A shield volcano is a broad, gently sloping volcano built from fluid lava flows. Think of it like a warrior's shield lying on the ground – wide and not very tall. These volcanoes are formed by low-viscosity basaltic lava, which can flow easily over long distances. This allows the lava to spread out, creating the characteristic shield shape. The Hawaiian Islands are excellent examples of shield volcanoes.
A stratovolcano (also known as a composite volcano) is a tall, cone-shaped volcano composed of many layers (strata) of hardened lava, tephra, pumice, and volcanic ash. These volcanoes are characterized by steep slopes and are associated with explosive eruptions. The lava is typically more viscous than that of shield volcanoes, and it contains a higher silica content. Mount Fuji in Japan and Mount Vesuvius in Italy are famous stratovolcanoes.
| Feature | Shield Volcano | Stratovolcano |
|---|---|---|
| Shape | Broad, gently sloping shield shape | Tall, cone-shaped with steep slopes |
| Lava Type | Low-viscosity basaltic lava | High-viscosity andesitic or dacitic lava |
| Eruption Style | Effusive (lava flows) | Explosive (ash, tephra, pyroclastic flows) |
| Composition | Primarily basalt | Layers of lava, ash, and volcanic debris |
| Silica Content | Low | High |
| Height | Generally lower | Generally taller |
| Examples | Mauna Loa (Hawaii), Skjaldbreiður (Iceland) | Mount Fuji (Japan), Mount Vesuvius (Italy), Mount St. Helens (USA) |
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