Volcanoes are classified into four main types based on their shape, size, and eruption style. These types include Shield Volcanoes, Composite Volcanoes also known as Stratovolcanoes, Cinder Cones, and Lava Domes. Each type has distinct characteristics formed by different volcanic processes. Volcanoes form when magma from Earth's mantle rises through the crust and reaches the surface.
Shield volcanoes are characterized by their broad, gently sloping sides that resemble a warrior's shield lying on the ground. They are built from highly fluid basaltic lava flows that can travel long distances before solidifying. These volcanoes typically have non-explosive eruptions, where lava flows quietly from the summit or fissures on the flanks. Shield volcanoes are among the largest volcanoes on Earth, with examples like Mauna Loa in Hawaii, which rises over 30,000 feet from the ocean floor.
Composite volcanoes, also known as stratovolcanoes, are characterized by their steep, conical shape and are built from alternating layers of lava flows, ash, and rock fragments. These volcanoes typically contain viscous, silica-rich magma that doesn't flow easily, leading to pressure buildup and explosive eruptions. The alternating layers result from changes in eruption style over time. Famous examples include Mount Fuji in Japan and Mount St. Helens in the United States. These volcanoes are known for their potentially devastating eruptions that can produce pyroclastic flows, lahars, and ash clouds.
Cinder cones are the simplest and most common type of volcano. They are small, steep-sided conical hills built around a single vent from ejected lava fragments called cinders or scoria. These fragments are blown into the air during eruptions, cool and solidify before falling back to the ground. Cinder cones typically result from relatively short-lived eruptions that may last only a few months or years. They rarely exceed 1,000 feet in height. A famous example is Paricutin in Mexico, which emerged from a cornfield in 1943 and grew to 1,200 feet within a year.
Lava domes are rounded, steep-sided mounds formed when highly viscous lava is erupted slowly and piles up around the vent. Unlike the fluid lava of shield volcanoes, the lava in domes is so thick and sticky that it cannot flow far from its source. Lava domes can grow by expansion from within as new lava is added, causing the surface to crack and split. They are particularly dangerous because they can collapse suddenly, creating pyroclastic flows. A well-known example is the dome that formed in the crater of Mount St. Helens after its major 1980 eruption.