Granite Landscapes
The nature of Granite.
• The name Granite comes from Latin
granum, a grain.
• Granite is an igneous, crystalline rock.
• Granite is made up of large interlocking
crystals that give it a granular texture.
Granite
• It has great physical strength and is resistant
to erosion.
• There are many types of granite which all
share certain characteristics.
• They contain Quartz, Mica and Felspar.
•
Three hundred million years ago the rocks at the
bottom of the crust became heated enough to be
turned into magma which floated up into the
surrounding rock.
• This magma did not reach the earth's surface but
cooled and crystallised into a vast mound of
granite below the surface, called a batholith,
below the south west of England.
• During the millions of years since the
granite's formation the rocks above have
been weathered away exposing the granite,
but it is the cracks in the granite that allow
the rock to quarry itself
The Main processes of
weathering on granite are:-
• FREEZE THAW
• and
• HYDROLYSIS
Characteristics of Granite
landscapes include:• Exposed large scale batholiths, which form
mountains. Examples include the Wicklow
mountains and Dartmoor.
• Tors are isolated masses of bare rock.They
can be up to 20m high, such as Hay Tor and
Yes Tor. Some of the boulders of rock are
attached to part of the bedrock; others
merely rest on top.
Formation of Tors
• The shape of the Tors is determined by
the granite's two types of cracks vertical and horizontal.
• The vertical cracks formed by
contraction of the granite as it cooled.
• The horizontal cracks probably formed
as pressure was released from
overlying rocks being eroded away
• Apart from the Tors it is the barrenness and
bleakness that makes the Dartmoor
landscape distinctive.
• This is because the soil here is acid and not
many plants can survive apart from heather
and moor grass.
• Rain is naturally acid and granite doesn't
provide any minerals that can neutralise the
acidity.
• The granite is rich in quartz (silica) and
low in potassium and calcium that would
help neutralise the acidity.
• Quartz is also the most resistant part of
the granite, so the soils that form are
very sandy.