12: Great Valley
- Page ID
- 20346
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The geologic history of the Great Valley of California (Figure \(\PageIndex{1}\)) is a fascinating story that spans millions of years. The valley's formation can be traced back to the tectonic forces that shaped the region. It all began with the subduction of the Farallon Plate beneath the North American Plate, which initiated the uplift of the Coast Ranges and the creation of a deep basin, known as the Great Valley. Over time, sedimentary rocks, eroded from the surrounding mountains, accumulated in the basin.
Around 20 million years ago, volcanic activity associated with the Cascades Range started to deposit ash and lava flows in the region. These volcanic materials, along with the continued sedimentation, contributed to the filling of the Great Valley. Subsequent tectonic activity, including faulting and folding, further shaped the valley's landscape.
Approximately 2.5 million years ago, the first of several glacial episodes occurred, affecting the region. The advancing and retreating glaciers modified the topography, carving out valleys and leaving behind moraines and other glacial deposits.
As the last Glacial Maximum ended 18,000 years ago, the valley experienced a period of increased volcanic activity, which resulted in the formation of volcanic cones and lava domes, and volcanic lava flows that came into the valley, oftentimes following existing riverbeds formed by glacial melt and tectonic uplift. This made for a true dance of fire and ice.
More recently, in the past several thousand years, the Great Valley has been shaped by the meandering of major rivers, such as the Sacramento and San Joaquin Rivers, which have deposited vast amounts of sediment and created fertile floodplain soils. Human activities, including agriculture and water management, have significantly influenced the landscape in the modern era.
Today, the Great Valley stands as a testament to the complex interplay of tectonic forces, volcanic activity, glaciation, and river processes. Its geologic history has played a crucial role in shaping the diverse ecosystems and agricultural productivity of this vast and dynamic region.
By the end of this chapter, you should be able to:
- Describe the Great Valley in terms of its rock types, age, and tectonic development.
- Assess the geologic hazards and risks associated with the Great Valley.
- Recall the major geologic units in this province as presented on a simplified map of California.
- Analyze the development and economic potential of natural resources within the Great Valley.
- Define how petroleum was formed and migrated to make the Great Valley’s oil and gas fields.
- 12.1: Geomorphology and General Overview of the Great Valley Province
- This page discusses California's Great Valley, or Central Valley, highlighting its 644 km length and 80 km width, split into the Sacramento and San Joaquin Valleys. Notably, the San Joaquin Valley is a major agricultural contributor, providing 13% of U.S. goods. The Valley's geology features deep sedimentary layers with varying sediment types and includes three main watersheds—Sacramento, San Joaquin, and Tulare Lake—draining mostly into San Francisco Bay.
- 12.2: Geology of the Great Valley
- This page covers the geological evolution of California's Great Valley, including the Sacramento Valley and Sutter Buttes. It details the region's history from the Precambrian to the Quaternary Period, shaped by tectonic forces, sedimentation, and volcanic activity. The Sutter Buttes, a volcanic feature, support unique ecosystems and spark geological curiosity. The San Joaquin Valley showcases complex geologic formations, including evidence of an inland sea and significant oil reserves.
- 12.3: Soil, Streams and Agriculture
- This page examines the geological and agricultural importance of sediments in California's Great Valley, shaped by Sierra Nevada streams. It outlines the three river zones—source, transport, and sink—detailing sediment erosion, transport, and deposition. The role of glaciation in sediment accumulation and terrace formation is discussed, indicating how older deposits are overlaid by newer ones. These processes improve soil fertility and boost the region's agricultural productivity.
- 12.4: Natural Hazards of the Great Valley Province
- This page examines the Great Valley Province's agricultural richness alongside its vulnerabilities to natural hazards like earthquakes, floods, droughts, and wildfires. It discusses the historical decline of Tulare Lake and ongoing flooding risks, while emphasizing the impact of seismic activity related to local faults.
- 12.5: Natural Resources of the Great Valley
- This page covers the rich natural resources of California's Great Valley, focusing on oil and natural gas formation from ancient marine sediments. It details petroleum exploration techniques, including subsurface mapping and seismic reflection, and highlights extraction methods used in Kern County. The discussion encompasses conventional and unconventional techniques, environmental concerns prompting carbon capture projects, and the importance of groundwater for agriculture and industry.
- 12.6: Chapter Summary
- A summary of the Great Valley chapter.
- 12.7: Detailed Figure Descriptions
- Descriptions of complex images within this chapter, as well as additional guidance for users who have difficulty seeing and interpreting images.
Thumbnail: "Great Valley Province" is licensed under CC BY-NC 4.0 by Allison Jones.