Make two complete observations and one inference about what this is a picture of.

Volcanoes Nature’s pyrotechnics

Causes Most occur at plate boundaries Most occur at plate boundaries –15% at divergent boundaries –80% at subduction –5% at hot spots (Hawaii, Yellowstone)

Volcano Distribution Volcanoes are found along plate boundaries & over mantle hot spots…

Ring of Fire … Approximately two-thirds of the active volcanoes are concentrated along the Pacific

Types of eruptions Nonexplosive Nonexplosive –Calm lava flows, often through fissures –Huge amounts of lava form the Columbia Plateau in central WA, Snake River Plain in southern ID

Lava Plateau: extensive plain formed when lava oozes from fissures ~ Columbia Plateau

Types of eruptions Explosive Explosive –Less common but most publicized –Beside lava, clouds of hot debris, ash, gas (Mt. St. Helens) –100,000X stronger than an atomic Bomb

Types of Volcanoes

Three types of volcanoes 1. Shield 2. Cinder Cone 3. Composite

Types of Volcanoes (Structures) Shield Volcano Shield Volcano –passive eruptions Cinder Cone Cinder Cone –explosive and passive eruptions Stratovolcano/Composite Cone Stratovolcano/Composite Cone –explosive

Comparison of Volcanic Landforms Comparison of Volcanic Landforms

Shield Wide, gently sloping Wide, gently sloping Nonexplosive Nonexplosive Mauna Kea, Hawaii Mauna Kea, Hawaii

Shield volcano

Mauna Loa, Hawaii

Shield Volcanoes Made of lava flows Made of lava flows Huge structure with massive width to height ratio Huge structure with massive width to height ratio Looks like a Roman shield lying on it’s side Looks like a Roman shield lying on it’s side

Cinder Cone Smaller, steeper Smaller, steeper Easily eroded Easily eroded Loose pyroclastic material Loose pyroclastic material Moderately explosive Moderately explosive In clusters In clusters Paricutin, Mexico Paricutin, Mexico

Cinder Cone Short-lived volcano that shoots “jets” of lava into air Short-lived volcano that shoots “jets” of lava into air Particles cool in mid-air and are deposited on flank of volcano Particles cool in mid-air and are deposited on flank of volcano Commonly associated with larger volcanic structures Commonly associated with larger volcanic structures

Cinder Cone

Cinder Cone Volcano

Composite volcano

Composite (stratovolcano) Most common Most common Most explosive Most explosive Alternating ash and lava layers Alternating ash and lava layers Gentle base, Gentle base, steep top Mt. Rainer, WA Mt. Rainer, WA

Composite Volcanoes or Stratovolcanoes Steep slopes, cone shape Steep slopes, cone shape Usually explosive Usually explosive Alternating layers of pyroclastic material, and high-viscosity degassed lava flows Alternating layers of pyroclastic material, and high-viscosity degassed lava flows

Composite Volcanoes Mt. Fuji, Japan Mt. Rainier

Crater ~ funnel shaped pit

Caldera: Large depression from collapsed volcano ex: Crater Lake, OR

What is a Caldera? Massive explosive eruption causes COLLAPSE of volcano into magma chamber Massive explosive eruption causes COLLAPSE of volcano into magma chamber Up to 60 km across Up to 60 km across Cyclical process Cyclical process Large caldera eruption could end human existence!!!

MISC. Three classes: active, dormant, extinct Three classes: active, dormant, extinct Airborn ash can disrupt world climate Airborn ash can disrupt world climate Ash makes fertile farmland Ash makes fertile farmland

Eruption from space