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Is This Philippine Town Sitting on Top of an Impact Crater?

Or it could be on the remnants of a collapsed caldera.
IMAGE Google Earth
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There is no official meteorite impact crater in the Philippines, but one could be hiding in plain sight. In fact, it could be under a town in Pangasinan, seen only from above.

While leisurely browsing Google Earth in search of long lost crash sites, hidden tribes, and interesting land features in the Philippines, we spotted a strange topographic anomaly in the plains of Pangasinan: a circular land feature almost like a caldera, but not quite as pronounced.

Switching to the topographic map, we see that the core is composed of hills that curiously form a circle. The circular hills are called Cabarungan Hills. In this circle lies the quiet town of Malasiqui, whose primary source of livelihood is cultivating and harvesting mangoes.

Topographic Map of Cabarungan Hills in Malasiqui, Pangasinan

Photo by Google Maps.

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The circular feature could mean one thing—a crater. It could have been created by one of two forces: a volcanic eruption or a meteorite impact. The presumed crater is 12 kilometers across.

It could be an ancient eroded caldera.

There are various explanations on why such a geological formation exists in Malasiqui. The natural assumption is that it could be a remnant of an ancient volcanic caldera that has eroded or collapsed over millions of years. The term for such collapsed calderas is a ring dike. This is likely, considering the Philippines has 23 active volcanoes, and even more inactive or extinct volcanoes.  

A Ring Dike

Photo by NASA.
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According to Twitter user @RosasXOso, it is an anticline, which is simply a type of fold produced during crustal deformations. 

One way to find if the site is the remnant of a prehistoric volcano is to see whether the rocks in the surrounding area are of volcanic origin. Radiometric dating can be used to determine the age of the rocks and whether these match the age of the soil within the crater.

Or it could be an ancient meteorite impact crater.

Another explanation is that the topographic feature is an ancient meteorite impact crater or an astrobleme. The hills on Malasiqui could be the peaks of the rebound structure produced by a meteor’s impact.

Possible Astrobleme at the Town of Malasiqui

Photo by Google Earth.
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An astrobleme is the remains of an ancient meteorite impact that generally forms a circular scar on the surface of the Earth. Unlike other meteorite impact craters that are well preserved and very well defined, astroblemes lack features such as crater walls because of erosion and weathering.

One famous astrobleme is the Sierra Madera astrobleme in Texas, U.S., which looks similar to the circular hills found in Malasiqui.

The Sierra Madera Astrobleme in Texas, U.S

Photo by Google Earth.
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The Sierra Madera Astrobleme is 13 kilometers in diameter, while the presumed crater in Malasiqui is 12 kilometers in diameter. Sierra Madera is also composed of hills concentrated in a circular formation in the middle of a vast plain, just like in Malasiqui. The hills in Sierra Madera are the rebound structures that were formed during the impact.

Unfortunately, it is very difficult to identify astroblemes because of their eroded features, being millions or billions of years older than impact craters that are more obvious and visible.

Town of Malasiqui

Photo by Ramon FVelasquez .
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One way to determine whether the circular topographic feature in Malasiqui is actually an ancient meteorite impact crater is by drilling core samples from the site, which will tell whether there are shatter cones underneath the bedrock. Shatter cones are subsurface shock structures produced by powerful and sudden impacts caused by meteorites.

 

Earth Impact Database

The possible crater in Malasiqui is a good candidate for study and submission to the Earth Impact Database, which is the world’s database for confirmed meteorite impact structures or craters on Earth. There are currently 190 confirmed impact sites around the world.

Regardless of whether the town is sitting on top of an ancient meteorite impact or a collapsed caldera of a dead volcano, it would be pretty cool to have a town situated in either of the two.

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About The Author
Mario Alvaro Limos
Features Editor, Esquire Philippines
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