dynamic earth Flashcards
earths spherical shape shows…
Earths spherical shape means that earth is dominated by gravity due to gravity pulling everything together. It also shows that earth has a low strength as gravity can pull the plant into a sphere.
- You could say the asteroid has greater strength as it has an irregular shape.( the asteroid Ida has an irregular shape)
what is the effect of the moon on earth?
it helps to stabalise the planet and effects the climate cycle
what do moving clouds give evidence for?
evidence of atmosphere
over large distances and long times, the earth behaves like..
a fluid with no strength
around what is the earths average radius?
6400km
-Equatorial radius 6,378,137 m
– Polar radius 6,356,752 m
– mean radius ~ 6,371,000 m
~ 6400km
- Though Everest is the highest peak (8,848m) and challenger deep is the deepest (10,898m) they are not the furthest away/ closest to the centre of the earth. why?
due to the earth not being completely sherical.
These records go to the summit of Kilimanjaro and the Aleutian trench.
why is challenger deep so deep?
it does not fill up with sediment like holes that are close to continents
what is the average height of land?
0-1 km
what is the average depth of the sea?
4-5km
the coastline does not represent …
the boundary between ocean and continent
the boundary between continent and ocean are normaly below water.
what does this image show?
The hypsometric curve shows % of earth at certain heights.
+ From this curve you can see most of earth is just above or well below sea level. There is a large jump between the two heights.
+ The boundary at 2km depth is around about the boundary between continent and ocean.
how can satellites tell the bathymetry of the sea?
A bulge in the sea floor will mean more mass, thus more gravity. This extra gravity means that the bulge can pull water towards it more than the flatter areas around it. This causes the overall sea level around it to also bulge. A satellite can then send microwaves to the sea level and then workout the distance. By doing this for several areas you can see changes in the sea level and thus workout the shape of the sea bed.
describe and name the areas at a passive margin boundary between continent - ocean transition.
The earth’s continents stick up out of the ocean because…
The earth’s continents stick up out of the ocean because the continental crust is made of thick, low density rock that floats high in the mantle
The earth’s ocean basins lie deep below the ocean surface because
The earth’s ocean basins lie deep below the ocean surface because the oceanic crust is made of thin, high density rock that floats low in the mantle.
state ocean
composition
Thickness
Age
height
structure
composition ~ basaltic
Thickness ~ 7 km
(7km gets you about 4-5 km below sea level)
Age < 200 My
depth ~ -5000 m
structure- simple
state continent
composition
Thickness
Age
Surface
structure
composition ~granitic
Thickness ~ 35 km
(35 km gets you a few 100m above sea level)
Age up to 3.5Gy
Surface~+500m
structure - complicated
what are the compositon of nitrigon, oxygen, argon and carbon dioxide in the atmosphere?
nitrogen - 71%
oxygen - 21%
argon - 1%
carbon dioxide - 0.035%
there are few crators on earth, what does this show?
Because there are few craters on earth it shows us that the crust is active and young as the craters are quickly removed. Through:
- Erosion
- Deposition
- Volcanism
- tectonics
Otherwise we would look like other planets with many craters (moon, mars and Venus)
The atmosphere, ocean, surface and interior are all active.
Evidence for active processes include lava and ash covering the land, ice sheets carving out valleys in the land.
Ice sheets are also changing size and shape often as environment changes
what do you normally find at tectonic plate boundaries?
volcanoes
earthquakes also follow the same pattern
what type of fault is this?
normal fault
what type of fault is this?
thrust fault
what type of fault is this?
strike - slip fault
what is the lithosphere, what does the lithosphere include and how deep is it?
the lithosphere is the material that the plate is made of.
the llithosphere runs from the top of the crust to a little bit down into the mantle.
it is about 100km thick
crust and lithosphere are not the same thing.
plates are made up of…
plates are made up of both the crust and the lithosphere
plates move laterally over a weaker interior, and carry the continents around.
there is little friction between ____________ and the _________, thus can move laterally without disruption.
• Plates move laterally over a weaker interior (the asthenosphere), and can carry the continents around
There is little friction between the lithosphere and the asthenosphere, thus can move laterally with disruption.
on average what is the plate movement each year?
plates move about 1-20cm per year
how are there thin and fat regions of earthquakes on this map?
In subduction zones the oceanic plate that heads downwards causes earthquakes. The smaller the angle the fatter the region.
At divergent margins there are only the two plates moving away from each other so is a thin margin
new lithosphere and new oceanic crust is formed at…
new lithosphere and new oceanic crust is formed at divergent boundaries at mid-ocean ridges.
describe the bathymetry at a mid-ocean ridge.
Dotted line is not a fault.
Both sides are moving together.
They are scars from when transform fault was there.
old oceanic lithosphere and old ocean crust is destroyed and recycled at…. and is marked by….
• Old oceanic lithosphere and old ocean crust is destroyed and recycled at convergent boundaries at subduction zones marked by ocean trenches, island arcs, and active continental margins.
trenches at subduction zones are normally not very deep. why?
the trenches normally fill up with sediment so its about 1km deep
_________ and __________ faults preserve lithosphere.
_________ are normally in the ocean and link ________
if it doesnt do this then its called a ________ _______ fault.
Transform and strike-slip faults preserve lithosphere
Transform faults are normally in the ocean and link two ridges.
If it doesn’t do this then it’s called a strike-slip fault.
name three things that cause melt, put them in order of importance, and give an example of where you would find them.
Hot - least important (hot spots)
Low pressure - most important (mid-ocean ridge)
Wet - second most important (island arcs, subduction zones)
around where is the boundary between lithosphere and asthenosphere?
what heat transport dominates the two depths?
and give a brief description of the overall rock type. in terms of temperature, rigidness, and ductileness.
at around 100km, however the boundary change is not well defined.
in the lithospere it is thermal conduction.
(heat is transferred through thermal conduction into the sea water and then ultimately into space
in the asthenosphere it is thermal convection.
(it is close to melting point but is still a solid)
in the lithosphere it is:
colder
more rigid
less ductile
in the asthenosphere it is:
hotter
less rigid
more ductile
as pressure increases, melting point _______
describe a temperature vs pressure graph including the solidus and liquidus( give an explanation of both).
as pressure increases, melting point increases.
solidus is where it just melts
liquidus is when its about to freeze
what is produced when a geotherm and solidus line crosses on a temperature vs depth graph
To produce melt, the geotherm and solidus must cross.
explain the effect of increasing the temperature on a geotherm and thus the amount of melt produced
increasing temperature causes melting.
this happens in regions called hotspots.
they do not cross much thus very little melt.
explain the effect of adding water has to the geotherm and thus the amont of melt.
The solidus is dependent of the material.
If we have ~3% water it changes the composition of the material thus changes the line.
However as the melt raises to the surface, it takes the water with it thus the melting system returns to its original state.
Water is normally pulled down in subduction zones.
explain the effect of reducing the pressure on the geotherm and thus the amount of melt produced.
Reducing the pressure allows the lines to cross.
When we pull the plates apart we make a hole.
This lowers the pressure which causes the melt, the melt is buoyant thus floats to the top and fills the gap.
explain/ describe the prosesses happening at a mid-ocean ridge.
When we pull the plates apart we make a hole.
This lowers the pressure which causes the melt, the melt is buoyant thus floats to the top and fills the gap.
It causes stripes in the rocks.
When it freezes it has a different composition to the mantle as it forms the crust.
what can we do to lead to even more melt then using just the normal processes and then use this to explain why iceland is part of oceanic plate and not continental.
We can combine two melting processes together. Normally this would be hot and low pressure. This will lead to more melt.
This causes Iceland to be part of the ocean. It is anomaly very hot and low pressure thus it protrudes above the sea due to isostaty as crust is much thicker ~ 35km.
why is the average calculated density of the earth greater than the average density of rocks found in the crust.
what can we infer from this?
the density of rocks in the mantle and core is much greater than that found in the crust.
its has a very high density due to the increase in pressure thus a decrease in voloume.
where is the transition zone?
the transition zone is between the upper and lower mantle. this depth can vary around earth.
what is the deepest place to see earthquakes?
the transition zone is the deepest point that we can see earthquakes.
if p waves cant travel through liquids, how can we image the inner core?
When a p wave hits the boundary between the lower mantle and the liquid outer core it can change to s waves thus we can image the inner core.
what is the process for the changing of the magnetic field?
The magnetic field doesn’t flip. The field shrinks and then grows in the opposite direction, this happens relatively quickly compared to geology time scale ~100 year.
radioactivity causes heat. what other way in the core creates energy?
The outer core is slowly freezing. When it freezes it falls down to the inner core, the iron and nickel freeze but the oxygen and sulphur don’t as they freeze at a much lower temperature.
These iron and nickel crystals that fall also creates energy.
what are the proportions of the earth made up of in terms of mantle and core?
mantle ~2/3
core ~1/3
in proprtion to other space objects what are sizes of the outer and inner core?
outer core is about the size of mars
inner core in about the size of the moon
what happens to waves that hit a boundry between two materials with different boundaries?
the waves get refracted.
describe p-waves
Compressional (or primary) waves
Alternately compress and dilate
Travels through solids, liquids and gases
Fastest seismic wave
Longitudinal
describe s-waves
Shear (or secondary) waves
Change in shape (no change in volume)
Slower than p-waves
Transverse
Particles move up and down not side to side
how can we use s-waves to find the size of the core?
s-waves can not travel through the core thus leaves a shadow on the opposite side of the earth.
the primary observation is that the outer core, if not the whole core must be liquid.
describe the low-velocity core p-wave shadow.
partial shadow zone
lower velocity in the core so wave is refracted
most of the mantle is made up of…
solid magnesium silicate
most of the crust is made up of…
metal silicates
which element dominates most rocks on earth?
Oxygen dominates – most rocks have oxygen in them
Oxygen has a large volume due to electron repulsion while other elements have less electrons so are attracted towards the centre thus less volume.
what is silica composed of?
silica - oxygen and silicon
what is silicate composed of?
silicate - oxygen silicate and a metal
how is the inner core solid while the outer core is liquid?
the inner core has a higher temperature however it is solid due to its very high pressure.
what is the magnetosphere?
the region surrounding an astronomical object such as the Earth, in which charged particles are trapped and affected by the object’s magnetic field
inside the magnetosphere it is dominated by _________
Inside the magnetosphere it is dominated by the Earth’s magnetic field
Outside the magnetosphere it is dominated by _________
Outside the magnetosphere it is dominated by the solar wind/ sun
how can a compass be used to find the latitude?
Inclination is related to (magnetic) latitude
Tan(inclination) = 2tan(latitude)
what is detrital remanent magnetization?
describe chemical remanent magnetization
describe termoremanent magnetization
describe the effect of the currie temperature on thermoremanent magnetization
above the currie temp. the rocks cant not hold a magnetic trace.
below it the rocks can hold a magneti trace.
if the temperature is raised again, close to the currie temp. but not above it, then the rock will hold a finger print of past magnetization which we can the observe. as soon as it raises above the currie temperature, all the fingerprints are lost.
describe the magnetic traces of mid ocean ridges. and what do these traces allow us to do?
- Magnetic anomalies measured at sea
- Magnetic stripes on the ocean floor
- Symmetric about mid-ocean ridges
- Allows identification of past plate boundaries
- Allows dating of sea floor
explain reasons for why the graph line is curved and not straight lines that you would expect for a quick change in poles.
- As the plates flow it smudges the rocks thus a more rounded graph
- Also the top crust will cool down quicker than the bottom of the plate so reaches below Currie temp. quicker and in this time difference the plates will have moved so again we would not have perfect straight lines on the graph
what is internal and external heating and about how large are their values?
internal heating is heating from inside the earth (0.06W/m2)
external heating is from out of space,
e.g. the sun (342 w/m2)
if the sun has more sun spots, what can we say?
the more sun spots on the sun the cooler it is.
what are the three major causes of changes in the environment?
change in plate tectonics
change in earths orbit
change in suns strength.
about 50% of electromagnetic radiation from the sun is?
infrared
about 41% of the electromagnetic radiation from the sun is?
visible
of the 342 Wm-2 incoming from the sun how much is absorbed and reflected?
30% is reflected
70% is absorbed
we can measure the heat radiated back to space using satellites.
if the heat in is equal to the heat out what can we say about the temperature of earth is?
the temperature is fixed.
if there was no green house effect there would be no________
if there was no greenhouse effect there would be no biosphere
what are the two important green house gases?
water vapour (changes dynamically)
carbon dioxide
all bodies above absolute zero radiate heat.
peak wavelength is inversely proportional to __________
peak wavelength is inversely proportional to temperature.
what is most carbon on earth stored as?
stored as carbonates/ organics in sediments and rocks.
how does the deep ocean have large amounts of carbon?
its so deep that there is a slow equilibrium between atmosphere and deep ocean.
what is the relationship between carbon dioxide and the ocean mixed layer?
ocean mixed layer and atmosphere are in equilibrium.
when we add carbon dioxide to the atmosphere it goes into the ocean mixed layer.
what is the effect of latitude on radiation absorbtion?
at high latitude:
less radiation per square metre of surface
more scattering in atmosphere (further distance to travel through atmosphere)
more reflection at surface
a ball being thrown at the equator to the north pole. it has a vector in the east direction of 500m/s thus the ball will curve even though the ball looks like it has been thrown straight.
how?
it is actually the earth/person that has moved. the ball is still going in a straight line.
in a low pressure atmosphere, the ________force and _________ force are in equillibrium, so winds go round and round.
in a low pressure atmosphere, the coriolis force and pressure force are in equillibrium, so winds go round and round.
density of water vapour is less than gasses so rises.
warm air rises
thus
dry air ______
cold air _______
density of water vapour is less than gasses so rises.
warm air rises
thus
dry air drops
cold air sinks
describe how weathering leads to a negative feedback in terms of temperature and carbon dioxide levels
the negative feedback means that a balance/equillibrium is kept.
cycles in temperature are dependent on earth and its milankovitch cycles (tilt, eccentricity, precession)
which cycle dominates through time?
it isnt one cycle that has dominated. the dominant cycle has changed through time.
explain the waves in the picture.
the biosphere is shrinking and expanding anually
trees take in co2 then drop leaves thus putting co2 back into the atmosphere
these waves happen differently depending on which hemisphere due to diffences in seasons
explain how eathquakes will form at the fracture zones. even though fracture zones are inactive?
one side will subside more than the older side due to being closer and hotter thus will subside quicker.
thus can cause earthquakes
