Archaeology is all about people and the clues that they have left us about their lives. Most of these clues come from their rubbish!
Rubbish is made by people. It is what gets left behind, thrown away, or even dropped down the toilet in the days when it was just a hole in the ground. As time goes on, buildings fall down, rubbish pits fill up and new things get built over the top of the old things.
Just think of new buildings being built where you live. The old building is knocked down, the site is flattened out and a new building goes up. When this happens again and again over a long time, layers of old buildings and rubbish get built up under the ground. The oldest layer of things is at the bottom and the most recent layer of things is at the top. These layers have a special name, strata, which is the Latin word for layers.
The best way to think of strata is by imagining an enormous cake â€“ the biggest, highest cake ever! The bottom bit of sponge is the oldest stratum (stratum means one layer, strata means several layers). The next layer, the jam, is the next oldest layer. The next layer, the cream, is the next oldest layer â€“ and so on until you have lots and lots of layers with the present (now) at the very top of the cake.
In Britain, the prehistoric strata make up the bottom layers of the cake, the Roman period is the jam, the Anglo-Saxon period the cream, the Viking period the next layer of sponge, the medieval period another layer of jam, the post-medieval period is another layer of sponge, and the icing right on the top of the cake is now! Thatâ€™s how archaeology works â€“ when we dig into the ground to take a look underneath, if we look very carefully we can see these strata and go backwards through time as we dig deeper and deeper through each layer.