第三章岩溶地貌讲述.ppt

* * * * * * * * * * A aerial view of central Jamaica’s “Cockpit Country”, a classic, tower-studded tropical karst landscape. /images/sized/600/s_cockpit_country.jpg.jpg * 照片- /Wallpaper/ /wiki/Chocolate_Hills The Chocolate Hills is an unusual geological formation in Bohol, Philippines.[1] It is composed of around 1,268 perfectly cone-shaped hills of about the same size, spread over an area of more than 50?square kilometres (20?sq?mi). They are covered in green grass that turns brown during the dry season, hence the name. The Chocolate Hills is a famous tourist attraction of Bohol. It is featured in the provincial flag and seal to symbolize the abundance of natural attraction in the province.[2] It is in the Philippine Tourism Authoritys list of tourist destinations in the Philippines;[3] it has been declared the countrys 3rd National Geological Monument and proposed for inclusion in the UNESCO World Heritage List.[3] There are a number of hypotheses regarding the formation of the hills. These include simple limestone weathering, sub-oceanic volcanism, the uplift of the seafloor and a more recent theory which maintains that as an ancient active volcano self-destructed, it spewed huge blocks of stone which were then covered with limestone and later thrust forth from the ocean bed.[11] Geologists have long debated about the formation of the hills, resulting in various ways the origin of the Chocolate Hills are stated or explained. The one written on the bronze plaque at the viewing deck in Carmen, Bohol states that they are eroded formations of a type of marine limestone that sits on top of hardened clay.[12] The plaque reads: The unique land form known as the Chocolate Hills of Bohol was formed ages ago by the uplift of coral deposits and the action of rain water and erosion.[12][13] Another statement says: the grassy hills were once coral reefs that erupted from the sea in a massive geologic shift. Wind and water put on the finishing touches over hundreds of thous