volcanos

Volcano Eruptions Statistics

• Average Yearly Eruptions:

  • 1-5 eruptions

  • 6-10 eruptions

  • 11-30 eruptions

  • About 60 eruptions

Current Active Volcanoes

• Active Volcanoes Today:

  • 5

  • 10

  • 20

  • About 33 active volcanoes

Volcanic Eruption Risks

• Risk of Death from Eruptions in Michigan:

  • Possible but not likely

  • Not a direct threat

  • Some view claims as a scare tactic for federal funding

Study Guide Topics

• Types and Characteristics of Volcanoes:

  • Size, slope, materials, composition

• Volcanic Materials:

  • Types of lava and pyroclasts (tephra)

• Eruption Violence Controls:

  • Factors that affect eruption styles

• Global Distribution of Volcanoes:

  • Locations and patterns of volcanic activity

• Volcanic Hazards:

  • Dangers associated with specific volcano types

Types of Volcanoes

1. Shield Volcanoes:

   • Low slope angles (2-3 degrees)

   • Primarily composed of long, fluid basaltic lava flows

   • Example: Mauna Loa in Hawaii

2. Composite (Stratovolcano):

   • Moderate slopes

   • Comprised of lava flows and pyroclastics (mostly ash)

   • Examples include Mount St. Helens and Mount Fuji

3. Cinder Cones:

   • Steep slopes

   • Formed from pyroclasts (cinders, bombs)

   • Smaller size, example: Sunset Crater (Arizona)

4. Lava Domes:

   • Steep slopes; formed from viscous lava (rhyolite)

   • Example: Mount Pelee

5. Calderas:

   • Depressions forming at the summit of volcanoes

   • Example: Yellowstone

6. Plateau Basalts:

   • Extensive sheets of basalt lava

   • Considered flood basalts

7. Mid-Ocean Ridge Volcanoes:

   • Formed from fissure eruptions of basalt lava

Volcanic Products Classification

• Pyroclasts:

  • Shot into the air; classified by size

  • Block (angular chunk > 64mm)

  • Bomb (molten rock that cools during flight)

  • Lapilli (solid fragments, 2-64 mm)

  • Pumice (vesicular, glassy, rhyolitic)

  • Ash (pulverized rock, <2mm)

Eruption Violence and Volcano Characteristics

• Eruption Styles:

  • Hawaiian (mafic)

  • Felsic eruptions (high silica content leads to increased viscosity)

• Volcanic Explosivity Index (VEI):

  • Measures eruption size and explosiveness

  • Scale from 0 (non-explosive) to 8 (super eruptions)

Hazards Associated with Different Volcano Types

• Shield Volcanoes:

  • Non-explosive eruptions, basalt lava

• Composite Volcanoes:

  • Explosive eruptions due to gas buildup

• Cinder Cones:

  • Eruptions may be short-lived but potentially hazardous due to steep slopes

• Calderas:

  • Massive collapses can result in widespread hazards

Examples of Famous Volcanoes

• Mount St. Helens:

  • Composite volcano in Washington State

  • Known for its catastrophic eruption in 1980

• Kilauea:

  • Active shield volcano in Hawaii, known for its eruptions and lava flows

• Yellowstone Caldera:

  • Supervolcano, last major eruption around 640,000 years ago