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Tectonic landscapes
What impact does tectonic activity
have on landscapes and why does
this impact vary?
•
Volcanic activity:
•
• Variations in the form, type and frequency of eruption to be considered in relation to
types of plate margin, vents and lava.
•
• The distinction between intrusive and extrusive volcanic activity.
•
• Extrusive landforms: volcanic cones the major sub-types being noted, lava plateaux,
and minor forms such as geysers, hot springs/boiling mud.
•
• Intrusive landforms: batholiths, laccoliths, dykes and sills.
•
• Case studies are needed for the above and these must range from the small scale,
e.g. for dykes and sills to the global when considering types of eruption.
•
• Candidates must be made aware of landforms in the UK which are related to
volcanic activity.
•
Extrusive volcanic landforms
• Volcano types:
fissure eruption
Mid-ocean ridge: creation of sea floor
Hotspots
• Extrusion= the upward movement of
magma through the earths crust and onto
its surface as lava. Extrusive volcanic
landforms form once the lava has cooled
and hardened.
Intrusive Volcanic Landforms
• Intrusion= the movement of magma
underground into spaces that exist within
rock strata. When this magma cools and
hardens, intrusive volcanic landforms are
created. Weathering and erosion causes
these landforms to be exposed.
Batholith
• Batholith is the name given to the largest of igneous
rocks that form as a result of magma forcing its way
into the rock above it. When it cools it forms granite
and this can be exposed due to weathering and
erosion.
Stock
• Stock is the name given to intrusive
igneous rocks smaller than 100km2.
Laccolith
• A Laccolith is a dome of igneous rock that
is formed between two layers of preexisting sedimentary rocks. It forms a
dome or mushroom shaped intrusion.
Plutons
• Taken from Pluto the Greek god of the
underworld. It is a general term to describe any
mass of rock formed by hardening magma
underground. See above
Dike
• A Dike is a vertical or near vertical sheet of
rock that is created when magma is thrust
into a body of rock. Dikes cut across
layers of existing rock. When exposed on
the earths surface Dikes can appear as a
wall of volcanic rock.
Sills
• Sills are long thin intrusions of rock that
form a layer between other sedimentary
rocks.
Vein
• Sometimes magma forces its way through
cracks in the rock. When it cools vein like
patterns may remain.
Landforms and Rock Structure
Exposed Batholiths and Monadnocks
Batholiths: huge bodies of intrusive igneous rock
• Form hilly or mountainous uplands
• Monadnock: a mountain that rises out of a
surrounding plain and that develops because it
consists of more resistant rock than the bedrock of
the surrounding region
Tectonic landscapes created by
Earthquakes
• Faults and Faulting
• Rift Valleys
• Ground displacement and folding
Faults
A fault is a break in the
crust where slabs of
crust slip past each
other. The rocks on both
sides of a fault can move
up or down or sideways
When enough stress
builds on a rock, the rock
shatters, creating faults
Faults usually occur along
plate boundaries, where
the forces of plate
motion compress, pull, or
shear the crust too much
so the crust smashes
Strike-Slip Faults
Shearing creates
this fault
In this fault, rocks
on both sides of the
fault slide past each
other with a little up
and down motion
When a strike-slip
fault forms the
boundary between
two plates, it
becomes a transform
boundary
Tectonic Landforms
Faults and Fault Landforms
Transcurrent or Strike-slip Faults are produced
when tectonic plates move past each other
horizontally
Normal Faults
Tension forces in Earth's crust
causes these types of faults
Normal faults are at an angle,
so one piece of rock is above
the fault, while the other is
below the fault
The above rock is called the
hanging wall, and the one below
is called the footwall
When movement affects along
a normal fault, the hanging wall
slips downward
Normal faults occur along the
Rio Grande rift valley in New
Mexico, where two pieces of
Earth's crust are diverging
Reverse Faults
Compression forces
produce this fault
This fault has the same
setup as a normal fault,
but reversed, which
explains it’s name
Just like the normal fault,
one side of the reverse
fault is at an angle of the
other
This fault produced part
of the Appalachian
Mountains in the eastern
United States
Tectonic Landforms
Faults and Fault Landforms
Reverse and overthrust faults are
produced by compression in the
crust
The Great Rift Valley
• The Great Rift
Valley is a name
given to the
continuous
geographic trench,
approximately
6,000 kilometres
(3,700 mi) in length,
that runs from
northern Syria in
Southwest Asia to
central Mozambique
in East Africa.
Graben
• Another name for a Rift Valley is Graben
(German for ditch) A graben is a
depressed block of land bordered by
parallel faults.
Tectonic Landforms
Faults and Fault Landforms
Normal faults are produced by crustal extension
Folding
• Folding creates mountain ranges and also
can influence coastal Geography.
Tectonic Landforms
Fold Belts
Compression from
tectonic activity
produces folds in rock
strata
Anticlines: upbends
Synclines: troughs
Folds: corrugations of
strata caused by crustal
compression
Tectonic Landforms
Fold Belts
Folds erode to form ridge-and-valley landscape
• Ridges and valleys parallel
• Folds may be plunging folds
Land deformation