Useless Bay State Tidelands trail

Location: Near Clinton, Whidbey Island

Length: Two miles each way.

Level of difficulty: Level to gentle sand beach, level paved path, and gravel access road above high tide.

Setting: Welcome to the field course for Geology 101. Here at the southwest end of Whidbey Island stretches a two-mile-long, sandy beach. This lovely driftwood-strewn shoreline owes its presence to the erosion of 300-foot-high Double Bluff, a giant calling card left by a series of geologic events.

An interpretive kiosk near the parking lot describes the origins of the cliff's different deposits. Although many layers were left by the retreat of a series of glaciers, other deposits reflect the area's geography between the various Ice Ages.

Dark brown layers in the bluff are remnants of the peat formed from plants that once grew here in ancient swamps. Meandering streams that once flowed down from mountains to the east left layers of blue clay. Look for "cauliflower" shapes halfway up the bluff - signs of a large earthquake that shook this area around 100,000 years ago. These sedimentary structures offer evidence of the large fault that runs across the south end of Whidbey Island.

Highlights: This beautiful shallow bay may have been useless for mooring deep-drafted ships, but the summer sun nicely warms the water for wading. Great blue herons find the shoals a perfect place to stalk dinner, so visitors can often get close-up views of these tall hunters. The park is serene at sunset, when the shallow waters of the bay shimmer with a coppery glow. For more park information, call 800-233-0321. Or try Island County Parks at 360-679-7373.

Facilities: Vault toilet (accessible) and phone.

Restrictions: Leash and scoop laws in effect for pets; off-leash area provided. Do not climb the bluffs.

Directions: Take the ferry from Mukilteo to Clinton. Follow Highway 525 northwest from the ferry dock for 8.2 miles, then turn left on Double Bluff Road and follow it 2.2 miles to the water.

Cathy McDonald is coauthor with Stephen Whitney of "Nature Walks In and Around Seattle," with photographs by James Hendrickson (The Mountaineers, second edition, 1997).