Final answer:
The three differences between shield volcanoes and stratovolcanoes are: shield volcanoes have gentle slopes and stratovolcanoes have steep profiles; shield volcanoes tend to have less violent, effusive eruptions, while stratovolcanoes often experience explosive eruptions; and shield volcanoes produce basaltic lava, whereas stratovolcanoes emit more viscous andesitic to dacitic lava.
Step-by-step explanation:
Differences between Shield Volcanoes and Stratovolcanoes
Shield volcanoes and stratovolcanoes, also known as composite volcanoes, are two distinctive types of volcanoes with several key differences. First, shield volcanoes have gentle slopes that rise gradually from the landscape, creating a broad, shield-like profile. They typically result from low-viscosity lava that can flow over great distances. In contrast, stratovolcanoes have steeper profiles and are characterized by a layered structure composed of alternating layers of hardened lava flows, volcanic ash, and tephra that have accumulated over time.
Second, the eruptions of shield volcanoes are generally less violent than those of stratovolcanoes. Because the lava is less viscous, it tends to flow rather than explode, leading to effusive eruptions. On the other hand, stratovolcanoes often exhibit highly explosive eruptions due to the higher viscosity of their magma that traps gases, leading to a buildup of pressure.
Third, the composition of the magma is different for these two volcano types. Shield volcanoes usually emit basaltic lava, which is lower in silicate content and more fluid. Stratovolcanoes typically produce andesitic to dacitic lava, which is higher in silica and creates thicker, more viscous flows.