geology exam 3

What’s the difference between reverse and thrust faults?

• Reverse fault: Compressional stress; hanging wall moves up; dip angle > 45°

• Thrust fault: Compressional stress; hanging wall moves up; dip angle < 45°

What’s the difference between strike-slip (left/right lateral) and dip-slip faults?

• Strike-slip: Horizontal motion along the fault plane

• Dip-slip: Vertical motion (up/down) along the fault plane

Explain the difference between right-lateral and left-lateral strike-slip faults.

• Right-lateral: Opposite block moves to your right

• Left-lateral: Opposite block moves to your left

What’s the difference between brittle and ductile behavior in rocks?

• Brittle: Breaks or fractures under stress

• Ductile: Bends or flows without breaking

Types of seismic waves; explain their propagation.

• P waves: Compressional; move through solids & liquids

• S waves: Shear; move only through solids

• Surface waves: Travel along Earth’s surface; cause most damage

Which seismic wave arrives first at a seismic station?

P waves

Which seismic waves propagate through all media?

P waves (solids, liquids, gases)

Which seismic wave causes the most damage to buildings?

Surface waves (especially Rayleigh and Love waves)

Which seismic wave travels fastest?

P waves

What is a seismogram? What is a seismograph?

• Seismogram: The recorded data of ground motion

• Seismograph: The instrument that records seismic waves

What’s the difference between hypocenter and epicenter?

• Hypocenter (focus): Point inside Earth where quake starts

• Epicenter: Point directly above it on Earth’s surface

How is the epicenter of an earthquake determined?

Use data from three seismograph stations to triangulate location

Where do earthquakes occur (tectonic setting)?

Mostly at plate boundaries: convergent, divergent, transform

Where do deep and shallow earthquakes occur?

• Shallow: Divergent & transform boundaries

• Deep: Subduction zones at convergent boundaries

A magnitude 8 earthquake releases how much more energy than a magnitude 4?

32⁴ = 1,048,576 times more energy (each magnitude = 32× increase)

What are the bases for long-term earthquake prediction?

Seismic gaps, historical patterns, strain accumulation

What is a seismic gap?

A segment of a fault that hasn’t ruptured in a long time but is under stress

What causes tsunamis?

Underwater earthquakes, landslides, or volcanic eruptions displacing water

What causes rock deformation?

Stress from tectonic forces

Define strain.

Strain: The change in shape or size of a rock due to stress

Which type of stress causes stretching? Shortening?

• Stretching: Tensional stress

• Shortening: Compressional stress

What’s the difference between a joint and a fault?

• Joint: Crack with no movement

• Fault: Crack with movement

Types of folds (anticline, syncline, dome, basin):

• Anticline: Arch-shaped; oldest rocks in center

• Syncline: Trough-shaped; youngest rocks in center

• Dome: Upward bulge; oldest rocks in center

• Basin: Downward depression; youngest rocks in center

What’s the difference between mass wasting and landslide?

• Mass wasting: General downslope movement of earth materials

• Landslide: Sudden, rapid mass wasting event

Factors affecting mass wasting and landslides:

Slope angle, water content, vegetation, rock type, earthquakes

Factors controlling slope stability:

Slope steepness, water saturation, vegetation, geological structure

How to minimize landslide hazards:

Grading, retaining walls, drainage systems, vegetation

What causes landslide hazards?

Heavy rain, earthquakes, volcanic activity, human construction

Differences between base level and gradient of a stream:

• Base level: Lowest point a stream can erode to

• Gradient: Slope or steepness of stream channel

Differences between drainage networks (dendritic, radial, rectangular, trellis):

• Dendritic: Tree-like; uniform rock

• Radial: Outward from central high point

• Rectangular: Right-angle bends; fractured rock

• Trellis: Parallel streams with perpendicular tributaries; folded terrain

What is an oxbow lake?

A U-shaped lake formed when a meander is cut off from a river