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Exploring Volcanoes and Their Eruptive Activity: Types, Zones, and Lava Characteristics

Volcanoes are dynamic geological structures where magma escapes from beneath the Earth's surface. The movement of magma leads to eruptions, which can vary dramatically based on the type of volcanic zone, such as mid-ocean ridges, subduction zones, and hot spots. This overview covers two primary types of lava—felsic and mafic—along with their characteristics. It details the formation of different volcanoes, including shield, cinder cone, and composite types, while explaining how volcanic activity shapes the landscape and impacts the environment.

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Exploring Volcanoes and Their Eruptive Activity: Types, Zones, and Lava Characteristics

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  1. Volcanoes

  2. volcanism:any activity that includes the movement of magma toward the surface of the Earth volcano: place where magma reaches the surface

  3. magma: liquid, molten rock underground • lava: magma that reaches the surface • lost gas, gained rock

  4. Major Volcanic Zones • MID-OCEAN RIDGE: occurs where plates are moving apart • lava flows out smoothly and fluidly from cracks

  5. SUBDUCTION ZONE: occurs at subduction boundaries • usually explosive and erupted material is mostly lava

  6. HOT SPOTS: areas of volcanic activity in the middle of a lithospheric plates

  7. Hawaiian Islands are an example

  8. two types of lava: • felsic: much silica (Rhyolitic), light-colored, slow moving (viscous), continental crust

  9. mafic: low silica (basaltic), dark-colored, fast moving (least viscous), oceanic crust

  10. Pahoehoe (puh-HOEEE-hoeee): thin mafic lava. • usually hardens with wrinkled surface • means “ropey” in Hawaiian Pahoehoe Lava

  11. Aa Lava • Aa (AH-ah): sharp block shapes of hardened mafic lava. • caused by rapid cooling on surface of lava • breaks into jagged chunks

  12. Aa Lava Pahoehoe Lava

  13. Pahoehoe

  14. Aa

  15. Pillow lava from Hawaii

  16. many magmas contain dissolved gases that are given off • water vapor, carbon dioxide (CO2), sulfur (S) • magmas with more gases have more explosive eruptions

  17. tephra:solid fragments ejected from a volcano ash (<2mm) bombs lapilli (<64mm) blocks Sometimes called pyroclastic material

  18. lapilli

  19. bombs

  20. bombs

  21. blocks

  22. Vent: opening from which lava flows • Crater: funnel-shaped pit or depression at top of volcano • Caldera:craters whose walls have collapsed

  23. Shield Volcano • composed of quiet lava flows • form gently sloping, dome- shaped mountain • basaltic (mafic) magma

  24. largest = Mauna Loa in Hawaii

  25. Cinder Cone Volcano • Made mostly of tephra and other rock particles • Formed from explosive eruptions • Not very high, narrow base, steep sides • Rhyolitic (felsic) magma

  26. Composite Volcano • built up of alternating layers of rock & lava • explosive eruptions at first with tephra, then quiet with lava • forms large, cone-shaped mountains • made of rhyolitic & basaltic magma

  27. Mount Fuji

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