The World's Foundations; or, Geology for Beginners · Ch. XXIV · Unit 4: Part III: Water at work today
27. Waters: rain, springs and the sea
Goal: Your child can explain what a spring and an artesian well are, and describe how waves wear away cliffs, using the book's English examples.
You'll need
- The book, open to this chapter
- A funnel and a length of clear plastic tubing (or a garden hose)
- A pitcher of water
- The sand tray from last lesson
- A ruler
- A notebook for a "rock journal" and a pencil
What's in the book
Chapter XXIV describes heavy tropical rains, underground streams and springs, and artesian wells, where water trapped between layers rises up a bored pipe. Then it shows the sea wearing away coasts: the Shetland arches, stones flung at the Bell-Rock Lighthouse, Yorkshire and Norfolk villages lost to the waves, an inn at Sherringham, and the shrinking chalk cliffs of Sussex.
The lesson, step by step
A question to start
SayWhere does rain go after it soaks into the ground?
Hear the guess, then read.
Read the chapter together
Read Chapter XXIV (pages 228 to 235). Two definitions:
When such a stream breaks out of the side of a hill, we call it a ' spring.'
Wells formed thus are called 'Artesian,' because the plan was first tried in Artois.
Model an artesian well
Push the funnel into one end of the tubing. Outdoors, hold the funnel up high (the hills where rain soaks in) and let the other end hang lower (the bored well). Pour water into the funnel. Water rushes out of the low end, and if you point it up it spurts.
Then raise the open end above the funnel. Nothing comes out. That is the book's point: the water must come from higher ground.
Waves against cliffs
Build a steep "cliff" of damp sand at one end of the tray and pour water into the other end. Make waves by pushing a ruler back and forth in the water. Watch the cliff foot wear away until the top collapses.
Lost towns
Read about the villages that disappeared: Auburn, Hartburn and Hyde in Yorkshire; Shipden, Wimpwell and Eccles in Norfolk. The author's footnote says she saw Eccles church tower standing on the beach. Find Norfolk and Yorkshire on a map.
Check the author's numbers
Read the story of the inn at Sherringham:
In 1805, full fifty yards lay clear between the house and the sea.
The book says that in 1829, "only fourteen years later", seventeen yards had gone. Ask: How many years is it from 1805 to 1829? (24.) The book seems to have slipped. Then read her point:
An instance this of how easily mistakes may be made in any such attempted calculations.
Tell it back
Ask your child to explain why an artesian well flows by itself, and why a well bored on top of a hill would not.
What we know now
The Yorkshire coast where those villages stood is still one of the fastest-wearing coasts in Europe, losing on average about six feet a year. Artesian wells are still used around the world.
Afterwards
Notice it this week: look for a spring, a drinking fountain, or water coming out of a hillside or drain pipe after rain. Where did that water start?
Answers to the book's problems
The water in an artesian well came from higher ground and is trapped between watertight layers, so the weight of the water behind pushes it up the pipe. On a hilltop there is no higher water behind to push it up. Arithmetic: 1829 minus 1805 is 24 years, not fourteen.
Worked out for this site from the scan. If a number in your copy differs, trust the book.