1. SPHERES OF THE EARTH
• The Earth has 4
spheres:
2. ATMOSPHERE
3. HYDROSPHERE
4. LITHOSPHERE
5. BIOSPHERE
2. EARTH’S INTERIOR
• The outer shell of the
Earth is called the
CRUST
• The next layer is
called the MANTLE
• The next layer is the
liquid OUTER CORE
• The middle bit is
called the solid
INNER CORE
5. PLATES
• The Earth's surface is made up of a series of
large plates (like pieces of a giant jigsaw
puzzle).
• These plates are in constant motion travelling
at a few centimetres per year.
• Plates 'float' on the molten rock magma. As
the core of the Earth heats up the materials
inside, the molten magma also gets heated up.
The heat causes convection currents, a
movement of rising and sinking caused by
heat, inside the molten magma.
6. PLATE MARGINS
• The place where two plates meet is known as plate
margin/ boundary.
• There are 3 types of plate margins/ movements:
3. Diverging Plate Margin
4. Converging Plate Margin
7. DIVERGING PLATE MOVEMENTS
• Places where plates are coming
apart are called divergent
boundaries.
• when Earth's brittle surface
layer (the lithosphere) is pulled
apart, it typically breaks along
parallel faults that tilt slightly
outward from each other.
• Magma (liquid rock) seeps upward
to fill the cracks. In this way,
new crust is formed along the
boundary.
• Earthquakes occur along the
faults, and volcanoes form where
the magma reaches the surface.
• For example, divergence along
the Mid Atlantic ridge causes
the Atlantic Ocean to widen at
8. CONVERGING PLATE MOVEMENTS
• When two plates move towards
each other, they would collide.
This is called a convergent plate
movement.
• As the plates collide, some crust
is destroyed due to the impact,
therefore this convergent
boundary is also called a
destructive boundary.
• Examples:
4. the collision between the
Eurasian Plate and the
Indian Plate which is forming the
Himalayas.
5. subduction of the Nazca Plate
beneath the
South American Plate to form
12. CONSERVATIVE PLATE
MOVEMENT
• A transform plate
movement is one where
two plates slide laterally
past each other.
• This movement is not
smooth due to friction
between the rocks of
the two plates.
• When there is
sufficient buildup of
pressure, rocks in the
plates break and get
jerked apart. This
results in earthquakes.
13. HAZARDS ASSOCIATED WITH
PLATES
• Most
EARTHQUAKES
and VOLCANIC
ERUPTIONS
occur in specific
areas, such as
along plate
boundaries.
16. EFFECTS OF EARTHQUAKES
• Negative effects of
earthquakes:
• Tremendous loss of life.
• Loss of property.
• Collapse of transport –
roads, railways, ports,
bridges.
• Fire, landslides, floods.
• Blocked roads
• Facilities disrupted –
electricity, water,
medical.
17. VOLCANO
• A Volcano is an opening or
rupture on the Earth’s Surface
which allows magma, rocks,
gases etc. to come out from
below the surface.
• Causes of Volcanic activity:
d) Diverging plates
e) Converging plates
f) Hot Spots
g) Faults
• Important Terms:
• Vent and Fumeroles
• Crater
• Pyroclastic material
• Lava flow
• Magma Chamber
• Cone shaped hill
18. TYPES OF MATERIAL - VOLCANO
Three types of materials are ejected out of a Volcano:
•SOLIDS: ash particles (< 2mm in size); Lapilli (2 – 64mm in
size); Volcanic bombs (>64 mm in size)
•LIQUIDS: Molten material – Magma, Hot water from
geysers and hot springs.
•GASES: Water-vapour, carbon monoxide, carbon dioxide,
sulphur dioxide, hydrogen chloride, hydrogen fluoride,
19. TYPES OF VOLCANOES
• On the basis of •
frequency:
• Active Volcano: which
erupt frequently & can
erupt any time. Eg. Mt.
Mauna Loa, Hawaii.
• Dormant Volcano:
which have erupted in
history but have not
erupted since then. Eg.
Mt. Rainier, USA
• Extinct Volcano: which
may have erupted
earlier but is now
almost dead (>1000
On the basis of shape and
material they are made of:
• Shield Volcano: Gentle slopes,
basaltic lava, low viscosity.
Eg. Mt. Mauna Loa, Hawaii
• Cinder Volcano: Steep slopes,
> 300 meters in height, made
of pyroclastic material. Eg.
Mt. Paracutin, Mexico
• Composite / Strato Volcano:
Steep upper slopes & then
gentle, Alternate layers of
20. TYPES OF ERUPTIONS
• There are five major
types of eruptions:
c) Hawaiian
d) Strombolian
e) Vulcanian
f) Pelean
g) Plinian
23. EFFECTS OF VOLCANO
• Positive Effects:
b) Ash add to the soil
fertility – farming
c) New minerals may be
discovered
d) Promotes Tourism
e) Research and
education purposes.
f) Geothermal Energy –
renewable energy.
• Negative effects
b) Loss of life
c) Loss of property (economic
loss)
d) Air Pollution (ash, smoke,
gases, acid rain etc)
e) Water pollution
f) Lahars (mudflows with
water)
g) Earthquakes
h) Increase in temperature
of the area
