Update 9-3-13: Better video showing close-up of vehicle after being hit by smaller debris…and suffering some major damage! (via)
Two people in Keelung City, Taiwan were extremely lucky the other day. The first, because they they were savvy enough to swerve before being pancaked by a boulder over twice the size of their little white sedan. The second person because – for some unknown reason – they were already video-taping their rainy day drive through the windshield – and caught all the action.
You typically see only the aftermath of landslides and rock falls through photos. This is because they happen so quickly and (often) without warning that rarely are they caught on film.
While the cause of the rock fall cannot be pinpointed from this video alone, the number one catalyst in slope failures is water. When water gets into the fractures, joints and pore spaces in a slope, it exerts an outward pressure on the surrounding rock (or soil, if such is the case). If this pore pressure is enough to overcome the forces resisting movement, such as friction and loading, the block of rock will break free and fall.
Reports show that Keelung and the surrounding region were experiencing a significant amount of rain. Flood warnings were in effect across the city, some major roadways were submerged in as much as 20 cm of water, and even their railway station had been flooded. In another part of the city, a house was caught up in a mudslide. Based on this video, it’s obvious this boulder broke loose during a period of significant rain, as the pooled water right at the base of the slope would suggest. This demonstrates that it had been raining substantially for some time, and the influx in rain water is most likely the straw that broke the camels back.