2. World Geography 3200/3202 October 2010

3. Outcomes 1.3.1 Describe the three stages in the life cycle of a river. (k) 1.3.2 State two ways in which water erosion occurs. (k) 1.3.3 Examine evidence to determine the life cycle stage of a river. (a)

4. Important Concepts Drainage Basin: an area of land drained by its rivers and tributaries Tributary: a river which usually flows into another, usually a larger one The Amazon Basin, is the planet's largest body of fresh water with 1100 tributaries 17 of which are more than 1000 miles long. Many of the tributaries begin in Colombia and Peru. The Nile river, in Africa is the longest river in the world

6. Life Cycle of a River Rivers change over time and seems to go through three main stages a). Youth b). Maturity c).Old Age We will examine these three stages in greater detail later today

7. Describe two ways in which water erosion occurs. (P. 31) Vertical erosion makes rivers deeper as is the case in young rivers Lateral erosion makes rivers wider leading to the meandering of mature rivers.

8. Evaluating Evidence to Determine the Age of Rivers There are six common pieces of evidence you can look for to determine the stage of a river. a). Slope of the river (steeper = younger) b). Relief of the banks (steeper = younger) c). Width of the valley (wider = older) d). Meandering (more = older) e). Size of flood plain (wider = older) f). Rapids or water falls (more = younger)