Revision Date: 24th February Venue : COM LAB 1

CNY HOMEWORK•P31 – Humidity•P33 – Land breeze•P37 – NE Monsoon•P42 – Climograph

Common Test Topic – Weather and Climate

• Both volcanoes and earthquakes are found at the Pacific Ring of Fire.

• Volcanoes are found along the boundaries of several converging plates such as Nazca Plate, Australian Plate and Eurasian Plate / Found at diverging plate boundaries such as East Africa and Mid-Atlantic Ocean.

• Earthquakes occurs more frequently at convergent plate boundaries.

• The Earthquake belt stretches from the Mediterranean Sea to the Himalayan Mountains, which is a zone of collision.

1. Oceanic-oceanic plate divergence

A) 2 oceanic plates move away from each other

Bi) Magma rises from the mantle to fill the gap between the plates as they diverge.

1. Oceanic-oceanic plate divergence

P11. The Mid-Atlantic Ridge is found in the middle of the Atlantic Ocean cutting across Iceland, a volcanic island.

Bii) New sea floor is formed when the magma cools and solidifies. This process is called sea-floor spreading.

Bii) Magma rises at the zone of divergence/spreading zone to form a ridge of new ocean floor called mid-oceanic ridge.

1. Oceanic-oceanic plate divergence

Ci) The newly formed (youngest) rocks are closest to the middle of the ridge/plate boundaries.

Cii) At various points along the ridge, magma builds up above the ocean to form volcanic islands.

P48 Sea Floor Spreading

1. A – older rocks , B – younger rock

2. When two oceanic plates move away from each other it causes cracks in the crust.

3. This makes it possible for magma to rise to the surface from below.

4. As it cools down, this lava creates new crust at the plate boundary.

5. The constant flow of magma causes new crust to form continuously (at B) and the old crust to be pushed further away from the plate boundary (A). This is known as seafloor spreading.

P53

Using Fig. 6, explain how it can lead to the formation of a mid-oceanic ridge. [4]• Convection currents in the mantle cause 2

oceanic plates to diverge • Result: fractures/ faults formed at plate

boundaries• Magma rise at the zone of divergence to fill

the gap between the plates as they move apart

• New sea floor is formed when magma cools and solidifies, known as sea-floor spreading. This forms a mid-oceanic ridge

2. Continental–continental plate divergenceA)2 continental plates move away from each other

B)Stretched and causes fractures at boundaries

C)Land in between sinks and forms rift valley and volcanoes

P52

2. Continental–continental plate divergence• Can result in the breakup of continents • E.g. Great Rift Valley (East Africa)– a lowland with steep sides and flat valley

floor– 6,000 kilometres long – between 30 to 100 kilometres wide

P50 – Location : formed by Somalian boundary

of the African Plate moving away from the Nubia plate boundary of the African Plate

– Features : 3 vertical fault lines, forming a depression in the African (Nubian Plate)

• Can result in the formation of linear sea• E.g. Red Sea and Gulf of Aden near the Great Rift

Valley – Elongated/linear shape– 1,900 km long– 300 km at its widest – Average depth of 500 m– Evidence of tectonic

activity formation of

new volcanic island in

Red Sea

2. Continental–continental plate divergence

IMPT! P25 Rift valleys and block mountains

2. Continental–continental plate divergence

P 50 Account for the formation of the East African Rift Valley. [3]•Formed at the divergent plate boundaries. •Plates are pulled apart and this results in faulting. Faulting is when tensional forces from these movements result in parts of the crust being fractured. •When section of the crust extends along fault lines, the central block of the land subsides between 2 parallel faults, a steep-sided rift valley is formed.

• A fault is a fracture in the rocks along which the rocks are displaced.

• The tensional forces result in parts of the crust being fractured.

• This process is called faulting.

FAULTING

• A rift valley is a valley with steep sides formed along fault lines. E.g. East African Rift Valley

Formation of Rift Valley

Identify Landform A and describe its appearance. [2]• Feature A – Rift Valley (1m)

Choose any of the 2 below (0.5m each)• Long/elongated/Linear • Deep• Stepped scarps at the valley sides• Presence of fault lines

P52 With the aid of well-labelled diagrams, explain how Landform A and its associated tectonic landform/feature are formed.

P52 With the aid of well-labelled diagrams, explain how Landform A and its associated tectonic landform/ feature are formed. [7]

(d)

P52 With the aid of well-labelled diagrams, explain how Landform A and its associated tectonic landform/ feature are formed. [7]

Explanation (0.5m each)1. Two continental plates move apart2. Tensional forces result in faults to form3. This cause the central block of land between 2 parallel faults to sink to form a rift valley4. Magma from below the earth’s crust rises 5. The release ejects hot volcanic material through the vent 6. These eruptions forms a volcano

• A block mountain is a block of land with steep sides. It is formed when sections of the crust extend along fault lines and rock masses surrounding a central block sink due to tensional forces.

Block mountains