Volcanoes Unit 2

Diagram to label: Blue = vent Green = crater Yellow = cone Orange = pipe Red = Magma chamber

What is a Volcano? Volcano—cone-shaped mountain or hill from which lava, rock, and hot vapors erupt Crater—the depression at the top Vent—the opening inside the crater Pipe—pathway magma travels from the mantle to the vent Cone—the mountain/hill Magma Chamber—where magma sits in the crust prior to an eruption

Magma vs. Lava Magma—molten (melted) rock inside the crust and mantle Lava—molten (melted) rock on top of the Earth’s crust Lava Magma

3 Types of Volcanoes Types are determined by 2 things: Cone Composition—cone made of cinders, lava, or both Explosive Power—strength of eruption Determined by: Amount of dissolved gases in magma Magma temperature Magma composition (type of rock)

3 Types of Volcanoes: Shield Volcanoes Cone: Composed mostly of cooled, hardened lava Gently sloped with a broad base Nonexplosive Example: Mauna Loa and Hawaiian Islands

3 Type of Volcanoes: Cinder-Cone Volcanoes Composed mostly of cinders Steep sides with a small base Very explosive Most common type Example: Nyamuragira Volcano, Rep. of Congo

3 Types of Volcanoes: Composite Volcano (Stratovolcano) Cone Alternating layers of cinders and lava Steep sides with a large base EXTREMELY violent explosions Example: Arenal, Costa Rica

Indicators of Imminent Eruption Increase gas emission Localized tremors/small earthquakes

Types of Pyroclastic Material Pyroclastic Material = ejected from volcano Volcanic bombs—large lava blobs Lava blocks—large pieces of rock; angular shapes; solid Lapilli—pea-size to walnut-sized pieces of volcanic rock Cinders—very small; cool very quickly; contain many air bubbles

Popular Volcano Locations 80% of volcanos occur at convergent boundaries (due to subduction) Oceanic-oceanic = volcanic island arcs Oceanic-continental = continental volcanoes 15% occur at divergent boundaries 5% occur at HOT SPOTS—magma punches through thin lithosphere where there is no boundary; example: Hawaii

Popular Volcano Locations

Popular Volcano Locations: Ring of Fire Pacific Plate is subducting on all sides West—by the Eurasian and Indo-Australian plates East—by the North American and Nazca plates Both subduction zones create sites favorable to both volcanoes and earthquakes

Volcanic Impacts Lahar (mud) flows Volcanic debris saturated with water from rain, melting ice, or snow Atmospheric Ash Ash leads to rain, lightning and thunder Volcanic fog—water vapor, carbon dioxide, nitrogen, & sulfur Sulfur condenses to form acid rain