Introduction to Earth Science: Final Exam (Uiowa)

Flood

what happened in Iowa City in 2008?

Four

How many 500 year floods have occurred in Iowa in the past ~200 years?

Oklahoma

Which state had the most earthquakes?

increase in wildfires, crop/pasture losses, shortages of water reservoirs, streams, and wells creating water emergencies

what are some of the consequences of the ongoing drought in California?

Took earthquake and tsunami: magnitude 9; 20,000 plus people killed; 130,927 displaced; 332,395 buildings destroyed; 13+ meter tsunami sunup; cost 309 billion US dollars; all power offline.

What happened on March 11, 2011, and how big was this event (both a number and a ranking, relative to other such events)?

1. Faunal Distributions

2. Fit of edges of continents

3. Matching Rock Types

4. Records of past glaciations

What were Alfred Wegener's 4 pieces of evidence to support his theory of continental drift?

Tillites

big piles of unsorted sediment

tillites

How does glacial evidence support the idea that contents used to be joined in one land mass?

the mechanism was insufficient, what we needed wis more evidence from the geosphere (the Earth's crust, mantle, and inner metallic core)

What did Wegener lack, as part of his theory?

1961

When did Bernhard Mumme write that (essentially) moving continents were unnecessary to explain

Earth's history?

Layers of the Earth

Speed of sound in water: 1500 m/sec

Depth= 1/2(1500 m/sec*travel time) it can tell us how deep the ocean is a specific location

How does sonar work and what does it tell us about the ocean floor?

how sediment depth and clean floor age changes with distance form the mid ocean ridges

New crust forms at ridges- Seafloor spreading. Pushes old crust out and eventually gets "recycled"

How old is the oldest ocean crust, and how much of the rock recored is therefore missing on the ocean floor given the age of the Earth (4.56 billion years)?

Oldest oceanic crust is 200 million years old

What feature of the Earth do minerals line up with that allow us to infer polar wander curves?

the earths magnetic field

What does magnetic polarity look like across the mid-ocean ridges?

there is a continuous chain of colonies on the ocean floor. Discovered that the Earth's magnetic field has reversed its polarity.

Are earthquakes distributed randomly on the Earth's surface?

No they are distributed along plate boundaries for the most part

What are some of the modern sources of support for plate tectonics theory?

InSAR (Interferometric Synthetic Aperture Radar)

measures post-earthquake displacements

Can a single tectonic plate contain both oceanic and continental crust?

one plate can contain both kinds of crust

How do oceanic and continental crust differ?

Oceanic: DENSE (3.2 g/cm3); Tinner (7-10km); Rocks include basalt and gabbros; The older, the colder; Accommodates pressure by either overriding or subducting.

Continental: LESS DENSE (2.7 g/cm3); Thicker (25-70km); Rocks include granite; Accommodates pressure by building enormous mountain ranges, this WILL NOT subduct!

Given how we zone the Earth by chemistry and by strength, what portions of the Earth make up the tectonic plates?

3 different kinds of boundaries?

1. Convergent

2. Divergent

3. Transform

2 different kinds of crust

1. Oceanic

2. Continental

Convergent Boundaries

-2 plates move towards each other

-Makes the crust in the area SHORTER: where we recycle old crust (destructive)

Who subducts? Ocean-Content

Oceanic crust always subducts

Who subducts? Ocean-Ocean

Old Oceanic crust will subduct

Who subducts? Continent-Continent

Neither Subduct, the pile up to create mountains

Ocean-Continent Convergence: the Andes

Nazca Plate subducting under the South American Plate. Convergent Boundary

How Volcanoes form (three main ways)

1. Lithosphere descends deep into the mantle and heats up, generating melt

2. Lithosphere descends deep into the mantle and releases water, generating melt (a term for this is flux melting)

3. The lithosphere is pulled apart and the asthenosphere rises and melts (decompression melting)1

How mountains are formed

1. Colliding plates with each other

2. We subduct lithosphere, generating volcanic mountain ranges

How we get earthquakes

1. We slide plates past each other

2. We push plates into each other

shaking of the ground caused by sudden motions along faults, or fractures in the earths crust

Wadati-Benioff zones

Where crust gets recycled: You can see the outline of the subducting plates, this is why we see such deep earthquakes: they occur in the subducting slab as it descends into the mantle.

Summary of Ocean-Continent convergence

-oceanic crust consumed

-earthquakes occur at great depths (up to 600 km!)

-Subduction zones are the only place on Earth we can get earthquakes at more than 100 km depth (Wadati-Benioff zones)

-Trench where plate goes down

-Huge mountains

-Volcanism

Ocean-Ocean convergence

Older colder plate subducts, deep ocean trenches, Wadati-Benioff zones of deep earthquakes deep ocean trenches and curveted island arc, volcanism

Continent-Continent Convergence

India and the Eurasian plates produce the Himalayas where they collide. Under Himalayas is some of the most thick crustal. Not many volcanos. extreme amount of earthquakes due to crust running into each other. Here, the crust is piled up, broken, and thirsted on top of itself. This is due to the extreme forces pushing these two tectonic plates together.

Divergent Boundaries

We make new crust, like mid Atlantic Ridge, African Rift Valley, plates pull away from each other.

African Rift Valley

we are making a new ocean basin, we see the development of horses and grabbers, these down dropped blocks result from the crust pulling apart as the rift widens. We get parallel faults (breaks in the ground surface) across the rift as well.

`Ocean divergence

best example is Mid Atlantic Ridge or East Pacific Rise. Crust pulls apart asthenosphere rises and melts, and we get new crust. Mid ocean ridges are massive underwater volcanic chains. Spreading rates vary from 1-20 cm/year.

Transform Boundaries

-plates slide past each other, conservative (crust is neither created nor destroyed)

-the Mid Ocean ridge is offset by transform boundaries. These link spreading sections of the ridge.

-Depth of earthquakes at oceanic transform boundaries is limited by transform faults.

-the San Andreas in California is a continental transform boundary.

San Andreas fault

large earthquakes every 150 years, different segments have behave in different ways. part of a very complex tectonic setting. Loma Pieta earthquake. Overall California is part of a very complex tectonic setting. cracks in the ground and earthquakes

conservative boundaries

crust is neither created nor destroyed, transform

destructive boundaries

crust is destroyed, convergent

creative boundaries

crust is created, divergent

What do hot spots tell us about, and what is a hot spot? examples???

crust moves over mantle plumes examples include, yellowstone and Hawaii.

Earthquake

Seismology is the study of earthquakes, and earthquakes is seismic release of energy from rocks that were locked. Cold, brittle rocks build up strain along fault planes until elastic strain in surrounding rocks overcomes frictional force, then release strain over a time period of seconds to minutes. This generates earthquakes.

Strain

the resulting deformation

Elastic strain

(what we see in the rocks bordering fault plains): this change in rock shape resulting from stress will be reversed when the fault plane slips (rocks will return to original shape)

What controls the global distribution of earthquakes (where do they occur)?

Mostly at plate boundaries, also at faults. Wadati-Benioff zones and other convergent boundaries: plates run into each other (compressional settings where we have reverse and thrust faults); Transform boundaries (like San Andreas) where plates slide past each other.

Earthquake Anatomy

Focus (hypocenter) point within the Earth's crust where energy is released from (x,y,z: latitude, longitude, and depth) KNOW DIAGRAM

Body waves

tell us about the interior structure of the Earth. Seismic wave velocity varies as the properties of the material that they are passing through changes (properties include density, elasticity, composition, pressure, and temperature). When waves pass from one material into a different material, they can be bent (redacted) and may also bounce off of it (reflected).

Body Wave: P-Waves

compressional (material is pushed): FASTEST. Deflected in interior of Earth when traveling through outer core

Body Wave: S-Waves

shear (material moves back and forth): SECOND FASTEST, cannot travel through liquid outer core.

Surface Waves

the most destructive waves produced by earthquakes: they can cause the worst ground shaking. travel the slowest of all seismic waves, and move along the surface of the Earth.

Types of Surface Waves

Rayleigh waves: vertical, these look like ocean waves

Love waves: horizontal, these slide back and forth

The Mohorovicic discontinuity

crust/mantle boundary, within lithosphere; change in velocity of seismic waves.

The Lehmann discontinuity

boundary between inner and outer core

What information do we use to locate earthquakes? What instrument do we use, and how many stations do we need?

It is possible to locate earthquakes because P and S waves have different travel times. We record their arrivals with instruments called seismographs, which produce seismograms (the recordings of ground motion). As distance from an earthquake increases, the distance in arrival time between P and S waves also increases. We can therefore look at seismograms and gauge distance from an earthquake's epicenter. three seismograms.

Richter scale

developed for earthquakes in California, performs poorly with very large earthquakes

Mercalli scale

we determine the size of historic events based on this, which uses reports of damage and what people felt

MW: Movement Magnitude

This is what most news outlets report. The Mw scale is based on the amount of slip that occurs and the length of the fault that slips. It is an estimation of energy released, and is a logarithmic scale: a 9 is 10 times more powerful than an 8 an 8,etc. Theoretically, there is no limit to how hight his scale could go (a Mw 16 would split the Earth in half) but we don't have any faults long enough to produce anything bigger than what we've seen.

Earthquake Hazards: Shaking

ground motion produced by surface waves. These are the destructive waves, and the force generated by them can knock buildings down, knock things off walls, etc.

Earthquake Hazards: liquefaction

unconsolidated sediment, when shaken by an earthquake, can liquefy - buildings on it will subside.

Earthquake Hazard: Tsunamis

generated by movement of the crust under the ocean, or by landslides. These can produce enormous and extremely devastating waves. Tsunamis are generated by movement of the entire ocean column and can travel at speeds exceeding 500 kmh and have extremely long wavelengths (100 km plus)

Earthquakes in the United States (New Madrid Fault Zone)

We do have record of big earthquakes in the United States, even in places that aren't California or Alaska. New Madrid Fault Zone, Historically Mw 7+, last major earthquakes in the 1800s. This zone may be building energy for another release. New York City frequently experiences EQ of magnitudes between 2-3 but historically has had a 6.

Earthquake forecasting

we look where faults are locked, and look at past events to estimate magnitudes and recurrence intervals. From this, we can estimate how likely an EQ might be in a certain time period.

Earthquake prediction

can't predict when a fault is actually going to slip.

what should you do if you feel an earthquake

get under a desk and hold on to it so it doesn't move

What do diamonds and pencil lead have in common

Carbon

1. Inorganic: not alive (or once living)

2. Naturally occurring: not manufactured.

3. Solid: firm and stable in shape

4. Characteristic chemical composition

5. Crystalline structure

What are the five requirements minerals have to meet to be classified as a mineral?

Why does a mineral differ from an element?

in minerals, the smallest unit that we can break down to is the UNIT CELL: this is where we see our orderly, repeating atomic structure. Elements can be broken down into one atom. There are native minerals that are composed of exclusively one element, such as gold and copper.

crystallize (mineral)

from magma or lava

precipitate (mineral)

out of water or other fluids

weathering reactions

minerals formed from weathering reactions.

Why are minerals environmental fingerprints?

Minerals are environmental fingerprints because they give us specific information about how and where they are formed (stability fields)

Protons

positive charge

Neutrons

no charge (neutral)

Electrons

negative charge (these form a cloud around the nucleus)

Atomic number

number of protons

Mass number

number of protons + neutrons

Isotopes

Atoms of a particular element that have different numbers of neutrons. they can be stable or unstable (unstable isotopes decay and can be used to estimate ages) and exam is uranium

Covalent Bond

share electrons and strongest

Ionic

take electrons, Ionic solid: electrostatic attraction between positive cations and negative anions. Ordered arrangement of oppositely charged ions but maintains overall electric neutrality

Mineral properties: Color

not always diagnostic- can vary due to different trace elements (example: red corundum is ruby; any other color of corundum is a sapphire)

Mineral properties: Clarity

a. Transpatent: see through

b. Translucent: foggy

c. Opaque: impervious to light (like metals)

Mineral proporties: Crystal Form (habit)

how a mineral grows when there is nothing inhibiting it. This reflects the internal crystal lattice structure, and different minerals may have characteristic crystal shapes.

Mineral properties: Luster

how light reflects from the surface of an object, two classes

a. Metallic (like metal)

b. Non-metallic (does NOT look like metal)

Mineral properties: Streak

Color of the mineral in powdered form.

Mineral properties: Hardness

use Moh's hardness scale

Mineral properties: Cleavage

tendency of some minerals to break along flat, parallel surfaces (cleavage planes) that are weak planes within the crystal. described by the geometric shape formed: the number of planes and the angles between them (as well as how good they are - are they shinny?)

Fractures

breaks that do not occur along cleavage planes. these look like broken glass, and can occur because bond strength is EQUAL in all directions.

how do Igneous rocks form?

cooled from molten material (hot material at the Earth's surface-these are extrusive)

how do Sedimentary rocks form?

aggregates of smaller grains

how do Metamorphic rocks form?

a sedimentary or igneous rock that has undergone high temperature or pressure but has NOT melted all the way

magna when gets to the earth is called lava. hot material at the Earth's surface is extrusive, and below the earth is intrusively.

What is the difference between magma and lava?

What determines our final type of igneous rock?

a. type of material that was melted (source), and addition/deletion of different components

b. way the material solidified (rate of cooling, related to whether rock is intrusive vs. extrusive)

Mafic minerals

dark in color and include pyroxene, olivine, amphibole, and biotite mica

Felsic minerals

lighter in color and include quartz, potassium feldspar, muscovite, and Narich plagioclase feldspar.

Oceanic crust: Mafic, dense, thinner

Continental crust: Felsic, Less Dense, thicker

Oceanic vs Continental Crust

What are our three different ways of generating melt and what plate tectonic settings are they associated with?

1. Add Heat (thermal melting) where plates run into each other, we can push one down to great depths, where it will heat up and melt.

2. Decrease pressure (decompression melting) where plates pull apart from each other, we can move solid mantle material into a lowe pressure environment (it moves upwards) and melt it by decompression.

3. Add Water (fluid-induced or 'flux' melting). Where we take plates and run them into each other, we can also force water-rich minerals down into the Earth. Water lowers the melting point of rocks, so this can generate flux melting.

Different minerals will form as temperature drops because they will be stable (i.e. olivine forms first)

What is fractional crystallization and how does it affect the rock that we might form?