With reference to earthquakes, which of the following statements are correct? 1. Earthquakes largely occur along the converging plate boundaries. 2. Point of origin of the earthquake in the lithosphere is known as the focus/Hypocentre. 3. The intensity of the earthquake decreases with distance from the epicentre. 4. The epicentre of the earthquake always remains over continents only.
1, 2 and 3
Understanding Earthquakes: Analyzing Statements
Earthquakes are natural phenomena involving the shaking of the ground caused by sudden shifts in the Earth's crust. Let's examine each statement provided in the context of earthquakes to determine their correctness.
Analysis of Earthquake Statements
Here is a detailed analysis of each statement concerning earthquakes:
- Statement 1: Earthquakes largely occur along the converging plate boundaries.
- The Earth's lithosphere is broken into large plates that are constantly moving.
- Most seismic activity, including earthquakes, happens at the boundaries where these plates interact.
- Converging plate boundaries are where plates collide. This collision creates immense stress and friction, which, when released, causes powerful earthquakes.
- While earthquakes also occur at divergent (moving apart) and transform (sliding past) boundaries, converging boundaries are known for producing the most significant and frequent seismic events.
- This statement is consistent with geological understanding.
This statement is correct.
- Statement 2: Point of origin of the earthquake in the lithosphere is known as the focus/Hypocentre.
- The focus, also known as the hypocentre, is the exact point within the Earth's crust or upper mantle where the earthquake rupture begins.
- Seismic waves radiate outwards from this point.
- The epicentre is the point on the Earth's surface directly above the focus.
This statement accurately defines the focus or hypocentre. This statement is correct.
- Statement 3: The intensity of the earthquake decreases with distance from the epicentre.
- Earthquake intensity refers to the degree of shaking and damage caused by an earthquake at a particular location.
- Seismic waves lose energy as they travel through the Earth.
- The strongest shaking and greatest damage are typically observed at the epicentre, which is the point on the surface closest to the focus.
- As you move further away from the epicentre, the intensity of shaking generally decreases.
This statement accurately describes the relationship between distance from the epicentre and earthquake intensity. This statement is correct.
- Statement 4: The epicentre of the earthquake always remains over continents only.
- The epicentre is the point on the Earth's surface directly above the earthquake's focus.
- Since the Earth's crust extends under both continents and oceans, earthquakes can occur beneath the seafloor as well as under landmasses.
- Many significant earthquakes occur in oceanic regions, particularly along underwater mountain ranges (like the Mid-Atlantic Ridge) or subduction zones where oceanic plates converge (like around the Pacific Ring of Fire).
- Therefore, epicentres can be located anywhere on the Earth's surface, including oceans.
This statement is incorrect because epicentres can be located in oceans as well. This statement is incorrect.
Summary of Statement Correctness
| Statement | Correctness |
|---|---|
| 1. Earthquakes largely occur along the converging plate boundaries. | Correct |
| 2. Point of origin of the earthquake in the lithosphere is known as the focus/Hypocentre. | Correct |
| 3. The intensity of the earthquake decreases with distance from the epicentre. | Correct |
| 4. The epicentre of the earthquake always remains over continents only. | Incorrect |
Based on the analysis, statements 1, 2, and 3 are correct regarding earthquakes.
Conclusion on Earthquake Statements
The correct statements are 1, 2, and 3. Statement 4 is incorrect as epicentres can be located over both continents and oceans.
Revision Table: Key Earthquake Terms
| Term | Definition |
|---|---|
| Earthquake | A sudden shaking of the ground caused by movements within the Earth's crust or volcanic activity. |
| Plate Boundaries | The edges where the Earth's tectonic plates meet and interact (convergent, divergent, transform). |
| Focus (Hypocentre) | The point inside the Earth where the earthquake originates. |
| Epicentre | The point on the Earth's surface directly above the focus. |
| Intensity | A measure of the effects of an earthquake at a specific location on people, buildings, and the environment. Often measured using scales like the Modified Mercalli Intensity Scale. |
Additional Information on Earthquakes and Plate Tectonics
Earthquakes are a direct result of the processes driven by plate tectonics. The lithosphere, composed of the crust and upper mantle, is divided into several large tectonic plates and many smaller ones. These plates float on the semi-fluid asthenosphere below.
- Convergent Boundaries: Where plates collide. This can lead to subduction (one plate sliding under another), forming trenches and volcanic mountain ranges (like the Andes) or volcanic islands (like Japan), and causing deep, powerful earthquakes. If continental plates collide, large mountain ranges are formed (like the Himalayas), also associated with significant earthquakes.
- Divergent Boundaries: Where plates move apart, often forming mid-ocean ridges. Magma rises to fill the gap, creating new crust. Earthquakes here are usually shallower and less powerful than at convergent boundaries.
- Transform Boundaries: Where plates slide past each other horizontally. This movement is often jerky, causing frequent, shallow earthquakes (like along the San Andreas Fault in California).
Understanding plate boundaries helps explain why certain regions are more prone to earthquakes than others. The release of accumulated stress along these boundaries, often built up over decades or centuries, causes the sudden rupture that we experience as an earthquake.
Similar Questions
Directions: The following seven (7) items consist of two statements, Statement I and Statement II. Examine these two statements carefully and select the correct answer using the code given below.
Statement I: By far the most common topographic form in a Karst terrain is the sinkhole.
Statement II: Topographically, a sinkhole is a depression that varies in depth from less than a meter to few hundred meters.
Which one of the following statements with regard to volcanoes is not correct?
Which one of the following is not related to wind erosion?
Which one of the following pairs isnotcorrectly matched?
Geomorphic factors influencing plant and animal distributions are
Which of the following statements regarding continent of Antarctica is/are correct?
1. It has the highest average elevation as compared to all other continents.
2. Mount Vinson is the highest peak of this continent.
Select the correct answer using the code given below.
Stalactites and stalagmites are features of __________.
Match List-I with List-II and select the correct answer using the code given below the Lists :
List-I List-II (Active Volcano) (Location) A. Mount Merapi 1. Hawaii B. Sakurajima 2. Italy C. Mount Vesuvius 3. Japan D. Mauna Loa 4. Indonesia What is the approximate percentage of carbon in the Earth’s crust ?
'Pingos' are associated with which one of the following process?
Important Questions from Geomorphology
Marble is the metamorphosed form of?
Asthenosphere is:
The discontinuity present in earth's interior between lower mantle and outer core is called _________.
Which of the following igneous rocks contain silica in excess of 65%?
Which type of rocks are found in Lafagarh and Podi Uprora ?
