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Just curious: Tsunami possible within the Visayas?


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RogerDat

I agree they have not updated that since 4 or 5 years ago when I showed them the "bomb" we found in the limestone. I started searching for where that could have come from, cannot remember where I found the info, but it obviously has not been active since before man got here.

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I'm moving next door to San Miguel factory! That way if the wave hits them first...I'll drown in a tsunami of beer !!!

Phivolcs has a good map called "Tsunami Prone Areas in the Philippines". (I'd upload it but the PDF is 35 MB).  But you can find it with Google. Heck, you can find anything with Google!        

The tsunami problem in the Tanon straight is because of the danger of underwater rockslide. There are large drop-offs like cliffs that could fall and produce tsunami like waves. I was in Tuble when th

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richard_ost

 

As a layman I don't get it when they classify Negros, Bogol and Leyte tsunami prone but not Cebu. Negros has quite a few possibly active bombs (volcanoes) and all the islands have faults.

 

http://newsinfo.inquirer.net/141731/tsunami-rumor-sparks-panic-in-cebu-city-streets

Philvocs even gave warning 2012

 

http://www.phivolcs.dost.gov.ph/html/update_SOEPD/hazard_maps/Tsunami_Prone_Map_Mar2013.pdf

that's the same map Bosshog posted earlier which shows that basically all of the shores in the PI are prone to (at least local) tsunamis.But they have a note there that states that "life-threatening tsunami waves are usually expected from trench related tsunami and commonly occur compared to those related to offshore faults and submarine landslides" which might explain the logic that Cebu isn't classified as "tsunami prone area" on that specific site, or it's because that classification is almost 10 years old?

 

 

I agree they have not updated that since 4 or 5 years ago when I showed them the "bomb" we found in the limestone. I started searching for where that could have come from, cannot remember where I found the info, but it obviously has not been active since before man got here.

 

What was this bomb?

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Volcanic "bombs" can travel many kilometers through the air. It is likely that any volcanic bombs found on Cebu originated on Negros. Negros has volcanoes, but as far as I can tell, Cebu has no volcanoes. Mount Manunggal is composed of block-faulted limestone. There is no volcano there. Almost every island in the Philippines is at least partially volcanic in origin, but Cebu and Bohol are exceptions. Both islands were created through block faulting (sediment being turned on its edge). According to the Geologic Map of the Philippines, there is volcanic sedimentary (fallout) on Cebu, but no actual volcanic activity.

 

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Kabisay-an gid

PHIVOLCS allays fear of volcanoes in Cebu

 

by bayanihan on March 3, 2012

 

DUMAGUETE CITY, Mar. 2 – The Philippine Institute of Volcanology and Seismology (PHIVOLCS) allayed fears of the existence of volcanoes in Cebu province following reports of discovery of boiling water along the shorelines of Dumanhug, in Cebu .

 

Phivolcs director Dr Renato U. Solidum Jr., clarified that there were no volcanoes in Cebu, in response to inquiry Rep. Luigi Quisumbing, through Rep. Rodolfo Biazon, during Friday's congressional hearing of the oversight committee on disaster risk reduction and management in Dumaguete City, Negros Oriental.

 

Solidum said the term used was wrong when the report stated a boiling water was discovered along the beach as a result of the recent earthquake.

 

He said the line of volcanoes could be found only in Negros Island to Zamboanga del Norte, down to the Zamboanga peninsula and Sulu.

 

Due to the shaking of the plates, water in between the sand was pressurized prompting it to come out like a sandboil, Solidum said in stressing that there was nothing to worry about the so-called boiling water found in Dumanhug after the recent earthquake.

 

http://bayanihan.org/2012/03/03/philvocs-allays-fear-of-volcanoes-in-cebu/

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What was this bomb?

 

Volcanic bombs are chunks of lava that are thrown out during a volcanic explosion. They can be thrown great distances, even up to hundreds of kilometers, depending on the magnitude of the explosion. The bombs are usually ejected in a semi-liquid form, but the solidify while going through the air, and are found as rounded basalt rocks or boulders on top of geologic materials that have nothing to do with volcanism. This geologic feature is common throughout the Rocky Mountains and Great Basin in the US. There were volcanoes in the region, lots of them, but the volcanic bombs are scattered over vast areas that had no volcanoes.

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RogerDat

The one we found was over 12 inches wide, surrounded by smaller bits in limestone. I thought Cebu Island had thermal lakes or such somewhere as they were trying to get a thermal electric plant.

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The one we found was over 12 inches wide, surrounded by smaller bits in limestone. I thought Cebu Island had thermal lakes or such somewhere as they were trying to get a thermal electric plant.

 

There are a few hot springs in Cebu. So volcanic/seismic activity exists. Somebody sure can explain their source.

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This rock is pretty typical of a volcanic bomb. the shape is somewhat rounded on the edges (although NOT round), The surface is somewhat smooth, but has numerous pockets that were originally gas bubbles in the lava. The bubbles are something that is common in most volcanic bombs, since the lava is ejected under great pressure due to a lot of gas being present in the lava during the eruption (causing it to explode rather than just flow smoothly. Volcanoes around the "ring of fire" (including those in the Philippines) typically have explosive eruptions at some point during their existence.

 

post-6379-0-26969400-1481611384_thumb.jpg

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RogerDat

The one we found was inside the limestone, and was exposed while leveling the ground, so it was flat (chiseling surface to make smooth)

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I would have thought Samar would be higher on the map....its closest to the trench..

I would have thought the East coast to be prone. Tsunami is usually caused by the movement of two plates under the sea affecting open coastal areas. Living anywhere else on the inward side of islands there would be no tsunami (Port wave) but the sea could rise to dangerous levels. We had one evacuation here some time back down by the water. We live 600 meters up here but we get a lot of tremors. There is a volcanic spring on my land. We go geothermal next year. I hope that is just the full extent of activity. The volcano we live on has a record of erupting every 160 years.

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