Geography Paper 3 WASSCE (PC 1), 2019

Question 6

  1. Name three mountains that have composite volcanic cones.
  2. With the aid of a diagram, describe the characteristics and formation of composite

volcanic cones.

 


Observation

 

This question was attempted by few candidates and their performance was poor. Examples of composite volcanoes are:

  • Mt Chimborazo in Ecuador
  • Mt Krakatoa in Jakata
  • Mt Kilimanjaro in Tanzania
  • Mt Cameroun in Cameroun
  • Mt Fujiyama in Japan
  • Mt Elba in Italy
  • Mt Versuvius in Italy
  • Mt Popocatepetl in Mexico
  • Mt Mayon in Phillipines
  • My Cotopaxi in Ecuador
  • Mt Etna in Sicily
  • Mt Stomboli in Italy

The characteristics of composite volcanoes include:

  • feature of extrusive volcanic activity
  • found in areas of volcanic activity
  • mainly made up of layers of ash, lava and cinder
  • has a crater at the top
  • makes the highest mountains in the world
  • has dykes at the flanks
  • broad at the base and tappers at the top/conical in shape
  • have very steep slopes or concave slopes
  • angle of slope is between 30⁰ to 40⁰
  • have parasitic cones or conlets
  • have subsidiary vents or dykes

The mode of  formation of composite volcanic cones goes thus:

  • formed in areas of volcanic activities
  • built by alternating eruptions of pyroclastic materials and lava
  • violent eruption of pyroclastic materials settle around the vent initially
  • lava pours quietly to cover the pyroclastic ash materials
  • eruption is mainly through a central vent
  • processes are repeated to build a volcanic cone (ash and cinder cone)
  • viscous lava blocks the vent and pipe
  • subsequent violent eruption causes cracks to appear along the flanks
  • volcanic materials are forced out through the flanks
  • the materials cool and solidify to form parasitic cones
  • many subsidiary cones /parasitic cones may develop at the flanks of the main volcano
  • this forms a composite volcanic cone