2.8: Chapter Summary
- Page ID
- 21447
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)2.1 Minerals
- A mineral is a naturally occurring crystalline solid with a distinct chemical formula.
- An atom is made up of protons and neutrons in the nucleus, and electrons arranged in energy shells around the nucleus.
- The main types of bonding in minerals are ionic bonding (electrons transferred) and covalent bonding (electrons shared).
- Minerals are grouped according to the anion part of their formula.
- Silicate minerals are the most common minerals in Earth’s crust and mantle. They all have silica tetrahedra (four oxygens surrounding a single silicon atom) arranged in different structures (chains, sheets, etc).
2.2 Mineral Properties
- Minerals can be identified using their properties such as hardness, cleavage/fracture, density, luster, color, and streak color.
- Hardness describes the ability or inability of a mineral to be scratched. Mohs hardness scale from 1-10 is used for assigning hardness values.
- A mineral exhibits cleavage when it breaks along regular planes as a result of its internal structure. If a mineral does not exhibit cleavage, it will simply fracture randomly or conchoidally.
- Luster is the quality of light reflected off of a mineral's surface. Minerals can generally be categorized as metallic or nonmetallic (though there are other terms that can describe luster).
- Color is not often useful for identifying minerals. However, streak, or the color of the powdered mineral is more useful.
- Other properties such as density or reaction with acid can be useful for identify particular minerals.
2.3 The Rock Cycle
- Rocks are consolidated aggregates of minerals and other materials. There are three main types: igneous, sedimentary, and metamorphic.
- The rock cycle relates different rock types (igneous, metamorphic, and sedimentary) and intermediate materials (magma, sediment) to the different processes they experience on Earth.
- Rocks may undergo various processes such as weathering, melting, and crystallization.
2.4 Igneous Rocks
- Igneous rock forms from molten rock (magma or lava) that has cooled and crystallized.
- There is a predictable order in which minerals will crystallize from a melt so long as the chemical constituents are present. This sequence is known as Bowen's reaction series.
- Igneous rocks can be identified using their texture (crystal size) and their composition (the minerals present).
- There are a number of textural terms that are useful for describing igneous rocks that can also help identify whether the rock cooled at the surface as extrusive igneous rock, or below the surface as intrusive igneous rock.
- The composition of an igneous rock depends on the composition of the melt from which it crystallized.
2.5 Sediments and Sedimentary Rocks
- Sedimentary rocks form from the accumulation and lithification of sediments derived from pre-existing rocks, biological material, or chemical precipitation.
- There are three main types: clastic, chemical, and biochemical sedimentary rocks.
- Common clastic rocks include conglomerate, sandstone, and shale, classified by grain size.
- Chemical sedimentary rocks form from dissolved minerals precipitating out of solution, like limestone and evaporites.
- California has extensive sedimentary rock formations, including marine deposits and river sediments.
2.6 Metamorphic Rocks
- Metamorphic rocks form when pre-existing rocks undergo heat, pressure, and chemical changes without melting.
- Foliated metamorphic rocks, like schist and gneiss, have a layered or banded appearance due to differential stress.
- Non-foliated metamorphic rocks, such as marble and quartzite, do not have layering and form under different conditions.
- Metamorphic grade indicates the intensity of metamorphism, ranging from low to high grade.
- California has extensive metamorphic rock formations, particularly in mountain ranges.
2.7 Where the Rocks Are: California's Geologic Map
- Geologic maps illustrate the locations of various geological features including rock units, faults, and folds.
- The generalized geologic map of California reflects the complex tectonic environment of the state of California.
- A static and interactive version of California's geologic map are included in this section.