Ethiopian Rift Valley
The great Rift Valley of Ethiopia is not only the cradle of humankind, but also the place on Earth where humans have lived with volcanoes, and exploited their resources, for the longest period of time. Perhaps as long ago as 3 Million years, early hominids began to fashion tools from the volcanic rocks from which the Rift Valley was floored, including basalt and obsidian.
Lake Awasa (Hawassa) is located in the Main Ethiopian Rift south of Addis Ababa. The lake is 16 km long and 9 km wide, with a surface area of 129 square kilometers. It has a maximum depth of 10 meters and is located at an elevation of 1,708 meters.
- Lake Shalla = 1570m a.s.l , 255m depth and 409 km2 area
- Lake Abyata = 1575m a.s.l , 14m depth and 205 Km2 area
- Lake Shalla is surrounded mainly by Pleistocene volcanic rocks which consists of Basalt , Rhyolith , pumice pyroclastic and Ignimbrites with some Obsidians flows .
- Lake Shalla is the deepest of the Ethiopian Rift Valley Lakes.
- GROVE AND GONDIE ( 1971) assumed that about 9,270 +(-) 190 years before present ( B.P) , ABYATA , LANGANO AND SHALLA were united and linked to ZIWAY according to radiocarbon dating of Melanoides tuberculate from the strand line deposits 84 m above Shalla.
- The present level of Shalla ( 1570m a.s.l ) is the lowest one of the Ziway Basin Lakes , possibly due to a gentle post pluvial tilting of the Rift floor down to the south.
- Two permanent creeks and several seasonal streams flow into the closed basin of Lake Shalla.
- Lake Ziway drains into Abyata through the Bul Bul river and Langano is linked to Abyata through a seasonal creek.
- The HOT SPRINGS are directly associated with Faults striking parallel to the NE – direction of the Ethiopian Rift.
- The average discharge of the Hot spring ranges from 1 – 10 liter per Minute .The temperature from 27 – 97 degree Celsius.
- The chemical composition in the areas of Chitu , Shalla , Abyata , Langano and Creek hot springs is comprising of more than 95 % is dominantly Sodium Bicarbonate.
- The water of Lake Shalla possesses almost the same ionic composition as the hot springs in the Ziway Lakes Basin but it is more Saline.
- Na ( Sodium ), is the most abundant element in the chemical composition with the bicarbonate and other are like , K , Mg , Cl , Ca , So4 , HCO3 , CO3 , Cu , Zn and Pb.