Transcript The Earth`s Structure

Tectonic Plates
Objective:
To learn how tectonic plates move
and what evidence we have for
continental drift
Starter: Word search –
rock cycle review
Tectonic plates
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The crust is made of about twelve plates.
These are like big rafts floating on the semimolten mantle.
Convection currents within the mantle cause
the plates to move.
Although they only move about 2 cm/year
(same speed as fingernail growth) this can
have huge effects over long periods of time.
Convection currents
Modeling convection currents
Put on goggles
 Fill the beaker about ¾ full with water
 Gently warm the beaker on one side with
the candle
 Using tweezers, place a crystal on the
heated side of the beaker
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NB: The crystals will stain
your clothes and fingers
Convection current demonstration
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Observe how the purple trails move
around in a loop
Convection current demonstration
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Observe how the
purple trails move
around the convection
loop
Continental Drift
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On average, the plates only
drift about 2cm/year. However
2cm multiplied by a million
years is a long way!
Scientists think the continents
were originally all together in a
super-continent called
Pangaea.
Over millions of years they
have drifted to their present
positions on the floating
tectonic plates.
Pangaea
Millions
of years
Continental Drift
People once thought that the oceans and the continents were formed by
shrinkage from when the Earth cooled down after being formed.
Alfred Wegener proposed something different:
These continents look
like they “fit” together.
They also have similar
rock patterns and fossil
records. These two
pieces of evidence led
me to believe that there
was once a single land
mass.
Evidence for Continental Drift
The theory is supported by
several pieces of evidence.
For example, if we consider Africa
and South America there is:
 The “jigsaw fit”
 The similarities in the rock
layers from Africa and South
America.
 Similarities in the type and
age of fossils.
 Evidence of related species
that definitely did not swim
the Atlantic Ocean!
Jigsaw fit
Similar rocks
and fossils
Main Task
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Write a memo from Alfred Wegener to a
fellow geologist (scientist who studies
rocks)
The memo should explain:
a)
b)
What is meant by continental drift
Evidence that proves the continental drift
theory
Wrap up
3 exam questions – class activity
 In pairs, write 3 questions of your own that
can be used as a quiz at the start of the
next lesson
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Q1 - The diagram shows the three main layers of the Earth.
The middle layer is called the . . . . .
crust.
lithosphere.
magma.
mantle.
Q2 - The diagram shows the three main layers of the Earth.
The middle layer . . . . .
has convection currents which move very slowly.
is made of solid rock which cannot flow.
is made up of metamorphic rocks.
is made up of sedimentary rocks.
Q3 - The diagram shows the three main layers of the Earth.
The inner part of the inner layer (core) is . . . . .
liquid and made from aluminum and silicon.
liquid and made from iron and nickel.
solid and made from aluminum and silicon.
solid and made from iron and nickel.
Home work
How are natural disasters such as
earthquakes/tsunamis linked to the
movement of tectonic plates?
 You should use the library/internet to
research this HW
 Aim to jot down at least 5 facts
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