The Chocolate Hills is an unusual geological formation in Bohol, Philippines. 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. It is in the Philippine Tourism Authority's list of tourist destinations in the Philippines; it has been declared the country's 3rd National Geological Monument and proposed for inclusion in the UNESCO World Heritage List.

Description

The Chocolate Hills are Bohol's famous attraction. Photographer Salvador Andre notes:

Most people who first see pictures of this landscape can hardly believe that these hills are not a man-made artifact. However, this idea is quickly abandoned, as the effort would surely surpass the construction of the pyramids in Egypt.

Further:

There is no natural formation like them in the world. From a distance, they look like half a ball grown out of the ground. The molehill-shaped and almost uniformly sized hills dot the landscape with green and brown.

The Chocolate Hills is a rolling terrain of haycock hills – mounds of general shape which are conical and almost symmetrical. Estimated to be at least 1,268 individual mounds to about 1,776, these cone-shaped or dome-shaped hills are actually made of grass-covered limestone. The domes vary in sizes from 30 to 50 metres (98 to 160 ft) high with the largest being 120 metres (390 ft) in height. They are scattered throughout the towns of Carmen, Batuan and Sagbayan in Bohol. Bohol's "main attraction", these unique mound-shaped hills are scattered by the thousands on the island's central plain, concentrated near the town of Carmen.

During the dry season, the precipitation is inadequate such that the grass-covered hills dry up and turn chocolate brown. This transforms the area into seemingly endless rows of "chocolate kisses". The branded confection is the inspiration behind the name, Chocolate Hills.

Topography

The Chocolate Hills and the area around it have relatively flat to rolling topography with elevation ranges from 100 to 500 metres (330 to 1,600 ft) above sea level. Higher karstic hills dominate the landscape inland then turning almost uniformly and naturally molded in Carmen.

Vegetation

The vegetation of the Chocolate Hills is dominated by hardy grass species such as Imperata cylindrica and Saccharum spontaneum. Several Compositae and ferns also grow on them. In between the hills, the flat lands are cultivated to rice and other cash crops. However, the natural vegetation on the Chocolate Hills is now highly threatened by quarrying activities.

Origin

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.

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. 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.

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 thousands of years.

Still another way the origin is stated is that they were formed centuries ago by tidal movement and by the uplift of coral deposits and the action of rain water and erosion. Another theory is that they were ancient coral limestone reefs shaped by many thousands of years erosion by both water and wind. Geologists think that the specific shape of the hills is caused by the influence of the weather over millions of years. The break down of the upper layers of the limestone formations, followed by the erosion processes, resulted in these cone-shaped remnants. It is likely that they were once limestone deposits beneath the sea, uplifted by the movement of plates and then smoothed by wind and rainwater erosion.

The Chocolate Hills are conical karst hills similar to those seen in the limestone regions of Slovenia and Croatia, except that the Chocolate Hills have no caves. According to the karst theory, "sea level changes and uplift combined with terrestrial erosion and air exposure of biogenic reef regions have given rise to hummocky landscapes that are often impregnated with sinkholes and caves." The Chocolate Hills are considered among the striking examples of this karst topography. The Bungle Bungles in the Purnululu National Park in Western Australia feature similar sedimentary formations.

Legend

Three legends explain the formation of the Chocolate Hills. The first tells the story of two feuding giants who hurled rocks, boulders and sand at each other. The fighting lasted for days, and exhausted the two giants. In their exhaustion, they forgot about their feud and became friends, but when they left they forgot to clean up the mess they had made during their battle, hence the Chocolate Hills.

A more romantic legend tells of a giant named Arogo who was extremely powerful and youthful. Arogo fell in love with Aloya who was a simple mortal. Aloya's death caused Arogo much pain and misery, and in his sorrow he could not stop crying. When his tears dried the Chocolate Hills were formed.

The third legend tells of a town being plagued by a giant carabao, who ate all of their crops. Finally having had enough, the townsfolk took all of their spoiled food and placed it in such a way that the carabao would not miss it. Sure enough, the carabao ate it, but his stomach couldn't handle the spoiled food, so he defecated, leaving behind him a mound of feces, until he had emptied his stomach of the food. The feces then dried, forming the Chocolate Hills.

credited to wikipedia and flickr:juan paulo;roomman