Volcanoes Flashcards
Crater:
A basin-like rimmed structure at top or on flanks of a volcanic cone
Vent:
Opening at Earth’s surface through which volcanic material is extruded
Magma Chamber:
A reservoir of magma in the shallow part of the lithosphere
Magma Formation-Rift at mid-ocean ridge:
Decrease in pressure lowers melting temperature of materials in the asthenosphere
Magma Formation-Asthenosphere at a hot spot:
Temperature increase can cause materials to melt
Magma Formation-Asthenosphere at subduction boundaries:
Increase in amount of water in the asthenosphere can lower melting temperature of materials there
What controls the magma type and eruption style?
The viscosity of the magma
What effects viscosity?
Temperature of magma:
-hotter, lower viscosity, more fluid
Composition of magma (amount of silica):
-more silica, higher viscosity, more resistant to flow
What makes magma/lava erupt?
- Magma is a liquid, less dense than surrounding material
- Gases within magma rise to surface
Low viscosity lava:
Gases easily rise and are gently released
High viscosity lava:
Gases build up resulting in explosive eruptions
Basaltic Magma:
- Silica Content
- Gas Content
- Viscosity
- Type of Eruption
- Melting Temperature
- Location
- Example
- Less than or equal to 50%
- Least
- Least
- Rarely explosive
- Highest
- Rifts, oceanic hotspots
- Kilauea
Andesitic Magma:
- Silica Content
- Gas Content
- Viscosity
- Type of Eruption
- Melting Temperature
- Location
- Example
- 60%
- Intermediate
- Intermediate
- Sometimes explosive
- Intermediate
- Subduction boundaries
- Mountain St. Helens
Rhyolitic Magma:
- Silica Content
- Gas Content
- Viscosity
- Type of Eruption
- Melting Temperature
- Location
- Example
- 70%
- Most
- Most
- Usually explosive
- Lowest
- Continental hotspots
- Yellowstone
What is a volcano?
An opening in Earth’s crust through which molten rock, gases and ash erupt
Types of magma:
- Basaltic
- Andesitic
- Rhyolitic
Lava:
Liquid molten rock
Pahoehoe:
Ropelike lava
Aa:
Crumbly lava
Pillow lava:
Thought to have formed under water
Solid pyroclastic materials:
- Ash
- Cinders
- Lapilli
- Blocks/Bombs
- Pyroclastic flow
Sizes- Ash: Cinders: Lapilli: Blocks/Bombs:
- Microscopic solids
- Pea sized
- Walnut size
- Football size or bigger
Pyroclastic Flow:
Avalanche of burning ash
Volcano types:
- Cinder cone
- Composite (stratovolcano)
- Shield
Cinder cone:
- Steep-sided, formed by explosive eruption of cinders
- Small height, short lived
- Sunset crater, Arizona
Composite:
Steep-sided, built by lava flows and pyroclastic deposits alternating layers, andesitic, most dangerous Osorno volcano in the Chilean Andes
Shield Volcano:
Gentle slope, resembles a warriors shield, quiet eruptions of fluid lava flows (basaltic), largest land forms on earth, Mauna Loa
Caldera:
Crater-shaped basin formed after the top of a volcano collapses
Crater Lake, Oregon
Lahars:
Volcanic mudflow often formed when hot ash mixes with water from melted snow and ice or a crater lake
