Part 3 Flashcards
(47 cards)
How might low sea level allow species to spread between continents?
Low sea level could expose dry land between continents removing the intervening ocean that was acting as a barrier to the natural spread of the species
What is the earths radius from the enter to the poles?
6357 km
What is the earths radius from the centre to the equator?
6378 km
What is the shape of the earth described as?
Oblate spheroid
Slightly flattened sphere
What distorts the earths shape?
It’s rotate
How does rigidity and density affect the speed of seismic waves?
Increasing rigidity acts to increase seismic wave speed, whereas increasing density acts to decrease it
What are seismic waves?
Vibrations from large earthquakes
What are seismometers?
They are sensitive vibration detectors that time arrivals of first vibrations at different distances from the known location of an earthquake
What is the deepest point in the ocean called and how many m deep is it?
It is called the challenger deep and it is 11034 m
What is the highest point about sea level called and how high is it?
Mount Everest 8848 m
Why is seismic speed halved when traveling through the earth?
Because the density of the core of the earth is about twice of the overlying mantle
So seismic speed is halved despite the greater rigidity of the mantle
What is the hard outer layer of the earth called?
The mantle
Is the outer part of the earths core solid?
Despite the immense pressure it is not solid
How many types of seismic waves concern us when dealing with the earths interior? And what are they called?
2 Types of seismic waves
Compressional wave (P wave)
A shearing wave (S wave)
What is a compressional wave also known as?
P wave
What is a shearing wave also known as?
S WAVE
Describe how a compressional (P) wave moves?
It is just like a sound wave in the air
It consists of alternate pulses of compression and dilation
Describe how a shearing wave moves?
It is an alternate side to side wobble traveling through the body of a material, rather like what happens inside a jelly of you shake it
What is the important distinction between compressional waves and shearing waves?
Compressional waves can travel through anything
Shearing waves can not pass through liquid as it offer no resistance to shearing motion
How can we tell that the earths outer core is made of liquid?
Using a seismometer which can distinguish between the two types of waves, we can see that only P waves are transmitted through the outer core which must therefore be liquid
Name the three main parts f the earths interior ?
Mantle (outer most)
Liquid outer core
Solid inner core
What are the properties of the solid inner core of the earths interior?
The solid inner core has the properties we would expect of solid iron mixed with a few percent nickel.
It’s properties fits with other metals but iron core is the only reasonable one because t fits with the earth being rich in the same metallic as we find in the sun and meteorites
What percentage of the earths liquid outer core is not metal?
It is thought to be about 10%
As it has a density too low to be pure metal
It is most likely composed of one of the relatively lighter elements like oxygen, carbon, hydrogen and potassium (however this has not been proved)
How is the earths magnetism related to us thinking the core is made of iron?
The earth has a magnetic field that is believed to be the product of electrical currents generated by motion (a bit like dynamo) with the fluid outer core
To generate a field in this way, the zone responsible must be a good conductor of electricity and liquid (iron is but rock isn’t)
