Interactive Explainer
What causes tides?
Tides are long, slow ocean bulges produced mostly by the Moon’s gravity and partly by the Sun’s. Local coastlines, bay shapes, and ocean basins then decide how dramatic that global pull feels where you stand.
The Moon is the main driver of tides, while the Sun strengthens or weakens the effect depending on how the three bodies line up.
Spring tides happen when the Sun and Moon line up and work together, not because of the spring season.
Some bays and coastlines funnel water so efficiently that the local tide range becomes much larger than the open-ocean average.
Try It Yourself
Tide Lab
Line up the Moon and Sun, move the Moon a little closer, or reshape the coastline to see why some tides barely creep while others expose huge mudflats.
What changes the fastest
What is driving the result
The Big Idea
What is actually happening?
An interactive explainer about how the Moon and Sun create tides, why spring and neap tides happen, and why local coastlines can amplify the range.
Gravity pulls unevenly across Earth
The Moon pulls more strongly on the side of Earth closer to it and less strongly on the far side. That difference helps create two broad tidal bulges.
Earth rotates through the bulges
As Earth spins, many coastlines pass through these bulges and the lower-water zones between them. That is why many places see two high tides and two low tides per day.
The Sun can reinforce or weaken the pattern
When the Sun, Earth, and Moon line up, the tide range grows. When the Sun is at a right angle to the Moon, the range shrinks.
Local geography edits the final result
Coasts, shelves, bays, and basin timing can amplify or damp the tide dramatically. The global pull is the start of the story, not the end.
Good Follow-Up Questions
The details are where this gets interesting
The short answer helps, but the edge cases and comparisons are what make the topic memorable.
Spring tides do not mean springtime
The word spring here means “to leap up.” Spring tides can happen in any month whenever the Sun and Moon line up strongly.
Open-ocean tides are often subtle
Far offshore, the tidal bulge may be broad and gentle. The dramatic shoreline effect usually appears when that slow-moving wave meets land and local geometry.
Timing matters as much as force
Some basins slosh back and forth at a natural period that matches the tide, which can make the local range much larger.
Compare Scenes
Why one coastline barely notices while another gets giant tides
The same gravitational forcing can look tame or dramatic depending on the shape of the coast and the timing of the basin.
Fast Answers
Questions people usually ask next
Good science pages should answer the obvious follow-ups without making the reader hunt for them.