Earth Science Exam: Review Part 1

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Questions and Answers

What is the point within the Earth where an earthquake originates?

Fault line

Hypocenter (correct)

Seismograph

Epicenter

What is the purpose of the epicenter in seismology?

To determine the depth of an earthquake

To map and identify the geographic area affected by the earthquake (correct)

To record seismic waves

To calculate the distance from the seismograph

What is the main difference between the focus and the epicenter?

One is on the surface and the other is subsurface (correct)

One is used to calculate the distance from the seismograph and the other is used to determine the source of the seismic activity

One is used to measure the depth of an earthquake and the other is used to measure the distance

One is used to map the affected area and the other is used to record seismic waves

What is the method used to determine the location of a point by forming triangles to it from known points?

Triangulation Signup and view all the answers

What is the purpose of measuring time differences in triangulation?

To calculate the distance from the seismograph to the epicenter Signup and view all the answers

What type of waves travel faster and arrive first at a seismograph?

Primary waves Signup and view all the answers

What is the term for the location on the ground where the effects of the earthquake are typically the strongest?

Epicenter Signup and view all the answers

What is the purpose of recording seismic waves at different locations?

To pinpoint the epicenter of an earthquake Signup and view all the answers

What happens to the effective stress between soil particles as water pressure rises?

It decreases, leading to a loss of cohesion and friction Signup and view all the answers

What is the method used to determine the epicenter of an earthquake?

Drawing circles on a map around each seismograph station with radii equal to the calculated distances Signup and view all the answers

What is the main consequence of ground instability during earthquakes?

The damage to buildings, roads, and bridges Signup and view all the answers

What type of seismic wave can only move through solids?

S waves Signup and view all the answers

What does the Richter scale measure?

The magnitude of an earthquake Signup and view all the answers

What is the main difference between magnitude and intensity?

Magnitude measures energy release, while intensity measures shaking and damage Signup and view all the answers

What is the primary difference in the formation of intrusive and extrusive igneous rocks?

Location Signup and view all the answers

What is the main difference between P waves and S waves?

P waves cause compression and expansion, while S waves cause shear motion Signup and view all the answers

What is the most common cause of tsunami formation?

Underwater earthquakes Signup and view all the answers

What is the process by which metamorphic rocks are formed?

Metamorphism of pre-existing rocks Signup and view all the answers

What is the characteristic texture of extrusive igneous rocks?

Glassy Signup and view all the answers

What is the primary way that sedimentary rocks are formed?

Deposition of sediments Signup and view all the answers

What is a characteristic of sedimentary rocks?

Layered appearance due to deposition of sediments Signup and view all the answers

What happens to S waves when they encounter the Earth's outer core?

They cannot pass through it and are instead reflected or converted into other types of waves Signup and view all the answers

What is the term for the phenomenon where saturated soil temporarily loses its strength and stiffness in response to an applied stress?

Liquefaction Signup and view all the answers

What is the main cause of landslides during earthquakes?

Liquefaction of soil Signup and view all the answers

What is the fundamental principle used for relative age dating of sedimentary rock layers?

Law of Superposition Signup and view all the answers

What type of seismic wave causes the most damage during an earthquake?

Long waves Signup and view all the answers

What is the purpose of identifying and correlating sedimentary rock layers across different regions?

To reconstruct the geological history of an area Signup and view all the answers

What is the Moment Magnitude Scale (Mw) used to measure?

The total energy released by an earthquake Signup and view all the answers

What is the significance of index fossils in relative age dating?

They help correlate the ages of rocks from different locations Signup and view all the answers

What is the result of liquefaction during earthquakes?

Loss of strength in soil Signup and view all the answers

What is the primary difference between P waves and long waves?

P waves travel through the Earth's interior, while long waves travel along the surface Signup and view all the answers

What is the Modified Mercalli Intensity (MMI) scale used to measure?

The intensity of shaking and damage Signup and view all the answers

What is the significance of geological features like faults and intrusions in relative age dating?

They help establish the relative order of geological events Signup and view all the answers

What is the purpose of drawing circles on a map around each seismograph station?

To determine the epicenter of an earthquake Signup and view all the answers

What is the primary difference between metamorphic and sedimentary rocks?

Formation process Signup and view all the answers

What is the term for the area on the Earth's surface where S waves are not detected directly?

Shadow zone Signup and view all the answers

What is the significance of reconstructing the geological history of an area?

To reconstruct the sequence of geological events Signup and view all the answers

What is the primary way that igneous rocks are classified?

Based on their texture and mineral composition Signup and view all the answers

What is the primary purpose of relative age dating?

To establish a relative chronology of geological events Signup and view all the answers

What is the result of radioactive decay?

The transformation of a parent isotope into a different element or isotope Signup and view all the answers

What type of radioactive decay involves the emission of an alpha particle?

Alpha decay Signup and view all the answers

What is the half-life of a radioactive isotope?

The time it takes for half of the atoms in a sample to decay Signup and view all the answers

What is the purpose of the half-life in radiometric dating?

To determine the age of materials Signup and view all the answers

What is a decay chain?

A series of radioactive decays that result in a stable isotope Signup and view all the answers

Which radioactive isotope has a half-life of about 5,730 years?

Carbon-14 Signup and view all the answers

What is the result of electron capture?

A decrease in the atomic number Signup and view all the answers

Study Notes

Seismology

Focus: The point within the Earth where an earthquake originates, also known as the hypocenter.
Epicenter: The point on the Earth's surface directly above the focus, where the effects of the earthquake are typically strongest.
Comparison: Both terms refer to locations related to the origin of an earthquake, but the focus is a subsurface point and the epicenter is a surface point.

Triangulation in Seismology

Method: Triangulation is used to determine the location of a point by forming triangles to it from known points.
Process:
- Record seismic waves using seismographs at different locations.
- Measure the time difference between the arrivals of P and S waves at each seismograph.
- Calculate the distance from the seismograph to the epicenter using the time difference.
- Draw circles on a map around each seismograph station with radii equal to the calculated distances.
- The point where the circles intersect is the earthquake's epicenter.

Types of Seismic Waves

P Waves (Primary Waves):
- Travel fastest and are the first to be detected by seismographs.
- Move through solids, liquids, and gases.
- Cause particles to compress and expand in the direction of wave propagation (longitudinal motion).
S Waves (Secondary Waves):
- Slower than P waves and arrive after them.
- Can only move through solids.
- Cause particles to move perpendicular to the direction of wave propagation (transverse motion).
Long Waves (Surface Waves):
- Travel along the Earth's surface and are slower than both P and S waves.
- Cause the most damage during an earthquake due to their high amplitude and complex motion.
- Can be further divided into Love waves (horizontal transverse motion) and Rayleigh waves (rolling motion).

Tsunami Formation

Causes:
- Underwater earthquakes
- Volcanic eruptions
- Landslides
- Meteorite impacts
Process: Displaced water forms waves that travel across the ocean at high speeds, increasing in height and causing destruction upon reaching shallow coastal areas.

S Wave Path

Generation: S waves originate at the earthquake focus and travel outward.
Propagation: S waves move through the Earth's crust and mantle in a transverse motion.
Interaction: S waves can only move through solid materials, not liquids or gases, and are reflected or converted into other types of waves when they encounter the Earth's outer core.
Refraction and Reflection: S waves can be refracted or reflected depending on the density and composition of the materials they encounter, creating a shadow zone.

Liquefaction

Definition: Liquefaction is a phenomenon where saturated soil temporarily loses its strength and stiffness in response to an applied stress, such as the shaking from an earthquake.
Process:
- Saturated soil
- Seismic shaking increases water pressure within the soil
- Loss of strength and cohesion between soil particles
- Soil behaves like a liquid
Implications: Ground instability, surface deformation, landslides, and lifeline disruptions.

Magnitude and Intensity

Magnitude: Measures the energy released during an earthquake, quantifying its size and strength.
Measurement: Richter Scale and Moment Magnitude Scale (Mw)
Intensity: Measures the effects of an earthquake at different locations on the Earth's surface, describing the severity of shaking and damage experienced.
Scales: Modified Mercalli Intensity (MMI) scale

Rock Formation

Metamorphic Rocks:
- Formation: Transformation of pre-existing rocks due to high pressure, high temperature, and/or chemically active fluids.
- Characteristics: Foliated or banded texture, or non-foliated if formed under conditions of minimal deformation.
Sedimentary Rocks:
- Formation: Accumulation and lithification of sediments.
- Characteristics: Layered appearance, may contain fossils, can be clastic, chemical, or organic.
Igneous Rocks:
- Formation: Cooling and solidification of molten rock material.
- Characteristics: Classified based on texture and mineral composition, can be intrusive or extrusive.
Comparison: Origin, formation environment, textures, and contrast between processes.

Law of Superposition

Definition: In an undisturbed sequence of sedimentary rocks, the oldest layers are at the bottom, and the layers become progressively younger toward the top.
Application: Relative age dating of rocks, stratigraphic analysis, identifying sequence of events, fossil correlation, and geological features.

Radioactive Decay

Definition: The process by which an unstable atomic nucleus loses energy by emitting radiation.
Types:
- Alpha decay
- Beta decay
- Gamma decay
- Electron capture
Half-life: The time it takes for half of the atoms in a sample to decay.
Decay chains: Series of decays until a stable, non-radioactive isotope is formed.

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Description

Review second semester Earth Science exam questions about focus and epicenter in seismology, including their definitions and differences.