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3.How Mountains are Formed 2

3 It takes millions of years for mountains to form Even though they rise high above the ground, mountains begin forming below the surface of the Earth

4 Mountains can be formed when plates that make up Earth’s crust move convergent divergent transform

5 Some mountains are formed when two plates push against each other (converge) The pressure causes one plate to bulge out

6 Often the bulge is round and is lifted into the shape of a dome Dome-shaped mountains are usually low mountains

7 Vocabulary Dome-shaped mountains Mountains formed when two plates push against each other (converge) and one plate bulge out

8 Fold mountains are formed when plates collide head-on Vocabulary: Fold mountains The folding of the Earth’s crust to form peaks when 2 plates collide head-on

9 Sometimes when plates collide, the rock breaks into blocks It is pushed up along fault lines.

10 These broken blocks form fault-block mountains Mountains, like the Sierra Nevada in North America, are often steeper than other kinds of mountains

11 Vocabulary Fault-block mountains Mountains formed by blocks of rock that are pushed up along fault lines and the rock is broken when the plates collide

12 Some mountains begin when one plate is forced down below another plate. The rock in the lower plate melts then rises to the surface

13 This hot melted rock, or lava, spews out of the ground Vocabulary: lava Hot melted rock spewed onto the surface of the Earth by a volcano

14 As the melted rock cools, it forms a hard layer More layers are formed as the lava piles up and cools

15 In this way, a volcanic mountain is formed Vocabulary Volcanic mountain A mountain formed when layers of lava pile up on the surface and cools

16 Most mountains are formed in a group, or range Mountains in a range have about the same shape and are usually made of the same kinds of rock

17 The longest range in the world is the Andes in South America

18 The Andes Mountains are found along the edge of the South American Plate

19 The oldest exposed igneous rock in North America is in Missouri The St Francios Mountains in eastern Missouri were formed through volcanic and intrusive activity

20 They are 1.4 billion years old and formed what we call “Elephant Rocks”

21 Another series of igneous rock has been exposed near Eminence where the Current and Jacks Fork Rivers have formed Rocky Falls Shut-In

22 Missouri has a third are of isolated igneous rock exposed between Lebanon and Camdenton It is thought an asteroid hit the area causing the sedimentary rock to be removed

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