The South Downs dominate Eastbourne and can be seen from most of the town. These were originally chalk deposits laid down under the sea during the Upper Cretaceous period, and were later lifted by the same tectonic plate movements that formed the European Alps, during the middle Tertiary period.[6] The chalk can be clearly seen along the eroded coastline to the West of the town, in the area known as Beachy Head and the Seven Sisters, where continuous erosion keeps the cliff edge vertical and white. The chalk contains many fossils such as ammonites and nautilus.[20]

A part of the South Downs, Willingdon Down is a designated Site of Special Scientific Interest. This is of archaeological interest due to a Neolithic camp and burial grounds. The area is also a nationally uncommon tract of chalk grassland rich in species.[21] Another SSSI which partially falls with the Eastbourne district is Seaford to Beachy Head. This site, of biological and geological interest, covers the coastline between Eastbourne and Seaford, plus the Seven Sisters country park and the Cuckmere valley.[22]

The town of Eastbourne is built on geologically recent alluvial drift, the result of the silting up of a bay. This changes to Weald clay around the Langney estate.[6]

Several nature trails lead to areas such as the nearby villages of East Dean and Birling Gap, and landmarks like the Seven Sisters, Belle Tout lighthouse and Beachy Head.

Eastbourne holds the record for the highest recorded amount of sunshine in a month, 383.9 hours in July 1911,[23] and promotes itself as "The Sunshine Coast". Other resorts, such as Jersey, Bournemouth and Weymouth lay claim to being the sunniest place in Britain too, using different criteria of "sunniest place".