To what extent does the nature of materials ejected influence the formation of volcanic relief land forms 

Candidates should define volcanic relief land reforms as features formed as a result of the ejection of Liquid, Solid or Gaseous materials on the surface of the Earth.

They should then describe the nature of materials ejected and the associated relief land forms, i.e.

• The liquid materials ejected consist of molten magma which reaches the surface as lava:
• Some Lavas{Acidic) contain much Silica, with a high melting point, very viscous and solidify rapidly building high-steep sided cones or may solidify in the vent causing recurrent explosive The resultant land reforms include:- . .
  • Cumulo domes g. Ntumhi in Tanzania.
  • Volcanic plug/ plug domes g. Mt.Kenya.
  • Co mposite volcanoes e.g. Kilimanjaro
• Where the Lava is basic i.e. poor in silica but rich in Iron and magnesium materials, it flows for a considerable distance before solidifying producing flatter cones of greater diameter. It is associated with the formation of:-
  • Basaltic domes/ shield volcanoes e.g. Nyamulagira- part of the Virunga ranges.
  • Lava plateaus/ plains e.g. Kisoro, Yatta, Kapiti, Nyabondo etc.
• Gaseous compounds emitted during eruption include sulphur, carbon dioxide and chloride etc. including steam. The gases inter – react generating great heat within the This affects the ra te of cooling, lava flow and the shape and type of volcanic landform formed.
• Solid materials generally known as tephra are ejected during a series of eruptions. These may include fragments of country rocks; angular fragments of solidified lava and finer materials such as Scoria, Pumice, Cinders, Dust and
• Gaseous and solid materials are ejected during violent emptions producing the following relief land reforms·-
  • Ash and Cinder cones I Scoria cones e.g. Shozi, Sagitwe in Kisoro, Teleki and Likaiyu in Kenya etc.
  • Strato/ composite volcanoes e.g. Kilimanjaro, Muhavura
  • Calderas e.g. Napak, Longonot, Menengai, Suswa etc.
  • Explosion craters e.g. Katwe, Nyamunuka, Nyangu etc. in low lying areas and mountain craters e.g. Muhavura crater. Kilimanjaro crater. Shozi crater etc.

However, other factors which bring about volcanic relief landforms should be cited e.g.

• Nature of passage/
  • Central or single vent leads to the formation of steep sided cones e.g. plugs and composite volcanoes.
  • Numerous fissures tend to produce gently sloping cones, usually low in height with a large base e.g. basaltic domes and lava plateaus.
  • Fault lines provides passages for the formation of volcanic cones e.g. Suswa, Longonot etc.
• Number /times of emissions.
  • Successive eruptions lead to complex composite volcanoes, basaltic domes etc.
  • Simple/ single eruptions lead to formation of small