Volcanoes

Volcanic Activity

• Volcanoes form when magma reaches the Earth's surface.
• Volcanoes occur most often along plate boundaries.
• Convergent plate boundaries where oceanic crust is subducted form many of the volcanoes found on Earth.
• Divergent plate boundaries produce huge mountain ranges under water in every ocean basin.
• Volcanoes like those that form the islands of Hawaii form over areas called hot spots.

Volcanic Eruptions

• Volcanoes are produced when magma rises towards the Earth's surface because it is less dense than the surrounding rock.
• Volcanic eruptions can be non-explosive or explosive depending on the viscosity of the magma.
• Explosive type eruptions happen along the edges of continents and produce tremendous amounts of material ejected into the air.
• Non-explosive type eruptions mostly produce various types of lava, such as a'a, pāhoehoe and pillow lavas.
• Some signs that a volcano may soon erupt include earthquakes, surface bulging, gases emitted as well as other changes that can be monitored by scientists.

Types of Volcanoes

• Composite cones, shield volcanoes, cinder cones and supervolcanoes are some of the types of volcanoes formed.
• Composite cones are tall, cone shaped volcanoes that produce explosive eruptions.
• Shield volcanoes form very large, gently sloped volcanoes with a wide base.
• Cinder cones are the smallest volcanic landform. They are formed from accumulation of many small fragments of ejected material.
• A caldera forms when an explosive eruption leaves a large crater when the mountain blows apart.
• Supervolcanoes are tremendously devastating types of volcanoes that could destroy large areas when they erupt.

Volcanic Landforms and Geothermal Activity

• Very thick lava that doesn't travel very far can produce lava domes at or near the Earth's surface or even within a volcano.
• Lava plateaus form from large lava flows that spread out over large areas.
• Many islands are formed from volcanoes.
• Magma can also cool and crystallize below the Earth's surface forming igneous intrusions.
• When magma heats groundwater, it can form hot springs and geysers.