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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 RiverWhat 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.
1.3.1 Describe the three stages in the life cycle of a river.
(P. 26)
Rivers change over time and seem to go through three stages:
1st Youthful rivers 2nd Mature rivers 3rd 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??
1.3.2 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.
Youth Stage
Mature Stage
Old Age Stage
1.3.4 Define 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
* 1.3.5 Distinguish 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 JoaquinSan 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
1.3.3 Examine evidence to determine the life cycle stage of a river. (P. 28 questions # 5 & 6)
1. Slope of the river2. Relief of the
banks3. Width of the
valley4. Meandering5. Size of flood
plain6. 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