This was the sort of land that the big basalt flows covered with a surprise layer of lava. The Central Valley in the Mesozoic was graced with streams, temporary lakes, a monsoon climate, plenty of vegetation, adjacent lofty mountains, and dinosaurs running around munching plants and each other. Suddenly, a big fissure opened up in the Earth and spilled out a 150-foot-thick layer of burning-hot lava that kept on coming. Plants incinerated on contact, animals ran for their lives, streams and lakes vaporized. In a matter of days, the Valley was transformed into a barren wasteland, with almost the whole basin covered by lava.

The eruption of basalt did not stop the flow of sediment. The mountains still eroded and the clouds still gave rain, and so streams brought new material from the Uplands to renew the Valley. Soil reformed, plants reappeared, and the Valley thrived with life once again. But the land was still under tension from Pangaea's break-up, and the trapdoor was still opening along the Eastern Border Fault. Eventually, another flow erupted and recovered the Central Valley with lava. Still later, the cycle of eruption and disruption repeated once again. All told, three flows of basalt poured into the Valley, separated by periods of sediment deposition. Then the flows stopped coming and, over millions of years, were buried several thousand feet by the continued flow of sediment-choked streams into the slowly sinking trench.

The continued slippage of land along the Eastern Border Fault had another important effect on the Newark Terrane. If one goes out and pokes around a few outcrops it becomes clear the strata here are not flat. Everything is sloped, like shelves nailed in place by a tipsy carpenter. Most of the strata dip toward the east at about 15 to 25 degrees. Gravity dictates that sedimentary strata are laid down flat when they first form, similar to the way a spill of rice or salt will level itself out flat against the kitchen floor. Continued slip along the Eastern Border Fault tilted the whole stack of rocks until the strata lost their level and tipped down toward the cast.

Tilting has had a major impact on the landscapes of the Central Valley. Wherever erosion has caused a tipped basalt layer to jut one end out of the ground, a traprock ridge formed. The pro ridges that run

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