Unit 15: Understanding Volcanoes

Volcanoes that have erupted in the past and are likely to erupt again.

Volcanoes that have not erupted in the past 10,000 years and are unlikely to erupt again.

Volcanoes that have not erupted in the recent past but are likely to erupt again in the future.

A system used to categorize volcanoes based on their activity level and eruption characteristics.

The process by which molten rock, ash, and gases are released from the Earth's interior, often with great force, through an opening in the Earth's crust.

A naturally occurring mound or cone-shaped hill formed by the accumulation of lava, ash, and other volcanic materials.

A shield volcano is characterized by a wide base and gentle slopes, formed by the effusive eruption of fluid basaltic lava.

A composite volcano, also known as a stratovolcano, is formed by the alternating eruption of lava flows and pyroclastic materials, resulting in a steep-sided cone.

A volcanic dome is a dome-shaped landform that is formed by the slow extrusion of viscous lava.

A caldera is a large, cauldron-shaped depression formed by the collapse of a volcano's summit after a major eruption.

A volcanic fissure is a long, narrow crack in the Earth's crust from which lava erupts.

Volcanoes that are currently erupting or have shown signs of activity in recent history.

Volcanoes that are no longer erupting and have shown no signs of activity for a long period.

The use of heat energy from the Earth's interior, often generated by volcanic activity, for various purposes such as electricity generation and geothermal heating.

Large igneous provinces (LIPs) are vast areas of volcanic activity, typically found on the Earth's surface. These provinces are characterized by enormous outpourings of magma that can cover vast areas, creating massive plateaus and volcanic features.

The Benham Rise is a submerged plateau located in the Philippine Sea, formed by volcanic activity. While it exhibits some features of LIPs, it is not generally considered a classic example of a large igneous province.

Ocean island basalts are volcanic rocks found on oceanic islands, formed by volcanic activity associated with hotspots. The Yellowstone Caldera, while a volcanic feature, originates from a hotspot and isn't a typical example of an ocean island basalt.

Plate tectonics states that the Earth's outer shell (lithosphere) is composed of large, moving plates. The theory emphasizes that the interactions between these plates, including their boundaries, are the primary drivers of tectonic processes like earthquakes and volcanic activity.

Divergent boundaries occur where tectonic plates move apart. As plates separate, magma rises from the Earth's mantle, forming new crust. Decompression melting at these boundaries, resulting in magma formation, leads to volcanic activity that manifests as mid-ocean ridges or fissure eruptions.

Convergent boundaries occur when tectonic plates collide. Subduction occurs at these boundaries, causing one plate to slide beneath the other, leading to melting. However, this melting is primarily caused by the addition of water from the subducting plate, not decompression.

Volcanism requires significant heat to melt rock and generate magma. Without sufficient heat, volcanic activity is unlikely to occur.

Most Philippine volcanoes are part of island arcs because they are located along convergent plate boundaries where subduction is occurring. Subduction zones are key locations for volcanic activity, leading to the formation of volcanic island arcs.