jumble appears along the Big Sur coast in the Franciscan formation, part of the Nacimiento block, which forms the underlying rock in the south half of the Santa Lucia Range.
The exposed cliffs at Andrew Molera State Park include excellent examples of Franciscan rocks. Formed from silica-rich sea creature skeletons, chert features jagged layering and an erosion-resistant glasslike texture. Sandstone is characterized by its tan color, rough surfaces, and fine sand grains. Comprising hardened, compressed mud, shale is gray-black in color with microscopic grains.
Serpentine, California’s state rock, forms in layers that solidify above molten rock. These layers are scraped off and jumbled near the surface, where they react with groundwater to form this slippery green stone. You’ll find dramatic serpentine outcrops in the Silver Peak Wilderness amid the Salmon Creek and San Carpoforo drainages.
Other younger rocks formed in the vicinity of the Santa Lucia Range before a single peak rose above the surface. A few million years ago, this area was a drainage basin that collected sediments in the form of sand, silt, and boulders. In time these solidified into sandstone, siltstone, and conglomerate. Conglomerate is least common, although at Point Lobos it is the dominant sedimentary rock and forms dramatic outcrops and cobblestone promontories.
While these theories may explain how the rocks formed, they don’t explain how the rocks traveled hundreds of miles and rose to form the Santa Lucia Range. That story begins along the San Andreas Fault system some 30 million years ago. Once again, tectonic forces brought oceanic and continental plates together. This time, the North American plate and the Pacific plate met and began to grind past one another, marking the San Andreas Fault boundary.
Two massive chunks of Earth’s crust, the Nacimiento and Salinian blocks, were ripped from their moorings along the North American plate and pushed northward along the numerous major faults associated with the San Andreas system. These faults generally run northwest-southeast, paralleling the coastline and general trend of the coastal mountains. A prime example is the Sur-Nacimiento Fault, which separates the Salinian and Nacimiento blocks, relieving pressure along the San Andreas Fault. As the tectonic plates collided, compressed, and fractured along these major fault lines, the land buckled in on itself like folds in a loose carpet, giving rise to the peaks, ridges, and gorges of the Santa Lucia Range.
Stream courses mark many of these otherwise indiscernible faults. The lower Big Sur River from the gorge to Andrew Molera State Park offers startling proof of how fault movement can alter a watercourse. Along this section, the river flows straight down the Sur Thrust Fault until it is forced into a conspicuous 90-degree turn out to Molera Beach.
Coastal bluffs, or marine terraces, offer evidence that the Santa Lucia Range continues its abrupt rise above sea level. These bluffs form as waves carve into the bedrock and deposit coarse sand and sediments. As land west of the San Andreas Fault buckles, these platforms rise above sea level, exposing the layered sand and cobblestones. Prominent marine terraces stretch from Point Sur to Andrew Molera State Park, while broader terraces form the flat terrain at Pacific Valley.
Erosion serves as a counteracting force to the recent uplifted Santa Lucia Range. As mountain flanks rise ever steeper, streams cut deep, fast channels through the rock, carrying away thousands of tons of sediment. A clear creek in summer can become a muddy torrent during heavy winter rains or after wildfires remove anchoring vegetation. Landslides are a common phenomenon in Big Sur. Of course, the Pacific Ocean also accounts for its fair share of erosion.
Geologists believe the recent uplift has thus far outstripped these erosive forces. If the uplift slows or stops, however, the tables will turn and gradually return the region to a rumpled landscape of low, rolling hills and plains.
Climate
CLIMATOLOGISTS HAVE LONG COMPARED California’s climate to that of the Mediterranean coastline, with dry summers, wet winters, and moderate year-round temperatures. Big Sur’s climate differs markedly, however, due primarily to consistent summer fog and the sheer topography of the Santa Lucia Range. Temperatures and humidity run the extremes along the fog-shrouded coast, atop 5000-foot mountain peaks, amid deep river canyons, and across the sun-drenched south-facing slopes.
An air circulation pattern known as the North Pacific High dominates regional weather patterns. From May through September, the sun most directly strikes the Northern Hemisphere. Surface air warms and rises into the upper atmosphere toward the North Pole. This heated air mass cools quickly in the upper atmosphere, subsequently sinking toward the surface as a large high-pressure cell. This massive high-pressure cell drives Big Sur’s westerly winds and summer drought, as well as its summer fog, a very stable phenomenon off the California coast that is absent in the Mediterranean basin.
Thick fog forms when westerly winds brought by the North Pacific High push cold ocean water inland, forcing warmer surface water offshore. Rich in nutrients from nearshore submarine canyons, the cold water wells to the surface, sustaining abundant marine life along the Big Sur coast. With temperatures in the low 50s Fahrenheit, it also makes a swim here brisk at best, even in summer. The cold water chills the air directly above it. When this cold water comes in contact with warm, moist air along the coast, water vapor condenses into fog.
In the wake of winter rains, fog retreats and grasslands and forests burst with new growth.
This pattern continues until late fall, when the sun strikes Earth farther south and the North Pacific High dissipates. No longer deflected by the high-pressure cell, the jet stream flows over California and brings with it strong winter storms. From November through April, California’s wet season, these storms batter the coastal ranges until the sun’s path again swings north to rebuild the North Pacific High.
Plant & Animal Communities
BIG SUR IS HOME TO A DIVERSE ARRAY of plant communities and associated wildlife. Botanists have long been fascinated by the proximity of northern and southern species living beside one another along the region’s steep-sided ridges, narrow valleys, deep canyons, sun-drenched grasslands, and chaparral. Here, moisture-dependent redwoods may tower alongside drought-tolerant yuccas.
The story begins 5 million years ago, when the Santa Lucia Range was more of a low, rolling plain blessed with a moderate climate. Winters were warmer and summers wetter than today’s more Mediterranean climate. The climate was likely too damp for chaparral species and too warm for redwoods and their shade-loving companions. Given the relatively uniform landscape and climate, botanists suggest the area supported fewer species than today’s diverse topography permits.
Squeezed by tectonic plates and compressed by massive faults, the region rose and folded in on itself, creating the Santa Lucias’ jagged peaks, steep ridges, and deep gorges. This topographic shift occurred in concert with climatic changes from the most recent Ice Age some 2.5 million years ago. These profound changes disrupted the uniform vegetation, paving the way for a major plant invasion.
The cool, damp climate allowed redwoods to take root in narrow, deep canyons along the coast. Fog encroached inland in dry months, supplying much-needed moisture to northern species. Thunderstorms became commonplace, as moist air rose abruptly to form thick cumulonimbus clouds, or thunderheads. These clouds arrived in summer, when temperatures were at a maximum and moisture at a minimum. Lightning sparked regular wildfires, and fire-adapted plant species thrived.
Drought-tolerant species also had an advantage. As the range continued to rise, coastal lands received the lion’s share of precipitation, depriving eastern slopes of moisture. The steep topography also meant accelerated erosion, preventing mature soils from developing. The resulting shallow, primitive soils held considerably less ground water. But the hardy vegetation that populated these
