The World's Foundations; or, Geology for Beginners · Ch. I · Unit 1: Part I: How to read the record
1. What the earth's crust is made of
Goal: Your child can say what the word geology means, what the earth's crust is, and why reading the rocks is like reading a torn-up book.
You'll need
- The book, open to this chapter
- A ball or globe and a sheet of thin paper
- An old magazine page or comic strip you can tear up
- A notebook for a "rock journal" and a pencil
- An egg carton or small box to start a rock collection
What's in the book
Chapter I asks what the earth is made of, explains the word geology, and pictures the crust as a sheet of brown paper on a school globe. It says that sand, clay, pebbles and even garden soil all count as rock, defines a theory, and ends with the geologist as a reader of a chopped-up book.
The lesson, step by step
A question to start
SayIf you could dig straight down under our house, what do you think you would find? How far down could you get?
Let your child guess freely. Then explain that nobody has ever dug or drilled more than a few miles down, and that this book is about how people learn about the earth anyway.
Read the chapter together
Read Chapter I aloud (pages 3 to 9), or take turns by paragraph. It begins:
WHAT is the earth made of— this round earth upon which we human beings live and move ?
Like every chapter, it opens with a Bible verse, and the author writes about God preparing the earth. Read it as she wrote it.
The word and the crust
Geology comes from two Greek words, ge (the earth) and logos (a word or teaching). It is the study of the earth's crust, its outside layer.
Giberne says that if the earth were a large school globe, the part geologists study would be no thicker than brown paper wrapped around it. Wrap your paper around the ball to see how thin that is.
What counts as rock
Read this sentence again:
The cliffs above our beaches are rock ; the sand upon our seashore is rock ; the clay used in brickmaking is rock ;
SayTo a geologist, sand and garden soil are rock too. Can you find three kinds of "rock" around our house or yard?
Look for gravel, sand, soil, a brick, a stone step. Put one small sample of each in the rock box.
A theory is not yet a truth
Read the author's definition:
A 'theory' is a possible explanation of a mystery, put forward as the best which can be offered, until something more shall be known about the matter.
Ask: What is the difference between a theory and something that has been proved? Giberne comes back to this idea all through the book.
The chopped-up book
The chapter ends by comparing the rocks to a big book that has been cut up, mixed, partly crushed and partly thrown away. Try it: tear a magazine page or comic strip into 10 or 12 pieces, quietly hide two or three, mix the rest, and ask your child to put it back together.
SayWhat was hard? How did you work out where the missing pieces went? That is what geologists do with layers of rock.
Tell it back
Ask your child to tell you, in their own words, what this chapter said. Prompts if needed:
What does "geology" mean?
Why can't we know for sure what is deep inside the earth?
Why is a geologist like someone reading a torn-up book?
What we know now
Giberne wrote that "nobody really knows" what the inside of the earth is like, and in 1881 that was true. Today we know the earth has layers: a thin rocky crust (about 3 to 6 miles thick under the oceans and about 20 to 45 miles thick under the continents), a thick mantle of hot rock that is solid but creeps very slowly, a liquid metal outer core, and a solid metal inner core. Scientists worked this out by timing earthquake waves as they travel through the earth.
Afterwards
Start a rock journal. This week, pick up one small stone on each walk and write where you found it and one thing you notice about it (color, weight, rough or smooth).
Tip
Rock-collecting safety: stay away from cliff edges and from the bottom of cliffs, where stones can fall. Ask before collecting on private land, and remember that collecting is not allowed in national parks.
Answers to the book's problems
Geology: teaching about the earth (Greek ge, earth, and logos, word). We cannot see far inside because we can only dig or drill a little way down. The geologist is like a reader of a torn-up book because the rock layers are broken, mixed up and partly missing, and have to be pieced together.
Worked out for this site from the scan. If a number in your copy differs, trust the book.