Final answer:
Cinder-cone volcanoes have steep sides and are generally the smallest volcanoes. They are formed from eruptions of gas-rich magma that explodes into the air and solidifies before reaching the ground.
Step-by-step explanation:
Cinder-cone volcanoes have steep sides and are generally the smallest volcanoes. They are formed from eruptions of gas-rich magma that explodes into the air and solidifies before reaching the ground. The solidified ash and cinder build up around the vent, creating a cone-shaped volcano with steep sides.