Changes

Areas where subsurface hydrocarbons are not actively seeping are referred to as characterized by '''passive seepage'''. Such seeps usually contain low-molecular-weight hydrocarbons and volatile high-molecular-weight hydrocarbons above background levels. Acoustic anomalies may be present, but water column anomalies are rare. Anomalous levels of hydrocarbon seepage may only be detectable near major leak points or below the zone of maximum disturbance.

Areas where subsurface hydrocarbons are not actively seeping are referred to as characterized by '''passive seepage'''. Such seeps usually contain low-molecular-weight hydrocarbons and volatile high-molecular-weight hydrocarbons above background levels. Acoustic anomalies may be present, but water column anomalies are rare. Anomalous levels of hydrocarbon seepage may only be detectable near major leak points or below the zone of maximum disturbance.

[[file:surface-geochemical-exploration-for-petroleum_fig18-2.png|300px|thumb|{{figure number|1}}Zone of maximum disturbance in shallow marine sediments. From Abrams, 1996a; courtesy AAPG.]]

[[file:surface-geochemical-exploration-for-petroleum_fig18-2.png|300px|thumb|{{figure number|1}}Zone of maximum disturbance in shallow marine sediments. From Abrams;<ref name=ch18r2 /> courtesy AAPG.]]

==Zone of maximum disturbance==

==Zone of maximum disturbance==