Plates move very slowly, at a rate of one or two centimeters per year. Over hundreds of millions of years, plates sometimes collide. When continents meet head-on, the crust tends to buckle and be pushed upward or sideways. This process, sometimes called "mountain building," is how some mountain ranges are formed. Some mountain ranges were formed so long ago that they have become eroded down to low hills. Other mountain ranges, such as the Himalayas and the Alps, are still slowly growing during the present day.
Volcano Formation  In some places, the crust on the ocean floor sinks back into the Earth's mantle. As the crust sinks, it melts, and hot melted rock rises up, squeezing through widening cracks. Magma escapes to the surface and creates volcanoes. A volcano is an opening in the Earth's crust from which lava, steam, and/or ashes erupt or flow. When a volcano erupts, the lava flows down and hardens to form new land. This new land may take the form of a volcanic mountain, a plateau, an island, or an archipelago. An archipelago is a chain of islands. Volcanoes are usually found in the ocean or along the coast. Volcanic eruptions can cause rapid destruction of habitats and changes to a landscape. They can also benefit the surrounding area. Volcanic ash and dust are rich with minerals. These minerals seep into the soil, making it more fertile and allowing new vegetation to grow back quickly. Another benefit is that many precious metals and gemstones can be found in cooled lava. 
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