Wind, water and ice can powerful forces that erode or wear down, land forms and sometimes threaten the places where people live.
Water can slowly wear away even the hardest of rocks, sometimes leaving strange structures behind. Some rivers, such as the Colorado River in the U.S., have eroded great canyons through the rocks around them. Wind and sand can whip around land forms in deserts and create fantastic shapes, such as those in the Pinnacles Desert, Australia. Colorado River flows from the Rocky Mountains for 2,300 km the sea.
Pebbles are stones worn smooth by the action of water and sand in a sea or river.
Flowing Water
The Grant Canyon, Arizona, U.S., is 350 km long and up to 1830 m deep. It cuts through layers of rock that are 2 billion year old. The colors of the rocks add to the beauty of the canyon. The Grand Canyon cut out by the fast-flowing Colorado River,starting about 6 million years ago. Grand Canyon is between 6 and 29 km wide.
Erosion By Ice
During the past 2 million years, ice wind and rain have worn away mountains that formed in Chile over 12 million years ago. In this way, the Torres or towers, of the Torres del Paine National Park were created. These peaks are over2,600m tall.
Wave Power
About 75 million years ago, in Phangnga Bay, Thailand, Earth movements pushed up limestone rocks from the ocean floor. The limestone was slowly eroded by sea's waves, until only the hardest rock was left. This formed peaks up to 100m tall.
Desert Wind and Sand
The strange peaks of rocks in Pinnacles Desert, Australia were formed when windblown sand wore away softer outer rock. Plants called lichen growing on the rocks give some protection from erosion, but the peaks are still being worn away. Some of the peaks are up to 5 m.
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