Volcanic mountain ranges are formed by the accumulation of volcanic materials, such as lava, ash, and rock, from eruptions over time. These mountains often have steep slopes and can be found at tectonic plate boundaries, where the Earth's crust is unstable. Notable examples include the Andes in South America and the Cascade Range in the United States. These ranges can create unique ecosystems and influence local climates. Volcanic activity can also lead to the formation of new landforms, such as calderas and volcanic islands. The presence of volcanoes in these ranges can pose risks, including eruptions and lava flows, affecting nearby communities.