- This is the second installment in the series of field trips to glacial and interglacial stratigraphy on Whidbey Island. The thick stack of geologic strata at Blowers Bluff are spectacular! Here is colorful and intricately stratified sediment from Whidbey interglacial times right above the beach, overlain sequentially by the Possession glacial till and glaciomarine drift, thin Olympia interglacial deposits, Vashon advance outwash (Esperance ‘sand’), Vashon till and, at the cliff top, the Everson glaciomarine drift. However, the sequence is in places deeply eroded, with Vashon sediments sitting directly on Whidbey, or even right at beach level. Refer back to the table listing Pleistocene glacial and interglacial units on Whidbey Island.