GeographyICSE Class 9 · Hydrosphere

Tides: Formation, Spring Tides and Neap Tides (ICSE Class 9 Geography)

Updated 17 October 2026 · Draft, not yet fact-checked

Tides are the regular rise and fall of the sea level caused mainly by the moon's gravitational pull, with a smaller effect of the sun. Spring tides (highest highs, lowest lows) occur at new moon and full moon when the sun, moon and earth are in line; neap tides (smallest range) occur at the first and last quarter when the sun and moon are at right angles.

When sun and moon pull along one line (new or full moon) the tidal range is greatest; at right angles (quarter moon) it is smallest.

Illustration drawn for QuestionBuddy.

Understand Tides: Formation, Spring Tides and Neap Tides

1. Meaning. A tide is the periodic rise (*high tide* or flood) and fall (*low tide* or ebb) of the sea. Most places have two high tides and two low tides in about 24 hours 50 minutes.

2. Formation. The moon's gravity pulls the water on the side of the earth facing it, forming a high tide there. On the opposite side, the pull is weakest, and the earth is pulled towards the moon more than the water, plus the effect of the earth-moon system's rotation, so a second bulge forms. Places at right angles have low tides. As the earth rotates, a place passes through both bulges each day. The moon takes about 50 minutes more than the day to return, so tides are about 50 minutes later each day.

3. The sun's role. The sun is far larger but much farther, so its tide-raising force is less than half the moon's.

4. Spring tides. At *new moon* and *full moon* the sun, moon and earth lie in a line; their pulls add and give very high high tides and very low low tides: the greatest tidal range.

5. Neap tides. At the *first and last quarter* the moon and sun are at right angles; the sun's pull partly cancels the moon's and the tidal range is least. Each occurs twice a month.

6. Importance. Tides help ships enter and leave ports, keep estuaries clear, move fish and nutrients, produce tidal energy and help fishermen.

Tides: Formation, Spring Tides and Neap Tides: key facts

Tides: High tide: rise
Low tide: fall
Two of each in about 24 h 50 min
Spring tide: New moon and full moon
Sun, moon, earth in line
Greatest range
Neap tide: First and last quarter
Sun and moon at right angles
Least range
Cause: Gravity of moon (main) | Gravity of sun (smaller)

Tides: Formation, Spring Tides and Neap Tides in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Beach picnic

Suppose a family plans a picnic on a flat beach and the tide table shows a high tide at 6 am and a low tide at about 12 noon.

Estimate the next high tide.

Try it first, then show the solutionSolution

High to low takes about 6 hours.
Next high tide is about 12 hours 25 minutes after the first: about 6:25 pm.

Answer: About 6:25 pm.

Memory hook: 12 h 25 min cycle.

Tricks to remember Tides: Formation, Spring Tides and Neap Tides

Short memory aids. Say each one aloud once, then use it on a question the same day.

Spring = Spring up
Spring tides spring up highest at new and full moon.
Use it when: Spring tides.
Neap = Nearly nothing
Neap tides have the least range.
Use it when: Neap tides.

Tides: Formation, Spring Tides and Neap Tides: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Define · 2 marks · Short answerBoard level

Define tide and state two causes. [2]

Try it first, then show the solutionSolution

Tide is the regular rise and fall of sea level.
Caused by gravitational pull of the moon and the sun.

Answer: Periodic sea level change due to the pull of the moon and sun.

Example 2: Spring tide · 3 marks · Short answerHarder board level

Why does a spring tide have a higher range than normal? [3]

Try it first, then show the solutionSolution

At new and full moon the sun, moon and earth are in line.
Their pulls combine.
High tides are higher and low tides lower.

Answer: The pulls of the sun and moon add together.

Example 3: Daily delay · 3 marks · Short answerHarder board level

A high tide occurs at 2:00 am today. Estimate the time of the next two high tides, taking a delay of about 12 hours 25 minutes. [3]

Try it first, then show the solutionSolution

Next = 2:00 am + 12 h 25 min = 2:25 pm.
The following = 2:25 pm + 12 h 25 min = 2:50 am the next day.

Answer: 2:25 pm today and about 2:50 am the next day.

Example 4: Neap tides · 4 marks · Long answerHarder board level

Describe the position of the sun, moon and earth during neap tides and explain why the range is small. [4]

Try it first, then show the solutionSolution

The sun and moon are at right angles to the earth.
Occurs at first and last quarter.
Sun pulls water in a different direction from the moon.
Their pulls partly cancel, giving small ranges.

Answer: Right angles; pulls cancel; small range.

Example 5: Case: port timings · 6 marks · Case-basedHOTS / competency

Case. A port with shallow water allows large ships only at high tide. (i) Why do ships wait? [1] (ii) When is the depth greatest in a month? [1] (iii) Why might a captain prefer spring tides? [2] (iv) How can tides help generate power? [2]

Try it first, then show the solutionSolution

(i) The water is too shallow at low tide.
(ii) At spring tides (new and full moon).
(iii) Higher high tides give deeper water.
(iv) Flowing water turns turbines.

Answer: (i) Shallow at low tide (ii) Spring tides (iii) More depth (iv) Tidal turbines.

Where students lose marks in Tides: Formation, Spring Tides and Neap Tides

The slips examiners see most often, and what to write instead.

Mistake: Writing that tides are due to the sun alone
Moon forgotten.
Do this: Moon is the main cause.
Usually costs: 1 mark.
Mistake: Mixing spring and neap
Names swapped.
Do this: Spring: highest range.
Usually costs: 1 mark.
Mistake: Only one high tide a day
Opposite bulge ignored.
Do this: Two high tides.
Usually costs: 1 mark.

Exam tips

Draw the earth-moon-sun positions for both tides.
Use words such as in line and right angles.
Give the 50 minute delay.
Link tides to ports.

Practice questions on Tides: Formation, Spring Tides and Neap Tides

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Spring tides occur at:
(a) first quarter
(b) new moon
(c) last quarter
(d) eclipse only
Hint
In line.
Answer
(b) new moon (and full moon).
Q2 · 1 mark · Very short answerBoard level
Name the main cause of tides. [1]
Hint
Moon.
Answer
The gravitational pull of the moon.
Q3 · 1 mark · Very short answerBoard level
What is a tidal range? [1]
Hint
Difference.
Answer
The difference between high and low water levels.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): The sun has a smaller effect on tides than the moon.
Reason (R): The sun is far farther from the earth.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
Distance.
Answer
(a).
Q5 · 3 marks · Short answerHarder board level
Why are there two high tides in a day and not one? [3]
Hint
Two bulges.
Answer
Bulges form on the side facing the moon and on the opposite side, so a place meets both as the earth rotates.
Q6 · 2 marks · Very short answerBoard level
State two uses of tides for people. [2]
Hint
Ports.
Answer
Tides help ships to enter ports and can be used to produce power.
Q7 · 3 marks · Short answerHarder board level
A high tide is at 5:00 am on Monday. Why is the next day's morning high tide not at 5:00 am and about when is it? [3]
Hint
Orbit.
Answer
The moon moves along its orbit in the same direction as the earth rotates, so the earth needs about 50 minutes more to face it again; the next high tide is near 5:50 am.
Q8 · 3 marks · Short answerHarder board level
Compare spring and neap tides on date, position and range. [3]
Hint
Table.
Answer
Spring: new and full moon, in line, large range; neap: quarter moons, right angles, small range.
Q9 · 4 marks · Case-basedHOTS / competency
Case. A fisherman notes that the water rises higher than usual on a full moon night. (i) Name the tide. [1] (ii) Give the reason. [2] (iii) Which tide is expected a week later? [1]
Hint
Cycle.
Answer
(i) Spring tide. (ii) Sun, moon and earth are in line. (iii) Neap tide.
Q10 · 3 marks · Long answerHOTS / competency
Case. A coastal town builds a barrage across an estuary. Suggest two benefits of using tides for power and one environmental concern. [3]
Hint
Renewable.
Answer
Tides are predictable and renewable and give no air pollution; a barrage may harm estuary ecosystems.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Main cause of tides?Show answer
Moon.
2.Spring tides at?Show answer
New and full moon.
3.Neap tides at?Show answer
First and last quarter.
4.High tides per day?Show answer
Two.
5.Delay each day?Show answer
About 50 minutes.

Tides: Formation, Spring Tides and Neap Tides: frequently asked questions

Do lakes have tides?

Very small ones.

Why not call it spring season?

Spring here means leaps up.

Are tides predictable?

Yes.