CHAPTER 14 Focus Points
14.1 About Volcanoes
Types of volcanoes: There are three main types of volcanoes: stratovolcanoes, shield volcanoes, and cinder cones.
Lava: Lava, the most conspicuous product of volcanic activity, ranges from runny mafic to thick felsic lava.
Pyroclasts: Volcanoes eject materials into the air ranging in size from fine ash to large blocks.
Gases: Gases, particularly carbon dioxide and water vapor, are a significant component of volcanic emissions.
Volcanic landforms: Landforms resulting from volcanism include columnar jointing, flood basalts, and calderas.
14.2 Pele’s Power: Volcanic Hazards
Shield volcanoes: Shield volcanoes have gentle, effusive eruptions.
Stratovolcanoes: Stratovolcanoes erupt both effusively and explosively. Explosive eruptions occur when gas in the magma chamber expands rapidly.
Volcanic geohazards: Lahars and pyroclastic flows are the two greatest threats posed by stratovolcanoes.
Eruption prediction: Scientists can sometimes predict a volcanic eruption by monitoring gas emissions and earthquake activity.
Pacific Ring of Fire: The Pacific Ring of Fire has the greatest number of explosive stratovolcanoes on the planet.
14.3 Tectonic Hazards: Faults and Earthquakes
Fault types: Faults occur as normal faults, reverse faults, and strike-
Fault indicators: Fault scarps indicate normal and reverse faults. Offset features indicate strike-
Earthquakes: Earthquakes are caused when the crust suddenly breaks and releases built-
Seismic belts: Earthquakes occur mainly in seismic belts that coincide with plate boundaries.
14.4 Unstable Crust: Seismic Waves
Intensity and magnitude: Earthquake intensity is determined by the amount of damage done to built structures, and earthquake magnitude is determined by the degree of measured ground shaking.
Earthquake prediction: Scientists cannot predict earthquakes.
Saving lives: Building codes and retrofitting greatly strengthen buildings and save human lives.
14.5 Geographic Perspectives: The World’s Deadliest Volcano
Tambora: The 1815 eruption of Tambora was the strongest and deadliest volcanic eruption in recorded history.