Unit 12: The Water Cycle and Groundwater
Water's endless loop between ocean, air, and land, and the hidden reservoir moving slowly underground beneath your feet.
4 topics · 12 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
The Water Cycle
- How it worksHow do evaporation, condensation, precipitation, and runoff move water in an endless loop between ocean, air, and land?
- How it worksWalk me through a single water molecule's path from the ocean surface to a cloud to a river and back to the sea.
- Common mistakeWhy doesn't the water cycle create or destroy any water, only move it between reservoirs?
Your turn1 of 2
Water molecules cycle endlessly between ocean, atmosphere, and land through evaporation, condensation, and precipitation. Why does the same water that fell as rain millions of years ago still exist somewhere on Earth today?Groundwater and the Water Table
- How it worksHow does rainwater soak down through soil and rock until it reaches the saturated zone below the water table?
- How it worksWalk me through the water table rising after heavy rain and falling again during a drought.
- Common mistakeWhy isn't groundwater sitting in underground rivers or open caverns almost everywhere it's found?
Your turn1 of 2
During a rainy season, the water table rises by about 8 centimeters per week. After 8 weeks of steady rain, about how many centimeters has the water table risen in total?Aquifers and Wells
- How it worksHow does a permeable, water-saturated layer of rock or sediment act as an aquifer a well can tap into?
- Worked exampleFind how many years a 1000 cubic meter aquifer lasts if it's pumped at 50 cubic meters a year with no recharge.
- Ties togetherHow does an aquifer's recharge rate from rainfall determine whether pumping it is sustainable long term?
Your turn1 of 2
An aquifer holds 3634 cubic meters of water and is pumped at a rate of 137 cubic meters per year with no recharge. About how many years will the aquifer last before it's depleted?How Caves and Sinkholes Form
- How it worksHow does acidic groundwater slowly dissolve limestone underground to hollow out a cave over thousands of years?
- How it worksWalk me through a cave's roof finally collapsing once dissolution has thinned it too much to support the ground above.
- Ties togetherHow does the same limestone dissolution process explain both cave formation and sinkhole collapse?
Your turn1 of 2
A sinkhole opens up suddenly on a quiet residential street with no visible cracks or warning signs in the days before it collapsed. Why can the ground suddenly collapse into a sinkhole with no warning at the surface beforehand?