EPS Exam 1

Stano's Principle: Original horizontality

- Sedimentary rock layers are deposited horizontally
- If they are an angle, you have 2 events - one that deposited rock and one that tilted them

Uniformitarianism

- Idea that Earth has always changed in uniform ways and that the present is the key to the past.
- Does not always work because it constrains our interpretation of the past; and it is based on unfounded assumptions of the dynamics of physical processes and land surface systems

Ibn Sina (Avicenna)

- One of the first geologists to comment on the rock cycle, which describes how rocks are formed and then transformed from one type to another through erosion, weathering, sedimentation, and then ultimately deep burial and melting.
- He identified two of the three main rock types (sedimentary and igneous)

Unconformity

- A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.
- Three types: Angular, nonconformity, disconformity

Angular unconformity

tilted rocks are overlain by flat-lying rocks

Nonconformity

- Undeformed sedimentary rock sitting on top of metamorphic and ingenuous rocks (in picture, the gray section)
- At one point, there was uplift and erosion

Disconformity

Sedimentary rocks form, then are eroded, and then new sedimentary rocks are laid on top of the eroded surface.

Index Fossil

A fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found. Fossils usually exist for a short period of time

Radioactive decay

- Use radioactive decay of isotopes as a clock. Decay is exponential.
- Number of atoms always stays the same. \#parents will eventually equal \#progency once decay is done.
- Half life - time it takes for a quantity reduce half its value

Sedimentation Rate

- Measure the thickness of the rock and divide it by the duration to see how much rock has accumulated over time
- This theory assumes constant sedimentation over time, which is usually incorrect.

Igneous Rock

Rock that forms when hot, molten rock crystallizes and solidifies

Metamorphic Rock

Rocks that have become changed by intense heat or pressure while forming. Generally underneath the surface

sedimentary rock

- Rock that is formed by the accumulation or deposition of mineral or organic particles at the Earth's surface, followed by cementation

Stano's Principle: Superposition

Older rock is on the bottom, younger on top

Stano's Principle: Lateral Continuity

- Layers of sediment initially extend laterally in all directions (were deposited in sheets)
- Can be separated by erosion

Stano's Principle: Cross-Cutting relationships

Geologic feature which cuts another is the younger of the two features

Stano's Principle: Inclusion

The thing that is included is older than the thing it is included in

Faunal Succession

A principle or law stating that fossil species succeed one another in a definite and recognizable order; in general, fossils in progressively older rock show increasingly greater differences from species living at present.

Age of the Universe

13.8 Ga (Ga \= billion years ago)

Events following big bang

- Hydrogen and Helium Atoms created
- Atoms condense into clouds to form galaxies
- Milky way formed 10 Ga
- Stars form in galaxy - atomic fusion (He and H bond together to form new elements)

Synthesis of earth's matter

- Up to Iron 26 formed by fusion of atoms (nucleosynthesis)
- Heavy elements are synthesized by supernova (like copper, gold, tungsten)

Origin of solar system

- Solar nebula contained 99% He, H
- Also contained

Formation of Earth (accretion)

- 4.55 Ga (from radiometric dating)
- Start with giant spinning ball of gas and dust
- Ball flattens into disc shape
- Materials sticks together or collides to form clumps
- Clumps eventually form into planets

Moon-forming impact

- Earth's history is dominated by repeated giant impacts by smaller planets
- Largest of these formed the moon (4.5 Ga)
- These impacts have a lot of kinetic energy, causing earth's surface to be very hot - "magma ocean"

Planetary differentiation

Core (Iron) separates from other layers since it is denser than other layers

Primitive Atmosphere

- ~ 4.6 Ga
- Atmosphere began to form by degassing of Earth's interior
- Mainly Co2 in atmopshere

Primitive Ocean

- 4.40 Ga
- Atmosphere cools and water vapor condenses to water
- Rain filled basins form primitive oceans - primordial soup

First Pollution Crisis

- Proterozoic (2.5-0.5 Ga)
- Cynobacterial success causes photosynthetic waste, which causes rise in oxygen in atmosphere
- Oxygen poisoned other organisms
- Rise of eukaryotes due to higher O2 levels

Snowball earth

- ~ 650Ma
- Planet's surface was entirely frozen
- Best explains sedimentary deposits and presence of glacial deposits in tropical latitudes

Cambrian explosion

- 545 to 525 Ma
- A burst of evolutionary origins when most of the major body plans of animals appeared in a relatively brief time in geologic history. Recorded in the fossil record
- First life - 3.7 Ga
- Cambrian to earliest hominins - 6 Ma

Giant insects— when were they around and why

- 360-252 Ma during Paleozoic Era
- There was a high Oxygen level which was harmful to larvae. So, young insects had to grow larger to avoid oxygen poisoning.

What geologic trends or events set the stage for Quaternary glaciation?

- Product of Earth's internal variability of its climate system
- Changes in Earth's orbital eccentricity
- Changes in Earth's tilt on axis
- Mountain building that exposes new rocks and draws out CO2 from atmosphere
- Changes in Ocean Circulation

Similarities and differences between major extinction (P/T; K/P) events

- Volcanic activity in Siberia - high rise in CO2 (P/T event)
- Asteroid impact or large volcanic explosion (dinos)

How do we know what happened over billions of years of history

- Radiometric dating - use half life of radioactive elements to date rocks and materials
- Stratigraphy - sequence of events from which relative dates can be extrapolated.
- Molecular clocks - genetic divergence
between organisms to extrapolate backwards to estimate dates.

Earth's density

5500 kg/m^3

Earth's moment of inertia

0.33mr^2

Seismology

- CAT-scan for Earth's interior -Seismic waves are produced during earthquakes
- Can learn more about the core since the energy of earthquakes starts at the core and radiates outwards.

Seismic Waves

- Surface Waves - Ocean waves
- Body waves - P-waves (compressional, through solids and liquids) and S-waves (shear waves, solids ONLY so disappear when they reach outer core (liquid))

Do waves travel faster in colder or warmer rock?

Colder

Earth Structure

- Concentric Shells
- Go towards the center, increase in P, rho, and T
- Inner core, outer core, mantle, crust, hydrosphere, atmosphere (in-\>out)

Pressure

- Pressure, P \= density * gravity * depth
- Center of Earth has highest pressure: 350 billion Pa

Geothermal Gradient

- Rate of temperature change with respect to increasing depth in Earth's interior

Continental Crust

- Thicker, less dense, granite, more bouyant

Oceanic Crust

Thin, more dense, basalt, less bouyant

Mantle

- Everything left over after the core and crust are formed
- mostly solid rock
- 3 shells -upper, transition, lower
- Peridotite - most abundant mineral

The core

-Metallic
- Two regions - solid and liquid
- Iron - most abundant element
- T is abount 4000-6000C

Mantle convection

- Rocks can convect - as they become warmer, they become weaker
- Earth's mantle is heated from below the core
- Heated from within by decay of isotopes
- Convection drives plate tectonics - drags plates around

Lithosphere

- A rigid layer made up of the uppermost part of the mantle and the crust
- 50-200 km thick

Asthenosphere

- Region below lithosphere
- Includes just part of upper mantle
- Squishy but still solid layer on which lithosphere moves

How did Earth's layered structure form?

As the planet cooled, dense elements became concentrated in the core of the planet, while lighter elements formed the mantle. A thin, rigid crust formed at the surface.

Tools to study earth's interior

- Done by studying seismic waves
- Can tell how much energy is lost by how deep the waves are

Plate tectonics

describes movement of lithosphere in response to mantle convection

Wegener's theory of continental drift

- The continents were once united into a single supercontinent named Pangaea
- Suggested that Pangaea broke up long ago and that the continents then moved to their current positions
- Wanted to explain
• Shape of continents
• Contiguous geological features
• Evidence of past glaciers near the equator
Fossils of similar animals on unconnected continents

Pangea

- Supercontinent that formed in 350 Ma, broke apart 200 Ma

Mid ocean ridges

- Underwater mountain ranges
- Occur along divergent plate boundaries, where new ocean floor is created as the Earth's tectonic plates spread apart

Earth's magnetic field and magnetism of the ocean crust

- Symmetric magnetic field across ridges
- Earth's rotation causes spiral flow in the liquid outer core that aligns with spin axis
- Electrically charged spiral flow generates Earth's magnetic field
- Earth's core spins faster/slower than Earth's crust
- Magnetic field is aligned parallel to its rotation axis

Age of Seafloor

- Oceans are very young compared to continents
- Ocean is no older than 180 Ma

Wilson Cycle

The process by which supercontinents form and break apart over millions of years

Continental rifting

- Crust is broken and stretched producing a rift valley
- South America and Africa probably split this way
- Eventually produces a linear sea
- Modern example - East African Rift Valley

Seafloor spreading

If spreading continues, sea will develop into an ocean

Subduction

- Cold, dense oceanic lithosphere begins to plunge into the mantle below
- As the plate subducts (or goes down), magma is generated which rises up to the continental crust to form volcanoes
- Source of largest earthquakes
- Linear feature

Accretion and orogenesis

Accretion - addition of material (terrane) to continental crust
Orogenesis - process of accretion, volcanism and uplift that produces large continental mountain ranges

Isostasy

State of gravitational equilibrium between Earth's crust (or lithosphere) and mantle such that the crust "floats"

Convergent plate boundaries

- Area on Earth where two or more lithospheric plates collide. (SUBDUCTION)
- Oceanic crust is often forced down into the mantle where it begins to melt, (due to increased heat AND pressure)
- Causes volcanoes
- Source of 80% of earthquakes

Divergent plate boundaries

- Areas where plates move away from each other, forming either mid-oceanic ridges or rift valleys.
- Volcanoes and earthquakes produced

Transformed plate boundary

-The boundary between two plates that slide past each other
- No volcanoes, just earthquakes

Evidence for plate tectonics

- continental drift, inspired by the observation that the continents fit together like pieces of a giant jigsaw puzzle
- Volcanoes, earthquakes, mountain building

Specific examples on Earth of different types of plate boundaries

• Nazca (O) and SA Plate - subduction
• Cocos and Caribbean plate - subduction
• Pacific, Nazca, and Cocos - Divergent
• Pacific, NA - Convergent
• NA, Eurasia - Unclear, behaving like one plate

Brittle deformation

- Rock breaks along discrete surfaces (fractures or faults)
- Insensitive to T and increases with P
- Dominates in shallow parts of the crust

Ductile deformation

- Rocks change shape in a distributed way, like a fluid
- Ductile strength of rocks decrease with Temp, and is insensitive to pressure
- Dominates deep in the crust

Folds

Places where rocks have been compressed into bends by colliding plates

Strike-slip fault

- A type of fault where rocks on either side move past each other sideways with little up or down motion
- Dominant in transform plate boundaries

Normal Fault

- Block above the fault has moved downward relative to the block below.
- Dominant for divergent boundaries

Reverse Fault (Thrust Fault)

- Upper block, above the fault plane, moves up and over the lower block
- Dominant for convergent plate boudaries

Global distribution of earthquakes

- Most earthquake zones are found at, or close to, tectonic plate boundaries, often in clusters.
- Higher percentage of earthquakes in southern hemisphere than northern due to nature of tectonic plates

Where are largest earthquakes?

- Subduction Zones
- Alaska/ring of fire, Indonesia, South American subduction zones

Measuring earthquakes

- Seismometer - detects earthquakes by picking up vibrations
- P waves and S waves travel at different speeds - time gap between tells how far away the earthquake is
- Earthquake magnitude \= seismic moment
- Mercalli intensity - qualitative approach about how intense an earthquake is

Locating earthquakes

Epicenter can be found by finding intersection of circles centered at cities of impact

Earthquake early signs

P waves and S waves travel at different speeds - time gap between tells how far away the earthquake is. S waves are more damaging waves

Why are some regions more susceptible (in terms of fatalities and financial costs) to earthquakes?

- Infrastructure - in poorer areas, buildings don't have as many codes, could be constructed poorly, causing more fatalities
- Being near a large population center

Remote sensing

A method of collecting data or information through the use of instruments that are physically distant from the area or object of study.

Geodesy

The science of measuring Earth's shape

Cartography

The science of making maps by measuring position, elevation, perimeters or areas

Geoinformatics

- Combination of software, hardware, and scientific methods used to store, analyze, produce and display geographic information
- example - google maps

Minerals

- Chemical basis for earth
- Must be: naturally occurring, inorganic solid, that possesses an orderly crystalline structure and a well-defined chemical composition
- Uses - constructing buildings, developing weapons for defence, machinery, making jewellery, synthesizing fertilizers

Atomic bonding rules

- Atoms form compounds when it is energetically favorable (based on number of valance electrons)
- Also based on atomic radii (easier for compounds to form when atoms are a similar size)

Abundnace of elements

- Amount of minerals is based on the abundance of particular elements
- On Earth, most abundant element is Iron, then oxygen

Abundance of elements in crust and mantle

Crust - more silicon and aluminum. Oceanic crust has LESS silicon
Mantle - less silicon, more magnesium. Olivine is main mineral
Different composition because the crust is derived from melting the mantle. Parts that melt rise to the crust are the elements that make up the crust.

Types of silicates

- Single tetra - Si:O \= 1:4 ratio, very dense, high melting T, Olivine
- Single chain - Si:O \= 1:3, Pyroxene
- 2 Chain - Si:O \= 2:5, Micas
3D - Si:O \= 1:2, Least dense, lowest melting point, Quartz and feldspar, most abundant in crust

Why are there so many different kinds of silicates?

Nature of the silicon atom, and even more specifically, the versatility and stability of silicon when it bonds with oxygen.

Lava

Material in liquid form that is exposed to earth's surface

Magma

Material in liquid form that is contained at depth

intrusive igneous rock

Sits around the magma chamber for a while, and crystallizes slowly, so grain size is larger and coarser.

extrusive igneous rock

Exposed to air/water - crystallizes very quickly and grain size is very small.

Decompression melting

- Melting due to a drop in pressure
- • Common at mid ocean ridges and plumes

Flux Melting

- Melting due to a change in chemical composition

Solidus

A curve in a graph of the temperature and composition of a mixture, below which the substance is entirely solid.

Liquidus

A curve in a graph of the temperature and composition of a mixture, above which the substance is entirely liquid.

Partial Melting

Solid and liquid mixture (not at solidus or liqiudus yet, in between)

Composition of igneous rock

- Felsic, intermediate, mafic, ultramafic
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