Pralayas , as per Hindu Mythology is described as destruction of the world,which took place in the past and will take place in future. After every completion of 100 year cycle of Bramha, Pralay takes place...At the time of pralay,the energy residing in all the living beings unite at a single place. Brilliance of Sun increases by many many magnitudes and this generates extreme heat. The heat causes huge fires and it devours everything, all the living beings die. Only ashes remain in the Universe. Then the Supreme Wind (Vaayu) gathers these ashes in one place. Afterwards the Supreme Rains start and it drowns everything. To understand Paralyas one must understand the time calculations ,of Pralayas,Yugas and Bramha
*1Year=360 days(as per Hindu Calender )
*Yuga=1Lakh Years(100,000 years)1
*There are 4 Yugas: Satyayug , Treta , Dwapar and Kali (each one having 100,0001years )
*4Yugas= 1Dev Yuga(which is equivalent to 4*100,000=400,000 years)
*71Dev-Yuga=1manvantar(that is,28,400,000 years) 28Manvantar= 1 day of Bramha(which is 795,200,000 years)*100 years of Bramha= (360*100*795200000=28,627,200,000,000 years)
Pralaya, as per, Hindu cosmology is an aeonic term which specifies different periods of time during which non activity situation persists, as per different formats or contexts.In the Samkhaya philosophy, one of the six schools of classical Indian philosophy, Pralaya means "non-existence, a state of matter achieved when the three gunas (principles of matter) are in perfect balance. According to Vishnu Purana & Agni Purana there are 4 different types of pralaya :Praakritik Pralaya , Naimittik Pralaya , Aryantik Pralaya&Nitya Pralaya
Praakritik Pralya which is of 311,040,000,000,000 solar years duration, occurs after the completion of life of Brahma (i.e. 100 Brahma years = 311 trillion and 40 billion earth years = one day of Vishnu = 1 Parama). After the completion of one Brahma life cycle, the complete dissolution of all the entities (i.e. thePanch Mahhbhoot or Universe ) takes place in the eternity (God). Praakritik Pralaya is the time for which Vishnu sleeps. The next morning, he again gives birth to a new Lord Brahma and ask him to create new worldly entities. Noticeably, Praakritik Pralaya and the Life of Brahma are of equal duration.
Naimittika Pralaya which is of 4,320,000,000 earth years, occurs just after the end of a Kalpa. Also, known as the Night of Brahma, it signifies the end of living world. In Bhagvata Purana sage Shukdeva told king Parikshit that if Lord Brahma is supposed to be a child (for example), then in a similar way as a child plays with his toys i.e. making various structures from his toys during day & breaking or dismantling them before he goes to sleep at night; Brahma makes the living world during his day (i.e. Kalpa) & destroys it before going to sleep during night (i.e. Naimittika Pralaya). A new living world is created by Brahma, when he wakes up the next day & so on the cycle continues till
Praakritik Pralaya. Again, Naimittika Pralaya & Kalpa are of equal duration.
Aryantik Pralaya also termed as Moksha(Salvation), is the final deliverance or the attainment of salvation by a jivan (soul) and after that the jivan is never again in the clutches of karma; nor bounded by the tight ropes of Sansaar(universe). It is therefore a variable time span conditioned or determined by the practice of the different kind of Yogas or Prapatti. It is the final immersion of a soul (i.e. aatmaa), thereby completely eliminating its individualism into the eternal almighty (i.e. Parmaatmaa).
Nitya Pralaya is the sleep or by an extension thereof, Death