Solid waste landfills can be affected by seismic activity. The tension in a landfill liner rises significantly during an earthquake, and can lead to stretching or tearing of the material. The top of the landfill may crack, and methane collection systems can be moved relative to the cover. Increasing the depth of a waste column typically leads to a decrease in the ground acceleration felt at the surface of that landfill during an earthquake. The weight of waste is important in the analysis of landfill liner puncture and pipe crushing during an earthquake.. Unstable rock under landfills such as limestone may yield during an earthquake, leading to a partial collapse of the fill. A major concern in this case would be the potential contamination of water sources that may be located below the landfill.