Quiz 1 Flashcards
Endogenic process
Internal process that builds up landforms
Powered by the heat within the Earth
Exogenic process
External process that tears down landforms
Powered by solar energy
Superposition
Rocks get younger as you move up
Original horizontality
Sediments are originally deposited in horizontal layers. If they’re tilted, they moved after deposition
Cross-cutting
Cut rocks are older than the rock cutting them
Unconformities
A gap in time when no rock layers are present — often due to erosion or change in conditions
Universe’s age
13.8 bi
Earth’s age
4.6 bi
Catastrophism
Earth’s features were produced by sudden, worldwide disasters of unknowable causes that no longer operated; based on Archbishop James Ussher’s study of the Bible in the mid-1600s
Through this school of thought, the Earth was thought to be only a few thousand years old
Uniformitarianism
Forces that appear small could, over long spans of time, produce the same effects as those resulting from catastrophic events; from James Hutton in the late 1700s
“The present is the key to the past”
Earth layers, as defined by composition vs by physical properties
Composition: Crust, mantle, core
Physical properties/mechanical: lithosphere, asthenosphere, mesosphere, outer and inner core
Continental crust
Light, thick, old, complicated
Felsic silicate rocks
Oceanic crust
Heavy, thin, young, simple
Mafic silicate rocks
Mohorovic Discontinuity
Sharp boundary between crust and mantle
Lithosphere
Composed of uppermost mantle and crust; the “plates” in plate tectonics. Deforms brittely if at all
Asthenosphere
Weak substrate on which plates ride. Deforms plastically. “Solid, but mobile”
Isotasy
Refers to lighter crust floating on deeper mantle. The weight of the crust affects the position of the mantle
Inner core vs outer core
Inner core is solid, outer is molten. The movement of Fe in the outer core generates Earth’s magnetic field. The inner core of earth rotates at a different rate than the rest of the Earth. Together, they form most of Earth’s mass
Rock
Consolidated of one or more minerals
Mineral (definition/properties)
Solid, naturally-occurring, characteristic crystal structure (orderly atoms), generally inorganic, homogeneous
Crystalline
Any natural solid with an ordered, repetitive, atomic structure
Polymorph
Minerals with the same chemical composition but different structure
Mineral types
Silicates, carbonates, oxides, sulfides, sulfates
Five most common minerals
Plagioclase feldspars: 39%
Potassium feldspars: 12%
Quartz: 12%
Pyroxenes: 11%
Amphiboles/Micas/Clays 5%, or nonsilicates are 8%
Ways for minerals to form
Change in temperature, crystallization from solutions in water, biological processes
Chemical formula and charge of a silica tetrahedron
SiO4, -4
Mafic silicates
Rich in iron and magnesium; darker in color/green: Olivine and Pyroxene
Felsic silicates
Have smaller proportions of iron and magnesium and higher proportions of silica and oxygen; lighter in color: Quartz and Feldspar
Most abundant elements in earth’s crust
Oxygen (47%) and silicon (28%), followed by aluminum and iron
In ionic bonds (which form 90% of minerals), ______ of similar size can substitute for each other
Cations (smaller than anions); different cations form different mineral colors
Second most abundant mineral group in the earth’s crust
Carbonates
Major minerals of carbonates
Calcite, aragonite, dolomite
Mineral examples of oxides
Hematite, magnetite, corundum
Mineral example(s) of sulfides
Pyrite, chalcopyrite
Mineral examples of sulfates
Gypsum, anhydrite
How many subclasses of silicate minerals are there? What distinguishes these subclasses from one another?
6 subclasses, based on the arrangements of the silica tetrahedra
Nesosilicates
Single tetrahedron; olivine and garnet (most important minerals in the upper mantle)
Inosilicates
Single chain: pyroxene
Double chain: Amphibole
Phyllosilicates
Sheet structure, good basal cleavage
Tectosilicates
“Framework” structure; quartz and feldspar minerals are the most important groups
Key points to how the Earth was formed:
- Event triggered gravitational collapse of a cloud of dust and gas (a nebula), which formed a spinning disk as it collapsed; “nebular hypothesis” describes how our solar system evolved from the solar nebula
- Collapse released gravitational energy that heats the center and goes on to form a star
- Outer, cooler particles collide and build plants (and other bodies) (this is called accretion)
- Younger stellar activity blows off any remaining gas and leaves an embryonic solar system
- Rocky/terrestrial planets form in the hotter interior, gas/jovial planets form in the colder outer regions
- Earth formed its layers because of temperature and density differences (Fe and Ni sank to form the core, molten rock rose to form the crust. While this was happening, a Mars-sized body hit the Earth (forming the moon)
Nucleosynthesis
Refers to how all elements before Fe (iron) were created. Under intense heat, atoms fused together to form other light atoms
Planetary differentiation
The processes of separating out different constituents of a planetary body as a consequence of their physical or chemical behavior, where the body develops into compositionally distinct layers.
This process has occurred on planets, dwarf planets, an asteroid, and natural satellites.
Terrestrial vs Jovian planets
Terrestrial planets: inner planets, are more rocky, smaller
Jovian planets: outer planets, gas and ice, bigger
Giant Impact Theory
Main theory of moon formation. Shortly after the Earth formed, a Mars-sized body impacted the earth, generating a cloud of dust and vapor that condensed and accumulated to form the Moon.
What three factors increase with depth of the Earth?
Density, temperature, and pressure
Is the mantle or crust more homogeneous? Why?
The mantle is more homogeneous because it convects.
Mantle
Made up of dense rocks (peridotite, silicates). Is a non-Newtonian fluid.
Cation
Atom that gives up electrons and has a positive charge
Anion
Atom that takes electrons and has a negative charge
Most stable form of bonding
Covalent bonding
Cleavage
The way a mineral breaks
Note: In silicates, the O bonds are much stronger than the cation bonds, leading to planes of weakness
Properties used to identify minerals
Hardness, cleavage, fracture, luster, color, density, streak, and crystal habit
Fracture
Any break in a mineral that doesn’t occur along a cleavage plane
Irregular fracture
Uneven surfaces
Conchoidal fracture
Smooth, curved surfaces
Luster
The way a mineral reflects light. Metallic, nonmetallic (glassy, glossy, greasy, waxy, pearly, earthy)
