Geography

Area & Location

Created by virtue of Republic Act No. 2711 of March 10, 1917, this island province of Bohol is the tenth largest island in the Philippines. This oval-shaped island has an area of 4,117 sq. km. and is located in the central portion of the Visayas lying between Cebu to the northwest and Leyte to the northeast. To its south is the big island of Mindanao which is separated from Bohol by the wide Mindanao Sea. Aside from the mainland, Bohol has 75 smaller offshore islands and islets. Bohol is about 700 kilometers directly south of Manila and is about 70 kilometers southeast of Cebu City.

General Geographic & Geologic Features

Bohol must have been developed from the magmatic tectonic mechanism which resulted from the underthrusting of the southwest Philippine Plate east of Samar and Surigao. The Alicia Schist, the oldest known rock formation in the island, is inferred to be part of the Bohol crustal rocks before plate interactions. All the succeeding igneous extrusive and intrusive events in Bohol are the results of these resurging interactions. Ongoing erosion, transport and sedimentation continue to accumulate marine and terrestrial deposits in the Bohol basin.

Topology & Drainage

Bohol's mainland exhibits the following salient physiographic units:

The east and west coast display northeast trending ranging up to 870 meters in elevation (Mt. Mayana) that drop steeply to the coast. These ranges reflect the major structural units of the island.
The central (Carmen area) and northern part of the island (Trinidad) are a vast expanse of relatively rolling plains and flatlands.
The development of beautifully-arranged, symmetrically formed "haycock hills" in Carmen-Batuan-Bilar-Balilihan area in the east central part of the island is suggestion of a well-defined system of shears and joints.
An elongated cluster of hills of moderate height lies in the northeastern part of the island (Ubay area).
An east-west ridge connects Alicia with Carmen.
The Anda Peninsula and Loon Peninsula strongly suggest elevated plateaus.
At least five different Plio-pleistocene terrace levels ranging in height from 10 to 300 meters have been etched both in Carmen sandstone and shales and Maribojoc limestone.
The drainage pattern is generally radial. The west is drained by the Abatan River (350 sq. km.) and Wahig-Inabanga Rivers (570 sq. km.); the north by Alog, Ipil (250 sq. km) and Soon Rivers; the east by the Mabini and Guindulman Rivers; and the south by the Loboc-Loay (160 sq. km.), Jagna and Garcia-Hernandez Rivers. These rivers are not important for navigation purpose.
The "Ilihan Plug" south of Tubigon with an elevation of 240 meters above sea level, presents a unique geomorphologic element. At a distance, this plug is suggestive of a limestone hill with white cliffy margins.

Mountain Ranges

   There are two sets of mountain ranges located between the municipalities of Alicia and Ubay on the northeastern side of the mainland which generally trend to the north and south directions. The first range attains a maximum elevation of 404 meters above sea level while the second range of elongated clusters of hills has a maximum elevation of about 120 meters above sea level. The northern end of the mountain range is drained by the Lomangog River while the southern end by the east-flowing San Pascual River which empties into Cogtong Bay.

          About two kilometers south-southwest from Tubigon is Mt. Ilihan which is 240 meters high with steep, almost bufflike sides. Farther east are two mountain ranges, Mt. Tan-awan and Mt. Candungao with 460 and 500 meters elevation, respectively. Both are prominent landmarks rising as they do several meters above the surrounding countryside. From Mt. Tan-awan going southwestward, the range presents a monotonous karst topography, declining gradually in height until finally it joins the foothills about 4.5 kilometers southwest of Calape. The main range of hills extending from Calape southwestward joins the southwestward trending mountain range from the interior, runs south and out to Loon Peninsula and terminating in Punta Cruz (Maribojoc).

          The Sierra Bullones Range follows roughly the trend of the south coast. It commences from the vicinity of Loboc, extends eastward and finally northeastward terminating at about Biabas, Candijay. The highest point of this range and in the entire province is Mt. Mayana (870 meters). Other prominent peaks found in this range are Mt. Gordo, Mt. Amicay and Mt. Binalao.

Soil and Vegetation Cover

There is relatively thin soil cover over Bohol, bedrocks cropping out even at the valley and shore areas. Over most of the hills and ridges are meager to no soil cover. This is due to the fairly rapid surface drainage over types of Bohol's land area. The soil derived from all the rock types are generally clay and silty with sandy soil limited to some parts of the coastal area.

Climate

Bohol's climate is characterized by having no pronounced maximum rain period and no dry season. It is typically warm and dry along the coasts and cold and humid in the interior. Typhoons are not a frequent occurrence and maximum precipitation occurs in June to October. Average annual temperature is eighty-two degrees Fahrenheit.
Bohol sits below the typhoon belt and is blessed with mostly mild weather year-round. From November to mid-April, the northeast monsoon (amihan) prevails. Except for a rare shower, this is the mildest time of the year. Daytime temperatures average 28 degrees Celsius, cooling down at night to around 25 degrees Celsius. Equatorial summer from May to the end of July brings higher temperatures and very humid days. During this season, the sun beats down and the days are windless and still, leaving the seas as flat as a mirror. This is the time of year when a day at the beach and a swim in the sea. Daytime summer temperatures hover 34 degrees Celsius, with humidity off the scale. August marks the beginning of the southwest monsoon (habagat). This weather during this season is less predictable, alternating between balmy weeks of calm seas, interspersed with weeks of rain and southwesterly winds. Typhoons rarely hit Bohol directly. When rains do come, they generally last only a few minutes and are actually a cool, welcome break from the heat of the sun.