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