The temple of Umananda is located on a small hillock in an island of Brahmaputra at Gauhati, named Bhasmachala.It is also called as Peacock island.
According to Kalika purana Lord Shiva sprinkled ashes(Bhasma) here and imparted Knowledge to Parvathi.
Lord Shiva dipped into Yoga samadhi after Sati lightened herself in Yogagni. Sati reborn as the daughter of Himavantha, by name Parvathi, and serving Shiva to marry him. But, he didn’t came out of the Meditation. Lord Indra send Kama deva to interrupt the Meditation. But,he couldn’t dare to throw his arrows on Shiva. He went to Kama rupa, where the Yoni of Sati fell, and tried from an island there. Lord Shiva was distrubed from his Meditation by the energy given by Goddess Kamakhya to the arrows of Kama deva. Shiva became angry and saw with his third eye. Kama deva turned in to ashes.
The name Bhasmachala came remembering the ashes(Bhasma) of Kama deva. Rati, the wife of Kama deva prąyed Shiva a lot to give life to her husband. Shiva told her to build a temple for Goddess Kamakhya so that her husband can get life. All the gods built a temple to the Goddess with the help of Vishwa karma. Goddess appeared and gave life to Kama deva. The name Kamakhya(Who gave fame to Kama deva or Who sees Shiva with love) came from this story.
Chandra sekhara temple:
It is an old temple of Lord Shiva present in Bhasmachala.
Once upon a time, the Oorvasi brought Amrutha from the Heaven to worship Goddess Kamakhya. A drop of that fell near Bhasmachala which formed Oorvasi kunda.