In general, irregular periods are very common during the perimenopause. The most common early menstrual irregularity noticed in the perimenopause is a shortening of cycle length.
Abiogenic petroleum origin. Abiogenic petroleum origin is a term used to describe a number of different hypotheses which propose that petroleum and natural gas are formed by inorganic means rather than by the decomposition of organisms.
Methane (CH4) is a gas formed as part of the process of coal formation. When coal is mined, methane is released from the coal seam and the surrounding disturbed rock strata. Methane can also be released as a result of natural erosion or faulting.