Download Volcanic Landforms

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
Extrusive landforms
● Vent Eruptions
○ Cone Shaped
Volcanoes
○ Dome shaped
volcanoes
● Fissure Eruptions
○ Mid-Atlantic Ridge
○ Antrim Plateau in
Ireland
● Hot Spots
○ Hawaiian islands
○ Not near plate
boundary
Mount Vesuvius - Cone Shaped
Volcano (Classic volcano shape)
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
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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
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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
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Fissure eruption are caused by crack in earth's crust
Fissure can be many kms long
Main example is Mid-Atlantic Ridge
Fissure eruptions produce basic lava (low silica content
and very runny)
● Lava can spread over 50km
● Antrim Plateau in Ireland (made of basalt & includes
Giant's Causeway
● Mid-Atlantic Ridge - includes Iceland (made of basalt)
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
Hot-Spots
● Hawaii Islands
● Caused by intense heat
from the mantle
● Causes break in the
crust that allow lave
through
● Basic lava -very runny
● Hot spot remains in the
same place
● Plate above the hot spot
moves
● This causes a chain of
volcanic islands to form
Hawaii Hotspot - the hotspot remains
stationary. As the pacific plate moves
north, new volcanoes are formed.
The oldest islands are now furthest
from the hotspot.
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
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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
Slow cooling magma
in earth's crust
Diagram of Batholith