GEO 101 Exam 3 Christina Robins

What is the main cause of an earthquake?

Sudden release of energy due to movement along faults.

What is the hypocenter (focus) of an earthquake?

The point within the Earth where the earthquake originates.

What is the epicenter of an earthquake?

The point on Earth's surface directly above the hypocenter.

What is the difference between the hanging wall and foot wall?

The hanging wall lies above the fault plane; the foot wall lies below.

What is a fault plane?

The surface along which the rock breaks and moves during an earthquake.

What is a seismometer or seismograph?

An instrument that records seismic waves.

What is a seismogram?

The visual record of seismic waves produced by a seismograph.

How are seismograms used to determine earthquake distance and strength?

By analyzing wave arrival times and amplitudes.

How do wave distances change with distance from recording stations?

The time between P and S wave arrivals increases with distance.

What are P waves?

Primary waves that travel fastest and move through solids and liquids.

What are S waves?

Secondary waves that travel slower and only move through solids.

What are surface waves?

Slowest waves that cause the most damage and travel along Earth's surface.

What types of earthquakes occur at different plate boundaries?

Convergent: large quakes; Divergent: shallow quakes; Transform: strike-slip quakes.

What are intraplate earthquakes?

Earthquakes that occur away from plate boundaries.

What is the New Madrid fault zone?

A seismic zone in the central U.S. known for intraplate earthquakes.

What hazards result from earthquakes?

Ground shaking, landslides, tsunamis, liquefaction, structural damage.

What is a tsunami and how does it form?

A large sea wave caused by underwater earthquakes or landslides.

How can we reduce earthquake damage?

Building codes, retrofitting structures, emergency planning, land-use regulations.

What is liquefaction?

When saturated soil loses strength due to shaking and behaves like a liquid.

What is an orogeny?

A mountain-building event caused by tectonic forces.

What is deformation?

Changes in rock shape due to stress.

What influences deformation?

Temperature, pressure, rock type, and rate of stress.

What is the difference between brittle and ductile deformation?

Brittle breaks; ductile bends.

How are joints different from faults?

Joints are fractures without movement; faults involve displacement.

What are the types of faults and their stress regimes?

Normal (tension), Reverse/Thrust (compression), Strike-slip (shear).

How can faults be recognized at the surface?

Offset features, scarps, linear valleys, and fault breccia.

What are the parts of a fold?

Limbs, axis, and axial plane.

What is the difference between an anticline and a syncline?

Anticline: arch-shaped, oldest rocks in center; Syncline: trough-shaped, youngest in center.

How do you recognize folds at the surface or in cross-section?

Look for patterns in rock layers and orientation.

What is strike and dip?

Strike: compass direction of a rock layer; Dip: angle of tilt from horizontal.

Why is strike and dip useful to geologists?

It helps map and interpret rock structures.

What happens during subduction, continental collision, and rifting?

Subduction: volcanic arcs; Collision: mountain ranges; Rifting: fault-block mountains.

What is a craton?

Stable, ancient part of continental crust; found in central North America.

What are the two types of dating?

Relative and absolute dating.

What are the principles of relative age dating?

Superposition, original horizontality, cross-cutting relationships, inclusions.

What is an unconformity?

A gap in the geological record due to erosion or non-deposition.

What is an index fossil?

A fossil used to define and identify geological periods.

What is the stratigraphic column and correlation?

A chart of rock layers used to compare sequences across regions.

What did Clair Patterson discover about lead?

Widespread environmental contamination from leaded gasoline.

What is the geological time scale?

A timeline of Earth's history divided into eons, eras, periods, and epochs.

What Eon and Era are we living in?

Phanerozoic Eon, Cenozoic Era.

What is an isotope?

Atoms of the same element with different numbers of neutrons.

What are parent and daughter isotopes?

Parent: original isotope; Daughter: product after decay.

What is radioactive decay?

The process by which unstable isotopes break down over time.

What is a half-life?

Time it takes for half of a radioactive isotope to decay.

How are half-lives used to date rocks?

By measuring the ratio of parent to daughter isotopes.

What is a fossil?

Preserved remains or traces of ancient life.

How does a fossil form?

Burial in sediment, mineralization, and preservation.

What conditions favor fossil formation?

Rapid burial, low oxygen, fine-grained sediment.

What types of rocks are fossils found in?

Sedimentary rocks.

What is a body fossil?

Physical remains like bones or shells.

What is a trace fossil?

Evidence of activity like footprints or burrows.

What is a mass extinction?

A rapid, widespread loss of species.

How many mass extinctions have occurred?

Five major ones.

What is the significance of the Moon's formation?

It shaped Earth's early evolution and tides.

Where did Earth's oceans and atmosphere come from?

Volcanic outgassing and comet impacts.

Where did life most likely first form?

In hydrothermal vents or shallow seas.

What is the role of photosynthesis in Earth's history?

It added oxygen to the atmosphere and formed Banded Iron Formations.

What was Snowball Earth?

A period when Earth was nearly entirely frozen.

What was the Cambrian Explosion?

A rapid diversification of life forms.

What was Pangea?

A supercontinent that existed during the late Paleozoic and early Mesozoic.

What time period are we living in now?

The Quaternary Period of the Cenozoic Era.