文档介绍：Book8 Unit5 Meeting your ancestors Listening, Speaking and Reading
1. Listen to the tape and fill the layers in the “wastepaper basket” diagram below.
yogurt pots
orange skin
wastepaper
used envelopes
The waste paper basket
Answer key for Exercise 2
Method
How it works
1. Layers in the ground
Each layer looks different as they are uncovered, so you can tell where one layer starts and another finishes. In the wastepaper basket, the most recent layer is _________, an older layer is below that and the oldest layer is ____________.
at the top
at the bottom
Method
How it works
2. Radio- carbon dating
All living things have ______ in their bodies. When they die, the carbon ________________ at a ____ rate. The method measures __________ of carbon in bones or plants using radioactivity and can ________ how old the remains are.
starts to disappear
fixed
the amount
work out
carbon
Note: The age of the building depends on the number of layers it is resting on. The more layers, the more recent the building.
Answer key for Exercise 3:
The oldest building is B because it has no layers underneath it.
The second oldest building is C because it has one layer underneath it.
The most recent building is building A. It has two layers underneath.
ZH: How can you tell how old the bones
are when you find them?
LISTENING TEXT(P42)
DATING METHODS
Zhou Heping e to ask the archaeologist, Richard Leakey, how he dates the bones he finds.
RL: There are two main ways: the first uses layers in the ground and the second uses the radiocarbon dating.
ZH: How does the layer method work?
RL: Well, many layers of soil were produced at different times. Each time people build houses and live
somewhere, they make an occupation layer. Each has a different color and texture.
ZH: How does that help?
RL: Look at the diagram in your book. Think of your wastepaper basket. When you came into work you threw the orange skin into it. Later
someone threw their empty yogurt pots in