World Geography 3200/3202October 2010

Outcomes1.3.1 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)

Important ConceptsDrainage 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

Life Cycle of a RiverRivers change over time and seems to go

through three main stages

a). Youthb). Maturityc).Old Age

We will examine these three stages in greater detail later today

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.

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)