The World's Foundations; or, Geology for Beginners · Ch. XXIX · Unit 5: Part III: Fire, coral and caves
33. Hot springs and geysers
Goal: Your child can describe slow rising and sinking of land (Sweden, Greenland, the Temple of Serapis), and explain what a geyser is.
You'll need
- The book, open to this chapter
- A memory-foam pillow or a thick sponge
- Paper and pencils
- A globe, atlas or free online map
- A clock or timer
- A notebook for a "rock journal" and a pencil
What's in the book
Chapter XXIX shows that land can rise or sink slowly as well as suddenly: Sweden has long been rising and Greenland sinking. The pillars of the Temple of Jupiter Serapis near Naples were bored by sea creatures and then lifted out of the sea. It suggests that sea-water turning to steam near hot rock may cause shocks and hot springs, describes the hot springs of Bath, and the geysers of Iceland and Yellowstone, including Old Faithful.
The lesson, step by step
A question to start
SayCould the land under a whole country be rising, so slowly that you would never feel it?
Read the chapter together
Read Chapter XXIX (pages 281 to 290). Look at the picture of geysers. Stop on the reasoning about Sweden:
If the sea were sinking at all, it must surely sink equally everywhere.
Ask: Why does that prove the land, not the sea, was moving?
Rising land
Press your hand firmly into the memory-foam pillow (or squeeze the sponge flat) and hold it there. Then let go and watch it slowly rise back. Keep that picture in mind for "What we know now" below.
The temple pillars
Draw one of the three pillars, about forty feet tall: at the bottom twelve feet of smooth marble, above it nine feet full of holes bored by sea creatures, and plain marble above that. Ask your child to explain what the band of holes tells us. (The pillars once stood in the sea up to that height, then the ground rose again.)
Geysers
Read:
The Geysers are, in fact, natural hot fountains; playing at intervals, with pauses between.
' Old Faithful ' is yet another, so named because of its curious regularity in action. Once in every sixty-five minutes, as a rule, it flings a jet to the height of a hundred and thirty feet.
Find Iceland and Yellowstone on a map. If you can, watch the Old Faithful webcam with an adult and time an eruption.
Watch only: the stones in the geyser
The book says people threw large stones down a geyser's pipe to make it erupt. Explain that this must never be done: it damages geysers, is against the law in Yellowstone, and the water is scalding. At hot springs, always stay on the boardwalks and paths.
Tell it back
Ask your child to explain one example of land rising slowly and one of land sinking slowly from the chapter, and what a geyser is.
What we know now
Sweden and Finland are rising because the thick ice sheet that pressed them down during the Ice Age melted, and the land is still slowly springing back, like the foam pillow. The Serapis pillars at Pozzuoli rise and sink because of magma and hot water moving under the volcanic ground there. Bath's hot water comes from rain that sinks more than a mile deep, where the earth's natural heat warms it, so no volcano is needed. Old Faithful now erupts on average about every hour and a half.
Afterwards
Notice it this week: feel how warm tap water is at its hottest. The book says Bath's springs are 114 to 120 degrees Fahrenheit, as hot as a very hot bath.
Tip
Never let a child touch water from a natural hot spring without an adult checking it; many are hot enough to scald.
Answers to the book's problems
Sweden: the sea seemed to sink at different rates in different places, which is impossible for the sea, so the land must be rising. Greenland: the coast has been sinking for six hundred years, and old boat-posts now stand under water. A geyser is a natural hot fountain that spouts at intervals, with pauses between.
Worked out for this site from the scan. If a number in your copy differs, trust the book.