Volcanic Landforms
Extrusive & Intrusive
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Volcanic Landforms: Extrusive and Intrusive, Study notes of Geology
An introduction to volcanic landforms, discussing both extrusive and intrusive types. Extrusive landforms include cone-shaped and dome-shaped volcanoes, vent eruptions, and fissure eruptions. Intrusive landforms, on the other hand, are formed in the earth's crust and include batholiths. The document also covers specific examples of each type, such as Mount Vesuvius, Antrim Plateau, and the Leinster Batholith.
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2021/2022
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Volcanic Landforms
Extrusive & Intrusive
Introduction to Volcanic landforms
Extrusive (above the
earth's surface)
● Vent eruptions
○ classic volcanoes
● Fissure Eruptions
○ mid-atlantic ridge
● Hot Spots
○ weak point in earth's crust ○ Hawaiian islands
Intrusive (formed in
the earth's crust
● Batholith
○ slow cooling magma in the earth's crust
● Leinster Batholith
○ Wicklow & Dublin Mts ○ Granite batholith exposed by weathering
What are vent eruptions?
● Eruptions through a vent ● Occur at destructive boundaries (subduction zones) ● Volcano made of lava and ash ● Crater on top - filled with water or cooled rock (^) Crater on Mount Vesuvius
Cone Shaped & Dome Shaped Volcanoes
Cone Shaped Volcanoes ● Made up of layers of lava and ash & cinders ● Lava glues with ash & cinders ● Steep cone shape builds up ● Mount Vesuvius
Cone Shaped Volcano in the Philippines
Dome Shaped Volcanoes ● Mound shaped volcano - made of slow moving lava that cannot flow far ● Slow moving lava due to high viscosity (very thick & high silica content)
Dome Shaped Volcano - Mt St Helens (USA)
Fissure Eruptions
Antrim Plateau Mid-Atlantic Ridge in Iceland
More on the Antrim Plateau
● Fissure Eruption
● Formed 65 million years ago due to
separating plates (North American &
Eurasian plate separating)
● Basalt Plateau (high flat topped land)
extending over Antrim & Derry
● Basic lava (low silica & gas content) flowed
onto the surface due to plate divergence
● Includes Giant's Causeway - rapid cooling of
lava led to shrinking and formation of
hexagonal shape
Intrusive Landforms
● Intrusive - formed
by magma that
does not reach the
surface
● Main intrusive
landform is a
batholith
● Example: Leinster
Batholith (Granite
Rock)
Leinster Batholith (Granite Rock)
The Leinster Batholith
● Large area - includes Dublin & Wicklow Mts ● Formed 400 million years ago as magma was injected into crust ● Magma cooled slowly to form granite ● Heat from magma changed surrounding rocks into metamorphics (Quartzite & Schist) ● Weathering & Erosion over millions of years of the over-lying rock have exposed this granite ● Leinster Batholith now form the granite Wicklow & Dublin Mts
Diagram of Batholith
Slow cooling magma in earth's crust