The World's Foundations; or, Geology for Beginners · Ch. XX · Unit 3: Part II: Reptiles, chalk, mammals, ice and people
22. The age of ice
Goal: Your child can describe the great Ice Age as the book tells it, explain river terraces, and describe the frozen mammoth.
You'll need
- The book, open to this chapter
- A bowl of ice water
- A plastic bag and a wool sock or mitten
- Paper and pencils
- A notebook for a "rock journal" and a pencil
What's in the book
Chapter XX describes the Post-Tertiary Age and the great Ice Age, when glaciers seem to have covered Canada, much of the United States, Scotland, Switzerland and parts of France and England. It discusses why elephants and rhinoceroses lived in cold England, the floods and river terraces that followed, and the huge beasts of the time: the mammoth found frozen in Siberia, the woolly rhinoceros, the mastodon and the giant sloth.
The lesson, step by step
A question to start
SayElephants live in hot countries. Why would elephant bones be found in England, Siberia and North America?
Read the chapter together
Read Chapter XX (pages 183 to 194). It begins with a good idea: the nearer the time, the harder it is to tell its story, because there are more details.
If you are looking at some object in the far distance, its outline is simple.
The Ice Age
Help your child sum up: after a long warm time, an age of intense cold came; glaciers covered huge areas; the signs are the till, scratched rocks and erratic blocks from Chapter VIII. The book says no one knew how long ago or why.
The woolly coat test
The book suggests the great beasts had warm coats. Test it: your child puts one bare hand in the ice water for a few seconds and takes it out. Then they put the other hand in the plastic bag, pull the wool sock over it, and dip it in. Which hand stays warm? (Keep both dips short, under 30 seconds.)
Read:
It was covered with thick black bristles, about fourteen inches long, with thick hair four inches long, and with wool about one inch long.
The frozen mammoth
A whole frozen mammoth was found in Siberia — a rare geological specimen !
The book says it was nine feet high and sixteen feet long, without the tusks. Measure nine feet up a wall (or two adults' heights) to see.
River terraces
The highest terrace or shelf is the oldest level, the next lower the next oldest, and so on.
Draw a river valley with three steps on each bank and number them oldest to newest. Ask why the highest step is the oldest. (The river has been cutting down, so it ran highest long ago.)
Tell it back
Ask your child to describe England after the Ice Age as the book does, naming at least five of its animals.
What we know now
There were many cold spells, not one. The last great ice sheets were at their largest about 20,000 years ago, when ice up to two miles thick covered most of Canada; by about 7,000 years ago nearly all of it had melted. Huge floods did follow in some places; the land in eastern Washington State was carved by enormous floods when an ice dam broke. Woolly mammoths were about the size of today's African elephants, and the last of them lived on an island off Siberia until about 4,000 years ago. The giant sloth (Megatherium) was a ground sloth as big as an elephant.
Afterwards
Notice it this week: look at any river or stream bank for steps or old flat shelves above the water.
Answers to the book's problems
The book gives three ideas: they wandered from warmer places, they migrated with the seasons (which it thinks unlikely), or they had warm woolly coats, as the frozen mammoth shows. The highest terrace is the oldest because the river has slowly cut its way down, leaving its old levels behind as shelves.
Worked out for this site from the scan. If a number in your copy differs, trust the book.