The earthquake and tsunami in Indonesia late last month triggered an unusual phenomenon called liquefaction, when the soil is turned to mud. From a bird's eye view, the aftermath of the liquefaction process at Petobo, a neighborhood in Palu city that has been effectively buried in a deep mud sludge, is jaw-dropping. Closer up, houses appear to have sunk into the mud up to their roofs. Cars and motorbikes stick out at odd angles.