State the structure of Earth Label the worlds crustal plates Explain that convection current causes plates to move
Innermost part of the Earth. 3450km. Consists mainly of iron and nickel Very high temperature of 4000 ◦C Quiz: How will the high temperature affect the crust?
Middle layer. 2900km thick Mostly solid with the upper most layers consisting of molten rocks known as magma.Lava flow onHawaii. Lava isthe extrusiveequivalent ofmagma. Quiz: What is the difference between magma and lava?
• Outermost layer of the Earth.• 60km thick and floats on denser mantle.• Broken up into pieces known as crustal plates.•
Continental plates are lighter and consist of land masses. Oceanic plates are heavier as they consist of large water masses.Quiz: what happens when an oceanicplate collides with a continental plate?
Worlds Crustal plates
Quiz: Explain how convection currents affects plate movement.
Extreme heat from the interior of the Earth causes the magma to be heated up, expand and rises. This generates convection currents. Quiz: Name an example of convection current that u can find in the kitchen
As the convention currents reach the crust above, they spread out carrying the plates above with it. Plates are dragged apart. As the magma cools, it gradually sinks back down to be re-heated. The process causes the plates to move towards each other.
12th sept Objective• Describe and explain the 3 types of plate movements• Identify the landforms that are formed
(1) Convergent plates movement- Crustal plates move towards each other(2) Divergent plates movement – Crustal plates moving away from each other.(3) Transform plate movement- plates sliding past each other.
Scenario 1: continental plate + oceanic plate
Scenario 1: continental plate + oceanic plateQuiz: Which plate is heavier? What landform is created?
Scenario 1: continental plate + oceanic plate Converging plate movement Convention currents within magma pulls two plates together. The heavier oceanic plate get subducted while the lighter continental plate floats on it. Subducted part of the plate melts under high heat to form magma. Magma then rises above the Earth’s surface to form volcanoes.
Scenario 2: continental plate + continental plateConverging plate movementQuiz: What is the landform created?
Scenario 2: continental plate + continental plate Converging plate movement When convention currents within magma push two crustal plates together, there is immense collision force. Rocks between the plates are pushed upwards, folded to form fold mountain. Eg: Himalayas mountains, Andes and Rocky.
When the convention currents in magma pull 2 oceanic plates apart, a ridge may form at the boundaries. Magma may rise up the cracks to from volcanoes.
Quiz: What landforms are formed when 2 continental plates collide?
• A ridge is a geological feature Ridge consisting of a chain of mountains or hills that form a continuous elevated crest for some distance.• Ridges are usually termed hills or mountains as well, depending on size.
Occurs at conservative plate boundary whereby the plates are not created nor destroyed Plates slide past each other. Eg; San Francisco fault.
Summary• Plates move because of convection currents within the earths crust• There are 3 types of plate movements• Convergent, divergent and transform plate movements
Content page 11. The earths structure 12. 3 types of crustal movement 13. Landforms created by crustal plate movements 14. Vulcanicity
Lesson objectives• Know where the pacific ring of fire is located at• Draw diagrams of the 3 types of plate movement
crustal plate movementsFold mountains and volcanoes
Pacific ring of fire The Pacific Ring of Fire (or just The Ring of Fire) is anarea where a large number of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean.Quiz: Why are the similaritiesbetween the locations of the volcanoes?
and volcanoesFold mountains and volcanoes are formed along the plateboundaries. Refer to text pg 75
Objective• Label the parts of the volcano• Describe the 3 stages/types of volcano
Row row row your boat gently down the streamQuiz: What happens after a volcanic eruption?
Vulcanicity is the process by which the molten materials are forced onto the Earth’s surface. The molten rock found below the earth is called magma. When magma flows onto the earth, it becomes lava. Lava flows through the earths surface through a single opening. Overtime, the layers of lava forms a volcano.
cinderPipe Layers of lava
Structure of a volcano • A volcano is an opening in the earths crust from which materials are ejected • During an eruption, molten rock or magma is ejected onto the earths surface as lava. • Gases such as steam and carbon dioxide may also be released.
Crater – opening at the top of a volcano where lava, rock fragments, gases and ash are ejected. Lava – Molten rocks that have been erupted onto the Earth’s surface. Pipe – Channel joining the magma chamber to the top of the volcano which the magma flows through. Vent- Opening in the Earth’s crust where magma rises and are ejected out
Magma chamber – An underground cavity which contains molten rocks. Cone – This is built up by successive layers of cooled and solidified lava, mixed with ash and rock fragments.
Quiz: Why are the volcanoes in different shapes?
(1)Basic lava flow•- more fluid and thin and the lava travels over a longer distance before solidifying.•- lava flow faster and spread widely•- Gives rise to a more gentle-sloping volcano (shield volcano).(2) Acidic lava flow• Lava is thicker and more viscous.• Travels over a shorter distance and cools and solidify faster.• Gives rise to volcano with steeper slopes.
Other examples are Mt Mayon in thePhilippines; Mt Merapi in Java.
One of the best examples of a dormant volcano is Mauna Kea, one of the five volcanoes that make up the Big Island of Hawaii. The peak of Mauna Kea is 4,207 meters above sea level, but 10,203 meters above the base of the floor of the Pacific Ocean. Geologists classify Mauna Kea in the post-shield stage of volcanic evolution. It stopped being a shield volcano about 200,000 years ago. Mauna Kea’s last eruption is thought to be 2460 BC.
(Different stages)• (1) Active volcano – A volcano that is currently erupting or is likely to erupt soon. (frequently)• (2) Dormant volcano – A volcano that is presently inactive but may erupt in the future(occasional)• (3) Extinct volcano – A volcano that is dead and not expected to erupt again.
Summary• Label the 7 parts of the volcano• Describe the 3 stages/types of volcano: active, dormant, extinct
Hot ash, gas and rocks are poisonous and hazardous to air. Disruption to traffic. High temperature lava flow, volcanic bombs, cinder and ash may kill people, bury farmlands and houses and destroy infrastructure. Volcanic eruption may trigger landslides that kill livestock and bury houses and people.•
Soil near volcanoes are rich and fertile which is suitable for crops to be grown. Geothermal energy generated by the heat from volcanoes is used to produce electricity for development of industries. Source of precious stones and minerals like diamonds, copper, zinc, gold and silver etc provide mining jobs. Volcanic rocks provide materials for landscaping, construction and road-building.
A form of tourism revenue as many religions and cultural rituals are conducted by people living on the slopes of volcanoes. Beautiful landscapes of volcanoes serve as a form of tourist attraction. Eg Bali and Java. This provides jobs and revenues to the locals.
Mock test questionIf volcanic eruptions are adangerous threat, why do people still choose to live near volcanoes? [4m]
If volcanic eruptions are a dangerous threat, why do people still choose to live near volcanoes? [4m]• The solidified lava provides fertile land for agriculture• Volcanic areas are rich in precious stones and minerals such as silver and zinc• Volcanic areas can be tourist destinations which can provide a source of income for people living near the volcanoes• There is a shortage of land for settlement• The volcano has erupted for a long period of time and people tend to forget the dangers that they pose