Volcanoes

Origin of Magma Magma forms in the crust and upper mantle when solid rock partially melts. Formation of magma depends on: Heat Pressure Water Content Magma that has reached the surface is called lava.

Volcanoes A volcano is a mountain formed of lava and/or pyroclastic material. A crater is the depression at the summit of a volcano. A conduit, or pipe, carries magma to the surface.

Which of the following does not determine the formation of magma? Heat Pressure Salinity Water Content

Magma that has reached the surface is called: Pyroclastic Material Lava Conduit Crater

A crater is a: Depression at the top of a volcano. Pipe carrying lava to the surface. Mountain made of lava. Partially melted rock.

Volcanoes and Plate Tectonics Divergent plate volcanism Convergent plate volcanism Intraplate volcanism

Divergent Boundary Volcanism The greatest volume of volcanic rock is produced along the oceanic ridge system. Lithosphere pulls apart. Less pressure on underlying rocks, Partial melting occurs Large quantities of fluid basaltic magma are produced.

Convergent Boundary Volcanism Slabs of oceanic crust are pushed down into the mantle and melt. The magma slowly migrates upward, forming volcanoes. More than half of Earth’s active volcanoes are located in the “Ring of Fire,” an area of subduction zones around the Pacific Plate.

Intraplate Volcanism A mass of hotter-than-normal mantle material, called a mantle plume, rises toward the surface. Can result in a volcanic region called a hot spot (example: Hawaiian Islands.) Most hot spots have lasted for millions of years.

What is the “Ring of Fire?” Subduction zones encircling the Pacific Ocean. Where over half the world’s active volcanoes are found. A great old Johnny Cash tune. All of the above.

“Ring of Fire” volcanoes are formed at which type of plate boundary? Divergent Boundary Convergent Boundary Intraplate Boundary 2. 1. Intraplate Boundary 3.

The Hawaiian Islands were formed by an Intraplate volcanic region called a: Volcanic Island Arc Continental Volcanic Arc Hot spot Mid-ocean ridge

Factors Affecting Eruptions Viscosity of the magma The more viscous the material, the greater its resistance to flow.

Factors Affecting Eruptions Dissolved gases Mainly water vapor and carbon dioxide Provide the force to extrude lava Violence of an eruption is related to how easily gases escape from magma.

Factors Affecting Eruptions The viscosity of the magma, plus the quantity of dissolved gases and the ease with which they escape, determine the nature of a volcanic eruption.

The factors that affect volcanic eruptions are: Permeability & dissolved metals Permeability & dissolved gases Viscosity & dissolved metals Viscosity & dissolved gases

Fluid lava with a low gas content would produce a(n): Quiet eruption Violent eruption Earthquake I’m not sure because I really wasn’t paying attention.

Volcanic Materials Depending on the type of eruption, volcanoes may produce any or all of the following materials: Lava Flows Basaltic – low viscosity & low percentage of gases Andesitic – intermediate viscosity & gases Rhyolitic – high viscosity & gases Gases – can exceed thousands of tons each day. Pyroclastic Materials

Two Types of Basaltic Lava Pahoehoe Hot, fast-moving. Forms a smooth skin that wrinkles as it flows. Aa Cooler, slower-moving. Forms a surface of rough, jagged blocks.

Pyroclastic Materials Particles produced in volcanic eruptions (ash, cinders, blocks, bombs, etc.)

Which of the following is not produced during volcanic eruptions? Mantle plumes Lava flows Gases Pyroclastic Materials

Which of the following is true of Aa lava? Very hot Fast-moving Forms a smooth skin that wrinkles Forms a surface of rough, jagged blocks

Particles given off during volcanic eruptions are called: Lava Magma Pyroclastic Materials Thermodynamic Materials

Types of Volcanoes

Shield Volcanoes Broad, gently sloping volcanoes built from fluid basaltic lava flows. Largest volcanoes on Earth (e.g., Mauna Loa.) Relatively quiet eruptions.

Cinder Cones Small volcanoes made from pyroclastic material, usually from a single eruption. Steep slope angle Rather small in size

Composite Cones (Stratovolcanoes) Volcanoes composed of both lava flows and pyroclastic material. Most are adjacent to the Pacific Ocean (e.g., Mt. Rainier). Most violent type of activity.

Which type of volcanoes are the largest on the Earth? Shield Volcanoes Cinder Cones Composite Cones

Which volcano is potentially the most dangerous? 1. Shield volcano Cinder cone Composite cone 2. 3.

Which type of volcanoes are often created from a single eruption? Shield Volcanoes Cinder Cones Composite Cones

Caldera A large depression in a volcano, formed by collapse.

Intrusive Igneous Structures Volcanic Neck – hardened magma, exposed by erosion. Lava Plateau – lava flows spread out over a wide area. Plutons Sills –magma flows between parallel layers of sedimentary rock. Laccoliths – lens-shaped plutons that have pushed the overlying rock layers upward. Dikes –magma flows into fractures that cut across rock layers. Batholith – exposed surface of more than 100 square kilometers.

Forming Igneous Features and Landforms Intrusive Igneous Structures Forming Igneous Features and Landforms To view this animation, click “View” and then “Slide Show” on the top navigation bar.

Underground igneous rock bodies are called: Lava flows Volcanoes Plutons Calderas

A large depression in a volcano, formed by collapse is called a: Crater Caldera Pipe Vent

What intrusive igneous feature in the diagram is labeled C? A dike A sill A batholith A laccolith

Volcanic Hazards Lava flows

Volcanic Hazards Volcanic ash

Volcanic Hazards Pyroclastic flows

Volcanic Hazards Mudflows (lahars)

Which of the following is not a common volcanic hazard? Lava flow Pyroclastic flow Mud flow Convective flow

What is a lahar? A tidal wave A mudslide An igneous intrusion A small volcano

Which of the following is the term for an avalanche of glowing volcanic particles and gases? Pyroclastic flow Lahar Lava flow Tsunami