Volcano Parts and Types

Study Notes

Summit: The highest part of a volcano.
Slope: The side of a volcano.
Base: The lowest part of a volcano.
Crater: The opening at the top of a volcano.
Caldera: A larger opening than a crater, formed when part of the volcano's wall collapses.

Volcanoes are natural openings in the Earth's surface where molten rock, smoke, gases, and ashes are released.

Ten active volcanoes: Kanlaon, Mayon, Pinatubo, Taal, Bulusan Iraya, Hibok-Hibok, Banahaw, Ragang, and Makaturing.
Inactive volcanoes: Cabaluyan, Cocoro, Urot, and Tamburok.
Total volcanoes: 300 Volcanoes in The Philippines, with 23 being active and the rest idle or inactive.

Shield Volcanoes: Non-explosive, very fluid lava flowing in all directions, forming a gently sloping cone (like a warrior's shield).
Cinder Cone Volcanoes: Sticky, fragmented lava that accumulates around the volcanic vent to create an oval or circular cone shape.
Composite Volcanoes: Highly viscous lava that forms a columnar pile in the vent, resulting in a near-perfect or perfect cone.

Strombolian: Relatively small, sporadic explosions or weak pulsating eruptions.
Phreatic: Ground or surface water heated by magma, causing an eruption.
Phreatomagmatic: Interaction between water and magma.
Vulcanian: Dense clouds of gas and ash explode from the volcano's crater, rising high into the air.
Plinian: Powerful, violent eruptions, producing a sound like an explosion.

Temperature: High temperature magma flows easily (low viscosity), while low temperature magma resists flow (high viscosity).
Chemical Composition: Magma's resistance to flow depends on internal friction from chemical bonds in the liquid magma. Oxygen and silicon are key factors in the degree of magma's viscosity.
Amount of Gases: All magmas contain gases that determine their explosive potential; gas content increases as pressure reduces.

Lava types: Silica content (low vs. high): Low silica lava flows easily, forming thin sheets; High silica lava is viscous, tending to break up as it flows. Low gas content lava is viscous and can pile up to form a dome shape; low gas content lava is viscous and can pile up to form a dome.
Magma compositions:
- Mafic (or basaltic): Not viscous, flows easily, high in iron, magnesium, calcium, low in potassium, sodium, and rich in silicon dioxide; temperature range about 1,000°C to 1,200°C.
- Intermediate (or andesitic): Moderate viscosity, temperature range about 800°C to 1,000°C.
- Felsic (or rhyolitic): Highly viscous, does not flow easily; high in potassium and sodium, low in iron, magnesium, and calcium, with silicon dioxide-rich. Temperature range about 650°C to 800°C.
Magma is a mixture of minerals and dissolved gases including water vapor, carbon dioxide, and sulfur.
Pyroclastic material: Cloud of ash, lava fragments carried through the air; and/or vapor, hot broken fragments are called pyroclasts.
- There are 12 types of igneous rocks: Basalt, Pumice, Obsidian, Rhyolite, Scoria, Dacite, Granite, Gabbro, Diabase, Diorite, Pegmatite, and Peridotite.