Transcript Rock Types

Soil 1 – Rock Types
 There
are about 6.8 million hectares in Ireland.
 25% of this area is covered with cities, roads and
buildings etc. so the remaining 5 million hectares
is covered in soil.
 This soil varies greatly in depth, composition,
fertility, appearance etc.
 Soils
can be classified as “rich” fertile soils or
poor “hungry”
 Soils
are the medium for the growth of land
plants.
 All
soils come from parent materials. Therefore
the type of soil in an area depends on the parent
rock.
 The condition of the soil is highly dependent on
the type of bedrock.
 Example:
• Soils formed from granite would be acidic (pH < 7)
• Soils from Limestone would be basic.
 Drainage
depends on the underlying rock.
 In
Ireland there is a vast range of soil types.
 They are classified accordingly:
• Residual: materials are rock deposits which weather
in situ long enough for soils to develop from them.
• Transported: materials are broken down rock which
have been transported some distance by natural forces
e.g. wind and water. Soils then develop from
transported materials in their new locations. In
Ireland ice was the main transporting agent.
• Cumulose: materials are organic materials derived
from preserved plant remains. This gives rise to peat
soils.
 All
these parent rocks can be divided into 3 main
groups.
 Igneous
 Sedimentary
 Metamorphic
Igneous
Granite
Sedimentary
Sandstone
Metamorphic
Marble
Basalt
Limestone
Slate
 First
ever rocks formed on the earth (4.5 billion
years ago).
 Formed when molten lava began to cool, solidify
and form rocks.
 Igneous rocks are made of the following
elements: Oxygen, Silicon, Aluminium, Iron,
Calcium, Sodium, Other metals and non-metals.
 Characteristics of igneous rocks: acidic soils and
fine grained soils.
 Examples of Igneous rocks include Granite and
Basalt.
 Granite
is made up of three main components:
Feldspar, Mica, and Quartz.
 Mica is black and contains the same as Feldspar
as well as Fe and Mg. Quartz contains both
Feldspar and Mica.
 Tends to form an acid solution.
 Is crystalline in structure and looks like glass.
 Feldspar is pink in colour and has K, Al Si.
 Basalt and Granite are formed from the same
material and differ only due to how they cooled
down. Granite cooled very slowly gave very large
and has large crystals. Whereas Basalt cooled
faster and lots of small crystals.
 Formed
when, sediments of different rocks,
shells and bones of animals joined together.
 Examples of sedimentary rocks are Sandstone,
Limestone and Shale.
 Sandstone is formed by sediments of quartz,
(broken up by water, heat and frost as well as
Glacial forces).
 Characteristics of Limestone rock: alkaline soils
and texture in between sandy (sandstone) and
clayey (shale).
 Limestone
(CaCO3 – Calcium Carbonate)
 This is a highly desirable rock type.
 Limestone is formed by the fusing of pieces of
sea shells and other materials containing
Calcium carbonate (CaCO3),
 It forms an alkali solution in water.
 Its pH provides the optimum range for plant
growth – 7.5.
 It is also a permeable rock.
 These
rocks arise from sedimentary rocks when
they are exposed to pressure and heat.
 Examples are Slate (changed from shale) and
marble (from Limestone)