Lake Chitu EarthCache
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Lake Chitu is part of the Abiyatta Shala Lakes National Park. It lies about 1.5 km south of Lake Shala. The park contains a large number of aquatic birds that live around lakes Abiyatta and Shala and the up to 10,000 flamingos that live on Lake Chitu. The flamingos tend to congregate along the windward side of the lake where the algae they eat is concentrated.
The lakes lie within the Shala basin, a caldera which probably collapsed about three to four million years ago. About 5,000 to10,000 years ago this area was covered by the large Galla Lake, which was named for the population which now inhabit the area. It is estimated that the current level of Lake Galla was 110 meters above the current level of Lake Chitu and incorporated not only Lakes Chitu, Shala and Abiyatta, but Lakes Langano and Ziway to the east and north. During this period eruptions of lava through the lake produced the tuff ring now occupied by Lake Chitu.
Chitu is a cup-like “maar” with a diameter of 1.6 x 1.2 km. A maar is a broad, low-relief, flat bottomed, volcanic crater that is caused by an explosion when groundwater comes into contact with hot lava or magma. The resulting crater is filled with water to form a relatively shallow crater lake. The lake covers approximately 800 m2, has a maximum depth of 21m and is highly saline. Evidence that the maar was formed through an eruption through a shallow lake include gray tuff (Rock made from volcanic ash) containing bomb sags (Chunks of rock that are ejected during the eruption that land in soft, wet soil and do not break upon impact and are distinctive from the surrounding sediment), cross-bedding (Near horizontal layers of sediment deposited from an outside force such as wind or water), dunes (hills of sediment formed by the movement of water or wind) and antidunes (Small ridges were sediment is eroded from the downstream side of the force and deposited on the upstream side.) Whitish colored sediment that slopes downward can be observed on the land leading up to the rim. In Gallinya, 'Chita' means 'that which is broken or separated' referring to a local tradition that Chitu was once connected with Shala.
To gain credit for this cache:
1) The surfaces of Lake Chitu and Lake Shala are approximately at the same elevation. Surveying the surrounding topography (and maybe using the elevation readings on your GPSr) estimate how much higher the two lakes would have to be for them to be joined into one lake.
2) The lowest high point (i.e. the elevation at which if the water level was high enough where all five lakes would be joined into one lake) is approximately 1660 meters. How much higher would the water level of Lake Chitu have to be for all five lakes to be joined together?
3) What physical evidence can be observed that the water level in Lake Chitu used to be higher than its current level? What is the highest level above the lake’s level is this evidence observed?
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Treasures
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