In the highway cuts and in the lower levels are remnants of small glacial formations, while the higher elevations disclose evidences of the Tertiary period. Few places afford a better opportunity to study the slow processes of nature over tens of thousands of years. In the dim past, Mount Rainier grew from successive volcanic eruptions, andesite and basalt in fragmentary condition forming the bulk of the deposits. Erosion through the centuries released much of the rich deposits to blanket the base of the mountain and to nourish wind-borne seed, watered by underground seepage and plentiful rain, until a mammoth forest arose. In the Snoqualmie Forest Reserve and the Mount Rainier National Park (now the Mt. Baker – Snoqualmie National Forest) are preserved the best of these unspoiled forests.