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What’s on your plate?
A teacher briefing on plate tectonics
This teacher briefing is for teachers and other educators to give young people an
understanding of the structure of our planet and how the physical geography of
Abu Dhabi today displays the consequences of dramatic geological activity.
If for a moment we could look inside the
Earth, we would see it’s made of four
concentric layers(2):
The inner core
The Earth’s inner core is in the centre and
is the hottest part of the Earth(3). It is like a
solid ball made up of the elements iron and
nickel(4). With immense temperatures of up
to 5,500°C(5), the temperature at the inner
core is thought to be similar to that of the
surface of the Sun(6).
The outer core
The Earth’s outer core is a liquid layer(7)
that surrounds the inner core. This layer
is about 2,250 kilometers(8) thick and it is
believed that this outer core is made up of
super-heated liquid molten lava(9). This lava
is believed to be mostly iron, and nickel(10).
The mantle
The next layer is the Earth’s mantle(11). It is
the widest section of the Earth(12). It has
a diameter of approximately 2,900 km(13)
and is about 85%(14) of the total weight and
mass of the Earth. The mantle is made up
of semi-molten rock called magma(15). In the
upper parts of the mantle, temperatures
reach 500°C(16) and the rock is hard, but
lower down at the boundary with the core,
the rock is soft and beginning to melt with
temperatures up to 4,000°C(17).
The crust
The Earth’s crust is the solid outer layer of
the Earth(18). It is a thin layer between 0-60
km thick(19) and makes up less than 1%(20) of
the Earth’s mass. The crust is the solid rock
layer upon which we all live.
When you look at our planet, you see that
the surface of the Earth consists of a lot
of water (71%)(21). The other 29%(22) consists
of land. You can divide this land into six(23)
big pieces, which are called continents.
The different continents - arranged in
decreasing order of size are: Eurasia
(Europe and Asia together), Africa, NorthAmerica, South-America, Antarctica and
Australia(24).
There are two different types of crust:
Oceanic crust
The oceanic crust is the crust below the
oceans. It is made up of extremely dense
rock which scientists call Sima(25). Sima is
made out of two basic substances. These
substances are silica and magnesium(26).
Here the crust is 6-11 km thick(27). The
rocks of the oceanic crust are very young
compared with the rocks of the continental
crust. The rocks of the oceanic crust are
not older than 200 million years(28).
Continental crust
The continental crust carries land. The
rocks found in the crust of the continents
is called Sial(29). Sial is made of silica, and
aluminum(30), and is much lighter than the
Sima beneath it. The continental crust is
older than the oceanic crust, some rocks
are 3.8 billion(31) years old.
Plate tectonics
The Earth’s crust is divided into a series
of plates that are continually moving,
colliding or pulling apart relative to each
other. (32) The Earth’s crust consists of nine
large plates (33) and twelve smaller ones(34).
The continents are in the continental plates
and the oceanic plates make up much of
the sea floor.
Heat rising and falling inside the mantle
creates convection currents generated in
the Earth’s core(35). The convection currents
move the plates. Where convection
currents diverge near the Earth’s crust,
plates move apart(36). Where convection
currents converge, plates move towards
each other. The movement of the plates
and the activity inside the Earth is called
plate tectonics(37).
The movement and collision
of the Earth’s plates has had
a profound impact on the
physical geography of Abu
Dhabi and the wider region.
Modern World
Present Day
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Plate tectonics cause earthquakes and
volcanoes(38). The point where two plates
meet is called a plate boundary(39).
Earthquakes and volcanoes are most
likely to occur either on or near plate
boundaries(40). There are three types of
boundaries that we can observe. These
plate boundaries are:
Divergent boundary
The word divergent is a big word used by
scientists to describe what happens when
two objects move away from each other.
So, a divergent boundary is a boundary
where two tectonic plates are moving away
from one another(41).
Where plates pull apart, hot molten
rock emerges as magma(42) and so new
matter is added to the plates. This is also
accompanied by earthquakes. When the
magma reaches the surface, it cools and
solidifies to form a new crust of igneous
rock. This process is repeated many times,
over a long period of time. Eventually the
new rock builds up to form a volcano. These
boundaries tend to be found under the sea.
Convergent boundary
Convergent is another big word that
scientists use to describe two objects
that come together. In the case of plate
tectonics, the two objects coming together
are plates of the Earth’s crust(43). As these
two plates push against each other, one is
eventually forced down beneath the other.
In many places the huge plates of the
Earth’s surface are slowly moving together
with unimaginable force. Sometimes the
edge of one plate is gradually destroyed
by the force of collision, sometimes the
impact just crimps the plates’ edges,
thereby creating great mountain ranges(44).
When one tectonic plate bends beneath
the other, it is called subduction(45).
Most of the time this happens because a
dense oceanic plate collides with a lighter
continental plate.
The oceanic plate is denser than the
continental plate so, as they move together,
the oceanic plate is forced underneath the
continental plate. The point at which this
happens is called the subduction zone(46).
As the oceanic plate is forced below the
continental plate it melts to form magma
and earthquakes are triggered. The magma
collects to form a magma chamber. This
magma then rises up through cracks in the
continental crust. As pressure builds up, a
volcanic eruption may occur.
As the plates push together, the
continental crust is squashed together and
forced upwards. This is called folding(47).
The process of folding creates fold
mountains(48). Fold mountains can also be
formed where two continental plates push
towards each other.
Transform boundary
A transform boundary is where two
plates slide against each other in a
sideways motion(49). These boundaries
between plates is referred to as transform
boundaries(50). As two plates slide past one
another, in a transform boundary, neither
plate is added to at the boundary, nor
destroyed. The result of two massive plates
pushing against one another is that massive
amounts of energy build up. Occasionally
this energy is released suddenly in the form
of large earthquakes(51).
Abu Dhabi
The physical geography of Abu Dhabi
today displays the consequences of such
dramatic movements, which still continue
– the Emirate is located close to an active
plate boundary between the relatively
small Arabian Plate and the massive
Eurasian Plate(52).
The following definitions are provided for the educator’s reference.
Young people should have the opportunity to explore definitions through
individual activities. Some definitions may have been deliberately simplified
for a young audience.
Boundary
A line which marks the limits of an area, a
dividing line like a plate boundary.
Dense
Closely compacted in substance, having
the parts crowded closely together.
Magma
Magma is molten rock often located inside
a chamber beneath the surface of the earth.
Concentric
Having a common centre; “concentric
rings”, the larger often completely
surrounding the smaller.
Diverge
To move or draw apart.
Molten
Reduced to liquid form by heating; “a mass
of molten rock”.
Convection currents
Convection currents in the hot, solid rock
of the Earth’s mantle help to drive the
movement of the rigid plates making up
the Earth’s surface.
Converge
To come together so as to form a single
thing.
Crimp
To compress something into small folds or
ridges.
Elements
There are more than one hundred
substances that cannot be broken down
into simpler substances and are the
simplest forms of matter.
Igneous
To have solidified from lava or magma.
Lava
Lava is molten rock which due to its high
temperature, it is quite liquid when it is first
released from a volcano or fissure, but soon
solidifies into rock. While it is still below the
earth’s surface it is called magma.
Sial
The material of the upper or continental
part of the earth’s crust, it relatively light
and rich in silica and alumina.
Sima
The material of the lower part of the earth’s
crust, underlying both the ocean and the
continents, it is relatively heavy and rich in
silica and magnesia.
Subduction
The sideways and downward movement of
the edge of a plate of the earth’s crust into
the mantle beneath another plate.
For more teacher resources including Teacher Briefings, Lesson Plans, Activity Worksheets,
and Fact Sheets, go to www.environmentalatlas.ae.
References: 2) S. Marshak (2007) Earth: Portrait of a Planet. W. W. Norton & Co. 3, 35) A. Bell (1997) How the Earth Works: How Plate Tectonics Works: Block
2 (Course S267). 4, 36, 37) A. Cox (2008) Plate Tectonics: How it Works. 5,6) F. P. Miller (2010) Geothermal Gradient: Earth, Internal Heat, Gravitational
Binding Energy, Potassium, Uranium, Radioactive Decay, Thorium, Mantle Convection, Plate Tectonics, Komatiite, Geothermal Power. 7) N. Oreskes (2003) Plate
Tectonics: An Insider’s History Of The Modern Theory Of The Earth. 8) R. Harman (2006) Earth’s Changing Crust: Plate Tectonics and Extreme Events. 9) P.
Keary (2009) Global Tectonics. 10) J D. Winter (2009) Principles of Igneous and Metamorphic Petrology. For full references, go to www.environmentalatlas.ae.