Earth Science Chapter 7 Flashcards

Volcanic Terminology

• Magma vs. Lava: Magma is molten rock beneath Earth’s surface; lava refers to molten rock that reaches the surface.

Factors Influencing Eruptions

• Three Key Factors:
  • Composition of magma affects its viscosity.
  • Temperature influences magma's fluidity.
  • Quantity of dissolved gases determines eruption force and nature.

Types of Lava

• Pahoehoe Lava: Characterized by a smooth or ropy appearance; results from fluid basaltic lava.
• Aa Lava: Has a jagged, sharp surface; forms from more viscous magma.

Gases Released in Eruptions

• Major Volcanic Gases:
  • Water vapor (70%)
  • Carbon dioxide (15%)
  • Nitrogen (5%)
  • Sulfur compounds (5%)
  • Trace amounts of chlorine, hydrogen, and argon.

Volcanic Features

• Volcanic Crater: Smaller depression at the vent for erupting materials formed through erosion by incoming magma.
• Caldera: Large depression from the collapse of a volcano after a massive eruption, resulting from magma chamber evacuation.

Types of Volcanoes

• Shield Volcanoes: Large, gently sloping domes associated with quiet eruptions and mostly fluid basaltic lava.
• Cinder Cones: Steep-sided, composed of pyroclastic material; the smallest volcano type.
• Composite Cones: Formed by alternating layers of lava and pyroclastic debris; steeper than shield volcanoes, known for violent eruptions.

Examples of Volcanoes

• Shield Volcano: Mauna Loa, Hawaii.
• Cinder Cone: Paricutin, Mexico, with smaller cones in Arizona.
• Composite Cone: Mt. Fuji, Japan; Mt. Shasta, California; volcanoes of the Cascade Range.

Shiprock Formation

• Shiprock, NM: Landmark formed from the erosion of surrounding sedimentary rock, revealing the hard igneous rock of a former volcano's plumbing system.

The Ring of Fire

• Definition: Extensive arc of volcanic and seismic activity, from New Zealand to North and South America, comprised of over 75% of the world’s active and dormant volcanoes.
• Tectonic Features: Located primarily at the borders where the Pacific Plate meets other major tectonic plates.

Plate Boundaries and the Ring of Fire

• Subduction Zones: The Ring of Fire’s volcanoes are primarily associated with subduction zones, where tectonic plates move beneath each other, leading to volcanic activity.