Types of Volcanoes, Lava, and Earthquake Zones

Shield Volcanoes

Volcanoes with broad, gentle slopes formed by low-viscosity lava and layers of cooled lava. Example: Mauna Loa in Hawaii.

Stratovolcanoes

Volcanoes with steep profiles, periodic explosive eruptions, and composed of layers of hardened lava, tephra, pumice, and volcanic ash. Example: Mount St. Helens.

Cinder Cone Volcanoes

The smallest type of volcano, built from congealed lava ejected from a single vent, forming a circular or oval cone. Example: Paricutin in Mexico.

Pahoehoe

Smooth, unbroken lava surface that moves relatively fast.

Aa

Rough, broken, sharp lava that moves more slowly than pahoehoe.

Andesitic Lava

Lava with intermediate composition, associated with stratovolcanoes and explosive eruptions.

Rhyolitic Lava

Lava with high silica content, very viscous, and associated with explosive eruptions.

Ring of Fire

Circum-Pacific belt known for intense seismic activity, including earthquakes and volcanoes.

Mid-Atlantic Ridge

Divergent tectonic plate boundary under the Atlantic Ocean, associated with volcanic activity.

Mediterranean-Asian Seismic Belt

Region stretching from the Mediterranean to the Himalayas, known for volcanic and earthquake activities.

Pumice

Light, porous volcanic rock formed during explosive volcanic eruptions.

Basalt

Dark, fine-grained volcanic rock formed from the rapid cooling of basaltic lava.

Rhyolite

Light-colored, fine-grained volcanic rock high in silica.

Andesite

Intermediate volcanic rock with a composition between basalt and rhyolite.

Silica's Role

Determines magma viscosity; high silica content leads to more viscous magma and explosive eruptions.

Viscosity

Measure of a fluid's resistance to flow, influencing the type of volcanic eruption.

Effusive Eruptions

Outpouring of lava onto the ground.

Explosive Eruptions

Magma torn apart as it rises, exploding into the air, often producing pyroclastic flows.

Pyroclastic Flow

High-density mix of hot lava blocks, pumice, ash, and volcanic gas moving at high speed down volcanic slopes, extremely dangerous.

Hot Spring and Geyser Formation

Formed by heating of groundwater by geothermal heat from magma; geysers erupt intermittently due to pressure.

Island Arc

Chain of islands formed above a subducting plate, where magma rises to the surface.

Hotspot

Volcanic region fed by anomalously hot mantle compared with the surrounding mantle.

Batholith

Large mass of intrusive igneous rock formed from cooled magma deep in the Earth's crust.

Laccolith

Smaller mass of igneous rock intruded between layers of sedimentary rock, causing overlying strata to bulge upward.

Magma

Molten rock beneath the Earth's surface.

Lava

Magma that has erupted onto the Earth's surface.

Mars Volcanoes

Shield and cone-shaped volcanoes with lava flows, similar to Venus and Earth.

Mount St. Helens Eruption

Famously explosive eruption in 1980 from a stratovolcano in an active stage.