The first event recorded in the rock of the Puente Hills began in the Meso­zoic Era, some 245 mil­lion years ago (Ma). These rocks were formed when an oceanic plate called the Far­al­lon began to slide under­neath the North Amer­i­can Plate. Vol­ca­noes erupted on the con­ti­nen­tal mar­gin, and oceanic sed­i­ments were com­pressed up against and […]

Over­head the sun coursed, time passed slowly but surely and under­neath, tec­tonic plates floated on molten rock, bump­ing and grind­ing against each other, try­ing to fit but always fail­ing. “Where two pieces rubbed edges, the earth twisted, folded, buck­led over,” slipped up and down, and sheared side­ways vio­lently. That hap­pened here for mil­lions of years, […]

Over­head the sun courses, time passes, and on those rare clear days in South­ern Cal­i­for­nia when the wind and rain have washed the sky clean, what appears on the south­west­ern hori­zon from the upper reaches of Clare­mont, Cal­i­for­nia, is a line of low slung hills that char­ac­ter­izes the geo­graph­i­cal basin and range topog­ra­phy of the greater […]