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Tectonic plates and
magnetic fields
· As lava and sediments that contain
magnetic crystal solidify and form new
crust. The crystals are then magnetised by
the earths magnetic field.
· The magnetization lines up in the earth's
magnetic field at that time.
· At equator- magnetisation lies
horizontally
· At poles- magnetisation lies at angle to
horizontal
· Angles that crystals are
at in the rocks shows
the latitude were
the rock was
Formed
· Shows continents
move…read more

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Evidence that also supports
theory of continental drift
· Sedimentary rocks contain clues to the earths
history.
· Because the tectonic plates move, rocks in
Britain could've been formed in different
places & different climates.
· Geologists look at features of rocks to learn
about the environment in which they were
formed: (they look at..)
­ Fossils: remains or imprints of dead organisms,
they tell you age of rock and conditions it was
formed in.
­ Shells or ripples on the rock: it tells you it was
created by the sea or rivers.
­ Shapes of grains found in sedimentary rocks:
sediment that forms the rocks will either have
been made in air or water. These grains can tell
you if its formed underwater (water borne grains)
or on surface (contains air-blown grains).…read more

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Clues in the rocks
· Find the history of sedimentary
rock by looking at the shape and
size of sand grains
· Grains show if formed in desert or
river
· Other clues from fossils and there
types can show the time period
the rock was formed
· Ripples can show if formed under
water…read more

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Formation of different rocks
Limestone-
· Sediment comes from shells, bones or sea creatures or
erosion from existing rock.
· Erosion creates tiny particles of sediment that wash
away and end up at the bottom of a sea or lake. Over
millions of years the layers of sediment get buried under
more, the weight of this squeezes out the water.
· Fluids flowing through pores in the sediment deposit
natural mineral cement that holds the sediment particles
together to form rock.
Coal
· formed over millions of years by fossilisation of layers
of plant matter.
· Its mainly carbon.
· Some types of coal are hard because they're put under
high pressure and temperatures
·Salt
· is left by evaporation.
· Salt is extracted by underground deposits.
· These were formed when seawater moved inland
leaving a chain of shallow salt marshes
· The water then evaporated leaving salt
· Rock then formed over the top of the salt deposits…read more

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Salt
· Was used to preserve meat- now is used in food
industry for flavour and preservation. It is also used
to on icy roads
· Sea Salt- sea water runs into pans and is allowed to
evaporate in hot sunshine .
· This contains mainly sodium chloride
· Rock salt ­Giant machines extract the salt from
underground
· The rock is 90% sodium chloride I the form of halite.
· Halite is mixed with insoluble impurities is not pure
and used on roads as grit.
· Solution mining- mines salt for the chemical industry
· Water is pumped into the rock
· The salt is dissolved and carried to the surface in
solution
· The salt crystals are recovered from the brine by
evaporating the water
· It is then filtered…read more

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