Fossilized Giant Clam Shell found in Mountains of San Fernando, Cebu

Posted in News & Events on November 17, 2014
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Scientists believed that the Philippines was once at the bottom of the sea and due to massive violent earthquakes, land masses formed and rises to the surface. Can this Fossilized Giant Clam Shell be an evidence that San Fernando Cebu was once submerged in water some thousands of years ago?

When seeing a Clam Shell, we Filipinos would always think it as a delicacy or a delicious sea food served in a restaurant. But what if you heard of a fossilized Giant Clam shell? Would you be imagining a prehistoric Clam that lives on the prehistoric area? The interesting thing is this Giant Clam Shell is eye-catching not just for its size but also for where it was found … high in the Mountains of San Fernando, Cebu!

Last Sunday of November 2014, we were attending a christening ceremony and we were hiking on the remote mountainous region of San Fernando to reach the place where the celebration was located. It was really a big feast. We ate a lot, we've talked much and shared a series of topics and stories to the local folks on the place. We heard different stories about their mountainous place but one of the most interesting story that attracted me was one of the local folks named as "Armando" who shared an interesting story of how he discovered some old giant fossilized Clam Shell (or taklobo in cebuano) somewhere in the mountain area near the place. I was quiet interested and at the same time wondering how on earth does this giant clam shell got into the mountain?

I'm very much interested in the story, so after eating lunch, I asked Mr. Armando if we could go and check on that fossilized shell he discovered on the mountain. He agreed to go and decided to guide us where the shell is located. Together with my family my brother in law and nephews, we excitedly go across the other mountain where the shell was located.

Together with my family, Mr. Armando lead us to the location
My Sister-Law and her Family decided to just wait on the area where the ground is level

Much to our surprise, we traveled to a very remote place, from trees to trees and bushes to bushes there are no signs of roads or even small trails. The mountain is really steep and we've reached to the point where we decided to have my wife, my in-laws and the children to just wait and stay put on an area where the ground is level, while Mr. Armando and I will still go up a little further to the mountain top where Fossilized Shell is located.

 At last we arrived on the location and it was really amazing. The Giant Clam Shell is really big, approximately more than 2ft long. It is very old and almost look like a stone already, it has some grass and plants already growing on the mouth of the shell.  See the picture below:

giant_clamshell6   giant_clamshell2

On the pictures above, the Giant Clam shell where half of its body is buried from the ground is found on the top mountains of San Fernando, about 6 kilometers away from the shorelines.

More Information on Giant Clam

Lets talk about the Giant Clam Shell for a minute first. The giant clam (Tridacna gigas) is a bivalve mollusc also known as taklobo in the Philippines. The giant clam (Tridacna gigas) is burrowing marine mollusk living on sand or mud; the shell closes with viselike firmness.

Photographed by Jan Derk in November 2002 on the Great Barrier Reef, Australia

Photographed by Jan Derk in November 2002 on the Great Barrier Reef, Australia

There are freshwater and marine varieties ranging in size from those that even as adults are nearly microscopic to others, such as the giant clam, which can weigh 200 kilograms (440 lbs), measure as much as 120 cm (47 in) across. Some have life cycles of only one year and have an average lifespan in the wild of 100 years or more, while at least one has been discovered that may be over 500 years old. They do not have heads and most are blind but some, such as the scallops, have rudimentary eyes. Though a common food item, many species of clam are too small to be useful as food, and not all species are considered palatable. These giant clams are also found off the shores of the Philippines, where they are called taklobo. Giant Clams is one of the most endangered type of clam species.

Giant Clam Shells has four or five vertical folds in its shell; this is the main characteristic that separates it from the other shells (like the southern giant clam). Bivalves have long been a part of the diet of coastal human populations. Researchers and scientist were able to analyzed that bivalves were rich in amino acids that trigger increased levels of sex hormones. Their high zinc content aids the production of testosterone. The giant clam is considered a delicacy in Japan (known as Himejako).

The numbers in the wild have been greatly reduced by extensive harvesting for food and the aquarium trade.

So let's go back to  the big question on:

How did this Giant Clam Shell got there?

Can this be an evidence that mountains or  San Fernando was once submerged into the water? Could this be a proof that the Clam Shell found in the mountain was really living there for more than 1000 years ago when the sea once did cover the areas where the fossil is found, but they were not mountains at the time; they were shallow seas. Seashells and other marine fossils have been found on mountaintops and  these are indication that the sea once covered the mountains. Which evidence show that the region was once under the sea or covered with water.

Gian Clam Shell was found about 6 kilometers from away from the Shorelines

Giant Clam Shell was found about 6 kilometers from away from the Shorelines

In my opinion, yes, this can be an evidence that the area (for extended periods of time) was once covered by water. Do we have any other evidence to backup our first evidence? Well, yes, there is. Let's take a look at the geography of the place.

Geography of San Fernando Cebu

Maybe some of you may not know, San Fernando is 2nd class municipality in the province of Cebu where its main products produced are Cements. It is also where the biggest cement manufacturer (Taiheiyo Cement) in Cebu is located. The reason why this large Cement facility is established  in San Fernando its because the place has a lot of limestone deposits which is the basic ingredients or elements for a Cement. The facility sits on a limestone deposit estimated to last at least 100 years.

In Science Definition:

"Limestone is a sedimentary rock composed primarily of calcium carbonate in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris. It can also be a chemical sedimentary rock formed by the precipitation of calcium carbonate from lake or ocean water. Limestone makes up about 10% of the total volume of all sedimentary rocks."

Scientists who studied the geology of the Philippines believed that once upon a time the Philippines was at the bottom of the sea and due to the thin Pacific crust moved below it land masses arose and continue to rise. It continues to rise until today. The country lies along great Earth faults that extend to deep submarine trenches. All of the Philippine islands are prone to earthquakes. The resulting violent earthquakes caused what is now the land masses forming the Philippines to rise to the surface of the sea.

For me, the fossilized shell indicates an evidence of marine life on the place where the place was once submerged under the water. And since San Fernando is known to have large deposits of Limestone which is a type of Sedimentary Rock that is formed by accumulation of shells, corals, algal and fecal debris over period of time, then we can only imagine that San Fernando was once submerged in water sometime thousands of years ago. So in my opinion, that could explains why Giant Shell got there!

Unfortunately the Fossil has not yet examined, so we can only express our thoughts to what we think our opinions are. We only have some evidence of a fossilized shell but we are not a geologist or an expert paleontologist that can examine the fossil. We need someone to check on this fossil. This could be the oldest fossilized Giant Clam Shells recorded in history of Cebu but we don't know yet until the fossil is examined. We appreciate if you could share this article to everyone so that there can be a chance a geologist or palaeontologist can read this article and might go and check the fossil. You can always send us an email at or contact us in our Contact page. We really appreciate and would like to hear any of your thoughts on this.

Have a good day!



Clam Definition
Giant Clam Definition

History of the Philippines

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