As per Hindu beliefs, Trimurti are the three main gods and rest are the Avatars per se. This Trimurti of Lord Brahma, Lord Vishnu and Lord Mahesh (Shiva) run and maintain the cycle of the whole universe. Brahma creates, Vishnu preserves it and Shiva destroys it. Its quite mystifying that destruction is a part of the cycle but start-over has always been considered as merit because it is believed that when the universe reaches a certain stage where it cannot be controlled, it needs to be destroyed so that it can start over again and Lord Shiva’s cosmic duty is to annihilate for the new beginning.
According to Hinduism when the pot of sins gets full and evilness rises above the world, Lord Shiva opens his third eye which signifies anger and he does the dance called Tandav. Lord Shiva is considered as the creator of dance, he does different forms of Tandav as per the circumstances and his Raudra Tandav is the embodiment of end. People believe that Lord Shiva doese the Raudra Tandav with his third eye opened, which would be the cause for Tsunami that will lead to the over all destruction.
Tandav comes from the word ‘Tandul’ which means to jump. It is to be said that his dance varies as creation, solace and liberation. So, when Lord Shiva performs Raudra Tandav, his jump generates the commotion in the whole universe and everything will be terminated.
Afterwards, all that has been destroyed will be resurrected and the same cycle will begin.