08 volcanism intrusive and extrusive features

As many adjectives as possible!As many adjectives as possible!

Your homework was to…Your homework was to…

Using internet research, create and example of a conservative boundary. You will need to include the following from the

check list!

•Location (atlas!)•Map onto your tectonic plate map!•Quick diagram•Description of processes•Explanation of effects•Future predictions•Historic earthquakes

Useful websites!http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Conservative/San-Andreas-Fault

http://www.youtube.com/watch?v=roIEtkuXbvk

http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Conservative/San-Andreas-Fault

http://pubs.usgs.gov/gip/earthq3/safaultgip.html

http://geology.com/articles/san-andreas-fault.shtml

http://www.sanandreasfault.org/Information.html

Learning OutcomesRecap volcano basicsDescribe intrusive featuresSort advantages and disadvantages of volcanoesDifferentiate between intrusive and extrusive features

VulcanicityVulcanicityLearning Objective:Learning Objective: Understand major forms of extrusive Understand major forms of extrusive

volcanism and intrusive features.volcanism and intrusive features.

The Specification!The Specification!

Our next area of focus….Our next area of focus….

Remember, you should Remember, you should highlight the specification as highlight the specification as we complete each section!we complete each section!

Crater Volcanic bombs, ash and gases

Main vent

Parasitic cone

Magma chamber

This 'cut through' is called a cross section. Make a sketch of the diagram below then add the labels in the correct place.

Crater Volcanic Bombs Main Vent Parasitic Cone Magma Chamber

Is it sleeping?Is it sleeping? There are three ways to classify a volcano:There are three ways to classify a volcano:

• ExtinctExtinct• Dormant Dormant • ActiveActive

Match up the definitions below with the Match up the definitions below with the correct term and write them outcorrect term and write them out

If it has not erupted

for years, or even

centuries, but still

seeps gas sometimes.

If it has erupted

recently and is likely

to do so again.

If it has not erupted for thousands of years and its shape has been worn away by

the wind and rain.

Active volcano – If it has erupted recently and is likely to do so again. e.g. Mt Etna.

Dormant (sleeping) volcano – If it has not erupted for years, or even centuries, but still seeps gas sometimes. For example, Mt Pinatubo erupted in 1991 after 500 years of dormancy.

Extinct volcano – If it has not erupted for thousands of years and its shape has been worn away by the wind and rain.e.g. Edinburgh.

However, it is often very difficult to tell whether a volcano will erupt again…El Chichon, Mexico erupted in 1982 after being dormant for approximately 1200 years!

Do all volcanoes erupt?

Volcancity; a beneficial hazard?!Volcancity; a beneficial hazard?!Sort these statements into benefits and hazards associated with volcancity. Then

explain which you think are the most beneficial and which are the most hazardous.

Submarine, coastal or island eruptions may cause

Tsunamis.

Ash fall ruins crops and machinery, pollutes the air,

and disrupts transport.

Dust emissions can seed torrential rainstorms causing dangerous wet ash and mud

lahars .

Flooding from laval flows block and divert rivers.

Pyroclastic flows of superheated gas, ash and pumice destroy life

and property.

Volcanic melting of snow creates lahars.

Volcanic ash absorbs solar energy so temperatures are

reduced.

Hot rocks can generate geothermal power.

Igneous rocks contain valuable minerals such as gold, silver and diamonds.

Volcanic sulphur is used pharmaceuticals and

agrochemistry industries.

Igneous rocks make great building materials e.g

granite.

Extinct volcanoes make great defensive sites e.g Edinburgh

Castle.

Lava and ash weather quickly to create fertile soils.

Volcanoes make great tourist attractions along with geysers,

fumeroles, hot springs and boiling mud.

Lava creates new land.

Volcancity; a beneficial hazard?!Volcancity; a beneficial hazard?!Sort these statements into benefits and hazards associated with volcancity. Then

explain which you think are the most beneficial and which are the most hazardous.

Submarine, coastal or island eruptions may cause

Tsunamis.

Ash fall ruins crops and machinery, pollutes the air,

and disrupts transport.

Dust emissions can seed torrential rainstorms causing dangerous wet ash and mud

lahars .

Flooding from laval flows block and divert rivers.

Pyroclastic flows of superheated gas, ash and pumice destroy life

and property.

Volcanic melting of snow creates lahars.

Volcanic ash absorbs solar energy so temperatures are

reduced.

Hot rocks can generate geothermal power.

Igneous rocks contain valuable minerals such as gold, silver and diamonds.

Volcanic sulphur is used pharmaceuticals and

agrochemistry industries.

Igneous rocks make great building materials e.g

granite.

Extinct volcanoes make great defensive sites e.g Edinburgh

Castle.

Lava and ash weather quickly to create fertile soils.

Volcanoes make great tourist attractions along with geysers,

fumeroles, hot springs and boiling mud.

Lava creates new land.

VolcanicityVolcanicityThe process through which gases and molten rock/ magma are either

extruded on the earth's surface or intruded into the earth's crust.

Intrusive- magma cools, crystallises and solidifies into

igneous rocks below the earths surface. Slow cooling results in larger crystals e.g granite and

dolerite.

Extrusive- magma surfaces as lava and cools, crystallises and solidifies through contact with air (fast) or the sea (rapid) into igneous rocks above the earths surface. Quicker cooling results in finer crystals e.g

basalt.

Handle with care and describe

the specimens!

Intrusive features form below the earths surface, thus they only become part of the landscape once erosional processes have removed

the overlying rocks. These are a common part of the UK landscape being visible in Scotland, Northern Ireland and Northern England.

Intrusive Volcanic FeaturesIntrusive Volcanic Features

Dykes Sills Laccoliths BatholithsUse the information sheets to describe and explain the formation of

these intrusive features and label them onto a diagram!

Sills Laccoliths

Intrusive Volcanic FeaturesIntrusive Volcanic FeaturesRemember- these only surface once the rock layers above have been eroded!

Over many years they solidify slowly within the earths surface.

Intrusive Volcanic FeaturesIntrusive Volcanic FeaturesRemember- these only surface once the rock layers above have been eroded!

Over many years they solidify slowly within the earths surface.

DykesDykesThese are vertical intrusions formed where magma solidifies in a vertical crack/ fissure. They often form in groups called swarms. Dyke material

tends to be more resistant than the surrounding rock leaving prominent wall like features on an eroded landscape. Erosion of less

resistant dyke material may leave ditch like features.

Isle of Mull, Scotland.

SillsSillsThese are horizontal intrusions formed where magma solidifies as

sheets in between layers of existing rock. When these are exposed at the surface through erosion, they form steep sided cliffs along the

landscape.

Great Whin Sill, Northumberland.

LaccolithsLaccolithsThese are formed when thick viscous magma which is

resistant to flow bulges and forces the overlying rock strata to arch into a dome.

Eildon Hills, Scotland.

BatholithsBatholithsThese are on a much larger scale than Laccoliths. Usually, dykes, sills and

laccoliths will feed off the domed granite batholith before it solidifies. The batholith is exposed to extreme heat and pressure which alters the adjacent rock through metamorphism which forms a metamorphic

aureole.

Dartmoor, England.

Outline the differences between the intrusive features shown in Figure 2. (4 marks)

• Batholith- large, deep-seated mass of intrusive igneous rock, usually granite, with a huge surface area of (more than 100 sq. km/40 sq mi.)

• Laccolith- intruded mass of igneous rock that forces apart strata and forms a round dome shaped mass wider than thick. Can dome the surface above.

• Dyke- These are vertical intrusions form where magma solidifies in a vertical crack/ fissure. They often form in groups called swarms. Dyke material tends to be more resistant than the surrounding rock leaving prominent wall like features on an eroded landscape. Erosion of less resistant dyke material may leave ditch like features.

• Sill is igneous rock intruded horizontally between layers of rock formed where magma solidifies as sheets in between layers of existing rock. When these are exposed at the surface through erosion, they form steep sided cliffs along the landscape.

Outline the differences between the intrusive features shown in Figure 2. (4 marks)

Types of LavaTypes of Lava

Watch the clip and describe the types of lava you see. Comment on the colour, thickness and quantity!

Major Extrusive Volcanic FeaturesMajor Extrusive Volcanic FeaturesRemember- these features which are eventually formed are dependent upon

the material ejected during eruption. This may be gaseous, solid or liquid.

Gaseous Emissions•Dominated by steam•Often superheated•Includes carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine.

Solids•Ash, dust, glassy cinders•Shattered blocks of material which previously plugged the vent of the volcano

Liquids•Lava bombs (tephra or pyroclasts) which solidify mid-air as pumice•Surface lavas which are acid or basic

Extrusive FeaturesExtrusive Features

Remember, these are the result magma rising to the surface and erupting as lava. The features are dependent upon the types of lava

and whether the extrusion is gaseous, solid or liquid.


Basic or Basaltic Lava- dominated by iron manganese and is low in silica. Gas bubbles have freedom to expand as the magma rises to the surface. Eruptions are fluid and free-flowing. Constructive margins!


Andesitic Lava- medium in silica content. Acid lava is medium in terms of viscosity. Temperature of eruption 750-950°C. Destructive margins.


Acid or Rhyolitic Lava- rich in silica. Acid lava is so thick and viscous the gas bubbles struggle to expand. This builds up pressure to create violent eruptions. Destructive margins.


Complete the following table to describe the chemical compositions, viscosity and temperature of each

type of lava.

Basaltic Lava Andesitic Lava Rhyolitic Lava

Silica Content

Viscosity

Temperature of Eruption

The thicker the lava, the more violent the eruption…give reasons for this general rule!



type of lava.


Silica Content Medium

Viscosity Low (runny) High (thick)


750-950°C Less that 750°C




type of lava.


Silica Content Low Medium High

Viscosity Low (runny) Medium High (thick)


1100-1200°C 750-950°C Less that 750°C


Decipher the types of lava and justify your answer!Decipher the types of lava and justify your answer!

A

B


A • Basic/Basaltic• Low Silica• Low Viscosity• High

Temperatures


B

• Acid/ Rhyolitic

• High Silica• High Viscosity• Low

temperature

Extrusive Features in action!Extrusive Features in action!

Remember, these are the result magma rising to the surface and erupting as lava. The features are dependent upon the types of lava

and whether the extrusion is gaseous, solid or liquid.Aa forms when lava flows rapidly. Under these circumstances, there is rapid heat loss and a resulting increase in viscosity. When the solid surface crust is torn by differential flow, the underlying lava is unable to move sufficiently rapidly to heal the tear. Bits of the crust are then tumbled in and coated by still liquid lava, forming the chunks.

Pahoehoe forms when lava flows more slowly. Under these circumstances, a well-developed skin can form which inhibits heat loss.

Fissures and VentsFissures and Vents

Lava can erupt from long cracks called fissures or localised vents. The resultant landforms created are greatly determined by the nature of

the opening from which the magma emerged to form lava.

Fissure eruptions- basic lava creates extensive lava plateaus. Hollow areas of the landscape

are filled to create flat, featureless basalt plans.

Vent eruptions- usually create cone shaped landforms such as

the iconic volcano images complete with a summit crater.

Classification of VolcanoesClassification of Volcanoes

Volcanoes are classified according to the violence of their eruption which is determined by the pressure and quantity of gas in the

magma.

Join me on a journey of discovery….lets go VOLCANO SPOTTING! Just say what you

see to name the types of volcano!

Classification of Volcanoes- Say what you see!Classification of Volcanoes- Say what you see!


magma.

Fissure



magma.

Basic Shield Volcano

ic



magma.

Acid Dome Volcano



magma.

Caldera

a



magma.

Ash/ Cinder Cone



magma.

Composite Cone

Classification of VolcanoesClassification of Volcanoes


magma.

Excellent job! Lets discover more about each type!

Learning OutcomesRecap volcano basicsDescribe intrusive featuresSort advantages and disadvantages of volcanoesDifferentiate between intrusive and extrusive features

VulcanicityVulcanicityLearning Objective:Learning Objective: Understand major forms of extrusive Understand major forms of extrusive

volcanism and intrusive features.volcanism and intrusive features.

Key Term Round Up!Key Term Round Up!

Watch the clip and trey to define the key terms in the time given!

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08 volcanism intrusive and extrusive features