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What is Geographic North
The direction towards the fixed point on
Earth called the North Pole.
What is Geographic South?
The direction towards the fixed point on
Earth called the South Pole.
What is magnetic North
Direction that a compass needle points to. This is the direction of the Earth's magnetic North pole, where the Earth acts as a magnet itself.
What is magnetic south?
The South direction that a compass needle points to. This is the direction of the Earth's magnetic South pole.
What is normal polarity?
When the Earth's magnetic North points towards geographic North and magnetic South points towards geographic South.
What is reverse polarity?
When the Earth's magnetic North points towards geographic South and magnetic South points towards geographic North.
Which of the magnetic stripping can change?
Magnetic North and South
What is magnetic stripping?
Magnetic striping is the zebra-like pattern where there are strips of normal polarity rocks alternating alongside strips of reversed polarity rocks on the seafoor
How does magnetic stripping look on mid-ocean ridge?
it is symmetrical
How do we know that magnetic stripping has occurred?
Basaltic rocks from the oceanic crust are volcanic rocks formed from iron-rich lava.
• They contain magnetic materials
When volcanic eruption occurs, what happens to earth's magnetism?
When the iron-rich lava erupts, it cools and solidifies.
• Its magnetic materials point towards Earth's magnetic North, recording evidence of Earth's polarity at that time.
What are the two divergent plate boundary?
Divergent plate boundary is where two tectonic plates move apart
Examples:
• Oceanic-oceanic divergent plate boundary
• Continental-continental divergent .
What are the types of convergent plate boundaries?
• Oceanic-oceanic convergent plate boundary between the
• Continental-continental convergent plate boundary
• Oceanic-continental convergent plate boundary
Give example of a transform plate boundary.
• San Andreas Fault where the Pacific Plate slides past the North American Plate
Name the two plates where mid-Atlantic ridge lies in between.
Oceanic North American plate and oceanic Eurasian plate
Give example of C-C convergent plate boundary.
• Continental-continental convergent plate boundary between the Eurasian Plate and the Indo-Australian Plate.
Give examples of O-O divergent plate boundary.
Divergent plate boundary is where two tectonic plates move apart
Examples:
• Oceanic-oceanic divergent plate boundary between the North American Plate and the Eurasian Plate.
Give example of C-C divergent plate boundary.
• Continental-continental divergent plate boundary between the Nubian Plate and Somalian Plate.
Give example of O-O convergent plate boundary.
• Oceanic-oceanic convergent plate boundary between the Philippine Plate and the Pacific Plate.
Give example of O-C convergent plate boundary.
• Oceanic-continental convergent plate boundary between the Naza Plate and the South American Plate
State in 5 steps, how underwater mountain chain or mid oceanic ridge forms.
1. Two oceanic plates move apart.
2. The decrease in overlying pressure causes parts of the underlying mantle to melt, forming magma.
3. Magma rises through weak areas in the crust to the Earth's surface, and fills gaps caused by the spreading plates.
4. Lava cools and solidifies to form basaltic rocks.
5. The rocks make up a new oceanic crust.
An extensive underwater mountain chain - the mid-ocean ridge
Explain how , volcanoes form from mid ocean ridge.
At the centre of the ridge is a deep rift valley with steep sides.
• Magma rises through weak areas in the crust to the Earth's surface, forming submarine volcanoes.
• After many eruptions, the volcanoes may break the surface of the ocean to form volcanic islands,
Describe the 4 steps how volcanoes form from C-C divergent plate boundaries.
1. Two continental plates move apart.
2. Rocks eventually fracture to form parallel faults.
3. The rock between these faults collapses to form a deep rift valley with steep sides.
4. As the plates move apart, the decrease in overlying pressure causes parts of the underlying mantle to melt, forming magma. Magma rises through weak areas in the crust to the Earth's surface, forming volcanoes.
Describe how mariana trench form.
1. Two oceanic plates collide.
2. The denser plate subducts beneath the other plate.
3. This forms a deep depression known as an oceanic trench.
4. As the subducting plate sinks into the mantle, the high pressure forces water out of its oceanic crust. Water lowers the melting point of the overlying mantle, causing it to melt, forming magma.
5. Magma rises through weak areas in the crust to the Earth's surface.
6. This forms a chain of volcanoes, known as a volcanic island.
Describe the formation of fold mountains at C-C convergent plate boundaries.
1. Two continental plates collide.
2. Subduction does not take place because continental plates are too buoyant to subduct.
Enormous pressure causes the rocks to be uplifted and buckled to form fold mountains.