EAR 105 1st Edition Lecture 7 Outline of Last Lecture I. Basaltic MagmaII. Silicate-Rich MagmaIII. Introduction to VolcanoesOutline of Current Lecture II. Sedimentary RocksIII. Detrital Sedimentary RocksIV. Chemical Sedimentary RocksCurrent LectureII. Sedimentary Rocks- Sedimentary Rocks: formed of pieces of other rocks, broken down through a process called weathering.- Weathering- the in-place break down of rocks, which turns them into sedimentso Physical weathering: relates to the breaking down of rock in smaller pieces Ex. frost-hedging- water expands when it freezes in cracks in rocks—expands the crackso Chemical weathering: relates to the alternation of a rock’s chemical composition Ex. dissolution: Minerals halite and calcite dissolve in water.- Sedimentary rocks are formed at the surface.- 75% of rocks exposed at surface are sedimentary.- If earth was the size of a basketball, the crust would be the thickness of a sheet of paper.-  Sedimentary rocks at surface don’t carry much volume, whereas they are prominent, visible features at the Earth’s surface- Have individual beds or layerso Law of Original Horizontality: States that sedimentary rocks are laid down horizontally. I.e. sediments lay flat at the bottom of the lake o Sequence of Sedimentary Rock- the older the sediment the deeper it is buried- Two types of sedimentary rocks: Detrital and ChemicalIII. Detrital Sedimentary Rocks- Formed of fragments of other rocks- Classified by particle size- Compacted and cemented from detrital sedimentsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- The process of lithification includes weathering, transportation, deposition, compaction, and cementation- The more rounded the individual sediment particles, the farther they have traveled.o Ex. Sand has very fine grains since the particles are light and easily carriedby water and wind- Energy moves and deposits sediments. Often the forming rock shows evidence ofthe nature of energy under which it was formed.o Ex. crossbed sediment patterns indicate that the energy that had initially moved the sediment was once flowing, sometimes in varying directions- Larger, heavier particles settle first, and are generally more angular than lighter particles which settle later and have more time to develop smooth edges.- Fossils are found almost exclusively in sedimentary rocks because preservation necessitates cool temperatures and relaxed pressures not found in most igneous or metamorphic rock- Many fossils are made of calcite, which precipitates at an especially cool temperature- Standard progression of deposition: sandstone (beaches) then shale (river basins)and limestone (deep underground, sediments survive only through solution)- Detrital sedimentary rocks are generally formed from processes of physical weatheringIV. Chemical Sedimentary Rocks- formed of mineral precipitates- Non-clastic sedimentary rocks: some chemical sedimentary rocks do not have sediment pieces (clasts) compacted together, but are rather homogenous.o Limestone- the most abundant non-clastic sedimentary rock Forms from dissolute calcite precipitated in ground water deep underground- Classified based on composition and texture—differing from detrital rocks which are classified simply by the size of the clasts.- Chemical sedimentary rocks are generally formed from processes of chemical