Lucsuhin Natural Bridge, locally called Cabag Cave or Lucsuhin Cave, is a

natural bridge A natural arch, natural bridge, or (less commonly) rock arch is a natural landform where an arch has formed with an opening underneath. Natural arches commonly form where inland cliffs, coastal cliffs, fins or stacks are subject to erosion ...

located between Lucsuhin and Kalubkob in Silang,

Cavite Cavite, officially the Province of Cavite ( tl, Lalawigan ng Kabite; Chavacano: ''Provincia de Cavite''), is a province in the Philippines located in the Calabarzon region in Luzon. Located on the southern shores of Manila Bay and southwest ...

province A province is almost always an administrative division within a country or state. The term derives from the ancient Roman '' provincia'', which was the major territorial and administrative unit of the Roman Empire's territorial possessions ou ...

in the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

."Municipality/City: Silang - Barangays"
. PSGC Interactive. Retrieved on 2013-06-18. The bridge, which crosses the Ylang-Ylang River, is the first large natural bridge reported in the country.

History

The first American to discover and study the bridge is Paul R. Fanning from the Division of Mines during the early part of the

American colonial period The Thirteen Colonies, also known as the Thirteen British Colonies, the Thirteen American Colonies, or later as the United Colonies, were a group of British colonies on the Atlantic coast of North America. Founded in the 17th and 18th centur ...

. He was making a geological reconnaissance in the vicinity of Silang, Cavite in July 1910 when he discovered the natural bridge of unusual size. Owing to its remoteness, Fanning believed no white men have probably visited the place before.Bureau of Science (1912)
"Philippine Journal of Science, Vol. VII, No. 4, August 1912"
p. 291. Bureau of Printing, Manila (University of Michigan Library).

Geology

The natural bridge is located in the great bedded

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

area lying between Manila and

Tayabas Bay Tayabas Bay is a large bay in the southern part of Luzon island in the Philippines. Several islands are located in the bay, largest of which is Marinduque. It has a total surface area of . The bay is bordered on the north and east side by Quezon ...

where the rock is favorable for their formation. The opening under the bridge span is tunnel-like and has a diameter of about and a length of about . It makes a double turn that roughly approximates the shape of the letter 'S.' During low water, the stream occupies a central channel consisting of a staggering series of small falls and potholes which are the result of the action of the water upon the horizontal bedding of the tuff rock.

Formation of the bridge

The floor of the bridge, which is about above the stream, was examined by Fanning and showed evidence of once having formed the bed of the stream. Erosion had nearly obliterated this old bed, but had not been sufficient to destroy the sides of the valley. At one time, the river must have flowed at this higher elevation to a place several kilometers down stream from the present tunnel and then passed over a cliff. This cliff gradually receded upstream forming the present

box canyon A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency to cu ...

. As illustrated by the sketches, seepage began at a point several hundred meters above the falls and, owing to the horizontal bedding of the rock, it first took a path at right angles to the river course, then descended from bed to bed to the bottom of the falls. The porous, soft nature of the rock favored the rapid enlargement of the underground channel, and eventually the entire stream followed this course. Subsequent

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

and caving had greatly decreased the length of the underground channel and produced the short canyon above the present entrance portal. Owing to the thinness of the roof, the first part of the tunnel caved rapidly, whereas the erosion and caving of the lower part was much slower. A condition now has been reached where the entrance and exit portals will be eroded with about equal speed and at the same time the tunnel will be greatly enlarged in diameter by down cutting and by caving of the roof. Under these conditions the bridge eventually should assume the arch structure characteristic of famous natural bridges in other parts of the world."Philippine Journal of Science, Vol. VII, No. 4, August 1912"
p. 293. Bureau of Printing, Manila (University of Michigan Library).

Protection status

The bridge and cave is not a protected area and need preservation for future generations, as well as the areas upriver to preserve the quality of water, lest it would end up like Hinulugang Taktak falls in Rizal province.

References

External links

Luksuhin Cave entrance pictures in Panoramio
{{coord, 14.214187, 120.953969, region:PH_type:landmark_scale:5000, display=title Silang, Cavite Landforms of Cavite Caves of the Philippines