SkillBuilder discussion Geographical inquiry 1. Identify the tectonic plates involved in the formation of the Great Rift Valley. 2. Describe why this valley has formed. 3. Draw a series of sketches to show what you predict will happen to the African landmass as the Great Rift Valley continues to rift. Include a map of Africa showing the change in shape that might occur. You need to annotate your sketches to justify the predictions you have made.
FIGURE5 The Great Rift Valley, Africa
SYRIA
Iranian Plate
Arabian Plate
ERITREA
African Plate (Nubian)
Indo-
Australian
Plate
ETHIOPIA
INDIAN
OCEAN
Mt Elgon
Equator
Mt Kenya
African Plate (Somalian)
Mt Kilimanjaro
Lake Victoria
0
500 1000 1500 km
Plate boundary
Plate movement
East African RiftValley
olcano
V
MOZAMBIQUE
Afar Triangle
Country border
Source: Map drawn by MAPgraphics Pty Ltd, Brisbane
14.9.2 Volcanic hotspots Although most volcanoes are formed on plate boundaries, some are located in the middle of plates, a long way from plate boundaries. These volcanoes have formed above a hotspot — a single plume of rising mantle. Volcanoes form as the plates slowly move over the hotspot and, over time, a chain of volcanoes can form. Hotspots are found in the ocean and on continents. Examples include the Hawaiian Islands and many of Australia’s extinct volcanoes. In Hawai‘i, the location of the volcanic islands gives a clue to the direction and speed of the plate movement. 14.9 SkillBuilder activity COMMUNICATING 1. Summarise the information that you have learnt about volcanoes. 2. Explain what you know about Hawai‘i’s hotspot. Complete some research of your own to provide some key facts on this location. 3. Using your notes, explain how hotspot volcanoes form.
TOPIC14 Geomorphological processes and hazards
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