N level 2014 Q4

4	(a)	Study Fig. 8 which shows the East African rift valley and plate boundaries in the area.
		Using Fig. 8, describe the location of the volcanoes and lakes.                                      [4]
		Location of volcanoes At plate boundaries between African Plate and Arabian Plate Along the fault lines of the East African Rift Valley / eastern Africa Mainly in the eastern branch of the rift valley; Less volcanoes in the western branch Location of lakes Within the rift valley Lakes mainly in western branch of the rift valley 4@1m
	(b)	With the help of an annotated diagram, explain how a rift valley is formed.       [4]
		2 continental plates diverge/move apart Tension occurs fractures formed at plate boundary Centre block sinks relative to side blocks Form a linear depression / long depression with steep sides called a rift valley 1m – diagram 3m - explanation 4@1m
		·        As two plates diverge, tensional forces pull rock layers apart in opposite directions. ·        As the two plates continue to diverge, normal faults are created, creating a central mass of rock bounded by the faults, known as a fault block. ·       As the side blocks of land continue to diverge, the fault block in the centre sinks, forming a rift valley.
	(c)	Read the details about Mt Nyamuragira (shown on Fig. 8) and its eruption in 2010, as described in Fig. 9.
		Mt Nyamuragira and the eruption in 2010 Most active volcano in Africa Low silica content of lava Low viscosity of lava Slopes of 3 to 20 In 2010 The lava flowed for 21 km Ash and gas emissions caused health problems Drinking water was contaminated Animals died and crops were destroyed.
		Fig. 9
	(i)	What is the evidence from Fig. 9 that Mt Nyamuragira is a shield volcano?       [4]
		Low silica lava – flows easily and spread over a large area; (elaborate) flows 21 km before solidifying to form a shield volcano (data) suggests that it has very gentle slopes (elaborate) Slopes of 3° and 20° degrees (data) 4@1m If no need to use Figure, differentiate strato and shield by - Height - Slope - Lava (resistance/viscoscity)
	(ii)	Using Fig. 9, explain what risks the volcano presented to the people when it erupted in 2010.                                                                                                                                [4]
		Respiratory problems [ash and gas emissions caused health problems] Ash got into the water courses, turned water into very acidic.  [Drinking water contamination] Destruction of livestock and crops [animals died and crops destroyed] … farmers cannot earn money 4@1m
	(d)	The Red Sea lies on a divergent plate boundary.  Explain the processes taking place at such a plate boundary.                                                                                                     [3]
		2 continental plates move away from each other Creates a fracture/ depression in the earth's crust Forms a linear sea that is elongated in shape 3@1m
	(e)	‘Earthquakes measuring the same magnitude on the Richter Scale cause similar kinds of damage.’  How far do you agree with this statement?  Give reasons for your answer.       [6]
		Same magnitude earthquakes cause similar kinds of damage: Other factors that cause damage earthquake damage: Population density Time of occurrence, i.e. day or night Level of preparedness