5.2A CS - The Amazon rainforest Flashcards
What is the importance of the amazon
- Now the largest river by discharge volume of water in the world (209,000 cumecs) and largest drainage basin.
- Represents 20% of global riverine (freshwater) discharge to the ocean
What was amazon originally like
Originally flowed westwards from central shield mountains into Pacific (when continents were joined).
What changes happened to the amazon
- Subsequent tectonic activity separated continents and created Andean mountain range to block westward flow.
- Enormous lakes formed between mountains until point when Andean uplift reversed land dip and direction of flow.
What type of system is the amazon
In this way, the Amazon rainforest can be thought of as a self-perpetuating ‘semi-closed’ system.
Why is the amazon a semi closed system
Interception of rainfall and subsequent Evapo-transpiration levels in the Amazon are extremely high owing to dense canopy cover.
Why does so much water reach the ground still?
As the precipitation levels are so high, there is still a large quantity that reaches the ground – either directly or via Stemflow (water runs down outside of stem).
How has bedrock changes in the amazon basin due to climate
High temperatures and moisture content have meant the shield bedrock has been subject to significant chemical weathering
Describe soil in amazon basin
Soil is extremely thin (nutrients only contained in decomposing plant matter), and overlies thick layers of Kaolinite clay (low permeability)
Describe levels of surface run off in the amazon basin
High levels of surface run-off / overland flow and nutrient depletion into ‘Whitewater’ Amazon River (limited infiltration)
Describe how percolation occurs in the amazon rainforest
Some carbonate rocks near Amazon source have allowed percolation into deep groundwater storage – flows very slowly as Rio Hamza (4km deep).
