ponor

Japanese: ponor

...Icicle-like stalactites hanging from the ceiling, bamboo-like stalagmites on the cave floor, travertine columns formed by connecting these two, and travertine terraces with ridge stone dams on the slopes, all create a very diverse landscape, and these are the main tourist attractions in many tourist caves. When a river flowing through a normal valley reaches a limestone area, it flows into a cave called a ponor (suction hole) and disappears. This river often dries up during the low rain season.

From [Doline]

...their size varies from a few meters to hundreds of meters. The inner slopes of the dolines are exposed limestone, and red clay soils are deposited at their bottoms. Sometimes suction holes called ponors are found in the dolines, which collect rainwater and drain it underground. When the bottom of a doline reaches the groundwater table, a doline lake is formed.

*Some of the terminology that mentions "ponor" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…天井から垂れ下がるつらら状の鍾乳石，洞床にたけのこ状に堆積した石筍（せきじゆん），この両者が連結した形の石灰華柱，また傾斜面につくられた畦石（けいせき）ダムが何段にもうろこ状に重なった石灰華段丘など，きわめて多彩な景観をつくり出し，多くの観光洞でこれらが重要な観光対象となっている。　普通の谷を流れる河川が石灰岩地のところに達すると，ポノールponor(吸込穴)と呼ばれる洞穴に流れ込んで姿を消す。この川は少雨期には涸れ川となっていることも多い。…