210 likes | 365 Views
Chapter 6 – VOLCANOES. Volcanoes & volcanic hazards. Volcano Vent where lava, solid rock debris, volcanic ash, & gases erupt from inside Earth onto its surface Can be explosive or non-explosive Mt. St. Helens Kilauea. Volcanoes & volcanic hazards. Lava
E N D
Volcanoes & volcanic hazards Volcano Vent where lava, solid rock debris, volcanic ash, & gases erupt from inside Earth onto its surface Can be explosive or non-explosive Mt. St. Helens Kilauea
Lava Molten rock that reaches Earth’s surface Magma Molten rock, which may include fragments of rock, volcanic glass & ash, or gas Beneath Earth’s surface Volcanoes & volcanic hazards
Eruptions, landforms & materials Eruption types: Hawaiian Shield volcano Broad, flat volcano with gently sloping sides Largest volcanoes Built of successive lava flows May also produce flood basalts or lava plateaus
Eruptions, landforms and materials Eruption types: Strombolian More explosive than Hawaiian Create loose volcanic rock called spatter cones or cinder cones Smallest volcanoes
Eruptions, landforms and materials Eruption types: Vulcanian More explosive than Strombolian Can generate clouds of ash up to 10 km Produce pyroclastic flows Hot volcanic fragments (tephra) that flow very rapidly
Eruptions, landforms & materials Eruption types: Plinian Most violent eruptions; ash columns over 20 km Produce stratovolcanoes Composed of alternating layers of solidified lava & pyroclastic material Steep sided
Eruptions, landforms & materials Viscosity Degree to which substance resists flow Less viscous = runny More viscous = thick Dissolved gases Up to ~10% of magma Water vapor, carbon dioxide, sulfur dioxide, etc.
Eruptions, landforms & materials Volcanic materials Pyroclasts Tephra Ash Agglomerates Tuff
Eruptions, landforms & materials Volcanic materials Pahoehoe flows A’a flows Lava tubes Vesicles Columnar jointing Pillow structures
Eruptions, landforms and materials Other volcanic features Crater Caldera Resurgent dome
Eruptions, landforms and materials Other volcanic features Thermal spring Geyser Fumarole
Eruptions, landforms and materials Other volcanic features Fissure eruptions Flood basalt Lava plateau
Volcanic hazards Primary effects Lava flows Pyroclastic flows Volcanic gases
Volcanic hazards Secondary effects Fires Flooding Mudslides (lahars) Debris avalanche
Volcanic hazards Tertiary and beneficial effects Landscape changes Climate changes; regional & global Benefits: Replenishes minerals & fertility Geothermal energy Specific mineral deposits
Predicting Eruptions Establish volcano’s history Active Dormant Extinct
Predicting Eruptions Monitor changes & anomalies Microseismicity Tilting or bulging Volcanic gases Changes in ground or surface water temperature