The rocks of the Quaternary period mainly consist of 10 metres of till and gravel. When the last ice age happened, around 500,000 years ago, the River Thames was diverted, causing a great amount of rock to be deposited. When it was diverted, it eroded a valley, making many sand and gravel terraces. The terraces made by the river are made up of unsorted rocks such as quartz and quartzite, as well as -in some places- deposits of a mixture of clay and sand, called brickearth, which has helped London's brick industry, which has been going on for hundreds of years. Many towns are named which are here today are named after these channels, including Dartford, Heath Gravel, Swanscombe and many more. Above the layers of the natural Quaternary Period is rock deposited by modern humans, and in some older parts of London this reaches up to 6 metres deep.
To find these Quaternary Rocks, visit the River Thames. There is also some near the Fincley area and Harlow.