Introducing Orange County

      From the look-alike cities in the north to the newer, planned communities of the south, Orange County seems little distinguished from its colossal neighbor and economic parent, Los Angeles. But a deeper identity, rooted in geography, transcends the urban sprawl. Orange Countians are reminded of their uniqueness not so much by the human architecture of city and suburb, but rather by the blue Pacific, the green and tawny coastal hills, and the purple wall of the Santa Ana Mountains.

      Out on the coastline and up along the foothills and mountains, you may discover for yourself Orange County’s place in the natural world. An hour or less of driving and less than two hours’ walk will take you from the frenetic city to any of several interesting natural environments, ranging from tidepools to fern-bedecked canyon streams to mountain peaks affording views stretching a hundred miles. You’ll discover fascinating rock formations, rich and varied plant life, a healthy population of native animals, and a sense of peace and tranquility.

      In the next few pages, you’ll learn briefly about the “other” Orange County: its climate, geology, flora, and fauna. Following that, you’ll find some notes about safety and courtesy on the trail and some tips on how to get the most out of this book. After perusing that material, you can dig into the heart of this book—descriptions of 124 hiking routes from the coast to the Santa Ana Mountains. Happy reading and happy hiking!

Land of Gentle Climate

      A succinct summary of Orange County’s climate might take the form of just two phrases: “warm and sunny” and “winter-wet, summer-dry.” But some variation in climate exists across the county’s width from coast to mountain crests. Without resorting to technical classification schemes, let’s divide the county into two climate zones: The coastal zone, extending inland 10–15 miles across the coastal plain and low coastal foothills, is largely under the moderating influence of the Pacific Ocean. This climate is characterized by mild temperatures that are relatively stable, both daily and seasonally. Average temperatures range from the 60s to 40s (daily highs and lows in Fahrenheit) in winter to the 70s to 60s in summer. Rainfall averages about 15 inches annually. Overall this climate closely matches the classic Mediterranean climate associated with coastal areas along the Mediterranean Sea.

      The inland zone, consisting of the Santa Ana Mountains and foothills, experiences somewhat more extreme daily and seasonal temperatures because it is less influenced by onshore flows of marine air. The higher summits of the Santa Ana Mountains, for example, have average temperatures in the 50s to 20s in winter, and the 80s to 50s in summer. Precipitation averages about 30 inches annually in the higher Santa Anas, which is just enough to support natural pockets of coniferous and broadleaf trees, such as pines, oaks, and maples. Almost every year, some fraction of the precipitation arrives in the form of snow, which briefly blankets the mountain slopes down to an elevation of about 3,000 feet.

      Despite its reputation for a gentle climate, Orange County is occasionally subject to hot, dry winds called “Santa Ana winds” (after Santa Ana Canyon, just north of the Santa Ana Mountains). These winds occur when an air mass moves southwest from a high-pressure area over the interior United States out toward Southern California. As the air flows downward toward the coast, it compresses and becomes warm and dry. Low passes in the mountains or river valleys that act as wind gaps (such as Santa Ana Canyon) funnel these desertlike winds toward the coast. During stronger Santa Anas, common in late summer and fall, Orange County basks under warm, blue skies swept clear of every trace of pollution (except possibly smoke from wildfires). Temperatures along the coast can then reach record-high levels; the city of Orange, for example, once recorded a temperature of 119 degrees during a Santa Ana.

      Rainfall in Orange County is as erratic as it is slight. On the coastal plain, the annual precipitation has ranged from merely 4 inches to a record of 32 inches. Up to 5 inches have fallen on the coastal plain in a single day, and in the Santa Ana Mountains, one storm dumped 9 inches in a single night.

      By and large, Orange County’s balmy, dry climate is remarkably well suited to year-round outdoor activity. Nevertheless, high temperatures, scarcity of water, and occasionally smoggy air during summer and early fall make that particular period less desirable for hiking in the inland foothills and mountains. During the other seven or eight months of the year, the weather is often ideal.

Reading the Rocks

      Of California’s many geomorphic (natural) provinces, Orange County claims parts of only two: the Los Angeles Basin and the Peninsular Ranges. The bulk of the county’s urbanized area lies in the Los Angeles Basin, while the mostly undeveloped Santa Ana Mountains and the semideveloped San Joaquin Hills belong to the Peninsular Ranges province.

      The Los Angeles Basin province extends from the base of the San Gabriel and Santa Monica Mountains (part of the Transverse Ranges province) to the north to the base of the Santa Ana Mountains and the San Joaquin Hills on the south. In a geologic context, it can be pictured as a huge, deeply folded basin filled to a depth of up to 7 miles by some volcanic material and land-laid sediments, but mostly by sediments of marine origin—sand and mud deposited on the ocean bottom from 80 million years ago to as recently as 1 million years ago.

      The Los Angeles Basin area has experienced uplift during the past 1–2 million years, and as this took place, the surface of the basin accumulated a layer of terrestrial sediment shed from the surrounding hills and mountains. The basin, in fact, would still be filling up with sediment were it not for the flood-control dams and channeled riverbeds that have largely replaced the original meandering Santa Ana, San Gabriel, and Los Angeles Rivers.