🌍 What Causes Earthquakes?
Earthquake causes are mainly linked to the movement of tectonic plates beneath the Earth’s surface. Our planet’s crust is made up of massive slabs of rock called tectonic plates that are constantly moving very slowly. When these plates grind against each other, get stuck, and then suddenly jerk free, they release enormous amounts of energy that travel through the Earth as seismic waves.
The point where the earthquake actually starts deep underground is called the focus, while the point directly above it on the Earth’s surface is called the epicentre. Most damage occurs at the epicentre because that’s where the seismic waves reach the surface first.
📏 How We Measure Earthquakes
The Richter Scale
The Richter scale measures the magnitude or energy released by an earthquake. It’s a logarithmic scale, which means that each whole number increase represents about 32 times more energy! So a magnitude 6 earthquake releases 32 times more energy than a magnitude 5 quake.
- 2.0-2.9: Minor – rarely felt
- 3.0-3.9: Often felt, but rarely causes damage
- 4.0-4.9: Light – noticeable shaking of indoor items
- 5.0-5.9: Moderate – can cause damage to poorly constructed buildings
- 6.0-6.9: Strong – can be destructive in populated areas
- 7.0-7.9: Major – serious damage over large areas
- 8.0+: Great – can cause tremendous damage
The Mercalli Scale
While the Richter scale measures energy released, the Mercalli scale measures the effects and intensity people experience. It uses Roman numerals from I to XII:
- I: Not felt except by very few under special conditions
- IV: Felt indoors by many, vibration like passing truck
- VII: Difficult to stand, damage to weak buildings
- X: Most masonry structures destroyed, ground cracked
- XII: Total destruction, objects thrown into air
💥 Primary Effects of Earthquakes
Primary effects are the immediate damage caused by the ground shaking. These include:
- Collapsed buildings and infrastructure
- Roads and bridges cracking or breaking
- Underground pipes and cables snapping
- People being injured or killed by falling debris
- Landslides and ground ruptures
🌊 Secondary Effects of Earthquakes
Secondary effects happen after the main quake and can sometimes be more destructive than the initial shaking:
- Tsunamis: Huge waves caused by undersea earthquakes
- Fires: From broken gas pipes and electrical lines
- Disease outbreaks: From contaminated water and poor sanitation
- Aftershocks: Smaller earthquakes that follow the main quake
- Economic impacts: Businesses closing, job losses, rebuilding costs
- Psychological trauma: People experiencing fear and anxiety
Understanding these earthquake causes and effects helps geographers and emergency planners prepare better for these natural disasters and protect communities more effectively.
📝 Earthquake 1-Mark Questions for Quick Assessment
Understanding Earthquakes: Key Assessment Questions
Here are 10 examination-style 1-mark questions about earthquakes to test your knowledge of earthquake causes, measurement scales, and effects. These questions cover essential earthquake geography topics from the UK curriculum.
Quick Assessment Questions
- What is the point on the Earth’s surface directly above where an earthquake starts? (Answer: Epicentre)
- Which scale measures earthquake intensity based on observed effects? (Answer: Mercalli)
- What is the sudden release of energy in the Earth’s crust called? (Answer: Earthquake)
- Which scale measures the magnitude of earthquakes using seismic waves? (Answer: Richter)
- What type of plate boundary often causes earthquakes? (Answer: Transform)
- What are cracks in the Earth’s crust where earthquakes occur called? (Answer: Faults)
- Which effect includes collapsed buildings and cracked roads? (Answer: Primary)
- What secondary effect can be triggered by earthquakes under the ocean? (Answer: Tsunami)
- What instrument is used to detect and record earthquakes? (Answer: Seismograph)
- What is the point within the Earth where an earthquake originates? (Answer: Focus)
These questions test your understanding of earthquake measurement, primary and secondary effects, and help you prepare for geography assessments on natural hazards and tectonic processes.
🧠 Earthquake 2-Mark Questions for Detailed Knowledge
Understanding Earthquake Causes and Measurement
What causes earthquakes to occur?
Earthquakes are caused by the sudden release of built-up pressure along fault lines in the Earth’s crust.
Describe how tectonic plates move to create earthquakes.
Earthquakes occur when tectonic plates slide past each other, collide, or move apart at plate boundaries.
What is the focus of an earthquake?
The focus is the point within the Earth where the earthquake rupture begins and seismic energy is released.
Explain what the epicentre of an earthquake is.
The epicentre is the point on the Earth’s surface directly above the focus where the earthquake is most strongly felt.
Earthquake Measurement Scales
What does the Richter scale measure?
The Richter scale measures the magnitude or energy released by an earthquake using seismic wave data.
How does the Mercalli scale differ from the Richter scale?
The Mercalli scale measures the intensity of shaking and damage caused by an earthquake rather than its energy release.
What type of measurement does the Mercalli scale provide?
The Mercalli scale provides a subjective measurement based on observed effects and damage to structures.
Primary and Secondary Effects
Name one primary effect of earthquakes.
Primary effects include ground shaking and surface rupture that occur immediately during the earthquake.
What are secondary effects of earthquakes?
Secondary effects are indirect consequences such as tsunamis, landslides, and fires that occur after the main quake.
Give an example of how earthquakes can trigger other natural hazards.
Earthquakes can trigger tsunamis when the sea floor is displaced, creating massive ocean waves.
📚 Earthquake 4-Mark Questions for In-depth Understanding
Understanding Earthquake Causes and Measurement
1. Explain the main causes of earthquakes and how tectonic plate movement creates seismic activity.
This question requires you to discuss earthquake causes and the relationship between tectonic plates and seismic events in your six-sentence answer.
2. Compare the Richter scale and Mercalli scale for measuring earthquake intensity, explaining their different approaches.
Your answer should contrast these measurement scales and describe how each assesses earthquake strength differently.
3. Describe the primary effects of earthquakes and provide examples of immediate damage caused by seismic events.
Focus on direct earthquake effects in your response, giving specific examples of primary impacts.
4. Explain secondary effects of earthquakes and how they develop after the initial seismic shock.
Discuss the chain of events that follow earthquakes and how secondary impacts emerge over time.
Earthquake Measurement and Impact Analysis
5. How does the focus and epicentre location affect the distribution of earthquake damage?
Your answer should explain the relationship between seismic focus depth and surface impact distribution.
6. Describe how building design and construction can influence the severity of earthquake damage in urban areas.
Discuss engineering solutions and how structural design affects vulnerability to seismic activity.
7. Explain why some regions experience more frequent earthquakes than others, referring to global tectonic patterns.
Connect geographical location to tectonic plate boundaries and seismic frequency in your response.
8. Compare the immediate and long-term responses to earthquake disasters, including both emergency and reconstruction phases.
Your answer should differentiate between short-term relief efforts and long-term recovery strategies.
Comprehensive Earthquake Understanding
9. How do scientists use seismic waves to study Earth’s interior structure and composition?
Explain the relationship between earthquake waves and our understanding of planetary geology.
10. Discuss the economic and social impacts of major earthquakes on affected communities, considering both developed and developing regions.
Your response should analyse how earthquake effects vary between different economic contexts and social structures.
🔍 Earthquake 6-Mark Questions for Comprehensive Knowledge
Understanding Earthquake Causes and Measurement
1. Explain how tectonic plate movement causes earthquakes and describe the different types of plate boundaries involved.
This question requires you to discuss the relationship between plate tectonics and seismic activity, covering convergent, divergent, and transform boundaries while explaining the build-up and release of seismic energy.
2. Compare and contrast the Richter scale and Mercalli scale for measuring earthquake intensity.
You should explain both measurement systems, their different approaches to quantifying earthquakes, and the advantages and limitations of each scale for assessing seismic events.
Primary Effects of Earthquakes
3. Describe the primary effects of a major earthquake on the built environment and infrastructure.
Focus on immediate physical damage including building collapse, road destruction, bridge failures, and utility disruptions that occur directly from the seismic shaking.
4. Explain how earthquake magnitude and depth affect the severity of primary impacts on human settlements.
Discuss the relationship between Richter scale measurements, hypocentre depth, and the resulting damage patterns to structures and infrastructure systems.
Secondary Effects and Consequences
5. Analyse the secondary effects that can follow a major earthquake, including tsunamis and landslides.
Examine the chain of events triggered by seismic activity, such as tsunami formation, landslide activation, soil liquefaction, and subsequent environmental hazards.
6. Discuss how earthquakes can lead to long-term economic and social impacts on affected communities.
Consider business disruption, reconstruction costs, population displacement, and psychological trauma that extend beyond the immediate physical damage.
Earthquake Measurement Techniques
7. Evaluate the usefulness of different earthquake measurement scales for emergency response planning.
Assess how Richter scale magnitudes and Mercalli intensity ratings help authorities prepare for and respond to seismic events effectively.
8. Explain how modern technology has improved our ability to monitor and predict earthquake activity.
Describe seismic monitoring networks, GPS technology, and early warning systems that enhance our understanding of earthquake patterns and risks.
Case Study Application
9. Using a specific example, analyse the causes and effects of a significant earthquake event.
Select a well-documented earthquake case study to demonstrate your understanding of tectonic processes, measurement scales, and both immediate and long-term consequences.
10. Assess the factors that influence why some earthquakes cause more damage than others of similar magnitude.
Consider location, population density, building standards, preparedness levels, and geological conditions that affect the impact of seismic events on human communities.
These earthquake 6-mark questions cover essential aspects of seismic studies including tectonic causes, measurement systems using both Richter and Mercalli scales, and comprehensive analysis of primary and secondary effects. Each question requires detailed ten-sentence responses that demonstrate thorough understanding of earthquake processes and their impacts on human and physical environments.
