The westernmost outlier of those Paleoproterozoic rocks crops out in the San Emigdio Range, which forms the rim of the Central Valley southwest of Bakersfield. The quickest way to see them is to turn west off of Interstate 5 toward Frazier Park, then drive up either Frazier Mountain or Mount Pinos (Cerro Noroeste is also possible if you're ambitious). The gneiss shown at the top of this post is on Mount Pinos. It was turned into gneiss around 1450 million years ago, but the rock originated as something else, probably a sandy mudstone, around 1700 million years ago (source, USGS OF-02-406).

Elsewhere in California, you can repeat Ben Burress's experience in Death Valley by walking up the canyon at Badwater, but a more interesting canyon hike with the same Paleoproterozoic rocks starts about 2 miles north of Badwater. And blogger Garry Hayes describes more Paleoproterozoic rocks in the San Gabriels.

The really old rocks in America are found in Wyoming and the states around Minnesota. They date from the Paleoarchean Era and are more than 3 billion years old. One example can be easily seen in Washington, D.C., in a prominent spot between the White House and the Washington Monument: the twin Haupt Fountains, each one made from a 55-ton slab of Montevideo Gneiss from Minnesota. At the time they were made, this was considered the oldest rock in the country.

The reddish, scrambled-looking Morton Gneiss is a popular stone for buildings and gravestones, and at 3524 million years of age it's considered to be the oldest bedrock in the United States. You could travel to Minnesota to see it (there's even an EarthCache for it west of Minneapolis), but don't bother—you probably have samples right in your own town. David B. Williams, author of Stories in Stone, calls it the country's most beautiful building stone.

But you can go older still. There's a Canadian rock from a spot in Labrador called Nuvvuagituq said to be 4.28 billion years old, but the date is still not settled. Today the Acasta Gneiss, also from northern Canada, is the world's oldest firmly dated rock at 4.03 billion years. You can see that one at Rocklin, just up the road. Go to the campus of Sierra College, on the south side, and locate the excellent Earth History Rock Walk.

There, among the assorted amazing and instructive boulders, is a nice chunk of Acasta Gneiss.

But whenever I want to experience the deepest possible deep time, I reach for a meteorite from my collection and lick it. Nearly every common meteorite is older than Earth itself.

meteoritemeteorite

Stardust and Sunbreath in the Sutter's Mill Meteorite

Help Find the Healdsburg Tektites

UFO? LGM? OMG! What is That Thing in the Sky?

California's (and the World's) Oldest Rocks

Treasure from the Sky

Asteroid 2005 YU55 Scores!

Mastodons, Mummies, and Meteorites: Evidence of Life Out There?

Reality Rocks: Prospecting on Mars

Panning for Starstuff