Earthquakes and Volcanoes

Earthquakes and Volcanoes

• Earthquakes and volcanic eruptions are caused by geological processes.

Earthquakes

• Earthquakes involve vibrations in the Earth's ground due to tectonic plate movement at fault lines.
• Most earthquakes occur along plate boundaries.
• A fault is a break in the Earth's lithosphere where a rock block moves.
• Strike-slip faults occur at transform plate boundaries.
• Normal faults occur at divergent plate boundaries.
• Reverse faults occur at convergent plate boundaries.
• Seismic waves are energy that travels as vibrations in the Earth.
• The focus is the point inside the Earth where an earthquake originates.
• The epicenter is the location on the Earth's surface directly above the focus.
• Primary waves travel in a push-pull motion, are the fastest seismic waves, and travel through solids and liquids.
• Secondary waves are slower, travel only through solids, and move particles up and down.
• Surface waves move in a round motion, are the slowest, and cause the most damage.
• S-waves cannot travel through liquid, but P-waves can.
• This shows that the Earth's outer core is liquid.
• Seismologists use indicators like past earthquakes, probability, population density, geology around the fault, and building design to assess earthquake risk.
• To find an epicenter, the distance between P-wave and S-wave arrival times is determined.
• Earthquake distance graphs help determine the distance from the epicenter.
• Circles are drawn around seismic stations, and the intersection point indicates the epicenter.
• The Richter scale measures the amount of ground motion.
• The moment magnitude scale measures the total energy released.
• The Modified Mercalli scale measures earthquake intensity based on damage levels, from I to XII.

Volcanoes

• Volcanoes are vents in the Earth's crust through which molten rock flows.
• Volcanoes form at convergent boundaries where one plate subducts, at divergent plate boundaries where plates separate, and at hot spots unrelated to plate boundaries.
• Hot spots often create chains of islands like Hawaii.
• Shield volcanoes are large, shield-shaped with gentle slopes and gentle eruptions.
• Composite volcanoes are large, steep-sided volcanoes resulting from explosive eruptions.
• Cinder cone volcanoes are small, steep-sided volcanoes that erupt gas-rich, basaltic lavas with moderately explosive eruptions.
• A caldera is a large volcanic depression formed when the summit collapses during a violent eruption.
• Quiet eruptions involve lava with high viscosity and gas content.
• Violent eruptions involve lava with low viscosity and gas content.
• Lava flows move slowly, destroy towns, and are rarely deadly.
• Ash fall can cause breathing problems, cool the atmosphere, and disrupt air traffic.
• Mudflows result from snow and ice melting and mixing with mud/ash.
• Pyroclastic flows are deadly and produced from violent eruptions, throwing gas and rock.
• Volcanoes are predicted through ground deformation, increased earthquakes, volcanic gas increase and acidic water nearby.
• Volcanic ash blocks sunlight, causing a decrease in global temperatures and acid rain.

Explore the causes of earthquakes and volcanic eruptions stemming from geological processes. Learn about tectonic plate movement, fault types like strike-slip, normal, and reverse faults, and seismic waves including primary, secondary, and surface waves.