How long have the Pismo-Guadalupe Dunes existed?
The dunes we see were formed during the past 3,000 years and continue to form today. Older dunes also exist. Some, known as the Old Dunes (at Los Osos, Grover Beach, Oceano, Nipomo Mesa, Casmalia Hills and VAFB), have eroded dune shapes and are 3,000-9,000 years old. Still more ancient dunes have been eroded down to sand plains and are up to 200,000 years old (Nipomo Mesa, Casmalia Hills, VAFB). The oldest sands are a part of the Orcutt Formation that are up to 500,000-1,000,000 years old (best exposed near Orcutt).
