Lake Narracan is an artificial lake on the Latrobe River built to supply cooling water for the nearby brown coal-fired power stations.
Lake Narracan is located on the Latrobe River in the Latrobe Valley. The dam wall is approximately 1.5 km upstream of the Yallourn Power Station. The reservoir was first constructed by the State Electricity Commission of Victoria between 1959 and 1961 and has the capacity of 8,600 megalitres (ML). In 2002 major works were undertaken to bring the reservoir up to modern day standards, including anchoring the dam wall to the foundation bedrock and strengthening the four gates.
In geology, bedrock is the lithified rock that lies under a loose softer material called regolith at the surface of the Earth or other terrestrial planets. The broken and weathered regolith includes soil and subsoil. The surface of the bedrock beneath the soil cover is known as rockhead in engineering geology, and its identification by digging, drilling or geophysical methods is an important task in most civil engineering projects.
Superficial deposits (also known as drift) can be extremely thick, such that the bedrock lies hundreds of meters below the surface. Bedrock may also experience subsurface weathering at its upper boundary, forming saprolite.
A solid geologic map of an area will usually show the distribution of differing bedrock types, rock that would be exposed at the surface if all soil or other superficial deposits were removed. Saprolite is a chemically weathered rock. Saprolites form in the lower zones of soil profiles and represent deep weathering of the bedrock surface.
In most outcrops its colour comes from ferric compounds. Deeply weathered profiles are widespread on the continental landmasses between latitudes 35°N and 35°S. Conditions for the formation of deeply weathered regolith include a topographically moderate relief flat enough to prevent erosion and to allow leaching of the products of chemical weathering.
A second condition is long periods of tectonic stability; tectonic activity and climate change can cause erosion.
The third condition is humid tropical to temperate climate. Poorly weathered saprolite grit aquifers are capable of producing groundwater, often suitable for livestock. Deep weathering causes the formation of many secondary and supergene ores – bauxite, iron ores, saprolitic gold, supergene copper, uranium and heavy minerals in residual accumulations.
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1. what is bedrock?
2. how many metres below the surface is the bedrock found?
3. what is rockhead?
4. how is saprolite formed?
5. when you arrive at the co ords and look to the left what do you see?