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STUDY OF
ROCKS
By,
M.SIRISHA
Types of Rocks
• There are 3 types of rocks:
1. Igneous Rocks
2. Sedimentary Rocks
3. Metamorphic Rocks
• These rocks are again classified based on
various features.
Igneous Rocks
• The word Igneous comes from the Latin word
‘Ignis’ meaning ‘Fire’.
• The Igneous rocks come from the magma inside
the volcano.
• Igneous rocks are classified into two types.
Igneous rocks
Extrusive
Intrusive
• Extrusive rocks :
The magma erupts and spills all over the surface and it then cools forming the
Extrusive rocks.
• Intrusive rocks :
These types of rocks are formed when the magma does not reach the surface
instead it forces its way into the cracks and spaces between other rocks forming the solid
slowly.
• Hypabyssal :
Hypabyssal igneous rocks are formed at a depth in between
the plutonic and volcanic rocks. These are formed due to cooling and resultant
solidification of rising magma just beneath the earth surface. Hypabyssal rocks are less
common than plutonic or volcanic rocks and often form dikes, sills, laccoliths, lopoliths,
or phacoliths.
Sedimentary Rocks
• Sedimentary rocks are types of rock that are formed by
the deposition of material at the Earth's surface and within
bodies of water.
• They are worn down by wind and rain and are washed
downstream which settle at the bottom of the rivers, lakes
and oceans.
• Due to pressure above the sediments, the sedimentary rocks
are formed.
Types :
• Clastic sedimentary rocks :
Clastic sedimentary rocks are composed of silicate
minerals and rock fragments that were transported by moving fluids.
• Biochemical sedimentary rocks :
Biochemical sedimentary rocks are created when
organisms use materials dissolved in air or water to build their tissue.
• Chemical sedimentary rocks:
Chemical sedimentary rock forms when mineral
constituents in solution become supersaturated and
inorganically precipitate.
Metamorphic Rocks
• Metamorphism means “to change”.
• Metamorphic rocks arise from the transformation
of existing rock types.
• The original rock is subjected to heat
(temperatures greater than 150 to 200 °C) and
pressure (1500 bars), causing profound physical
and/or chemical change.
• Through heat and pressure an igneous rock or a
sedimentary rock becomes a metamorphic rock.
Types of metamorphism
• Contact metamorphism:
Contact metamorphism is the name given to the
changes that take place when magma is injected into the surrounding
solid rock (country rock). The changes that occur are greatest wherever
the magma comes into contact with the rock because the temperatures
are highest at this boundary and decrease with distance from it.
• Regional metamorphism:
Regional metamorphism, also known as dynamic
metamorphism, is the name given to changes in great masses of rock
over a wide area. Rocks can be metamorphosed simply by being at
great depths below the Earth's surface, subjected to high temperatures
and the great pressure caused by the immense weight of the rock layers
above.
A contact metamorphic rock made of
interlayered calcite and serpentine from
the Precambrian of Canada. Once thought to
be a fossil called Eozooncanadense.
Dynamic metamorphism
Properties
Igneous Rocks
• TEXTURE
Sedimentary Rocks Metamorphic Rocks
1. Glassy
1. Surface texture
2. Aphanitic
(no visible crystals)
3. Phaneritic
(visible crystals)
4. Porphyritic
(Some visible and
some not visible
crystals)
1. Slaty
2. Rounding
( general smoothness)
3. Sphericity
(degree to which the
grain approaches a
sphere)
4. Grain form
(includes slate and
phyllite)
2. Schistose
(includes schist)
3. gneissose
4. granoblastic
5. hornfelsic
(three dimensional
shape of the grain)
• FORMATION Igneous Rocks are
formed by melting,
cooling, and
crystallization of
other rocks.
Sedimentary rocks are Metamorphic rocks
formed by weathering form near lava
erosion, deposition, intrusions, at plate
compaction and
subduction zones, and
Cementation.
in deep mountain.
Igneous rocks - Formation
• Sedimentary rocks are likely to form
in areas such as:
– Deltas
– Beaches
– Rivers
– Glaciers
– Sand dunes
– Shallow seas
– Deep oceans
Metamorphic
rocks
Formation
Properties
Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
• EXAMPLES The most common Some of the most Some common types
types of igneous common types of of metamorphic rock
rocks include
sedimentary rocks include:
1. Rhyolite
include:
1. Slate
2. Andesite
3. Basalt
4. Granite
1. Gypsum
2. Sand Stone
3. Lime Stone
5. Gabbro
4.Shale
6. Diorite:
5. Conglomerate:
Schist:
2. Schist
3. Gneiss