The World's Foundations; or, Geology for Beginners · Ch. XXVII, part 2 · Unit 5: Part III: Fire, coral and caves
31. Volcanoes: Vesuvius and Hawaii
Goal: Your child can compare a volcano that throws out mostly solid material (Vesuvius) with one that pours out runny lava (Hawaii).
You'll need
- The book, open to this chapter
- Honey (or ketchup) and water
- A plate or tray and two spoons
- A globe, atlas or free online map
- A notebook for a "rock journal" and a pencil
What's in the book
The second part of Chapter XXVII (pages 264 to 269) compares Vesuvius, which throws out much solid matter, with the Hawaiian volcanoes, which are full of very liquid lava. It tells of the burial of Herculaneum and Pompeii in the year 79, Monte Nuovo rising in less than a week in 1538, Vesuvius blowing out its crater in 1822, the boiling lava-lake of Kilauea, and a great Hawaiian eruption with earthquakes.
The lesson, step by step
A question to start
SayWhy do some volcanoes explode while others just pour out rivers of lava?
Read together
Read pages 264 to 269, to the end of the chapter. Stop on:
The first known eruption was the famous one of 79, wherein the towns of Herculaneum and Pompeii were buried beneath showers of ashes.
Thick and runny
Put a spoonful of honey at the top of a tilted plate and a spoonful of water beside it. The water races down and spreads far; the honey piles up and creeps.
SayHawaii's lava is runny like the water, so it flows out in long rivers. Vesuvius throws out much solid stuff, cinders, stones and ash, so it builds a steep cone and can explode.
The lava-lake
Read:
You have seen the bubbles which break out upon the surface of water boiling in a pot.
The book says Kilauea's lava-lake was a thousand feet across with fire-fountains thirty or forty feet high. If you are cooking a thick porridge or soup, watch the bubbles burst from a safe distance; this is an adult's job, as hot porridge spits.
Building an island
Read the traveler's words the author quotes:
We see a clothed and finished earth ; they see the building of an island, layer on layer, hill on hill,
Ask: What does she mean, that in Hawaii you can watch new land being made?
Find them
On a map, find Naples, Vesuvius and Pompeii in Italy, and the Hawaiian Islands (the book calls them the Sandwich Islands) in the middle of the Pacific.
Tell it back
Ask your child to compare the two kinds of volcano in a few sentences, using the honey and water.
What we know now
The Hawaiian volcanoes sit over a "hot spot" deep beneath the Pacific plate. As the plate slides slowly northwest, new volcanoes form over the hot spot and older islands are carried away and worn down, which is why the islands form a chain. The book's Mount Loa and Mount Kea are now written Mauna Loa and Mauna Kea. Vesuvius last erupted in 1944.
Afterwards
Notice it this week: look at photos of Pompeii with an adult, and of a Hawaiian lava flow. Which looks like "honey" and which like "water"?
Tip
Watch only, don't try: never heat thick liquids to make them bubble as a "lava" experiment; boiling syrup and porridge cause bad burns. Look up a video of Kilauea's lava lake filmed by scientists instead.
Answers to the book's problems
Vesuvius throws out a great deal of solid material (stones, cinders, ash) and can explode, building a steep cone; Hawaii's volcanoes hold very runny lava that pours out through the crater rim or cracks in the side and flows far over the land.
Worked out for this site from the scan. If a number in your copy differs, trust the book.