WhAt Is HiStOrY?


How can archaeologists tell how old things are? There are a number of ways for an archaeologist to tell how old an artefact is.


1. Stratigraphy


Stratigraphy is a method that dates artefacts by the other objects found at the same level in the ground. The older the artefact, the further down it is likely to be. For example, if you dropped something, it would lie on the top of the ground or near the top. Over hundreds or thousands of years, new things may fall on top of it and it is pushed further down.


2. Carbon dating


Every living thing contains an element called carbon-14. When the plant or animal dies, the carbon-14 in it slowly and steadily decays. Therefore, the older the object, the less carbon-14 it has in it.


3. Dendrochronology


This method is used to date wooden objects. Each year a tree adds a layer of wood to its trunk and branches. When it is a good summer of growth, the ring is much wider. The tree rings create a sort of pattern that can be compared to other trees. Archaeologists have created a record of the pattern going back thousands of years. Whenever a wooden artefact is found, it may be possible to work out when it was alive from the pattern in its rings.


More recent


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Fig 1.13 Archaeologists use stratigraphy to date artefacts found buried in the ground.


More ancient


Fig 1.14 The Giant Sequoia of Yosemite Park, USA. This section was cut from the giant sequoia in 1919, when the great tree was felled by a storm. At that time the tree was 996 years old – a baby compared to some of the trees in Yosemite National Park which are 3,000 and 4,000 years old. Naturalist A.F. Hall is measuring the span of life of the tree for tourists visiting the park. The various markings show the time of life of the tree at various historical events, such as the discovery of America, the signing of the Declaration of Independence and others.


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