The first lake is named Tiwu Ata Mbupu (lake of the ancestors’ souls ); the second is named Tiwu Nuwa Muri Koo Fai (lake of young people’s souls); and the third is called Tiwu Ata Polo (lake of evil spirits).
Tiwu Ata Mbupu, is the western-most lake and is structurally different from the other two in that the pit crater it is in is itself located in the center of a larger crater. Small landslides constantly add to the steep rubble slopes along the lake’s shore, and large boulders periodically drop into the lake. TAM’s shoreline is coated with a film colored in different shades of red, orange, and yellow depending on how thick it is. Gypsum crystals grow in the cracks of the crater wall in the first few meters above the prosent water surface.
Tiwu Nua Muri Koo Fai, is adjacent to Tiwu Ata Polo and is the deepest lake. A sizable tear in the western wall was the location of a pre-1929 breaching and overflow event. Subaerial fumarolic or hydrothermal activity is implied by a large thermal plume in the center of the lake which slowly convects the water. A fresh supply of yellow froth is brought up by the plume and pushed out toward the crater wall. A particularly large cover of this froth has accumulated at the base of the north wall. During rainstorms the froth is scattered by inflowing water and landslides, though some of it may be disappearing altogether.
Tiwu Ata Polo, lies on the southeastern side of the volcanic peak. A thermal plume in the northwest part of the lake indicates underlying subaerial fumarolic or hydrothermal activity. A white froth is present on the lake’s surface around the plume when the convective activity momentarily increases. Rock debris is often carried into Tiwu Ata Polo during rainstorms by water draining the volcano summit around the lake. Two peaks abutting the crater rim help stabilize the east and northeast crater wall, while further around to the southeast a dip suggests a possible one-time overflow outlet. Such an outlet would have fed the river Ria Mbuli, whose upland source is in that area.
Source : http://www.lovelynature.net