daneilla desgoutte westwood high school grade 11p n.
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Daneilla Desgoutte Westwood High School Grade 11p. Volcanoes. Objectives. Students should be able to: Define and explain the formation of a volcano. Differentiated between the types of lava and list features of each. Label the features of a volcano.

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daneilla desgoutte westwood high school grade 11p
Daneilla Desgoutte

Westwood High School

Grade 11p


  • Students should be able to:
  • Define and explain the formation of a volcano.
  • Differentiated between the types of lava and list features of each.
  • Label the features of a volcano.
  • Differentiate between the types of volcanoes.
  • List three (3) Extrusive and intrusive features and explain there formation
  • Describe how volcanic activity can affect people.
what is a volcano
What is a volcano
  • Rocks below the crust have a very high temperature, but the pressure keeps the rocks in a semi solid state.
  • If the pressure weakens the rocks become liquid ( Magma).
  • Magma forces its way into cracks of the crust and may either reach the surface where it forms volcanoes, lava flow or it may collect in the crust and form batholiths, sills, dykes.
  • A volcano is a conical hill or mountain build up by the ejection of magma from a vent.
types of lava
Types of lava

Viscous lava-

  • High in silica content
  • Light in colour
  • Volcanic eruption is very loud
  • Contains gas which cannot escape easily
  • Does not flow fast, but cools fast
  • Creates tall and steep volcanoes

Caribbean volcanoes are normally made up of viscous lava.


Basic Lava –

  • Low in silica content
  • Dark in colour
  • Flows quietly
  • Flows easily
  • Spreads thin
  • Cools slowly
  • Volcanoes will be lower and broader
types of volcanoes
Types of volcanoes
  • A volcanic cone is made of either lava or a mixture of lava and rocks torn from the crust, or ash and cinders.
  • There are three types of volcanoes:
  • Ash and Cinder Cone
  • Lava Cone
  • Composite Cone
ash and cinder cone
Ash and Cinder cone
  • In violent eruptions the molten lava is thrown high into the air.
  • It breaks into small particles, cools and solidifies before falling back to earth as volcanic ash.
  • A series of ash eruptions may build up build up and form a cone.
lava cones
Lava Cones
  • The slope of the cone is depend upon whether the lava was fluid or viscous, when it was molten.
  • Fluid lavas give rise to gently sloping cones, e.g. Mauna Loa ( Hawaii).
  • Viscous lava give rise to steeply sloping cones.
  • At times the lavas are so vicious that when they are forced out of the volcano they from a spine or plug.
composite cone
Composite cone
  • Volcano is made up of alternate layers of lava and ash.
  • Begins each eruption with great violence which produce layers of ash.
  • As the eruption continues the violence ceases and the lava pours out forming layers on top of the ash.
extrusive features of a volcano
Extrusive features of a volcano
  • Basalt Plateau-

Basalt lava flows, may smoother hills and valleys of a pre-existing landscape producing a wide flat plateau. The largest basalt plateau is in India.


Geyser –

Every 65 minutes the water come out the water is pre –heated. They also form natural fountains


Hot springs-

Hard rock on top of lava. The water is then heated and the runs as hot spring.



An area where gases are released from volcanoes (sulphur).


These features are formed by magma that have cooled and hardened before it reaches the surface. They do come to the surface due to weathering.

  • Sill-

is formed where magma flows horizontally between two rock layers and cools. It is formed parallel to the surface.



is a vertical or inclined sheet of magma that has cooled.


is a underground reservoir of magma. The rocks cool and harden below the surface. If a dyke become expose if its under a river a water falls will form.

effects of volcanic activity
Effects of Volcanic activity

Negative Effects:

  • Displacement of population
  • Destruction of crops and economy
  • Change in weather pattern
  • Landslides
  • Environmental Pollution
  • Death

Positive Effects:

  • Valuable for minerals ,e.g. Nickel, Copper, Gold.
  • Fertile farming soil
  • Hot springs, Spas
  • Forms tourist attractions
  • Exporting of volcanic rocks
predictions of volcanic eruption
Predictions of volcanic eruption
  • Seismograph
  • Minor shacks
  • Gradual swells in volcano
  • Deformed rocks

1.Magma becomes lava when it reaches a volcano’s

a. Geyser

b. Pipe

c. Magma chamber

d. Vent


2.A volcanic mountain made up of volcanic ash, cinders, and bombs is called

  • Shield volcano
  • Cinder cone
  • Composite volcano
  • caldera

3.Magma that hardens in a volcano’s pipe forms a

  • Volcanic neck
  • Sill
  • Volcanic crater
  • Hot spot
  • Jan Jenner, Ph.D. California Focus on Earth Science,2008,Pearson Education Inc.
  • R.B. Bunnett, General Geography in Diagrams,1985,Longman Group Ltd.