15: Peninsular Ranges
- Page ID
- 20349
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)
( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\id}{\mathrm{id}}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\kernel}{\mathrm{null}\,}\)
\( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\)
\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\)
\( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)
\( \newcommand{\vectorA}[1]{\vec{#1}} % arrow\)
\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow\)
\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vectorC}[1]{\textbf{#1}} \)
\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)
\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)
\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Introduction to the Peninsular Ranges
The Peninsular Ranges province of California, which includes the coasts of Orange and San Diego counties, is known throughout the world as the home of beautiful beaches, surfing, usually fantastic weather, and many theme parks. It’s also just south of the Transverse Ranges, which makes for an easy drive north to the winter ski resorts of the San Gabriel and San Bernardino Mountains. This is how the challenge known as “California Double” began, to both surf and ski between sunup and sundown of the same day. Life here can be downright delightful, but geologically, things are complicated.
The province is named after a series of northwest-southeast trending mountain ranges starting south of the Transverse Ranges and extending into Mexico, where the mountains form the spine of the Baja California Peninsula. These mountains are underlain by a batholith. The California portion of this batholith has historically been referred to as the Southern California batholith, ignoring the reality that most of the batholith and the mountains are actually in Mexico and only the small, northernmost tip is in California. In an effort to help correct this misconception, more recent publications have started to refer to the batholith as the Peninsular Ranges batholith instead.
These ranges formed as part of the Mesozoic volcanic arc that dominated what is now the western coast of California (see 6.4: Mesozoic Era (250 – 66 Ma)) and are therefore similar, but not identical, in rock type and timing to the Sierra Nevada. While there are small exposures of pre-Mesozoic rock in the mountains, most of the rock exposed in the Peninsula Ranges and on the coastal plain is Mesozoic and younger.
The coastal plain to the west of the mountains, along with its beaches, is dominated by marine terraces, headlands, sea cliffs, wave-cut platforms, pocket beaches, and other landforms common on erosional coasts where earthquakes are common (see 16.2: California Coastline Anatomy). While the province is named after the mountains, most of the population, and the resources in use today are concentrated on the coastal plain. Generally, when people think of this part of California, they think beaches, not mountains. For most people, the mountains form a picturesque background that enhances living near or vacationing on the beach (Figure \(\PageIndex{1}\)).
By the end of this chapter, you should be able to:
- Describe the Peninsular Ranges province in terms of its key geographic and geologic features.
- Explain how the Peninsular Ranges fit into the broader context of the tectonics and geologic history of California.
- Describe the timing of the formation and characteristics of the rocks of the Peninsular Ranges, including their similarities and differences with the Sierra Nevada.
- Assess the geologic hazards and risks associated with the Peninsular Ranges.
- Describe the natural resources within the Peninsular Ranges.
- 15.1: Geomorphology of the Peninsular Ranges
- The Peninsular Ranges are the remains of the Mesozoic volcanic arc that once dominated the west coast of North America. The volcanoes are long gone, but the batholith that was below them now forms the southernmost mountain ranges along the California coast and they are more closely related to the Sierra Nevada of eastern California than to the northern and central California Coast Ranges. Along their western boundary is an erosional coast dominated by marine terraces.
- 15.2: Tectonics and Geologic History of the Peninsular Ranges Province
- The earliest history in the rock record of the Peninsular Ranges is a Paleozoic passive margin offshore. During the Mesozoic, the geology became more “active” and a subduction zone was offshore and volcanism began and an island arc formed. The mid-Cenozoic brought more change as the subduction boundary switched to a transform boundary and volcanism ended. The transform boundary then jumps eastward, and suddenly the Peninsular Ranges are now on the Pacific plate.
- 15.3: Rocks of the Peninsular Ranges
- The tectonic and geologic history of the Peninsular Ranges is a story in the rocks. Most of the rock in the Peninsular Ranges is plutonic igneous rock telling the story of subduction, formation of batholiths and of the volcanoes that are no longer here. Or, for the sedimentary rock of the coastal plain, a story of uplift, erosion, deposition, and the never ending changes caused by the rise and fall of sea level.
- 15.4: Geologic Hazards of the Peninsular Ranges
- The Peninsular Ranges province is no different than any other province in California, amid all the beauty, and the crazy, wonderful geology, there are hazards that can present a challenge. Sometimes hazards are foreseeable, even if not predictable, and sometimes they are seemingly spontaneous and take everyone by surprise. But to live anywhere in California is to be reminded that the world moves with its rhythms and patterns, and when it comes to hazards, human wants are just wishful thinking.
- 15.5: Natural Resources of the Peninsular Ranges
- The Peninsular Ranges province is a place of beauty, both along the coast and in the mountains, but as with humans, looks are not enough. Fortunately, because much of the province is urban, many of the mineral commodities necessary to support an urban society are also present in the province. The one commodity not present in abundance is water and much thought, energy, and expense has gone into trying to improve the water situation.
- 15.6: Chapter Summary
- A summary of the highlights of this chapter
- 15.7: Detailed Figure and Video Descriptions
- Descriptions of complex images and video animations within this chapter, intended for users who have difficulty seeing and interpreting images.