earths magnetic field

earths magnetism

Earth is surrounded by a magnetic field (Figure 1.1) that behaves as if the planet had a gigantic bar magnet inside of it. Earths magnetic field also has a north and south pole. The magnetic field arises from the convection of molten iron and nickel metals in Earths liquid outer core.

magnetic reversals

Many times during Earth history, even relatively recent Earth history, the planets magnetic field has flipped. That is, the north pole becomes the south pole and the south pole becomes the north pole. Scientists are not sure why this happens. One hypothesis is that the convection that drives the magnetic field becomes chaotic and then reverses itself. Another hypothesis is that an external event, such as an asteroid impact, disrupts motions in the core and causes the reversal. The first hypothesis is supported by computer models, but the second does not seem to be supported by much data. There is little correlation between impact events and magnetic reversals. Click image to the left or use the URL below. URL: Earths magnetic field is like a bar magnet resides in the center of the planet.

textbook_image

instructional diagrams

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questions

without earths magnetic field

a) compasses would not work

b) solar winds would strip away ozone from the atmosphere.

c) life would be exposed to ultraviolet radiation

-->  d) all of the above

what generates earths magnetic field?

a) convection in the atmosphere.

b) a giant bar magnet inside the planet.

-->  c) convection in the liquid outer core

d) solar wind.

earths magnetic field

-->  a) has a north and south pole.

b) behaves like iron filings are inside the planet..

c) arises due to radiation in the liquid outer core.

d) all of these.

sometimes earths magnetic north pole becomes its magnetic south pole and vice versa.

-->  a) true

b) false

scientists know that the reason the magnetic field flips is this:

a) convection becomes chaotic and reverse direction.

b) an asteroid impact disrupts motions in the core.

c) excess volcanism causes chaos in the mantle.

-->  d) none of these; scientists do now know why this happens.

scientists model magnetic reversals to try to determine why they occur.

-->  a) true

b) false

the outer core is made of

a) iron alone

-->  b) iron and nickel

c) peridotite

d) peridotite, iron and nickel

which of these is a possibility for why earths magnetic field has flipped?

a) the convection currents reversed itself

b) an asteroid impact disrupted the motion in the core

c) the heat from the sun

-->  d) both a and b

earths magnetic field has disappeared for long periods of time in earth history.

a) true

-->  b) false

without earths magnetic field, complex life could probably not exist.

-->  a) true

b) false

diagram questions

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