Geology Exam One
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Historical views of Earth's place in the universe (helicocentric and geocentric).
- 1000 b.c.e.– Greeks distinguish stars and planets– Stars rotate around a fixed point– Planēs: “wanderer”
- – What was the Sun? • A burning bowl of oil(A ball of red hot iron)
Draw and describe Eratosthenes' calculations and significance.
What is Ptolemy's model for a geocentric universe? What is the most important thing Ptolemy was able to do that got people to believe the geocentric model?
Know the contribution for the helocentric model by Galileo, Newton and Foucault and pendulum.
They made this machine that they noticed the ball would swing at different angles at different types which the swing helped them determin which way out Earth rotated.
How old is the universe?
- • Big Bang Theory
- – 13.7 billion years ago
- – Explosion of matter from a single point
- – Evidence for the theory
- • Unsolved mysteries
- – Where did matter come from?
- A meterorite
- – Multiple cycles of expansion and collapse
What is the Big Bang Theory? and is it flawed?
- • When did the expanding begin?
- – All of the mass and energy in the Universe was packed into a single small point
- – 13.7 Ga it exploded and has been expanding ever since
- • A rapid cascade of events.
- – Protons and neutrons formed within 1 second.
- – Hydrogen atoms formed within 3 minutes.
- – Hydrogen fused to form new light elements (He, Be, Li, B) via big bang nucleosynthesis
- After Big Bang
- With expansion and cooling...
- – Hydrogen forms H2
- - The fuel of stars
- – Molecules coalesced into gaseous nebulae
What are the characteristis of our solar system and how it formed?
- • Heavier elements– From stellar nucleosynthesis.
- • The mass of a star governs its element production.
- Large mass stars burn more rapidly, are short lived, and create heavier elements up to Iron.
- Small Mass stars burn slowly, burn slowly, live longer, create lower elements up to carbon.
- • A 3rd, 4th or nth generation nebula forms 4.56 Ga• The nebula condenses into an accretion disc
- • Particles coalesce to form planetesimals and stars
Have an idea of what geologic age is.
- Multiple mass, extinctions, 90% of Earth's history is void of complex life, stable oxigenation. 1 billion years ago.
- • Earth is 4.5 billion years old
- – Stable oxygenation 1 billion years ago
- • Life evolves
- – Positions on watch
- • Humans
- – Primitive: 3-4 million years ago
- – Modern: 90,000 years ago
Definition of mineral.
A mineral is a naturally occurring inorganic solid element or compound, with a definite chemical composition and a repetitive internal crystal structure.
- ~ Atoms in a mineral are specifically ordered.
- ~A solid with disordered atoms is called a glass.
- ~Crystalline structure based on atomic patterns.
What is important about a crystal lattice in a mineral? Are we able to identify crystal structure by a sample in our hand?
- ~ Ordered atoms in crystals form a 3-D lattice
- ~ Lattices are patterns that repeat in 3 dimensions
- ~ This internal pattern controls mineral properties• Crystalshape • Symmetry
- ~No it can not be fully seen by the Human eye.
- ~Instrumentation allows us to “see” atoms • A beam of electrons passes through material • Atoms scatter electrons, which pass between them • A shadow on the detector indicates a row of atoms • This principle drives theelectron microscope
- ~X-Ray Diffraction (XRD) probes crystal lattices
- ~Unique lattice spacing is used to ID minerals
What is a polymorph?
- A polymorph is one or two or more minerals with an identical chemical composition but with different arrangements of atoms. Example, diamond and graphite.
- ~Same composition but different crystal structure
- ~Polymorphs reveal the importance of bond type
- ~Diamond and graphite are carbon polymorphs• Diamond–Strongcovalentbonds;hardestmineral • Graphite – Weak Van der Waals bonds; softest mineral
What is a nucleation point and what happens at it?
A nucleation point is a pit in a rock or mineral which becomes filled with a carbonite. When these two meet it forms a fissing at the surface. Example, HCL and calcite.
- Luster - vitreous, waxy-greasy, pearly, satiny, earthy/dull, and porcelaneous.
- Hardness - talc 1, fingernail 2.5, nail 4.5, glass plate 5.5, quartz 7, diamond 10
- Streak - color of residue
- Cleavage - near or at 90 degrees, number of cleavage planes
Types of cleavage and their characteristics.
Near or at 90 degrees, number of cleavage planes
- Silicates - olivine, amphibole, pyroxene, biotite, muscovite, quartz, potassium feldspar, plagioclase fledspar, serpentine
- Carbonates - caclite, dolomite
- Oxide - corundum, hematite, magnetite
- Halaide - halite
- Sulfate/Sulfide - gypsum, chalcopyrte, pyrite, galena, sphalerite
- Native Element - gold, copper
Contributions to Science
- • Contributions to Science
- – Developed the mechanism for the formationof various magmas
- – Intimate understanding of the behavior of mineral crystallization
- – Insight into Earth history
What is the difference between plutonic rocks and volcanic rocks?
- Plutonic (intrusive) - rocks that form below the Earth's surface.
- Volcanic (extrusive) - rocks that form by being shot out of a volcano.
What is the difference between intrusive and extrusive egneous rocks?
- Plutonic (intrusive) - rocks that form below the Earth's surface.Volcanic
- (extrusive) - rocks that form by being shot out of a volcano.
- Mafic - composed mostly of pyroxene, calcium-rich plagioclase feldspar and olivine that have relatively high magnesium and iron contents and a relatively low silicon content.
- Intermediate - (e.g., andecite and diorite) and the magmas they crystalize from, that have a composition in between that of mafic and felsic rocks and magmas.
- Felsic - composed mostly of quartz, sodium-rich plagioclase, and potassium feldspars
Why are there different types of magma and how did they form?
- There are different types of magma due to the composition of each type. Explain how it was formed.
- •Partial melting
- Heat up the rock
- More felsic minerals melt out first
- Transport the melt separating it from more mafic crystals
- Between 2% to 30% of a rock melts under most conditions found in the Earth
- Oppisite of Bowen's Reaction Seires
- Differentiation-Mafic crystals settle, Remaining magma more silicic
- Not Efficient Enough-Process normally can produce an intermediate magma• Rarely extensive enough to make felsic
- • Differentiation
- – Mafic crystals settle
- – Remaining magma more silicic• Not Efficient Enough
- – Process normally can produce an intermediate magma
- – Rarely extensive enough to make felsic
What do Zircons in granites show us? How does it relate to Bowen's Reaction Series?
Glassy, vesicular, aphanitic, porphyrtic, phaneritic, pegmatitice, this tells us how and where the rocks were formed.
Why are Sedimentary Rocks so imporantant?
- • The most important rock type
- – Sedimentary rocks record history
- – What a geologist sees
- – Formations in the Grand Canyon
- • Location of formation
- – Only form at the Earth’s surface
- – Cover 80% of the surface
- – Less than 1% of Earth’s mass
What are the three types of sedimentary rocks?
- • “Klastos” – Greek word meaningbroken
- • Sediment = Clasts
- – Where do clasts come from? loose sediment
- – How are clasts made? by combining loose sediment into the 5 step process
- – What process takes loose clasts and makes them into solid rock? Cementation
- Chemical• Precipitation
- – Make minerals out of water solutions
- – A major process is evaporation
- • Evaporites
- – 80% of water evaporates = Gypsum
- – 90% of water evaporates = Halite
- • Seawater evaporation
- – 80% of minerals formed are halite
- – 13% of minerals formed are gypsum
- – 7% are carbonates and other salts
- • Chemical Balance
- – Travertine (Chemical Limestone)
- • CO2 degasses from groundwater
- • Water now becomes less acidic
- • Calcium carbonate (Limestone) precipitates
- – Limestone
- • CaCO3
- • WILL REACT WITH HCl
- • Reacting with preexisting rock
- – Limestone turns to dolostone whengroundwater has Magnesium present
- – Silica replacement
- • Dissolved silica begins to replace less stable minerals in a rock
- • Most fossils are not the minerals that make up bone
- • Just like petrified wood
- Biochemical / Organic Rocks
- • Organisms do work
- – Concentrate mineralsin shells and skeletons
- – Can make limestones
- – Biochemical chert
- • Planktonic shells of silica accumulate on the ocean floor
- – Coal and oil shale
- • Contains pure carbon
- • EXTREMELY IMPORTANT
Do all Chemical rocks precipitate at the same time, or with the same amount of water evaporation?
No because rocks differ in composition which can increase or decrease the speed of parcipitation.
What do Clast size, clast roundness, clast sorting, and mineral composition each tell us about a sedimentary rock?
How far it has traveled
Be able to put rock types and decribe their characteristics for several enviromnents.
Look at lab book
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