What happens to a Tsunami wave as it moves from deep water towards the coast? 1. The wave length decreases. 2. The travel speed increases significantly. 3. The height of the wave increases. Select the correct answer using the code given below:

Correct Option The correct option is (c) 1 and 3 only. Explanation Tsunamis behave as shallow-water waves because their wavelength is extremely long compared to the ocean depth. Their physical characteristics change drastically as they transition from the deep ocean to shallow coastal waters through a process known as shoaling. Statement-wise Analysis: - Statement 1 is Correct: In deep water, tsunamis have very long wavelengths (often exceeding 100 km). As the wave approaches the coast, the shallow depth causes the leading edge of the wave to slow down while the trailing part continues at a higher speed. This causes the wave to compress or "bunch up," resulting in a significant decrease in wavelength. - Statement 2 is Incorrect: The speed of a tsunami is directly related to the depth of the water ($v = \sqrt{g \cdot d}$). In the deep ocean, tsunamis travel at very high speeds (up to 800 km/h). However, as they enter shallow coastal waters, the decrease in depth causes friction with the seabed to increase, leading to a significant reduction in travel speed. - Statement 3 is Correct: As the wave slows down and the wavelength shortens, the energy flux remains conserved. This energy is compressed into a smaller volume of water, forcing the wave amplitude to rise. Consequently, the height of the wave increases dramatically as it reaches the shore. Key Takeaway: As a tsunami moves from deep to shallow water, its speed decreases, its wavelength decreases, and its wave height increases due to the shoaling effect.

NCERT Class 7 Geography — Chapter 1: Water

mcqhard

What happens to a Tsunami wave as it moves from deep water towards the coast?

The wave length decreases.
The travel speed increases significantly.
The height of the wave increases.

Select the correct answer using the code given below:

Official previous-year question

Verified 1 Aug 2026.

Options

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

Did you get this right?

Solution

Correct Option

The correct option is (c) 1 and 3 only.

Explanation

Tsunamis behave as shallow-water waves because their wavelength is extremely long compared to the ocean depth. Their physical characteristics change drastically as they transition from the deep ocean to shallow coastal waters through a process known as shoaling.

Statement-wise Analysis:

Statement 1 is Correct: In deep water, tsunamis have very long wavelengths (often exceeding 100 km). As the wave approaches the coast, the shallow depth causes the leading edge of the wave to slow down while the trailing part continues at a higher speed. This causes the wave to compress or "bunch up," resulting in a significant decrease in wavelength.
Statement 2 is Incorrect: The speed of a tsunami is directly related to the depth of the water ($v = \sqrt{g \cdot d}$). In the deep ocean, tsunamis travel at very high speeds (up to 800 km/h). However, as they enter shallow coastal waters, the decrease in depth causes friction with the seabed to increase, leading to a significant reduction in travel speed.
Statement 3 is Correct: As the wave slows down and the wavelength shortens, the energy flux remains conserved. This energy is compressed into a smaller volume of water, forcing the wave amplitude to rise. Consequently, the height of the wave increases dramatically as it reaches the shore.

Key Takeaway:
As a tsunami moves from deep to shallow water, its speed decreases, its wavelength decreases, and its wave height increases due to the shoaling effect.

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?

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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?

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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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Correct Option

The correct option is (c) 1 and 3 only.

Explanation

Statement-wise Analysis:

Statement 1 is Correct: In deep water, tsunamis have very long wavelengths (often exceeding 100 km). As the wave approaches the coast, the shallow depth causes the leading edge of the wave to slow down while the trailing part continues at a higher speed. This causes the wave to compress or "bunch up," resulting in a significant decrease in wavelength.
Statement 2 is Incorrect: The speed of a tsunami is directly related to the depth of the water ($v = \sqrt{g \cdot d}$). In the deep ocean, tsunamis travel at very high speeds (up to 800 km/h). However, as they enter shallow coastal waters, the decrease in depth causes friction with the seabed to increase, leading to a significant reduction in travel speed.
Statement 3 is Correct: As the wave slows down and the wavelength shortens, the energy flux remains conserved. This energy is compressed into a smaller volume of water, forcing the wave amplitude to rise. Consequently, the height of the wave increases dramatically as it reaches the shore.

Key Takeaway:
As a tsunami moves from deep to shallow water, its speed decreases, its wavelength decreases, and its wave height increases due to the shoaling effect.