Class Notes #4 9/11/13
crust: bristle shell varied of composition (Table 1.2); plates “float” on molten mantle
continental crust=granitic
granitic materials are very crystalline, when it weathers it breaks down and forms sand, silt and other ground surface materials
oceanic crust=basalt
able to mine u to 15 km deep
mantle: composed of iron, magnesium, silicon, oxygen; partly molten
melted rock zone of the earth, measured in the 1000’s of degrees
crust and upper mantle form lithosphere
volcanoes tapped into the upper mantle area
core: central, iron and nickel rich zone
outer core is molten
Inner core is solid
*Life on Earth
1 BYA + single cell organisms
1 BYA multi celled )S breathing organisms
550 mya marine animals with shells
550 mya fish with backbones
400 mya early land plants
300 mya insects
200 mya reptiles, amphibians, dinosaurs, early mammals 150 mya birds
100 mya land animals
5 mya human ancestors (genus Homo)
500 kya homo sapiens
200 kya homo sapiens sapiens
*Rocks and Minerals
basic components of the lithosphere
diverse textures, compositions, physical properties
Physical properties determine their use or purpose (construction, mental extraction, water extraction, agriculture)
Physical properties also signal the conditions under which it was formed and in what environments it may be found in the future
*Basic Building Blocks: Atoms
atom: the smallest particles into which an element can be divided while still retaining the chemical characteristics of that element
nucleus: center of an atom containing protons (positively charges particles) and neutrons (particles which have no charge)
electrons: negatively charged particles which circle the nucleus
atomic number: characteristic number of protons
atomic mass: characteristic number of protons and neutrons in the nucleus of an atom
isotopes: atoms of a given element that have the same number of protons but a different number of neutrons
scientifically useful for geochronology (absolute dating)
ions: atom of a given element that has a positive or negative charge due to a change in the number of electrons
cation: positively charged ion
anon: negatively charged ion Class Notes #5 09/11/2013
*Periodic Table of Elements Class Notes #5 09/11/2013
published 1869 by Medeleyev
arranged based on similarities of behaviors
90 commonly/naturally occurring chemical elements. If count observed there are 168.
*Components of the Earth’s crust
important elements
oxygen, silicon, aluminum, iron, calcium
various isotopes of those elements
periodic table of elements organizes the known elements (fig 2.2)
Elements and Compounds form the rocks of the earths crust
Ionic (electrical attraction) vs covalent (electron sharing) bonding.
Mineral: naturally occurring, inorganic solid element or compound with a definite chemical composition and a regular
internal crystal structure.
Silicone tetrahedron. Has a regular internal structure that will build relationships
*Identification of Minerals
mineral id based on
chem. Composition
crystalline structure
other id characteristics based on:
color and streak (color of powdered material)
hardness: resistance to scratching (table 2.1)
diamond is the hardest mineral Class Notes #5 09/11/2013
talc is the softest
Mohs Hardness scale is based on 1 to 10
cleavage: distinctive way minerals break when struck
luster: appearance of the surface
shiny, pearly
magnetism
very low number have a reaction to this test
density
acid test
hydrochloric acid and has a reaction to carbonate minerals
*Types of Minerals
Silicates: mineral compound that contain silica and oxygen, most common mineral in earths crust
Quartz
Feldspar: most common, breaks down into clays, used for ceramics
Ferromagnesians: dark, iron magnesium rich, semi precious gems
Micas: sheet silicates
Clays
Nonsilicates: a mineral that contains oxygen and another element
Carbonate: carbon and oxygen in a 1:3 ratio
Sulfates: sulfur with oxygen
Sulfides: sulfur without oxygen Class Notes #5 09/11/2013
Oxides: metals combines with oxygen
Hydroxides: metals plus oxygen and hydrogen
Halides: metal plus halogen
Native elements: single chemical element
*Rocks
defined as solid, cohesive aggregates of one or more minerals or mineral materials
3 types: igneous, sedimentary, metamorphic
Rocks record their own formation history which can be examined by looking at the nature of their mineral constituents
*Rock Cycle
Igneous: rocks, formed from magma
Sedimentary: rocks formed from low temp accumulations of particles or by precipitation from solution
Metamorphic rocks formed from preexisting rocks through the change of temperature and pressure
Geologic processes working on old rocks change the old into new and different ones continuing the cycle
*Igneous Rocks
Formed from magma
magma: molten rock. At temperatures and pressures beneath the crust, rocks and minerals melt
Silicates are the most common minerals and thus magmas are rich in silica
Magmas also contain water, gases and solid crystals suspended in the melt
Iron content varies and is the basis for igneous rock classification
An igneous rock is formed by the solidification and crystallization of a cooling magma Class Notes #6 9/16/2013
*Sedimentary Rocks Class Notes #6 9/16/2013
sediments are produced by weathering of pre existing rocks and minerals (igneous, metamorphic, sedimentary)
sediments are loose, unconsolidated accumulation of mineral or rock particles (clasts)
sediments are eroded, transported and deposited in many sedimentary environments
sediments will be buried and experience lithification
lithification involve compacting the sediments with burial and cementation of the sediments forming a sedimentary
rock
gravity plays a role in the formation of all sedimentary rocks
layering is a very common feature of sedimentary rocks and is used to identify the origins of sedimentary rocks
sedimentary rocks can yield information about the settings in which the sediments were deposited
sedimentary rocks are formed at or near the earth surface and temperatures close to ordinary surface temperatures
igneous rock bodies in the steep mountain slopes because subject to high winds, ice and work on eroding and
loosening up the material. Carries it down stream and deposits in periodic points until reaches a final depositing point
where sedimentary rock forms
Classic Sed Rocks
Formed by lithification of mechanically weathered pieces of rocks and minerals
Grain sizes range from boulder, gravel, sand, silt and mud
Grains are continuously broken down in size and shape until deposited
Once deposited these clasts are cemented
Chemical Sedimentary Rock
Chemical processes occur in water bodies such as lakes, seas or oceans
Minerals precipitate form the water and form thick deposits (evaporates)
Examples: halite, calcite, gypsum
*Metamorphic Rocks Class Notes #6 9/16/2013
“Changed Form” rock formed from existing rock or minerals
heat, pressure, and chemicals in solution cause changes in rock
Burial or proximity to magma chamber causes temperatures to increase
Burial or collision (plate margins) causes pressure to increase
Fluids are heated and circulate within burial zone or nearby magma chamber
Temperatures required to form metamorphic rocks are below the magmatic temperatures
Significant changes can occur in a rock at temperatures well below melting
Temperature and pressure can cause the minerals in the rocks to recrystallize
Pressure may cause the rock to be deformed
The sources of elevated temperatures of metamorphism: burial, magma, mountain building, and plate tectonic
movement
The sources of elevated pressures of metamorphism: burial, mountain building and plate tectonic movement
Contact Metamorphism: localized metamorphism of rocks adjacent to a magma chamber
Regional Metamorphism: large scale stressing and heating of a rock by deep burial or continental plates moving and
colliding
Any kind of preexisting rock (another rock) can be metamorphosed
Floiation: when a rock is subjected to directed stress, its minerals form elongated/ platy crystals and line up parallel to
each other
Metamorphic rocks without foliation do not show directed stress
Marble is metamorphosed limestone
Quartzite i
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