Fifty percent of the total mass of the atmosphere is located in the lower 5.6 km (18,000 ft) of the troposphere. It is primarily composed of nitrogen (78%) and oxygen (21%) with only small concentrations of other trace gases.
Having irregular periods is very common. I see them in my practice all the time. The causes can range from something insignificant to something that requires treatment. For example, if you're a teen, your body's hormones can fluctuate and take some time until they find a balance.
Many women will experience irregular periods at some point in their lives. Itâs particularly common for young women to experience highly irregular periods â including very long periods â during their first few years of menstruation. Their periods will often shorten and stabilize between one and three years after menstruation begins.