GEOL 2300 Midterm

The ocean interacts with

chemistry, physics, society, geology, and biology

Problems in the world that have an effect on the ocean

climate change, acidification, deoxygenation, and pollution

Seafloor bathymetry is studied using

echo sounders and satellites

How do we know the earth is layered?

seismic waves and earthquakes

What are p-waves?

primary compressional waves that are extremely fast, like a slinky, not destructive, travel through solids and liquids, and are first to be recorded on seismographs

What is Moho discontinuity?

changes in p-wave velocity and angles due to the boundary between the crust and the mantle

What are s-waves?

secondary shear waves that pass through the earth moderately fast, go up and down, are not destructive, travel through solids, and stop traveling in the Shadow Zone

What waves travel along the earth’s surface?

L-waves and R-waves

How did the earth become layered?

density

What relationship do density and temperature have?

inverse

Where is the earth the most dense?

the core

Warmer temperature =

less density

Colder temperature =

more density

A liquid moves to areas of equal density as itself. Density below this liquid is ____, and density above this liquid is ____.

higher, lower

The earth is how many years old?

4.6 billion years

Reasons for the formation of the earth

cold accretion, solar winds, and added heat

What happens during cold accretion?

unsorted materials are very cold, which eventually become layered

How did solar winds influence the formation of the earth?

gravity compacted the earth, solar winds boiled away lighter elements, and heat arose from collisions

How did added heat influence the formation of the earth?

the earth heated up due to gravitational contraction, radioactive decay, and large meteorite impacts

What is differentiation?

materials becoming molten due to high temperatures (ex: iron and nickel sink to create the core)

What happens to the lighter materials due to differentiation?

they compose the surface crust

What happens to the mantle due to differentiation?

it becomes magnesium

What is the lithosphere?

the rigid layer composed of all the crust and part of the upper mantle

What is the asthenosphere?

the part of the mantle that can flow, which is not liquid

What is the continental crust?

basement rocks that are very old; 31% is submerged; rich in aluminum silicates

What is the oceanic crust?

younger and thinner crust than continental; has 3 layers; rich in magnesium silicates

How is the outer shell of the crust different than the mantle?

different chemistry that includes oceanic and continental crust

What is convection overturn?

internal heat from the interior that is transferred to the surface by convection

The earth has been cooling since ____________

4.4 Ga and is still cooling

Who came up with the theory of continental drift and Pangaea?

Alfred Wegener

What evidence is there for Pangaea’s existence?

paleoclimate data, distribution of fossils, and matching geologic units

How is paleoclimate data evidence for Pangaea?

certain biomes were at different latitudes in the past

How is the distribution of fossils evidence for Pangaea?

same species fossils are found on distant continents

How are matching geologic units evidence for Pangaea?

rock layers are the same on different continents (ex: mountain ranges)

What observation did Harry Hess make?

seafloor spreading, as thickness of sediment decreases towards ocean ridges, deep sea drilling, and the age of the crust were evidence for it

How were deep sea trenches and ocean ridges discovered?

sonar and bathymetry during WWII

What exist along continental margins?

shelfs, slopes, and rises

Where is ocean sediment thickest and thinnest?

thinnest at mid-ocean ridges and thickest at continental margins

What is ocean crust made of, and what is continental crust made of?

basalt and granite

What causes uneven heat distribution beneath mid-ocean ridges?

more heat rises there

What is seafloor spreading?

magma rising that pushes mid-ocean ridges apart

Where is earth’s magnetic field strongest?

near the poles

What is geomagnetism?

earth’s magnetic field polarity reverses poles periodically

What is paleomagnetism?

iron bearing minerals align with earth’s magnetic field when magma cools

What is the plate tectonic theory?

plate movement causes continents to move and interactions at boundaries result in earthquakes, volcanoes, and mountain building

What is the Ring of Fire?

where a lot of seismic activity occurs around the Pacific plate

How many plates does the lithosphere consist of, and where are they located?

20, in the lithosphere which floats on the soft asthenosphere

What is the ridge push force?

the force that drives plates away from mid-ocean ridges

What is the slab pull force?

the force that down going slabs apply to the lithosphere at a convergent margin

What are the types of plate boundaries?

divergent, convergent, and transform

What happens at divergent plate boundaries?

plates move apart, new crust is formed, and earthquakes/small volcanic eruptions occur

Where are divergent plate boundaries found?

in oceans and mid-ocean ridges

Explain seafloor spreading at divergent boundaries

the seafloor is elevated, forming oceanic ridges, where some have deep rift valleys along their axis

What is continental rifting?

divergent plate boundaries that develop within a continent

What happens at convergent plate boundaries?

plates move together, the more dense plate sinks under the less dense plate, one plate is consumed, and earthquakes/large volcanic eruptions occur

What happens during a convergent oceanic-continental collision?

continental volcanic arcs and felsic rocks are formed (ex: Chile)

What happens during a convergent oceanic-oceanic collision?

ocean island arcs and felsic rocks are formed (ex: Aleutian island arc)

What happens during a convergent continental-continental collision?

mountain ranges and metamorphic rocks are formed (ex: Himalayan mountains)

What happens at transform plate boundaries?

plates move along each other and earthquakes occur

What is an example of a transform boundary?

the San Andreas Fault

What are the types of continental margins?

passive and active

Describe passive continental margins

not on a plate boundary, wide shelf, shallow slope, and no earthquakes/volcanoes

Describe active continental margins

on a plate boundary, narrow shelf, steep slope, and has earthquakes/volcanoes

What is a hot spot?

at the base of the lithosphere where high temperatures cause melting

How do hot spots create island chains like Hawaii?

the hot spot under oceanic crust stays in the same place while the lithosphere above moves

What is an atoll?

forms around a hot spot as the island created moves off the hot spot; causes coral reef and lagoon formation

What is a triple junction?

meeting point between 3 plates

How are ocean basins formed?

through continental rifting

Between what temperatures does water exist at?

273-373 K

What is used as an alternative for testing how much water is in the mantle?

meteorites

What is the cometary ice hypothesis?

the theory that ocean water came from comets

What are the sources of water on earth?

outgassing and cometary ice

How much of all water is in the ocean?

96.5%

How much of all water is freshwater?

3.5%

How much of freshwater are ice caps/glaciers?

1.78%

How much of freshwater are surface waters?

.013%

How much of freshwater is air/soil?

.002%

How much of freshwater is groundwater?

1.69%

How is the earth unique with water on it?

water is in all forms of solid, liquid, and gas

How strong is the Van der Waals force in water?

it is the weakest

What bonds can exist between water?

hydrogen, ionic, and covalent

What is heat capacity?

amount of heat needed to change an object’s temperature (high for water)

What is latent heat?

the amount of heat needed for a phase change

What is sensible heat?

heat you can sense/feel

What are the 2 types of latent heat?

fusion and vaporization

What happens during thermal expansion for water?

a solid is normally denser than a liquid, which is denser than a gas, but this is the opposite for water

What affect the ocean’s freezing point?

temperature and salinity

What type of solvent is water?

universal

What are examples of biogeochemical cycles?

water and carbon cycles

What are the major constituents?

chlorine, sodium, magnesium, sulfur, calcium, and potassium

How are the major constituents created?

erosion

How are the major constituents removed from the ocean?

they precipitate out of solution due to the concentration increasing from evaporation

How are minor constituents and trace elements removed from the ocean?

biological processes through marine life (ex: phytoplankton absorbing elements)

What percentages are major/minor constituents and trace elements?

99.6% and .4%

What do radionuclides do?

measure ocean circulation and food webs

What are organic compounds helpful to?

bacteria and archaea

Where are dissolved gases?

they move between the atmosphere and ocean

At what temperatures are gases more soluble at?

colder

The ocean is similar to a reservoir how?

it is a major carbon dioxide sink

What causes surface tension of water?

Van der Waals force