Waterfalls

Objectives

To be able to:Define waterfallExplain, using specific terms,

how they are formedExplain, using specific terms,

how they are worn awayMake clear links to your

previous work on rivers

What is a waterfall?

• Definition?

What is a waterfall?

• DefinitionA waterfall is a geological formation where flowing water rapidly drops in elevation as it flows over a steep region or a cliff.

How are waterfalls formed?

Waterfalls occur when ______ flow over different types of ____. The ____ rock wears away faster than the ____ rock. In time a step develops over which the river _______ as a waterfall. _____also cuts away rock behind the _________. This causes the falls to move back and leave a _____ as it goes.

HARD RIVERS WATERFALL ROCK SOFTWATER PLUNGES GORGE

How are waterfalls formed?

Copy out the paragraph below and insert the missing words from the word bank.

Waterfalls occur when RIVERS flow over different types of ROCK. The SOFT rock wears away faster than the HARD rock. In time a step develops over which the river PLUNGES as a waterfall. WATER also cuts away rock behind the WATERFALL. This causes the falls to move back and leave a GORGE as it goes.

How are waterfalls formed?

The hard rock collapses into the plunge pool to be broken up and washed away by the river. The position of the falls moves back.

Falling water and rock particles or boulders loosen and wear away the softer rock.

Erosion continues and the waterfall slowly eats its way upstream leaving a gorge behind.

The hard rock above is undercut as erosion of the soft rock continues.

The diagrams below have been given the wrong labels. Can you figure out which description matches each diagram?

How are waterfalls formed?

The hard rock collapses into the plunge pool to be broken up and washed away by the river. The position of the falls moves back.

Falling water and rock particles or boulders loosen and wear away the softer rock.

Erosion continues and the waterfall slowly eats its way upstream leaving a gorge behind.

The hard rock above is undercut as erosion of the soft rock continues.

How is a waterfall worn away?In your exercise books, stick in the circular flow diagram.

Put the labels below on the cycle in the right order.

• Hard rock collapses• Soft rock worn away• Waterfall moves back• Plunge pool deepens• Hard rock undercut

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How is a waterfall worn away?Soft rock is worn away

Hard rock is undercut

Plunge pool deepens

Hard rock collapses

Waterfall moves back

Waterfall labelling

Waterfall diagram

• Use the word bank to label the photograph.

A = WATERFALLB = PLUNGE POOLC = RIVERD = SOFT ROCK UNDERCUTE = HARD ROCK OVERHANGSF = GORGE

Waterfalls of the World; Fact File

• Angel Falls, Venezuela (979m high, 47 drops)• Niagara Falls, Canada & USA (52m high, 1

drop)• Iguazu Falls, Argentina (82m high, 275 drops)• Victoria Falls, Zimbabwe (108m, 1 drop)