Thursday, February 7, 2008

Strange Ring Structure in the Philippines Visible from Space

If you look at the Moon, you will see how much it's surface is cratered. Some of these craters are caused by meteoroids and small asteroids that have impacted the surface. But the picture above is not of the Moon. It's somewhere closer to home. In fact, it is home.

Unknown to many people, the Earth has also been subject to the bombardment of space rocks in the past and most recently in Peru (more links at the end of this post) such that it also has many craters. But unlike on the Moon, which has no atmosphere, less erosion, and geological changes, the craters on Earth have gone through upheavals and changes that have left them diminished, except for a few like the Wolf crater in Arizona.

This diagram of Asia (left) shows the general distribution of craters made by asteroids that have impacted in the past. It is from the Earth Impact Database, which documents impact sites all over the world. It is interesting to note that most countries in Asia, including the Philippines are not marked. Does this mean there are no impact sites in those places? Possibly. But it is also possible that they haven't been found yet.

The Philippine archipelago does get it's share of meteorites, the most recent that's been authenticated is the one that went down in the Mountain Provice of Bontoc. This rare rock from space is now in the possession of amateur astronomer Allen Yu of the Astronomical League of the Philippines (ALP) and consultant to Pyxis Astronomy Education Services.

The Philippines also has numerous tektites scattered in what is called strewn fields. There is a number of ideas about the origin of tektites, and one of them is the asteroid-impact theory.

Philippine tektites have been associated to geological events as far away as the Zhamanshin crater in Kazakhstan (left). But this is only a theory. The source of the Philippine tektites, the dark, glassy rocks used as amulets by locals, is still pretty much a matter of debate. It is possible that they came from a much closer, even local, source. The latest studies point to an Indochina crater.

I tried using Google Earth to look for impact sites in the Philippines. I managed to find circular structures, but most of these have definite volcanic origins, like the perfectly round lakes in San Pablo, Laguna and Quezon province (below). However, there is one structure in the big island of Luzon that is sizable enough to be noticed and it looks like a crater (top).

This landscape ring structure is in the province of Pangasinan and while it appears to be relatively flat, it is nevertheless outlined by a river system much like the Manicouagan crater in Canada, shown here from a space shuttle photograph (left). However, this crater is much larger and has a broader waterway.

The Pangasinan Ring, though small, has tree-lined river banks and rice fields that define a circular structure, making it more distinct from above with a whitish outline. A smaller ring is at the upper left corner. If you look closely, you will also see a road that bisects the "parent" ring. In the middle is a town where a grove of trees south of the long building with the blue roof, mark the very center (below).

The strange landscape feature is very easy to miss at ground level, and may not even be apparent from an aircraft flying at 30,000 feet. But it is very visible from outer space and an astronaut in orbit would readily see it.

Is it an ancient dried up lake? Is it an extinct volcanic basin? Is it an impact site that's been missed all these years? Is it the source of the tektites (left, from the alvinwriter collection) that are plentiful in Bicol region, further south? Perhaps it's just an odd landscape formation with nothing to it but the quirky path of the rivers?

Rocel Pereira, a remote sensing specialist, says its possible that the area inside the ring is of a higher elevation than the land outside. "Notice, that the area inside the ring is well vegetated," she says. "But my inference is only based on Google Earth. My suggestion is to check out the elevation and contours in the area using topographic maps, which can be purchased from the National Mapping and Resource Information Agency (NAMRIA)."

The Earth Impact Database has set criteria for determining if a structure that resembles a crater is an asteroid impact site or not. Included here are shatter cones, multiple planar deformation features in minerals, the presence of high pressure mineral polymorphs, the existence of an impact melt sheet or dikes, and the presence of pseudotachylyte and breccias.

The Pangasinan Ring can only be classified as an impact site if many of the criteria for authenticating a crater-like geological structure are found there. The findings will also need to be verified by experts. While intriguing to think and speculate about, it is likely that this landscape feature is not an impact site, as suggested by Pereira's initial impressions. But if you have a personal opinion or a clue as to what this strange structure is, feel free to comment. It would be interesting to know what people think. If you like, you can even view and study the Pangasinan Ring yourself using Google Earth. You can download the program here.

Satellite views of the Philippines are from Google Earth.
Asteroid impact site pictures and Asia diagram are from Earth Impact Database.
Picture of Moon and Earth together is from TwilightEffect.

Search for source of Australasian tektites crater source move to Indochina.

Physical evidence of prehistoric tigers in the Philippines unearthed in Palawan.

Click here for news and a video about the meteorite crash that sickened people in a Peruvian village.

More videos about research done on the sickening qualities of the Peruvian crater here.


Jeff - Melbourne said...

I was using Google Maps just before and stumbled across the very same ring structure and it was so similar to impact craters I'd seen that it got me looking for more information... and 2 minutes later I found your blog discussing it. It does look like an impact crater but the open side makes me wonder if it is in fact a collapsed volcano. It's possible the basin was filled with water at one stage and broke apart, washing away the sediment to the nearby bay. Not sure. It is a well defined circle though.

alvinwriter said...

Hello Jeff. Thanks for your comment. I'm impressed by your patience in looking for impact sites using Google Earth. That would be quite a chore. I tried looking for Ayers Rock and even with the coordinates, it was really difficult because one would tend to assume it would be bigger, when in fact you have to zoom in a lot closer to see it clearly. Anyway, I hope geologists can get to study the Pangasinan ring and shed some light on its origins.

Anonymous said...

You could always try the local water utilities. Villasis have one. The feasibility study normally include a geological survey of the area ranging from electro resistivity to analysis of the geologic layers from ground drilling or exploration. If it is pyroclastic materials then it is volcanic. The area seems to be an alluvial plain of very recent origin. Considering the tropical conditions of the area and high erosion rates, it is difficult to determine the original conditions unlike those in the desert areas of Australia and US or the frigid conditions in Russia.

Anonymous said...

Yes, I have been to Sampaloc Lake in San Pablo and look around for evidence but they cemented the rims of the lake. I will try to look for the other evidences on the adjacent lakes next time. Although the geological explantion is of volcanic origin.

I will also try to look for field evidence if I happen to pass by Pangasinan.I might collect some rocks "shock metamorphosed rocks"? and send to laboratory for petrographic analysis.

alvinwriter said...

It's good to know somebody's trying to determine if there really are impact sites in the Philippines. Perhaps you can reveal your identity next time. Do keep us updated. Thank you for your comment.

Antonio Jose said...

I used to look for this structure whenever I used to take the Baguio-Manila-Baguio PAL flights in the 1970s. The center of the "crater" is definitely of a lower elevation. There are concentric circles of rice paddies inside the depression and, in fact, water gathers in a large pond at the center during the rainy season.

Anonymous said...

Sorry to disappoint you guy, am no professional but i think its a dried up basin. The evidences are all over it. Smaller dried lake on its westside, circular patterns all over the place. The river and trees making it more prominent. Plus lakebeds are rich in minerals making it more ideal for vegetations making it even more noticeable. Also the irregular pattern making it look like number six gave it self away. Its definitely concave because of the erosion patterns on its rim.The possibility of it being volcanic? I'll give it a 5% for some smaller criteria. A volcano bigger than mt. arayat in that place is very unlikely with regards to its position and geologic history of this part of Pangasinan.

Anonymous said...

Hi I was looking for a reference for any meteor impact sites in the Philippines when I stumbled on your blog, the reason for it was that I found an interesting site in google map using the terrain map, it was Mt Amorong, what is interesting about this particular site was its structure ... looking down from a satellite image doesn't really give an image of a crater as the vegetation completely hides it, but using a terrain map you can clearly sea the entire crater, it is rougly 500 meter across and 100 meter or so deep, the crater wall is around 300 meters high, I really don't know if this is an extinct volcano or meteor impact but it sure does warrant a study

alvinwriter said...

Thank you for taking the time to scrutinize the Pangasinan Ring Structure. The suggestion that Mt. Amorong in Ilocos may be an impact crater is interesting, but there are many volcanic craters in the archipelago. Who knows? Maybe the lost crater that caused the Australasian tektite strewn field is in this country? The one who finds it will indeed be lucky and famous, too.

Anonymous said...

Greetings. My findings in 2006 (using Google Earth) and a report to PAGASA last 2007 is now in discussion. The Pangasinan Eye is arguably similar to Manicouagan Impact Crater. My message to PAGASA has no reply upon their investigation. If proven as a astrobleme, it would be an attraction and a new topic in science books.

Anonymous said...

Another great topic noticeable because of 100% unproven accuracy as a impact crater is the Nastapoka Arc in Hudbon Bay of Canada, just located west of Manicouagan astrobleme. It is near-perfect circular arc with an stunning diameter of 279.67 miles. Findings revealed that its a landform but its perfect shape (see Google Earth) and Hudson Bay's low magnetic field suggest that it is something else.

Anonymous said...

if there's tektite you will find meteorites! kyler

Buzz Lightyear said...

Wow, that is amazing, just like Jeff from Melbourne (top of the list of comments), I happened to look up Dagupan City in Pangasinan on Google Maps (just because someone from there visited my blog). As soon as I saw that nearby ring structure just to the southeast, it immediately made me think that this is some kind of an impact crater. So, like Jeff, I googled "meteor impact craters in Philippines" and I came across your blog. Glad I did.

I'm really curious about this also. Have you had any updates? I just returned home to the U.S. from the Philippines a few weeks ago (my wife is from the Philippines), but Pangasinan is farther north than the region where we usually travel. I will try to see if any of my friends in or from the Philippines might know anything further about it -- I am sure some Filipino geologists have checked it out at some point in time.

alvinwriter said...

Hi Buzz Lightyear. Curiosity is always good and our imagination can be helpful in determining the truth behind a mystery. From overhead photos, the Pangasinan Ring appears to be a depression or basin, but if you look at it at ground level using the 3D features of Google Earth, you can see that it's really a vast mound with undulating hills. Its extremities form the ring shape. But who knows, there may actually be an undiscovered asteroid crater out there.

Anonymous said...

Where exactly in pangasinan is this located when you're on the ground?!