Local soil conditions also play a role, as certain soils greatly amplify the shaking in an earthquake. Seismic waves travel at different speeds in different types of rocks. Passing from rock to soil, the waves slow down but get bigger. A soft, loose soil will shake more intensely than hard rock at the same distance from the same earthquake. The looser and thicker the soil is, the greater the energy movement will be. Fires are another major risk during earthquakes as gas lines may be damaged and particularly hazardous.