Tectonic Plates

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Tectonic Plates
Objective To learn how tectonic plates move and
what evidence we have for continental drift
Starter Word search rock cycle review
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Tectonic plates

• The crust is made of about twelve plates.
• These are like big rafts floating on the
  semi-molten 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.

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Convection currents
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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

NB The crystals will stain your clothes and
fingers
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Convection current demonstration

• Observe how the purple trails move around in a
  loop

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Convection current demonstration

• Observe how the purple trails move around the
  convection loop

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Continental Drift

• 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.

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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.
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(No Transcript)
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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!

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Main Task

• Write a memo from Alfred Wegener to a fellow
  geologist (scientist who studies rocks)
• The memo should explain
• What is meant by continental drift
• Evidence that proves the continental drift theory

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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.
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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.
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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.
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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