south coupons are carved with four circular cross-bar reliefs, and the middle is a roc goldenwing bird. There are six pictorial images of whales, dragons, boys riding monsters, and two elephants.
The main Buddha statues of the five mandalas on the inner wall of the Yuntai gate, from north to south, are: Sakyamuni Buddha (Tathagata Buddha), Amitabha Buddha (Bodhisattva Buddha), Buddha (Bodhisattva Buddha), Vajradha Bodhisattva, and Puming Bodhisattva. In addition to Shakyamuni as the Buddha, the other four Bodhisattvas appear here, which has the meaning of the four masters. Five mandala together with other Buddha statues, total 197. There are also 102 small Buddhas carved around each of the ten Buddhas, totaling 1020 small Buddhas, which means a total of thousands of Buddhas. These small Buddhas were made during the construction of Tai 'an Temple during the Orthodox period of the Ming Dynasty. Together with Bodhisattvas and bhikkhus under the ten Buddhas, there are 1060 statues engraved on both sides of the top of the voucher.
Your task
To log this Earthcache, you must carefully read the documentation and observe the structure of the head and the characteristics of the marble in the field. Before logging in, you must answer the following questions by sending a message.
If no answer is sent without email or website SMS, the answer is incomplete or the answer is obviously wrong, or the log sent does not contain a picture or the picture shows the head itself, the log will be deleted.
Question：
1. What is the type of marble (pure, siliceous, argillaceous marble) used to build the Yuntai?
2. From your observation, is the marble used to build the Yuntai smooth or rough?
3. What color do you think the marble is now? Why is that?
4. What are the characteristics of the ground on both sides of the Yuntai coupon hole? How did it come about?
5. What are the words in these three pictures? What pattern?
6. Please provide a photo at the login location, but do not include the head itself. It is suggested that you can take photos with other scenic spots in Juyongguan scenic area. Of course, it's all voluntary.