14.3.4
Plateau mountains
Plateaus are high areas of land that are large and flat. They have been pushed above sea level by tectonic forces or have been formed by layers of lava. Over billions of years, streams and rivers cause erosion, leaving mountains standing between valleys. Plateau mountains are sometimes known as erosion mountains. Examples of plateau mountains include parts of the Great Dividing Range in Australia (see FIGURE8 ) and the Colorado Plateau (see FIGURE9 ) in the United States.
FIGURE8 The Blue Mountains in New South Wales are an example of a plateau mountain.
FIGURE9 The Colorado Plateau in the United States was raised as a single block by tectonic forces. As it was uplifted, streams and rivers cut deep channels into the rock, forming the features of the Grand Canyon.
14.3.5 How were the Himalayas formed? Before the theory of tectonic plate movement, scientists were puzzled by findings of fossilised remains of ancient sea creatures near the Himalayan peaks. Surely these huge mountains could not once have been underwater? The mystery was solved when scientists came to understand plate movements. About 220 million years ago, India was part of the ancient supercontinent we call Pangaea . When Pangaea broke apart, India began to move northwards at a rate of about 15 centimetres per year. When the plate carrying India collided with Asia 40–50 million years ago, the oceanic crust (carrying fossilised sea creatures) crumpled and was uplifted, forming the high mountains we know today. Therefore, the Himalayas were formed when India crashed into Asia and pushed up the tallest mountain range on the continent.
368 Jacaranda Humanities Alive 8 Victorian Curriculum Third Edition
Made with FlippingBook interactive PDF creator