plate movements ppt

SPHERES OF THE EARTH

• The Earth has 4 spheres:

1. ATMOSPHERE2. HYDROSPHERE3. LITHOSPHERE4. BIOSPHERE

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     

CONTINENTAL DRIFT THEORY

EARTH - PLATES

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.

PLATE MARGINS

• The place where two plates meet is known as plate margin/ boundary.

• There are 3 types of plate margins/ movements:1. Diverging Plate Margin2. Converging Plate Margin3. Transform (Conservative) Plate Margin

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 only about 2 centimeters per year.

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:1. the collision between the

Eurasian Plate and the Indian Plate which is forming the Himalayas.

2. subduction of the Nazca Plate beneath the South American Plate to form the Andes Mountains.

WHEN TWO CONTINENTAL PLATES CONVERGE

WHEN AN OCEANIC & CONTINENTAL PLATES CONVERGE

WHEN TWO OCEANIC PLATES CONVERGE

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.

HAZARDS ASSOCIATED WITH PLATES

• Most EARTHQUAKES and VOLCANIC ERUPTIONS occur in specific areas, such as along plate boundaries.

EARTHQUAKES

EARTHQUAKE ZONES OF THE WORLD

EFFECTS OF EARTHQUAKES• Negative effects of

earthquakes:1. Tremendous loss of life.2. Loss of property.3. Collapse of transport –

roads, railways, ports, bridges.

4. Fire, landslides, floods.5. Blocked roads6. Facilities disrupted –

electricity, water, medical.

7. Tsunamis

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:a) Diverging platesb) Converging platesc) Hot Spotsd) Faults

• Important Terms:a) Vent and Fumerolesb) Craterc) Pyroclastic materiald) Lava flowe) Magma Chamberf) Cone shaped hill

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,

TYPES OF VOLCANOES• On the basis of

frequency:

a) Active Volcano: which erupt frequently & can erupt any time. Eg. Mt. Mauna Loa, Hawaii.

b) Dormant Volcano: which have erupted in history but have not erupted since then. Eg. Mt. Rainier, USA

c) Extinct Volcano: which may have erupted earlier but is now almost dead (>1000 yrs.) Eg. Mt. Kilimanjaro, Tanzania

• On the basis of shape and material they are made of:

a) Shield Volcano: Gentle slopes, basaltic lava, low viscosity. Eg. Mt. Mauna Loa, Hawaii

b) Cinder Volcano: Steep slopes, > 300 meters in height, made of pyroclastic material. Eg. Mt. Paracutin, Mexico

c) Composite / Strato Volcano: Steep upper slopes & then gentle, Alternate layers of lava & ash. Eg. Mt. Vesuvius, Italy

TYPES OF ERUPTIONS

• There are five major types of eruptions:

a) Hawaiianb) Strombolianc) Vulcaniand) Peleane) Plinian

TYPES OF ERUPTIONS

VOLCANIC ZONES OF THE WORLD

EFFECTS OF VOLCANO

• Positive Effects:a) Ash add to the soil

fertility – farmingb) New minerals may be

discoveredc) Promotes Tourism d) Research and

education purposes.e) Geothermal Energy –

renewable energy.

• Negative effectsa) Loss of lifeb) Loss of property

(economic loss)c) Air Pollution (ash,

smoke, gases, acid rain etc)

d) Water pollutione) Lahars (mudflows with

water)f) Earthquakesg) Increase in temperature

of the area

ZONES OF EARTHQUAKES & VOCANOES