Ch. 4 - Igneous Rocks and Volcanoes (Extras)

- Silica

- Na (Sodium)

- K (Potassium)

Increase

- Fe (Iron)

- Mg (Magnesium)

- Ca (Calcium)

Decrease

Decompression melting

Divergent boundaries

Flux melting

Subduction zones

Heat-Induced Melting

Hotspots, continental crust

Mid-Ocean Ridge

Mafic

Continental Rift

Mafic to Intermediate

Ocean-Ocean Subduction

Mafic to Intermediate

Ocean-Continent Subduction

Intermediate to Felsic

Continental Collision

Felsic

Hotspots

Ocean - Mafic; Continent - felsic to intermediate

Slower Cooling

Larger Crystals

Faster Cooling

Smaller Crystals

Felsic

Quartz

Felsic

Feldspar

Felsic Characteristics

High silica, low Fe/Mg; light-colored

Intermediate

Andesite

Intermediate

Diorite

Intermediate Characteristics

Mixed composition

Mafic

Basalt

Mafic

Gabbro

Mafic Characteristics

Low silica, high Fe/Mg; dark

Ultramafic

Peridotite

Ultramafic Characteristics

Very low silica, very high Fe/Mg

Scoria (Cinder) Cones

Small, steep, short-lived, gas-rich mafic lava

Shield Volcanoes

Broad, low-sloped, mafic lava flows

Stratovolcanoes

Steep, tall, alternating layers, intermediate-felsic

Lava Domes

Small, steep-sided, viscous felsic lava

Calderas

Large depressions formed by collapse after massive eruptions

Flood Basalts

Extensive flat layers from fissure eruptions of low viscosity mafic lava

Scoria Cones

Mafic

Shield Volcanoes

Mafic

Stratovolcanoes

Intermediate to Felsic

Lava Domes

Felsic

Calderas

Intermediate to Felsic

Flood Basalts

Mafic

Lava Flows

Destroys Infrastructure

Ash Fall

Respiratory Hazard, Collapses Buildings

Pyroclastic Flows

Fast-Moving, Deadly

Lahars

Mudflows of Ash & Debris

Landslides

From Slope Collapse

Volcanic Gases

CO2, SO2 - Health Hazards

Tsunamis

From Landslides or Caldera Collapse