Ancient Shores — Jack McDevitt

They opened the door to another Universe

It turned up in a North Dakota wheat field: a triangle, like a shark's fin, sticking up from the black loam. Tom Lasker did what any farmer would have done. He dug it up. And discovered a boat, made of a fiberglass-like material with an utterly impossible atomic number. What it was doing buried under a dozen feet of prairie soil two thousand miles from any ocean, no one knew. True, Tom Lasker's wheat field had once been on the shoreline of a great inland sea, but that was a long time ago--ten thousand years ago.

A return to science fiction on a grand scale, reminiscent of the best of Heinlein, Simak, and Clarke, Ancient Shores is the most ambitious and exciting SF triumph of the decade, a bold speculative adventure that does not shrink from the big questions--and the big answers.