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# Volcanology Volcanoes are natural openings in the Earth's crust that connect the Earth's interior to the exterior, and through which magma moves in different physical states. Volcanology is the branch of Earth sciences that studies the formation, distribution, and classification of volcanic phen...

# Volcanology Volcanoes are natural openings in the Earth's crust that connect the Earth's interior to the exterior, and through which magma moves in different physical states. Volcanology is the branch of Earth sciences that studies the formation, distribution, and classification of volcanic phenomena. Two types of volcanism are distinguished: * **Primary** * **Secondary or Residual** ## Primary Volcanic Manifestations Primary volcanism is characterized by volcanic eruptions. **Volcanic Apparatus:** A volcano consists of several components: * **Volcanic Cone** * **Fume** * **Crater** * **Products of Volcanic Activity** * **Secondary Fume** * **Secondary Cone** * **Magma Chamber or Pouch** **Caldera:** The emptying, total or partial, of the magma chamber makes the volcanic apparatus unstable due to the lack of support for the cone, which may lead to its collapse. A depression, limited by irregular edges, forms, where water accumulates over time, creating lagoons. Example: Lagoa do Fogo (Azores). Eruptions can be associated with: * Volcanic Cones * Fissure Eruptions (extensive fractures through which volcanic materials are expelled) ## Volcanic Ejected Materials During volcanic eruptions, various materials in different physical states are released, including: * **Solids (pyroclasts)** * **Liquids (lava)** * **Gases** **Pyroclastic Flow:** A large quantity of fluids and gases under high pressure, mixed with lava and pyroclast fragments. They are often violently expelled from volcanoes and can move down the slopes at high speeds (sometimes over 100 km/h), causing destruction and burning. **Pyroclasts:** These are solidified lava materials in various sizes. Examples include: ash, lapilli (small fragments), volcanic bombs, and volcanic scoria. **Lava:** Is a molten rock originating from magma, but with a different chemical composition because it has lost significant amounts of gases. **Gases:** During eruptions, the predominant gas is water vapor, followed by other gases such as carbon monoxide, carbon dioxide, hydrogen, nitrogen, hydrochloric acid, and sulfur compounds.