Strata vs. Shield Volcanoes

Strato Volcanoes

Strato Volcanoes comprise 60% of the Earth's individual volcanoes and most are characterized by eruptions of andesite and dacite - lavas that are cooler and more viscous than basalt.  Stratovolcanoes also have steep sides with cones that stick out like huge bumps. They are built up when eruptions of viscous lava, tephra, and pyroclastic flows happen. It takes thousands of years for the pressure to build up enough in stratovolcanoes to cause an eruption. More than one kind of magma builds up in stratovolcanoes. They are basalt, andesite, dacite, and rhyolite magma. All of those magmas cause explosive eruptions except basalt magma. There are a lot of different vents around stratovolcanoes. Some of the vents are cinder cones and domes low on the sides of the volcano. Sometimes stratovolcanoes are called composite cones.

Shield Volcanoes

Shield Volcanos' slopes are made by liquid basalt lava that pushes up from a vent under the ground. Shield volcanoes do not have sharp steep slopes. They are the largest volcanoes on Earth. Shield volcanoes are huge in size.  They are built by many layers of runny lava flows. Lava spills out of a central vent or group of vents. Unlike strato volcanoes shield volcanos have many openings where lava comes out.  They are also made by hotspots.