GEOS 1004 Lecture Notes - Lecture 15: Geologic Time Scale, Particle Size, Calcite
8 Mar 2018
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Lecture 15: the rock cycle iv sedimentary rocks, geologic time. Relevant reading: interlude b , p. 170-185; chp. Can be physical (ice, plant roots, cracking due to expansion, falls); mechanical breakdown into particles, or physical sediment. talus = broken up rock chemical weathering = chemical breakdown into unbound ions in aqueous solution. Some minerals dissolve completely (e. g. calcite), leaving behind cavities. Other minerals break down via other reactions (e. g. oxidation) into ions or new minerals that are left behind as residue; clay minerals, creating soil. Step 2: erosion; pick up, transport particles or ions by gravity in water (most common), ice, or wind. Step 3: deposition settling by gravity (physical sediment) into layers or chemical reactions (chemical sediment). sedimentary layers = stratigraphy. Look-up items: define clastic. denoting rocks composed of broken pieces of older rocks. Step 4: burial, subsidence, lithification the sediment is buried by younger sediment, experiences heat and pressure, changes chemically, hardens into sedimentary rock.
