World Geography 3202 Understand how running water acts as an agent of erosion and deposition. (Chapter 2)

Introductory Terms / Information Tributaries are branches of a river that feed water into the larger river Rivers flow from high elevation to low elevation Rivers empty into the sea at sea level = 0 ft Look for elevation legend, often color coded, symbols or contour lines.

Amazon River What direction does the river flow?Where is the high elevation? Where are the tributaries? Where does the river begin?

Define the term drainage basin. (p. 26) Drainage Basin = the area of land drained by a river and its tributaries. Try question #4 p. 26

Drainage Basin-Circled in red

Drainage Basin. (p. 26) 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. WHY????

Nile River Basin The Nile river in Africa is the longest river in the world. The green area on the map marks the Nile River basin.

1.3.1Describe the three stages in the life cycle of a river. (P. 26) Rivers change over time and seem to go through three stages: 1 st Youthful rivers 2 nd Mature rivers 3 rd Old rivers

Young Rivers Usually found in highland or mountain regions Steep slope (high gradient) Small volume of water Rapid flow of water Rapid erosion More vertical erosion than lateral Narrow “V” shaped valley Water falls & rapids common

Mature Rivers Most high relief is eroded Gentler slope Many well developed tributaries Broad flat river valley Well developed flood plain More lateral (↔) erosion than vertical Meandering results

Late River Maturity Remember the stages are not distinct. These changes occur over long periods of time.

Old River Almost no slope Very little relief Elaborate meandering Often swampy areas around river Very muddy due to slow speed and deposition Most susceptible to flooding because of large flood plain.

The Amazon- What stage??

1.3.2Describe 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.

Youth Stage Mature Stage Old Age Stage

1.3.4Define the term Delta. (P.32) Delta = low lying area at mouth of river formed by deposition of silt deposition occurs because river slows as it enters ocean or lake

* 1.3.5Distinguish among the terms arcuate delta, digitate delta and estuarine delta. (P. 32) Arcuate Delta= Named from Latin word for curved in the shape of a bow. Fan shaped Example Nile Delta p. 32

Nile Delta

Digitate Delta Digitate Delta = From Latin for finger Delta with long fingers of sediment reaching into the sea Example Mississippi

Mississippi Delta

Estuarine Delta p. 32 Estuarine Delta = Formed when river runs into bay or estuary Tidal mud flats form which can be seen at low tide Sediment deposited from river outflow and from Tidal inflow

Sacramento River – San Joaquin San Francisco Bay Delta

Delta Similarities & Differences Similarities Arcuate & digitate both flow into open ocean All three allow river water to flow out All have channels or distributaries cut into them by the river Differences Estuarine empties into a bay whereas other 2 empty into open water Three different shapes

1.3.3Examine evidence to determine the life cycle stage of a river. (P. 28 questions # 5 & 6) 1. Slope of the river 2. Relief of the banks 3. Width of the valley 4. Meandering 5. Size of flood plain 6. Rapids or water falls Evidence to look for!!

What stage is this river in? Young Water falls & rapids Steep slope

What stage is this river? Early maturity Some meandering However still some relief Associated with mountain

What river Stage? Youth Rapid water movement Rapids & water falls High relief on banks