Broad, gradual slopes are shield volcanoes, while tall, steep slopes are composite volcanoes.
Shield volcanoes usually have broad, gradual slopes. Shield volcanoes form when a large amount of low viscosity lava flows gradually and widely to form a low, broad, dome-shaped mountain around the vent. The more the amount of lava that forms a volcano, the broader will be its base and the higher its slopes. Mauna Loa on the Big Island of Hawaii is an example of a shield volcano.
Composite volcanoes usually have tall, steep slopes and they are formed by eruptions that starts with explosions of lava and volcanic debris from a central vent or crater. Examples of composite volcanoes are Italy's Mount Vesuvius and Japan's Mount Fuji.
