Consistency of lava determines what it looks like on the surface. Least runny makes steep-sided volcanoes like Mt. St. Helens. Lava moves slowly and solidifies before traveling far. Need high internal temperature and thin lithosphere to get volcanoes . Formed when they were younger and hotter.
Gases erupting from volcanoes contribute to atmospheric gases.
The volcanoes of the Pacific rim area are caused by the collision of two places. The Himalayas are also due to plate collisions with one plate going under the other and the edge of the second plate forming the mountains. Rio Grande Valley is caused by crust pulling apart, as is Guinevere plains on Venus. Like with volcanism, need thin lithosphere and hot core to have tectonic features. Erosion Breakdown and transport of rocks by atmospheric effects.