Earthquakes, Seismic Waves and Faults

• Earthquakes involve vibrations in the Earth's ground due to plate movement at fault lines.
• Most earthquakes occur along plate boundaries.

Faults

• A fault is a break in Earth's lithosphere where rock blocks move.
• Strike-slip faults occur at transform plate boundaries.
• Normal faults occur at divergent plate boundaries.
• Reverse faults occur at convergent plate boundaries.

Earthquake Terminology

• Seismic waves involve energy that travels as vibrations on and in Earth.
• The focus is a point inside Earth where the earthquake starts.
• The epicenter represents the location on Earth's surface directly above the focus.

Types of Seismic Waves

• Primary waves (p-waves) move in a push motion and are the fastest, traveling through solids and liquids.
• Secondary waves (s-waves) move slower than p-waves, travel only through solids, and involve an up-and-down particle motion.
• Surface waves move in a rolling motion, are the slowest, and cause the most damage.

Earth's Interior

• Scientists discovered that the Earth's outer core is liquid because s-waves cannot travel through it, unlike p-waves.

Triangulation

• To find an epicenter, determine the time difference between p-wave and s-wave arrival, the distance from the epicenter using an earthquake distance graph.
• Draw circles representing the distance around at least three stations; the intersection is the epicenter.

Earthquake Scales

• The Richter Scale measures ground motion at a given distance.
• The Moment Magnitude Scale measures accumulated energy released by an earthquake.
• The Modified Mercalli Scale measures earthquake intensity based on damage levels I-XII.

Earthquake Risk Assessment

• Seismologists use 5 indicators to assess earthquake risk: past earthquakes, probability, population density, geology around a fault, and building design.

Volcanoes

• A volcano is a vent in Earth's crust where molten rock flows.

Volcano Formation

• Volcanoes form at convergent boundaries where one plate subducts.
• They also from at divergent boundaries where plates separate and magma emerges.
• Volcanoes can form at hot spots not associated with plate boundaries, often creating island chains like Hawaii.

Volcano Types

• Shield volcanoes are large & shield-shaped and exhibit gentle slopes and eruptions.
• Composite volcanoes are large & steep, resulting from explosive eruptions.
• Cinder cone volcanoes are small & and steep volcanoes erupting gas-rich, basaltic lavas with moderately explosive eruptions.

Volcano Features

• A caldera is a large volcanic depression that forms when a volcano's summit collapses during a violent eruption.

Types of Volcanic Eruptions

• Violent eruptions involve lava with high viscosity/gas content.
• Quiet eruptions involve lava with low viscosity/gas content.

Effects of volcanic eruptions

• Lava Flows move slowly and destroy towns, but are rarely deadly.
• Ash Flows cause breathing problems, cool Earth's atmosphere, and disrupt air traffic.
• Mudflows are the result of snow and ice melt, causing mud/ash mixes.
• Pyroclastic Flows which are deadly, result from violent eruptions, throwing gas, ash, and rock into the air.

Predicting Volcanoes

• Predicting volcanoes involves monitoring ground deformation, increased earthquakes, volcanic gas increases, and more acidic water.

Climate Impact

• Volcanic ash blocks the sun, decreasing global temperatures and potentially causing acid rain.

Learn about earthquakes, faults, and seismic waves. Explore the different types of faults like strike-slip, normal, and reverse faults. Understand the characteristics of primary, secondary, and surface seismic waves and their impact.