The Water Cycle
Lesson notes
Overview
Water evaporates, condenses into clouds and returns as precipitation. This topic is rated beginner and is number 16 of 98 in Earth & Space. Core ideas and first intuitions. No prior knowledge needed.
What you are seeing
The panel above shows the steps of a process, laid out in order. Click a step to see what happens next. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.
In depth
Water moves continuously between oceans, atmosphere and land. The Sun’s heat evaporates water from oceans, lakes and plants, which condenses into clouds as the vapour rises and cools, and falls as rain or snow. It then runs off in rivers, soaks into the ground as groundwater, or is stored in ice, before returning to the sea. About 97% of Earth’s water is salty, and only about 1% is easily accessible fresh water.
Reading the relationship
The expression "evaporation → condensation → precipitation" is a compact summary of the idea. It uses the symbols e, v, a, p, o, r; name what each one stands for before you start. Then use the sliders to see how changing one quantity changes the others.
A guided exploration
1. Run the animation once with the default settings and describe in words what happens. 2. Change one slider at a time and note which quantity responds most. 3. Push each slider to its extreme and decide whether the result still makes sense.
Try this
Start by only moving one slider at a time. Say aloud what you expect, then check.
Common pitfalls
Earth and space systems work on very different scales of time and distance. Check which scale a number refers to before comparing it with another.
How it connects
It builds on “Layers of the Atmosphere”, the topic before it in Earth & Space. Once you are comfortable, continue with “The Greenhouse Effect”.
Why it matters
Earth and space science helps us understand our planet, its climate and the wider universe.
Where you might use it
- Revising “The Water Cycle” before a class, exam or certification
- Forecasting weather and understanding climate records and their uncertainty
- Planning for earthquakes, floods and other natural hazards in cities
- Interpreting satellite images, space missions and the age of rocks and stars
Frequently asked questions
What is The Water Cycle?
Water evaporates, condenses into clouds and returns as precipitation. It is a beginner topic in Earth & Space.
How do I use the The Water Cycle simulation?
The panel at the top shows the steps of a process, laid out in order. Click a step to see what happens next. Move the sliders one at a time, then press Space to pause the animation and look closer.
What does the formula mean?
The expression evaporation → condensation → precipitation packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.
Who is this topic for?
Core ideas and first intuitions. No prior knowledge needed. If the quiz feels hard, reread the lesson notes and try the previous topic first.
What should I learn before this?
Start with “Layers of the Atmosphere”, the previous topic in Earth & Space. Each topic in a subject builds on the ones before it.
How do I track my progress?
Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.
Quick quiz
More in Earth & Space
See all →The Greenhouse Effect
Gases such as CO₂ absorb outgoing infrared radiation and warm the surface.
Enhanced Greenhouse Warming
More greenhouse gases trap more heat and raise the equilibrium temperature.
The Coriolis Effect
On a rotating planet, moving air and water curve — right in the north, left in the south.