6.6: Chapter Summary
- Page ID
- 21473
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)6.1 Developing a Geologic History
- Quantitative global plate tectonic reconstructions can provide a starting point for understanding the geologic development of a region.
- Detailed studies of rock units and their relationships can provide more information about how a region has changed through time.
- Sedimentary rocks can be used to reconstruct the surface conditions at the time they were deposited.
- Metamorphic and igneous rocks can be used to reconstruct processes that occur beneath the surface of the Earth.
6.2 Proterozoic Eon (2500–540 Ma)
- Initial stages of rifting of the supercontinent Rodinia creates basins that fill with sediment along the western margin of Laurentia.
- Continued rifting results in the creation of a oceanic spreading center and new oceanic lithosphere.
- As the rifted margin cools, thermal subsidence creates additional space for sediment accumulation
- Thick deposits of marine sedimentary rocks accumulate along the passive margin.
6.3 Paleozoic Era (540–250 Ma)
- Marine sedimentary rocks continue to accumulate across the passive margin.
- A subduction zone initiates offshore and creates a compressional environment.
- Large packages of rock are displaced from where they formed and thrust onto the continent.
6.4 Mesozoic Era (250–66 Ma)
- An ocean-continent subduction zone forms with the Farallon plate going beneath the North American plate.
- Flux melting above the subducting plate produces magmas that intrude into the earlier sedimentary sequences.
- The Sierra Nevada represents the intrusive component of the Mesozoic arc while the extrusive component has mostly eroded away into great valley sediments.
- The subducting plate brings with it island arcs that get added to North America.
6.5 Cenozoic Era (66 Ma–Present)
- The Pacific-Farallon spreading ridge intersects the subduction trench and creates a new tectonic boundary between the Pacific and North American plates.
- The new Pacific and North American plate boundary has a right-lateral transform sense of motion.
- The zone of contact between the Pacific and North American plates grows as the Mendocino triple junction migrates north.
- Migration of the triple junction is accompanied by a slab window that creates a migrating pulse of volcanism along the coast.
- A wide zone of extension, the Basin and Range province, also develops in response to the changes at the plate boundary.