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.
1 Your periods become very irregular after having had regular, monthly cycles. 2  Your period occurs more often than every 21 days or less often than every 35 days. 3  You are bleeding for more than 7 days. 4  You are bleeding more heavily than usual or using more than 1 pad or tampon every 1 to 2 hours. Your periods become very irregular after having had regular, monthly cycles. 2  Your period occurs more often than every 21 days or less often than every 35 days. 3  You are bleeding for more than 7 days. 4  You are bleeding more heavily than usual or using more than 1 pad or tampon every 1 to 2 hours.