3. Shearing leads to breakdown of grain-to-grain contacts; upon liquefaction, the pore-water pressure increases severalfold within seconds in many field situations. The pore-water pressure now carries the full weight of overlying soil and water. This pressure can do things such as hydraulically fracture an overlying fine-grained cap and lead to the venting of large quantities of sediment and water to the ground surface, subsequently forming sand volcanoes. The pressure is adequate to permit the cap to shift about easily, more or less like ice cubes floating on water, as strong shaking continues.