With reference to the Tsunami of 2004, consider the following statements: 1. It was caused by an earthquake with an epicenter close to the western boundary of Sumatra. 2. The Burma plate subducted below the Indian plate causing the sea floor movement. 3. The tsunami waves traveled at a constant speed of 900 km/h until they hit the coast. Which of the statements given above is/are correct?

The correct option is (a). Explanation A Tsunami (Japanese for "harbour wave") is a series of large ocean waves caused by the sudden displacement of a large volume of water, typically due to earthquakes, volcanic eruptions, or underwater landslides. The 2004 Indian Ocean Tsunami was triggered by a massive undersea megathrust earthquake. Statement-wise Analysis: - Statement 1 is Correct: The tsunami was triggered by a massive earthquake (magnitude 9.1–9.3) on December 26, 2004. The epicenter was located off the western coast of northern Sumatra, Indonesia. - Statement 2 is Incorrect: The earthquake was caused by plate tectonics involving the Indian Plate and the Burma Plate (a microplate part of the Eurasian Plate). Specifically, the Indian Plate subducted beneath the Burma Plate. The statement incorrectly suggests the reverse (Burma plate subducting below the Indian plate). - Statement 3 is Incorrect: The speed of a tsunami wave is directly related to the depth of the water ($speed = \sqrt{gravity \times depth}$). In the deep ocean, tsunami waves travel at high speeds (up to 700–900 km/h). However, as they approach the coast and the water becomes shallow, friction with the seabed causes the waves to slow down significantly, while their height increases (a process known as shoaling). Therefore, the speed is not constant. Key Takeaway: Tsunami waves behave differently in deep versus shallow water: in deep water, they have high speed and low amplitude (height); in shallow water, speed decreases while amplitude increases drastically. The 2004 event resulted from the subduction of the Indian Plate under the Burma Plate.

NCERT Class 7 Geography — Chapter 1: Water

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With reference to the Tsunami of 2004, consider the following statements:

It was caused by an earthquake with an epicenter close to the western boundary of Sumatra.
The Burma plate subducted below the Indian plate causing the sea floor movement.
The tsunami waves traveled at a constant speed of 900 km/h until they hit the coast.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 only
B2 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

The correct option is (a).

Explanation

A Tsunami (Japanese for "harbour wave") is a series of large ocean waves caused by the sudden displacement of a large volume of water, typically due to earthquakes, volcanic eruptions, or underwater landslides. The 2004 Indian Ocean Tsunami was triggered by a massive undersea megathrust earthquake.

Statement-wise Analysis:

Statement 1 is Correct: The tsunami was triggered by a massive earthquake (magnitude 9.1–9.3) on December 26, 2004. The epicenter was located off the western coast of northern Sumatra, Indonesia.
Statement 2 is Incorrect: The earthquake was caused by plate tectonics involving the Indian Plate and the Burma Plate (a microplate part of the Eurasian Plate). Specifically, the Indian Plate subducted beneath the Burma Plate. The statement incorrectly suggests the reverse (Burma plate subducting below the Indian plate).
Statement 3 is Incorrect: The speed of a tsunami wave is directly related to the depth of the water ($speed = \sqrt{gravity \times depth}$). In the deep ocean, tsunami waves travel at high speeds (up to 700–900 km/h). However, as they approach the coast and the water becomes shallow, friction with the seabed causes the waves to slow down significantly, while their height increases (a process known as shoaling). Therefore, the speed is not constant.

Key Takeaway:
Tsunami waves behave differently in deep versus shallow water: in deep water, they have high speed and low amplitude (height); in shallow water, speed decreases while amplitude increases drastically. The 2004 event resulted from the subduction of the Indian Plate under the Burma Plate.

Your note

More from Chapter 1: Water

The process by which water continually changes its form and circulates between oceans, atmosphere, and land is best described by which of the following terms?

easy

With reference to the distribution of water on Earth, consider the following statements: 1. Groundwater has a larger volume than inland seas and salt lakes. 2. Inland seas and salt lakes contain more water than the atmosphere. 3. The volume of water in the atmosphere is greater than that in rivers. 4. Rivers hold the least volume of water among these four sources. Which of the statements given above are correct?

hard

Consider the following statements regarding the Earth's water: 1. The water cycle ensures that the water existing today is entirely different from the water that existed centuries ago. 2. The major sources of fresh water include rivers, ponds, springs, and glaciers. 3. The amount of water in the atmosphere is higher than that in fresh water lakes. Which of the statements given above is/are correct?

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In the context of water distribution, which of the following accounts for the largest percentage of fresh water on Earth?

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Consider the following statements regarding salinity: 1. Salinity is defined as the amount of salt in grams present in 1000 grams of water. 2. The average salinity of the oceans is generally 45 parts per thousand. 3. Most of the salt in the ocean is sodium chloride. Which of the statements given above is/are correct?

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The correct option is (a).

Explanation

Statement-wise Analysis:

Statement 1 is Correct: The tsunami was triggered by a massive earthquake (magnitude 9.1–9.3) on December 26, 2004. The epicenter was located off the western coast of northern Sumatra, Indonesia.
Statement 2 is Incorrect: The earthquake was caused by plate tectonics involving the Indian Plate and the Burma Plate (a microplate part of the Eurasian Plate). Specifically, the Indian Plate subducted beneath the Burma Plate. The statement incorrectly suggests the reverse (Burma plate subducting below the Indian plate).
Statement 3 is Incorrect: The speed of a tsunami wave is directly related to the depth of the water ($speed = \sqrt{gravity \times depth}$). In the deep ocean, tsunami waves travel at high speeds (up to 700–900 km/h). However, as they approach the coast and the water becomes shallow, friction with the seabed causes the waves to slow down significantly, while their height increases (a process known as shoaling). Therefore, the speed is not constant.