Geology of the Park

Image by Chris Hawkins 2022

Sixty-five million years ago, at the end of the Cretaceous Period, Greenwich Park was the seabed of a tropical ocean where chalk had been laid down as a thick layer of shells from marine animals. As sea levels fell, a layer of silt, sand and clay covered the chalk (Lambeth Group) and eventually, the area became an estuary. Hard flints made of silica had formed in cavities in the chalk and, as the dry land was eroded, these were washed downstream, creating smooth black pebbles. Sea levels rose again, and these pebble beds (Blackheath Pebble Beds) were covered by a thick layer of clay (London Clay).

Twenty million years ago, during the Early Miocene Period, the formation of the European Alps caused massive earthquakes that faulted the land under Greenwich Park. This pushed the southern area up and formed an escarpment. The soft London Clay was washed away from the higher ground, eventually exposing the pebble beds, which resisted erosion.

Twenty thousand years ago, the Ice Age was at its peak, and glaciers had pushed the River Thames south until it reached this escarpment and could go no further. As the river tried to cut through, it made the escarpment steeper and created river terraces. In heavy rain, water would run down the hills in streams, carving out valleys and creating the current landscape.

The sandy layers under the high ground soaked up water like a sponge. When the water reached the impervious layer of clay, it emerged as springs on the hillside. This feature was eventually exploited in the Tudor period, when a series of underground conduits were constructed to collect and supply water for the various royal buildings in Greenwich.