Lecture 14 Flashcards
What are the major zones of the earth?
- Crust
- Mantle
- Core
Mineral
A naturally occuring, inorganic, element or compound, with a definite internal arrangement of ions(solid) and a chemical composition that is fixed or varies within narrow limits.
Rock
Aggregates of one or more minerals, found on earth’s crust.
What is the most abundant mineral in earth’s crust?
Oxygen
How can oxygen be part of the crust?
Very reactive, so reacts with other elements
Native elements
Pure elements
What are the most abundant mineral groups?
Silicates
When is the chemical make up of minerals more common?
In ion substitution
What are the ways to identify minerals?
- Hardness
- Color, luster, streak
- Density
- Cleavage/fracture
- Magnetic properties
silica tetrahedron
Silicon atom attached to four oxygen atoms by tetrahedral bonds, results in a 4- charge on the SiO4 (silicate) group. Basic building block of silicates.
Pyroxenes
Single chains of tetrahedra balanced by similar metal cations and sodium(Na)
Amphiboles
Double chains of tetrahedra balanced by similar cations.
Micas and Clay materials
Sheets of tetrahedra are the building blocks. Aluminum is also involved in these sheet structures which are charge balanced by the cations Mg, Na and K
Feldspars
A second group of alumino-silicates, the tetrahedra form three-dimensional frameworks with Ca, Na and K as the balancing cations.
Quartz
Three dimensional framework structure without cations an just silica tetrahedra. Very stable
What are mineraloids?
Not minerals include Opal and amber
How are minerals formed?
Formed by crystallization. The center of the earth causes rocks to melt forming magma. When magma cools various elements and ions come together to form very specific structure. Different minerals form at different temperatures.
What are the three categories of rocks?
Igneous, Sedimentary and Metamorphic
Igneous rock
formed by the crystilization of magma. Two forms:
1) Extrusive(volcanic)-rapid cooling, usually derived from upper mantle high quantities of iron and magnesium
2) Intrusive(plutonic)-slowly cooling, usually derived from crust so relatively rich in silicates and aluminum.
Sedimentary rock
formed by the sedimentation and campaction of material(lithification)
-tends to form in layers
Metamorphic rock
Rock that has been chemically altered while in the solid state from exposure to high temperatures and pressures. The process is re-crystallization
Rock cycle
Goes from igneous to sedimentary to metamorphic and back to igneous. Look at slide photo
What are the parts of the earth’s core?
inner (solid) core
outer (liquid) core
Seismograph
Measures and records the minute tremors of the earth
How have the properties of the inner earth been analyzed?
Looking at meteorites(similar in composition to earth) and the seismograph
What are the two waves propogated by the earth?
Surface waves(travel along the surface) and Body Waves(travel on earth interior)
What are the forms of body waves?
P-waves and S-waves
P-waves(primary waves)
compression waves like sound waves
S-waves(secondary or shear waves)
Involve displacement perpendicular to the direction of the wave.
What body wave type is fastest?
P-waves
The S Shadow
S-waves do not propogate through the liquid outer core. Since S-waves only travel through solid material, it has been concluded that the outer core must be composed of molten metals.
Does the earth interior have an effect on wave velocity?
Yes, changes in the properties of the earth interior with depth cause the waves to bend.
lithosphere
composes the first 70-125km of the solid earth, consists of the oceanic and continental crustal material plus the uppermost portion of the mantle. It is rigid and acts as a single unit.
asthenosphere
(~100km in depth) characterized by low p-wave velocities. Because of low velocities geologists have deduced that the layer is plastic(not liquid or solid) as a result provides.
- source of material ejected in volcanoes
- rebound of crust following ice ages
- provides malleable layer upon which plates can flow
