Mountains can and have served to effectively hamper movements of people, trade, ideas and technology, armies, religions, and a variety of other physical and cultural things. A mountain is a landform that rises prominently above its surroundings, generally exhibiting steep slopes, a relatively confined summit area, and considerable local relief. Mountains generally are understood to be larger than hills, but the term has no standardized geological meaning. The Himalayas, for example, developed from the collision of the Eurasian and Indian plates. As you have now read about, associated with many mountain ranges are volcanoes.
Volcanoes form where rising magma breaks through the Earth's surface.
If the solidified magma of a volcano builds up, it can become a mountain like Mount St. Helens. If the collision involves two oceanic plates a string of volcanic mountains, an island arc, can form on the ocean floor. Earthquakes are also associated with the tectonic processes, but are a by-product of mountain building, not a contributor to mountain building. Very rarely do mountains occur individually. In most cases, they are found in elongated ranges or chains.