GEOL 100: Volcanoes!

in progress <- adding more info post lecture (if needed)

Most volcanoes are the result of what, and what does that “what” result in?

1. “plate” movement

2. Results in Magma and Lava

What kind of volcanic eruptions are there?

Effusive or Explosive

How do explosive eruptions occur?

Gasses trapped in lave rapidly escape (think soda analogy)

What element of lava determines how fast its gases escape?

Viscosity!

What factors increase or decrease lava’s viscosity?

• Temperature

• Silica Content (SiO₂)

• Dissolved Gases

What do high viscosity eruptions result in? What about low viscosity?

1. Aa

2. Pahoehoe

What is Columnar Jointing?

The vertical cracking that occurs in lava as it cools, solidifies, and contracts

• Due to release of thermal energy

What do volcanic eruptions typically include?

• Toxic Gases

• Water Vapor

• Pyroclastic material

Volcanic types are based on what?

The shape of the volcanic core

What are the characteristics of shield cone volcanoes?

• Broad

• Dome shaped

• Sides gently slope

• Forms hot, low viscosity Mafic Lava (e.g. Hawaii)

What are the characteristics of cinder cone volcanoes?

• Small

• steep-sided

• Form from Pyroclastic Material ← settles after erruption

• Sometimes erupt mafic lava

What are the characteristics of composite cone volcanoes (also called Stratovolcanoes)?

• Tall

• Large

• Multiple layers of Pyroclastic Material + Felsic Lava flows

Where are most composite volcanoes located on?

Ring of Fire

What are lava dome volcanoes?

• Small

• Generally form inside volcanic craters

  • From very viscous, mostly felsic lava flows

What are the circumstances for a caldera to form?

• After eruption of super volcano

  • Yellowstone

Or

• Collapsed magma after eruption

  • Crater Lake

What is the santorini?

A composite volcano in ~1620 BC and it could be the origin of the Lost City/Continent of Atlantis

What do fissure eruptions create?

Lava plateaus!

• Columbia River plateau

  • May have contributed to extinction of dinosaurs

How many times has the Yellowstone Supervolcano erupted?

• 3 in the last 2.1 million years

What terms are used to generally describe volcanoes?

• Active

• Dormant

• Inactive

• Extinct

What are active volcanoes?

A volcano that is erupting or has erupted in the last 10,000 years or is predicted to erupt in the near future

What are dormant volcanoes?

A volcano that HASN’T erupted in the last 10,000 years but is expected to do so in the future

What are inactive volcanoes?

A volcano that may or may not erupt in the future

What are extinct volcanoes?

A volcano that is not expected to ever erupt again