TOPIC TWO: “WHEN DID IT HAPPEN?”
Topic two, “When Did It Happen?”, aims to teach about how archaeologists establish
chronology (timing) of events through stratigraphic principles.
LEARNING OBJECTIVE
RESOURCES
To introduce children to the
 Slides
basic concepts of archaeology,
 Photographs
as a foundation for studies in
 Maps
KS2 and onward
 Activity Sheets
CURRICULUM
KS1: History; Science (working
scientifically, everyday
materials); Art and Design
KS2: History (Iron Age Studies
and subjects); Science (working
scientifically, everyday
materials); Art and Design
(planning and drawing)
LEARNING QUESTIONS:
1. What do archaeologists do?
2. How are fossils formed, and where are they found?
3. How to archaeologists find out when something happened in the past?
ACTIVITIES
 Make Fossils and Sedimentary Rocks
 The Trifle Principle
 Out Of Order Story
LEARNING QUESTIONS:
LEARNING QUESTION 1: WHAT DO ARCHAEOLOGISTS DO?
In brief: Archaeologists study the material remains of past human activity, to learn what
human life was like in the past. These remains include the fossils of ancient humans, plus
more recent burials that are too young to have become fossils, as well as the objects, tools,
artworks, buildings and monuments that people made. Archaeologists don’t do: dinosaurs
(that’s palaeontologists), aliens (that’s conspiracy theorists), Bigfoot and the Loch Ness
Monster (that’s cryptobiologists) or treasure (unless they’re very, very lucky).,
This teaching pack will show how archaeologists look at the evidence to tell stories about
the past. An important part in any story is when things happened. This lesson explains how
archaeologists find out when things happened in the past, by looking at the stratigraphic
relationships between fossils, other remains, artefacts and the landscape.
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LEARNING QUESTION 2: HOW ARE FOSSILS FORMED, AND WHERE ARE THEY
FOUND?
This lesson provides background information on how rocks are formed and from there how
fossils are formed (by animal or plant remains becoming trapped between layers of
sediment, which then become sedimentary rocks). The types of fossils (mould fossils, cast
fossils and trace fossils) are explained with photographs for reference – the fossils shown
are all examples of human fossils, to emphasise that it’s not just dinosaurs which become
fossilised.
Rocks are formed in several ways. Igneous rocks are made of cooled magma (molten lava)
and are very dense and hard. Igneous rocks are worn down by wind and water into tiny
particles (sands and mud) called sediments – these deposit in layers at the bottom of water
(rivers and seas), and over many years harden into stone, called sedimentary rocks.
Metamorphic rocks are igneous or sedimentary rocks that have been changed through
extreme pressure and heat.
Fossils are found in sedimentary rocks. Why aren’t fossils found in igneous rocks? (Because
nothing would survive in molten lava). Why are fossils found in sedimentary rocks? (Because
dead creatures are buried in the layers of sediments and become fossils, rather than being
completely destroyed by scavengers and decomposition).
How are fossils made? When an animal or person dies, their body usually doesn’t last very
long. The body decays (rots away through bacterial/microbial action), or is eaten by
scavengers (insects, birds and animals), and after a few years almost nothing is left. A fossil
is made when a body is quickly buried beneath a layer of sand or mud, perhaps in the
bottom of a river or under a landslide. The body decays away, but it leaves an empty space
in the sediments around it…
A mould fossil is a negative impression left after the body has decayed away – an empty
void, in the shape of the body, like a “bubble” inside the sediments which buried it. A cast
fossil is a model of the organism made by minerals, which had been dissolved into
groundwater and then slowly build up inside the mould fossil or “bubble” as the water flows
through. Trace fossils are the fossilized traces of an animal, like footprints.
Mini-class challenge 1: All of the fossils shown in this slide are from humans or related
species. Slide 1: Homo Habilis, an extinct ancestor of humans (a CAST fossil). Slide 2: Human
footprints from Olduvai Gorge, Laetoli in Africa 3.6 million years ago (a TRACE fossil). Slide 3:
the Lloyds Bank coprolite, a palaeofeces (dried out human waste) from the 9 th century
Viking settlement at York, 1100 years ago. All of these fossils show that humans have lived
in many places for a very, very long time.
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Archaeologists investigate human fossils. Fossils take a very long time to form.
Archaeologists also demonstrate more recent human remains – skeletons and artefacts that
are too recent to have become fossils. Archaeologists investigate them in the same way – by
examining the evidence to tell a story about the past.
LEARNING QUESTION 3: HOW DO ARCHAEOLOGISTS FIND OUT WHEN
SOMETHING HAPPENED IN THE PAST?
When telling stories it is important to say when things happened, and the order of events –
otherwise the story does not make sense. This is just as important for reporters, detectives,
and historians as it is for archaeologists – but unlike the others, an archaeologist can’t ask a
“witness” to events. Luckily archaeologists are able to piece together the story of the past
through two types of dating: relative dating and absolute dating.
RELATIVE DATING IN ARCHAEOLOGY
Relative dating is informed by understanding the principles of stratigraphy. It is called
“relative” dating because it uses the stratigraphic relationship between two artefacts to
determine which artefact is older.
Stratigraphy is the study of layers (strata = layers). It is a geological idea – layers of rock in
the earth’s crust build up in layers. The layers of material in an archaeological site also built
up in layers. If we understand the order in which these layers built up, we can understand
how the site was formed and the order in which things happened there in the past. These
principles were applied to archaeology by an archaeologist, Dr. Edward Harris, in his 1973
book Principles of Archaeological Stratigraphy.
There are four rules of stratigraphy:
1. Layers form horizontally: they start out being flat.
2. The oldest layer is at the bottom, and the youngest layer is at the top
3. Layers get thinner towards their edges.
4. A layer that cuts another layer, is younger than that layer.
If we understand these rules, we can tell several parts of the story:
When something happened: Deeper artefacts and fossils are older than shallower ones.
Have things changed over time?: If the younger (shallower) fossils/artefacts are
different to the older (deeper) ones, you can say that they have changed over time. Early
human fossils are very different from more recent human fossils, because we have
changed a lot as we’ve evolved. Also human behaviour changes over time, and so do our
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artefacts – so older/deeper artefacts can look different from newer/shallower ones,
perhaps because fashions changed, or people adopted different technology.
Did things happen at the same time? If things are found in the same layer, you can say
they happened at the same time. Human remains and extinct animal remains found in
the same layer, show that the people and the animals were alive at the same time
Looking at the “Which Layers are Older?” slides – Although these are section drawings of
the layers inside two ditches, they tell a simple story. In the first slide, a large ditch was dug
first. It filled up with different layers of soil. A second smaller ditch was dug cutting into the
top of the first one. In the second slide, two ditches were dug. We can tell that they were
dug at the same time because they cut through the same layer (layer 3013).
Stratigraphic principles can be applied to finding out the relative ages of many
archaeological features. For example:


You can determine the relative ages of earthworks by using stratigraphy: a stone wall
that is built over an earth bank must be older than the earth bank. The earth bank
had to be there first, so the stone wall could be built on top of it. In some ancient
monuments like hillforts, there are many stages of building with earthworks
overlapping one another, or different structures being built on top of earlier ones,
like a medieval yard being built over an Iron Age hillfort embankment.
You can determine the relative ages of artefacts by using stratigraphy: an artefact
that is inside a layer must be at least the same age as that layer. It is therefore older
than any artefacts found in shallower layers, and younger than any artefacts found in
deeper layers. This is a useful rule of thumb. Of course, artefacts can be moved up
and down through stratigraphic layers by natural forces like burrowing animals, plant
roots, and freezing/thawing of the earth creating cracks in the soil which artefacts
can fall into.
However, relative dating can only tell you how old a feature or artefact is in relation to other
parts of the same site. To discover how many years old something is, you need to find an
absolute date.
ABSOLUTE DATING IN ARCHAEOLOGY
There are several scientific methods archaeologists use to get an absolute date for an
artefact: this education pack will briefly introduce the best-known: Radiocarbon dating.
Radiocarbon dating measures how old an artefact is by measuring how much carbon-14 is
left in the object. Carbon-14 is a radioactive isotope in carbon. Living things (all plants and
animals) absorb carbon-14 from the atmosphere while they live, and then start to lose it
after they die. Radioactive atoms decay at a set rate known as a half-life, and carbon-14 has
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a half-life of 5,730 years: after 5,730 years there will be half as many carbon-14 atoms left in
the organism.
Only things containing carbon can be dated this way: the remains of living things (plants,
animals, shellfish, humans, trees and artefacts made from living things like leather, bone,
feathers, wooden planks, charcoal and teeth). By counting how many carbon-14 atoms
remain in an object, we can work out how long ago it died (BBC 2014). Samples older than
50,000 years are generally too old to date as there is not enough carbon-14 left to measure,
unless special methods are used.
Archaeologists can use carbon-14 dating to get an absolute date for an artefact, that is, to
find out how many years old it is. This is sometimes also called giving an artefact a calendar
date. Carbon-14 dating actually gives a range – a date in years Before Present (before 1950,
because after 1950 the levels of carbon-14 in our atmosphere increased due to atomic
bomb tests) and then a plus-or-minus number of years based on how precise the dating
was. Dates are then calibrated into calendar years. It is a very complicated process and
archaeologists follow strict procedures for consistency and accuracy.
This method of dating is helpful even to date artefacts which do not have carbon in them.
For example, gold and silver artefacts cannot be dated this way. For example, say a golden
ring is found in close association with a piece bone. Close association means that the
archaeologists can confidently say that the piece of bone and the golden ring were buried at
the same time. Then the archaeologists can get a carbon-14 date for the piece of bone and
say that the golden ring is at least as old as the piece of bone. This comparison can then be
extended to other sites: if the gold ring has a distinctive design, and other gold rings of the
same design are found elsewhere, you can say that these other rings are also at least as old
as the first gold ring as dated by the piece of bone. Of course it is best to have many carbon14 dates from many sites to make sure that this pattern of relationships is repeated in other
places – just in case your discovery was an exception!
Then these absolute dates can be combined with the relative dates from stratigraphic
relationships to start building up a timeline of prehistory.
FURTHER READING AND RESOURCES LIST:
BOOKS, ARTICLES AND DOCUMENTARIES
Introductions to Archaeology and Fossils
Adams, Simon 2008. Archaeology Detectives. Oxford University Press: Oxford
Grant, Jim, Sam Gorin and Neil Fleming 2008. The Archaeology Coursebook: an Introduction
to Themes, Sites, Methods and Skills. Routledge.
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Hibbert, Claire 2014. The History Detective Investigates: Stone Age to Iron Age. Wayland:
Hachette Children’s Books.
Park, Graham 2010. Introducing Geology: A Guide to the World of Rocks (Second revised
edition). Dunedin Academic Press.
Ward, David 2010. Fossils (DK Handbooks). Dorling Kindersley.
White, John 2005. Hands-On Archaeology: Real-Life Activities for Kids. Prufrock Press.
Archaeology in Northumberland and the North Pennines
Frodsham, Paul 2004. Archaeology in the Northumberland National Park. Council for British
Archaeology: York.
Frodsham, Paul 2006. In the Valley of the Sacred Mountain: an introduction to prehistoric
Upper Coquetdale 100 years after David Dippie Dixon. Northern Heritage: Newcastle Upon
Tyne.
Petts, David and Christopher Gerrard eds, North-East Regional Research Framework [.pdf].
URL: <http://content.durham.gov.uk/PDFRepository/NERFFBook2.pdf > Accessed 1st
January 2014
Waddington, Clive & David Passmore 2004. Ancient Northumberland. Country Store:
Wooler.
Young, Robert, Paul Frodsham, Iain Hedley and Steven Speak 2004. An Archaeological
Research Framework for Northumberland National Park: Resource Assessment, Research
Agenda and Research Strategy – Section 4, Prehistory [.pdf] URL:
<http://www.northumberlandnationalpark.org.uk/understanding/historyarchaeology/archa
eologicalresearchframework > Accessed 1st January 2014
WEBSITES
BBC 2014. History: The Story of Carbon Dating [website] URL:
<http://www.bbc.co.uk/history/ancient/archaeology/carbon_dating_01.shtml > Accessed
30th September 2014
British Museum 2014a. The Portable Antiquities Scheme [website] URL: <www.finds.org.uk >
Accessed 20th June 2014

This is the website of the Portable Antiquities Scheme. People who find
archaeological artefacts by accident or through metal-detecting are encouraged to
report their discoveries to this Scheme so that others can use the information.
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Searching this website by region and historic period allows you to see what
archaeological finds have been reported in your area.
Cope, Julian 2014. The Modern Antiquarian [website] URL: <
http://www.themodernantiquarian.com/home/> Accessed 11th January 2014
Council for British Archaeology 2013. The Young Archaeologists’ Club: Leaders’ Area –
Activity Ideas. URL: < http://www.yac-uk.org/leaders/ideas > Accessed 12th January 2014

Very useful list of archaeology-related activities for 8 to 16 year olds.
Durbin, Gail, Susan Morris and Sue Wilkinson 1992. Learning from Objects: A Teacher’s
Guide. English Heritage: London. Now made freely available as a .pdf as part of an ongoing
digitization project to make previously published information about English Heritage
properties accessible to teachers. URL: <http://www.tes.co.uk/teaching-resource/Learningfrom-Objects-a-teacher-s-guide-6059739/ > Accessed 15th July 2014
English Heritage 2014. PastScape [website] URL: <http://www.pastscape.org.uk/ >Accessed
10th February 2014

This website allows you to search by location and historic period to find ancient
monuments in your area, and provides links to further information.
Harrismatrix.com 2014. Harrismatrix.com, home of archaeology’s premier stratigraphy
system [website] URL: < http://www.harrismatrix.com/ > Accessed 10th January 2014.

Dr. Harris has made his book Principles of Archaeological Stratigraphy available to
download for free from this website.
Hirst, K. Kris 2014. Radiocarbon Dating. About.com Education [website] URL:
<http://archaeology.about.com/od/rterms/g/radiocarbon.htm > Accessed 30th September
2014
The Megalithic Portal 2014. The Megalithic Portal [website]
URL:<http://www.megalithic.co.uk/ > Accessed 10th January 2014
Northumberland County Council 2014. Keys to the Past [website] URL:
<http://www.keystothepast.info/> Accessed 12th January 2014
Northumberland National Park 2014. The Northumberland National Park site [website] URL:
<www.northumberlandnationalpark.org.uk > Accessed 20th June 2014

Visiting the Northumberland National Park website and searching for “Neolithic”,
“archaeology” and “The Ancients” plus the names of specific sites mentioned in this
education pack will bring up more information.
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Tyne and Wear Museums 2014a, The Great North Museum Hancock [website] URL: <
http://www.twmuseums.org.uk/great-north-museum.html > Accessed 10th March 2014.

Many of the artefacts photographed for the slides accompanying this education pack
are on display at the Great North Museum Hancock. Additional educational materials
are available to download from their website. Contact the museum for information
on activity materials that can be borrowed to use on a visit to the museum.
Tyne and Wear Museums 2014b, Boxes of Delight Artefact Loan Programme [website] URL:
< http://www.twmuseums.org.uk/schools/boxes-of-delight/find-boxes.html > Accessed
10th August 2014

The Tyne and Wear Museums offers free loan of handling collections of artefacts,
including a Celts and Romans collection. Please contact the museum through the
above website for more information.
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