The following sections describe selected important geosites within Bohol Island Geopark that showcase its dynamic geologic setting and its resulting highly diverse landforms.
The unique karst landscape is composed of smooth, uniformly shaped conical isolated hills that cover a vast area in the central portion of the island. The site was once a platform of thick widespread buildup of coral reefs that thrived during the Pliocene, approximately 2-5 million years ago and later to form a sedimentary formation. Soon, this limestone formation was raised above the sea level and fractured. Rainwater, streams and groundwater dissolved the limestone, gradually forming the present landscape of cone karst.
The Hinagdanan Cave is one of the many wondrous karst caves in the Province of Bohol. This cave was accidentally discovered by a farmer while clearing his land. Stumbling on a hole in the ground, curious, he dropped stone and heard a splash. He built a ladder, “hagdan”, and went down to find the cave’s hidden beauty, hence the origin of its name Hinagdanan. It boasts of several stalactite and stalagmite formations and a clear lagoon that is about 10 to 20 meters deep. Aside from its awe-inspiring natural beauty, Hinagdanan also played a significant role in the history of Bohol. The cave was used during Second World War as a hideout by locals to escape from the Japanese Imperial Army.
INABANGA RUPTURE SITE
The Magnitude 7.2 earthquake in October 15, 2013 in Bohol damaged billions worth of infrastructures and properties including several centuries-old churches. It was caused by a previously unmapped fault which manifested on the land surface as an elongated fissure on the ground and can be traced for 6 kilometers from Brgy. New Anonang in Buenavista up to Brgy. Napo in Inabanga, and is believed to extend even further offshore. The most prominent expression of the fault is in Bgy. Anonang, Inabanga, where, a formerly flat rice field was cut and the northern part raised to up to 3 meters high, forming a conspicuous wall called a fault scarp. The scarp stretches for up to 2 kilometers long. The movement along the fault wherein one side moved upwards with respect to its opposite side as manifested in the fault scarp can only be caused by a tremendous amount of energy which is released during the Magnitude 7.2 earthquake.
MARIBOJOC UPLIFTED MARINE TERRACE
A 7.2-magnitude earthquake that rocked Bohol on October 15, 2013 brought devastation everywhere on the island and some nearby island provinces. The shaking was the result of a demonstration of nature’s power that has been changing the face of the Earth for millions of years: uplift of blocks of land during movement along a fault. This time the coastal areas of Loon-Maribojoc were pushed approximately 1.5 meters upwards when motion occured along a new fault in Inabanga. What was once a portion of the sea bottom and an underwater reef was now thrusted above sea level, creating a newly raised marine terrace and shifting the coastline 50 meters seaward. This is the Maribojoc Uplifted Marine Terrace. It is declared as the Loon-Maribojoc Geologic Monument by the Department of Environment and Natural Resources under the DENR Administrative Order No. 2015-08. The geological monument covers 1.37 kilometers (137 hectares) of uplifted coastline within the towns of Loon and Maribojoc.
Older marine terraces can also be found inland as part of the limestones of Maribojoc Formation. They too were a result of tectonic uplift in the not so distant geologic past, proof of the immense power of nature to create ever changing landscapes.
LOON UPLIFTED MARINE TERRACE (LOON CORAL GARDEN)
One of the shoreline areas uplifted during the earthquake of October 15, 2013 is the presently named Loon Coastal Geomorphic Conservation Park which covers an area of 417 hectares. This former intertidal zone, where the tide sometimes submerged or exposed the land, is now an uplifted terrace and completely on dry land. It was raised approximately 1.5 meters vertically and the shoreline shifted 50 meters seawards. The former barren land right after the earthquake is now teeming with sea purslane, a creeping succulent seagrass plant of the family Aizoaceae, that covers the land with a mat of red and orange color during sunny days, and a luxurious green color during rainy days. The locals call the area the Coral Garden, a popular new destination for tourists and residents alike.
The Alicia Schist which appears to be Cretaceous is the lowest formation in Bohol area and the Ubay Volcanics which appear to be Paleocene approximately 100-145 million years old are exposed in the eastern to northern Bohol. The entire basement complex is overlain unconformably by a 2000m thick sequence of Lower Miocene to Pleistocene carbonate and clastic sedimentary rocks and igneous units.
ALICIA PANORAMIC PARK
The Alicia Panoramic Park features the breathtaking landscape of Binabaje Hills of Brgy. Cambaol in Alica Municipality. The hills, which rise to 400 meters above sea level, are mostly covered in tropical perennial grasses commonly known as Cogon. These tall green grasses wave gently as the breeze passes, giving a soft furry-like appearance to the hills, which is composed primarily of metamorphic rock – the Alicia Schist, the oldest rock in Bohol (Late Jurassic – Early Cretaceous, 146 mya – 66 mya). Many adventure-seekers enjoy trekking the ridge trails over the hills and the picture-perfect and stunning green scenery.
BACLAYON ANCIENT UPLIFTED MARINE TERRACES
The uplifted marine terrace in Baclayon is a similar landform to the more recently uplifted marine terrace in Maribojoc. However, the terraces in Baclayon are much older. It was formed during the Pliocene-Pleistocene time (5 miion years – 10,000 years ago). Fault movement along the coast caused the uplift of formerly underwater reefs raising it at height above the sea and creating marine terraces seen at Baclayon. The three-step terraces there stand at 20 meters, 40 meters and 60 meters above sea level signifying at least three episodes of progressive tectonic uplift in the area. The Ancient marine terraces can be observed in the step-like quality of uphill roads that branches inland from the highway in Baclayon.
Can-Umantad Falss is regarded as the tallest waterfall in the entire province of Bohol. From a height of 60 meters, its source water from Cadapdapan River falls down over a backdrop of horizontal to slightly dipping beds of calcareous and tuffaceous sediments of the clastic member of the Carmen Formation (Middle Miocene, 16 mya – 11 mya)
PRINCESS MANAN-AW CAVE
Princess Manan-aw cave is one of the numerous caves included in the Cagong-cagong cave system. It has a total length of 195.5 m, the entrance is measured to be 5.6 m. and width f 3.7m. The cave is carved out of coarse and reefal calcareous rocks belonging to the later Milocene Sierra Bullones Limestone. It has plenty of speleothems and underground river flowering inside the cave.
CANAWA COLD SPRING
Tucked within a lush green forest in the town of Candijay is a popular leisure area for locals known as the Canawa Cold Spring. Its name came from the local term “Cawa” which means “pan”, taking from the natural shape of the spring. The depth of the spring is still unknown; several attempts has been made to dive at the floor of the spring but it was said that the water is too deep no one has been able to reach the bottom. Even the actual source of the spring water is still unknown.
The spring is carved out of the Middle Miocene Carmen Formation comprised of 400 to 800 m thick calcareous sedimentary formation. Concrete walls and stairs were built on the spring entrance to be of help to those who cannot swim especially to the children, but the main part of the spring which is the circular pool, was kept in its natural state.
CAVE POOLS OF ANDA
Aside from the fine white sand beaches in Quinale, the Cave Pools of Anda are becoming common destinations in the southeastern part of Bohol for adventure seekers. Due to the large percentage of land underlain by limestones, cave pools or basically limestones filled with spring water forming pools are common sights in Anda. Among the famous cave pools are Cabagnow and Combento, and the smaller Kaligoon Cave Pool, East Coast Cave Pool and Kalorenzo Cave Pool.
The area is underlain by the Middle Miocene Anda Limestone belonging to the Sierra Bullones Limestone Formation. Years of dissolution and weathering of this limestone body resulted in karst features like these caves.
Lamanoc is famous for its limestone cliffs and flourishing plant life and wildlife. Check out the caves and you’ll find old clay jars, several boat coffins and a rock shelter that contains graffiti dated during prehistoric era. Relics of prehistoric painting made using hematite painted on cave walls are observed, but age and meaning of these figures are unknown. The locals practice their centuries-old tradition they were accustomed to, such as offering gifts to a “diwata” whom, according to them, is the protector of the island. For the people of Lamanoc, the observance of such tradition will bring them abundant food harvest which is rooted in their strong ancestral beliefs even before they were converted to Christianity by the Spaniards.
TRINIDAD CAVE SYSTEM: BATUNGAY CAVE
Underlain by extensive calcareous rock unit, Trinidad municipality, located in the northern part of the island, is also home to a number of caves. The most popular of these caves is the Batungay Cave located in a forested area of Brgy. Santo Tomas, in the interior part of the town. Batungay is derived from the word “bato”, meaning rock, and “ngay”, meaning twins. Literally, it means that the cave is beneath two solid rocks known as Batungay Twin Peak. Inside the cave is a flowing stream of clear water and majestic stalactites hanging from the cave ceiling and stalagmites jutting out from the cave floor forming different shapes like chandeliers and curtains.
The cave is uniquely known as having designated habitats for some species and unique cultural practices. The “Langub sa Has” or the cave of the snakes houses some snakes in the cave. The “Langub sa Kabyaw” is a habitat for the bats, and is a rich source of guano or bat manure used as fertilizer. The “Langub sa Simbahan” contains magnificent stalactites that glitter in the dark, hanging from the ceiling like huge chandeliers in cathedrals. There is also the “Langub sa Binlanan” where the traditional healers or the “tambalans” prepare their medicinal herbs and do their oraciones or rituals. They leave some of the concoctions they made in the cave, along with some food as an offering to the “apo” of the cave. The tambalans can go through the cave’s canals to reach a cave in Ilihan, Alicia, in another town. Ilihan Cave is known to be a sister cave or Batungay.