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Slide 2

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The Driving Force
Convection Currents
· Very slow convection
currents flow in this
asthenosphere.
· These currents provide
horizontal forces on the
plates of the lithosphere
· Much as convection in a
pan of boiling soup (must
be Heinz tomato!) causes a
crouton on the surface of
the water to be pushed
sideways.…read more

Slide 3

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The Driving Force 2
· The convection
currents are driven by
heat generated within
the earth.
· This emanates
primarily from the
core and is
transferred to the
surface by the
convection currents.…read more

Slide 4

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Geothermal Gradient:
· T is very variable with
depth.
· On average close to
the surface the T
changes at 0.03°C/m
or 30°C/km.…read more

Slide 5

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The majority of the heat
is generated by the
decay of certain long-
lived radioactive
isotopes e.g. U, Th or
K.…read more

Slide 6

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Other ways in which internal heat can be generated:
· 1. Residue from Earth's
formation as it grew during
impact of particles.
· 2. Heat from short-lived
isotopes that died out soon
after Earth's formation.
· 3. As the Earth slows down the
kinetic energy changes to heat
(slow).
· 4. Formation of the Earth's
core released gravitational
energy estimated could be
responsible for 20% of the
present heat.
· 5. Latent heat of crystallisation
as the solid inner core formed.…read more

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