Forms of igneous rocks

Forms of Igneous Rocks

1. Forms of Igneous Rocks
Lavasareextrusiveformsofmolten
magmawhichhavebeenpouredout
onthesurfaceoftheearth.
Lava
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])
Md. YousufGazi
Lecturer
Department of Geology
University of Dhaka

2. Forms of Igneous Rocks
A. Extrusive Igneous Forms
Volcanicorextrusiveigneous
rocksformwhenmoltenelements
eruptfromEarth'sinteriorthrougha
volcanicventorfissureandcool
rapidlyatthesurface
B. Intrusive Igneous Forms
Intrusiveigneousrockisformedfrom
solidifiedmagmabelowthesurfaceof
theEarth.
Magma
Isnaturallyoccurringmolten
mobilerockmaterialgenerated
withintheearth.
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

3. Extrusive Igneous Forms Intrusive Igneous Forms
Pyroclastic
Deposits
Lava Flow
Agglomerate Lapilli Volcanic Tuff
Concordant Others
Sills Laccoliths Lopoliths Phacoliths
Composite
Intrusion
Multiples IntrusionChonoliths
Disconcordant
Dyke BatholithsVolcanic PipeVolcanic NeckRing Dykes
Forms of Igneous Rocks
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

4. Emittedfromindividual
coneslikevolcanoorfrom
fissures
Formtabularbodies,wide
extent
Formoflavaflowdepends
onfluidityofmagmai.e.
composition,temperature
oferuption,viscosity.
LavaFlows
Extrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

5. Pyroclastic Deposits
Intermittentlyexplosiveactionthat
takesplacesinvolcaniceruption
producedfragmentaltypeofigneous
material.
1.Agglomerate
2.Lapilli
3.Volcanic Tuff/Volcanic Ash
Extrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

6. Agglomerate
Thefragmentsofrockassociatedwithlava
flowthatareejectedduringexplosive
volcaniceruptionsanddistributedinand
aroundthecreator.
Extrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

7. Lapilli
Thesmallfragmentsbetweenthesizeofwalnut
andpea(2inch-64mmdiameter),whichare
ejectedtoagreaterdistancethanthelarger
agglomerate.
Extrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

8. Volcanic Tuff
Thefinestofall,thevolcanicdusts,ashorsands
maybedepositednearthevolcanooroverthe
surroundingcountry.
Extrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

9. Intrusive Igneous Forms
Two main types are distinguished
1. Concordant
Theinjectedstrataremainmoreorlesshorizontalor
paralleltothecountryrocksoverwidearea.Example:
Sill,Laccoliths,Lopolithsetc.
2. Discordant
Cutacrossthebeddingoftherocksinwhichtheyintrude
Verticaltosteeplyinclinedandsheetlikebody(extensive
inlateraldimension)
Thicknessvarywidelyfromaninchuptohundredoffeet
Injectedthroughfractures,joints,andweakplanes
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

10. Relativelythintabularsheetsof
magma
Paralleledalongapproximately
horizontalbedding
Sillsspreadtoadistance
dependentonthehydrostaticforce,
theirtemperature,degreeof
fluidityandweightoftheblockof
strata.
Sills
Intrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

11. Flatbottomandconvexupward
domeshapedigneousbody
Whenviscousmagmaisinjected
rapidlyalongthebedding,asitcannot
spreadsitpushesuptheoverlying
layersandkeeponpilingup.
Itcausesfoldingoftheoverlyingrock
layers
Laccoliths
Intrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

12. Thesearebasinorsaucershaped
concordantbodieswithtopnearlyflatand
convexbottom.
Theseareveryhugebodywithdiameter150
miles(app).(DuluthGabbroMass,Minnesota,
USA).
Lopoliths
Intrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

13. Theseareconcordantbodiesthat
occursalongthecrestsandtroughsof
thefoldedsedimentarystrata.
Infolding,thecrestandtroughare
regionsofweaknessandtension,
magmaoftenintrudedintothese
troughandcrest.
Phacoliths
Intrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

14. Intrusionofmagmaintomoreorlessvertical
fissuresi.e.joints,fractures,faults.
Cutacrossthebeddingorotherstructures.
Narrow,elongated,parallelsidedwallofigneous
rock.
Thicknessmayvaryfrom1inchtohundredsof
feetandlengthmayfewyardstomanymiles.
Dyke
Intrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

15. Ringdykesformacylinderaroundasubsided
blockofcountryrock,fillingthering-shaped
fracturewithmagma.
Ring Dyke
Intrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

16. Thesearetheigneousmasseswhichsealuptheventsofancientvolcanoes.Avolcanicneckformsinsidea
volcanowhentheheatandpressurefrombelowarereducedsothatthemagmainsidethevolcano'svent
solidifies.Overaperiodofafewhundredthousandyears,thesurroundingsofterrockerodesaway,
leavingthevolcanicneckstandingalone.(ShiprockVolcanicNeck,NewMexico,USA)
Volcanic Neck
Intrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

17. Averticalconduitbelow
avolcanothroughwhich
magmahaspassedand
thathasbecomefilled
withsolidifiedmagma,
volcanicbreccia,and
fragmentsofolderrock.
Volcanic Pipe
Intrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

18. BatholithsarethelargestbodiesofIgneousrock,
irregularinshapeandoccupieslargearea.Their
occurrenceiscommonlyassociatedwiththe
mountain-buildingprocess.Theseareeither
granitesorgranodioritesincomposition(Sierra
NevadaBatholoiths,USA)
Batholiths
Stocks
Stocksareirregularmassesofbatholithshabitof
smallerdimension.
Intrusive Igneous Forms
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

19. Others Intrusive Igneous Forms
1. Chonoliths
Thistermisappliedtoallotherintrusiveigneous
bodieswithirregularshape,i.e.thebodywithno
specificshape.
2.MultipleIntrusion
Whenamagmaofauniformcompositionhasbeen
injectedalongasinglechannelintwoormore
successivepulses,theresultisamultipleintrusion.
3.CompositeIntrusion
Adikeorsillcomposedoftwoormorevarietiesof
igneousrockpresumablyresultingfromsuccessive
injections.
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])

20. Label the Diagram
Md. YousufGazi, Lecturer, Department of Geology, University of Dhaka ([email protected])