Download Internal structure of the earth

Y10 Science
Earth Structure, Tectonic
Plates, Faults and
Earthquakes
Internal structure of the earth
Inner structure of the earth.
The structure of the Earth
The Earth is made up of four distinct layers:
• The inner core is in the centre and is the hottest part of the
Earth. It is solid and made up of iron and nickel with
temperatures of up to 5,500°C. With its immense heat energy,
the inner core is like the engine room of the Earth.
• The outer core is the layer surrounding the inner core. It is a
liquid layer, also made up of iron and nickel. It is still extremely
hot, with temperatures similar to the inner core.
• The mantle is the widest section of the Earth. It has a diameter
of approximately 2,900 km. The mantle is made up of semimolten rock called magma. In the upper parts of the mantle
the rock is hard, but lower down the rock is soft and beginning
to melt.
• The crust is the outer layer of the earth. It is a thin layer
between 0-60 km thick. The crust is the solid rock layer upon
which we live.
• There are two different types of crust: continental crust, which
carries land, and oceanic crust, which carries water.
Activities:
• Stick the picture of the Internal Structure of the Earth into
your Science book and label the different sections.
• Go to Onstream and click on e-chalk on the Y10 Science
page. Click on Geography then scroll down to the section on
Tectonic Activity. View the animation on The Structure of the
Earth.
• Use the information from the e-chalk animation and p205 of
your SciPad to produce a summary in your Science book on
the temperature, size and composition of the different layers.
• Answer the questions on p205 of SciPad.
• Find out how scientists study the earth’s interior and write a
brief summary on how this is done.
• http://study.com/academy/lesson/how-scientists-studyearths-interior-structure.html
Plate Tectonics
https://www.youtube.com/watch?v=tcPghqnnTVk
History of the discovery of plate tectonics.
• In 1915, a German scientist called Alfred
Wegener proposed the idea that the
earth’s continents were not fixed in
position but could move around.
• He called his idea ‘continental drift’.
• He proposed that the continents were
once all joined together into one super
continent called PANGEA, which means
‘all the earth’ in Greek.
Pangea initially broke up into a large northern continent called Laurasia and a
large southern continent called Gondwana.
Pangea
• Wegener noticed how the
continents fitted into each
other like jigsaw puzzle
pieces.
• He also noticed other things
that the now separate
continents had in common
like matching rocks,
sediments and fossils.
Gondwanaland Glaciation
There were
similar glacial
deposits on all of
the continents
suggesting they
were once
connected
Current Glacial Deposits
Fossil Evidence
Alfred Wegener also
noticed the same plant
and animal fossils on
different continents.
Since these plants and
animals could not swim
he suggested these land
masses must have been
joined.
He said they were
joined to make Pangea
Plates of the earth
• We now know that the Earth's crust, is broken up into 7 large, rigid pieces
called tectonic plates: the African, North American, South American,
Eurasian, Indo-Australian, Antarctic, and Pacific plates.
• Several minor plates also exist, including the Arabian, Nazca, and
Philippines plates.
Plate movement
• The plates are all moving in different directions and at different
speeds, from 2 cm to 10 cm per year (about the speed at which your
fingernails grow) in relation to each other.
• As the plates move they sometimes crash together, pull apart, or
sideswipe each other.
• The place where the two plates meet is called a plate boundary.
What causes the plates to move?
• The tectonic plates making up the earth’s crust are floating on the
mantle layer of the earth.
• The magma in the mantle layer is a very thick slow moving molten rock.
• The magma nearer the core gets heated up by heat from the core. As it
heats up it expands, becomes less dense and rises up towards the crust.
• Near the crust the magma cools becomes denser and sinks down. This
creates large circular movements of rock called convection currents
which move the plates.
http://www.classzone.com/books
/earth_science/terc/content/visu
alizations/es0804/es0804page01.
cfm?chapter_no=visualization
Plate boundaries 2
What happens when an oceanic plate and a continental
plate collide?
This is known as
SUBDUCTION!
The thinner, more dense oceanic plate is driven down
into the mantle.
Thicker, less dense continental
plate
Thinner, more dense
oceanic plate
Convection current
Convection current
Oceanic plate melted
Plate boundaries 2
Plate boundaries 3
What happens when oceanic plates move apart due to convection currents
in the Earth’s mantle?

Oceanic plate
Magma moves up to
the surface, cools
and forms new
oceanic plate.
Convection
current
Oceanic plate

This is known as
Convection SEA-FLOOR
current
SPREADING.
Constructive Plate Boundary
Plate boundaries 3
Activities:
• Stick the map showing the earth’s main tectonic
plates into your Science book. Highlight NZ.
• View the animations on e-chalk under Tectonic
Activity in Geography.
• Read p206 in SciPad and complete the questions on
this page.
• Copy and label the diagram from p207 of SciPad into
your Science book and write a paragraph explaining
how convection currents in the mantle layer cause
the tectonic plates to move.
• Complete the questions on p207.
How New Zealand was formed
Maori legend for how NZ began
http://www.youtube.com/watch?v=1ZVKu4pRWqw&safe=active
New Zealand as we know it today is part of a landmass called Zealandia.
Most of Zealandia lies beneath the sea at depths of up to 1500 metres.
New Zealand
New Zealand lies on the
boundary of two plates.
The Indo Australian plate
which is moving north-east and
the Pacific plate which is
moving west.
The boundary is marked by the
Alpine Fault.
In the North Island
The Pacific plate is diving under the Indo-Australian plate.
This causes lots of deep earthquakes and volcanoes.
Eg- White Island, Ruapehu, lots of dormant volcanoes in
Auckland and the dormant volcano of Lake Taupo.
In the South Island
The South Island is being squashed and twisted by the pressure of the
Pacific and Indo-Australian plates.
Down very deep, the Pacific plate is diving under the Indo-Australian
plate.
However closer to the surface, the plates are colliding and sliding past
each other.
This collision pushes up the Southern Alps as much as 10 mm a year.
Southern Alps uplift
25-15 million years ago most of NZ was still covered by water.
Plates begin to collide and alpine fault beginning to form.
15-5 million years ago – new areas of land are
pushed above the sea level. Southern Alps forming
The rate of the uplift has accelerated in the last 5 million years, around about 20km of
uplift has taken place along the Alpine Fault. If it was not for weathering then the
Southern Alps would be up to 6 times the height they are today.
What is a fault?
A fault is a break in the rocks that make up the earth's
crust, along which rocks on either side have moved
past each other.
Because rock doesn’t move easily, strain can build up
along a fault. When the rock suddenly gives way at
weak points, an earthquake occurs.
Land movement causing a fault trace
The rock surfaces along a fault, which move against each other when an
earthquake occurs, are called the fault plane.
Not all faults reach the ground surface, but where they do we often see
gaps called rifts and bumps called scarps.
The evidence of a fault, visible on the surface, is called the fault trace.
The main Alpine fault runs in a north-south direction but many smaller faults,
such as the Greendale fault that ruptured during the September 2010
earthquake, run east-west.
• At the north eastern end of the
South Island, there is a complex
system of faults that radiate out
in the north east direction from
the Alpine fault.
• Six faults are known to have
ruptured during the 7.8
magnitude earthquake on 14
November, 2016.
• Four went along the coast and
out into the sea.
Earthquakes along the Alpine Fault
As the tectonic plates collide and slide past
each other, they sometimes get stuck
because of friction and stop sliding.
This causes pressure to build up.
Eventually this pressure is released and the
plates suddenly slip past each other.
This sudden slipping causes an
EARTHQUAKE.
Earthquakes
• An earthquake is a shaking or trembling of the ground caused by the
sudden release of energy when a fault ruptures and rocks break.
• The energy travels in waves which spread out and cause damage on the
surface.
• Aftershocks occur as the rocks continue to adjust their position.
The Focus and Epicenter of an Earthquake
• The point within Earth where
a fault ruptures and an
earthquake begins is called
the focus of the earthquake.
• The point directly above the
focus on the surface of the
earth is called the epicenter.
Types of Earthquake movement.
Normal
Oblique
Reverse
Strike slip
https://www.youtube.com/watch?v=AEkbkghWJeI
Where do most earthquakes occur?
• Most earthquakes result from tectonic plates converging or sliding past
each other.
• 80% of all earthquakes occur around the boundary of the Pacific plate.
Measuring earthquakes