November 3, 2013: We were looking for a day trip idea. With Chris’ parents visiting us for a couple of weeks, we’d exhausted our list of interesting things to see and do in and around Subic Bay (more on that in future posts).

While poking around Google Maps in satellite view, we noticed a massive white patch along a riverbed about an hour’s drive from town. Knowing it was a result of the eruption of Mt. Pinatubo, but having no idea what to expect, we decided to go and see for ourselves. Sometimes these explorations take us to surprising destinations, sometimes not.

This time, we were not disappointed. First, we drove to the town of San Marcellino and turned right at the big blue-roofed public market. Then out of town to the end of the road. At first we thought we’d arrived at an enormous garbage dump or a refugee camp. There were big piles of sand and rows of tents made of tattered blue tarps set up on a rise. We followed a dirt track up the rise and suddenly found ourselves atop an enormous megadyke built along the edge of the Sto. Tomas River. It stretched for miles in both directions.

On one side far below the dyke was a picturesque Filipino farmland scene. Rice paddies, small huts and palm trees with lush jungle-covered hills off in the distance. But the other side was something else altogether. It looked like a moonscape. Whitish-grey sand flats now filled what was once fertile farmland.

We were looking at one of several lahar sandflows caused by the 1991 eruption of Mt. Pinatubo. Up to 20 feet deep in places, it clogged the river and destroyed much of the town of San Marcellino.

A lahar is a debris flow, in this case a mix of water, ash, sand and whatever else it picks up as it moves downstream. The lahars were what caused most of the deaths associated with the eruption of Mt. Pinatubo.

It’s been estimated that more than 6.5 billion cubic metres of the stuff settled in the Sto. Tomas River and the nearby Maloma and Bucao rivers in Zambales province. And that doesn’t even count the myriad other rivers in Pampanga and Tarlac provinces. In the years since, the siltation often caused severe flooding during rainy season and typhoons forcing local governments to mount expensive projects to dredge the sand from the rivers.

It may have been a sand flat, but it was not entirely devoid of life. There wasn’t much in the way of vegetation, but there was a buzz of human activity. We saw a few jeepneys off in the distance, ferrying people across the sand flats to the other side of the river. From a distance it looked like the people got off a jeepney on one shore, waded knee deep across the river and hopped on another one waiting on the other side to continue their journey. When the jeepney came closer, we discovered it wasn’t a run of the mill machine. This one had a big, fat, single tire in front, for traction. The driver suggested we not try driving on the sand ourselves since we didn’t have a four-wheel drive.

Content to travel along the road atop the dyke, we drove toward a hive of activity upstream. Here we discovered mining operations, both large and small.

At the larger end of the spectrum, front end loaders deposited scoops of dredged sand onto trucks which then travelled to separating machines. We later learned that they were separating out black sand (aka iron sand or magnetite sand) from the white, construction-grade sand. Small amounts of titanium are also present.

At the other end, labourers manually separated the black sand out using a small rectangular box. One lady told us the miners make 45 centavos per kilo for the black sand. That’s just a little over one cent per kilo, people. She said it was good money and asked if we wanted a job!

These days the lahar sand is exported to Singapore for reclamation and expansion projects, while the black sand is used for making iron. And the local governments receive extraction fees to have the rivers dredged.

It should provide jobs and revenue for years to come. They haven’t made much of a dent in dredging the Sto. Tomas River. And apparently the sand is still flowing down the mountains more than 20 years after Mt. Pinatubo erupted.

To top off the day, on the way back to town we came across a rice farmer and his 18-year-old carabao (water buffalo) with horns that spanned more than six and a half feet across. Not quite a record, but certainly impressive.