The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. Why did the Himalayas and the Alps form? (F)

Plate tectonics is a theory that explains the large-scale motion of Earth's lithosphere (the outer shell of the Earth composed of the crust and upper mantle). The Earth's lithosphere is divided into several rigid plates that move relative to each other on the more fluid asthenosphere (the layer of the Earth's mantle below the lithosphere). The movement of these plates is what causes the different geological features, like mountains, earthquakes, and volcanic activity.

There are three main types of plate boundaries: convergent, divergent, and transform. Convergent boundaries occur when two plates move towards each other, resulting in the formation of mountains, volcanoes, and trenches. Divergent boundaries occur when two plates move away from each other, resulting in the creation of new ocean floor, seafloor spreading, and rift valleys. Transform boundaries occur when two plates slide past each other, causing earthquakes.

The Himalayas were formed as a result of a convergent plate boundary. Specifically, the ongoing collision between the Indian Plate (a continental plate) and the Eurasian Plate (another continental plate). This convergence began around 50 million years ago when the Indian Plate started moving northwards towards Eurasia. As they collided, the immense pressure caused the sedimentary rocks along the boundary to be pushed up and folded, resulting in the formation of the highest mountain range on Earth - the Himalayas.

The Alps were also formed due to a convergent plate boundary, specifically between the African Plate (a continental plate) and the Eurasian Plate. This collision began about 30 million years ago when the African Plate started moving northwards towards the Eurasian Plate. Similarly, to the Himalayas, the immense pressure from this convergence caused the rocks along the boundary to be pushed up and folded, resulting in the formation of the Alps mountain range. In conclusion, the formation of the Himalayas and the Alps can be attributed to the process of plate tectonics. Their formation resulted from the collision of continental plates at convergent boundaries, causing immense pressure and uplifting of rocks to form these majestic mountain ranges.