Geosites
Interesting geological places 

Geosites are geological spots where we can learn about the geological history of Geopark. Here, we introduce two Geosites that help us  understand the volcanic history of the Moon.

The Marius Hills is a volcanic plateau, which is located at ∼13.4°N, ~55.6°W of the Moon. The name "Marius" is the name of the crater near the hills. 

The Marius Hills are organized by several types of volcanic features, including domes (moutain with gentle slope), cones, sinuous rilles. So far, approximately 360 cones and 22 domes have been identified. The Marius Hills are a region where many volcanic activities occurred in the past. 

In addition to the volcanoes, a deep hole (pit) has been observed on the Marius Hills' surface. This hole is located within a rille. The hole appears to have a lateral cavity at its bottom. However, it is not yet known how far this cavity extends. So far, no one knows the detailed internal structure of the hole. 

It is considered that this hole is caused by the collapse of a lava tube. Lava tubes are created when flowing lava cools and solidifies on the outside while the interior remains molten and continues to flow. If this hole is indeed related to a lava tube, we can know that intense volcanic activity occurred in the Marius Hills.

Mare Tranquillitatis is a lunar mare located at approximately 8.5°N, 31.4°E. Apollo 11 landed in Mare Tranquillitatis in 1969 and collected samples from the site. Many domes—mountains with gentle slopes of less than 5 degrees—have been observed in this region. These domes are considered to be volcanic in origin. Although the detailed formation mechanism is still unknown, it is possible that Mare Tranquillitatis was formed by numerous volcanic eruptions (it has also been suggested that Mare Tranquillitatis was caused by one large volcano).

Near the Cauchy crater, two faults have been observed, which are named as Rima Cauchy and Rupes Cauchy.

As well as in the Marius Hill, there is a vertical deep hole(pit) in Mare Tranquillitatis. This hole is also considered to be generated by a lava tube. 

The vertical holes in the Marius Hills and Mare Tranquillitatis are very interesting spots for future exploration.