Download Clastic Sedimentary Rock

Rocks
Rock makes up the solid part of the earth.
Rock is made from minerals or
rock can be made of solid organic matter.
Three classes of rock:
Igneous, Sedimentary, and Metamorphic.
Any of the three types of rock can
be changed into another of the
three types or rock
Bowen’s Reaction Series
• In igneous rock, different minerals crystallize and
solidify out of the magma at different
temperatures.
• So different minerals form at different
temperatures.
• The Bowen’s Reaction series represents the order
that minerals crystallize as magma cools.
• The Bowen’s Reaction series is based on the
minerals composition and melting point.
Felsic – light colored;
Mafic – dark colored.
The Formation of Magma
• Magma forms as rock melts.
• Influenced by temperature, pressure, and
presence of fluids (usually water) in the rock.
• Different minerals melt at different temperatures
– The magma’s composition changes as it becomes
hotter and more minerals are added to it as they melt.
– As magma cools, the reverse happens as minerals
crystallize.
Igneous Rock Textures
• Intrusive – cools deep inside crust from magma;
– Coarse grained texture
– slowly cools and hardens
– Example: Granite
• Extrusive – cools on surface from lava;
– Fine grained texture
– rapidly cools and hardens
– Examples: Basalt or Rhyolite
• Both Intrusive and Extrusive
– Porphyritic texture – both coarse and fine grained; starts cooling inside
crust and finishes cooling and hardening on surface.
• Others
– Glassy texture – very fast cooling on surface.
• Example: Obsidian
– Vesicular texture (holes) – rapidly cooling, traps gases as it hardens.
• Example: Pumice
coarse-grained texture
vesicular texture
Composition of Igneous Rocks
• Felsic Rock
– High in silica
– Light colored
– Mostly potassium feldspar and quartz, but also contains
plagioclase feldspar, biotite and muscovite mica.
• Mafic Rock
– Rich in iron and magnesium; low in silica (ferromagnesium
minerals)
– Dark colored
– Minerals include plagioclase feldspar and pyroxene, hornblende,
olivine
• Intermediate Rock
– Minerals: Plagioclase feldspar, hornblende, pyroxene, and biotite
mica.
– Lower proportions of silica than felsics but higher than mafics.
Sedimentary Rock
• Made up of combinations of sediments.
• Sediments are formed from the weathering
and erosion of rock.
• Then the loose sediment is deposited.
• Two main processes convert loose sediment to
sedimentary rock:
– Compaction – squeezes sediments together
– Cementation – sediments are “glued” together.
3 Main Classes of Sedimentary Rock
• Chemical Sedimentary
Rock
– Forms from minerals
that were once
dissolved in water.
– Dissolved minerals
precipitate out of water
– Can be caused by
evaporation =
evaporites
– Examples: halite,
gypsum, some
limestones
3 Main Classes of Sedimentary Rock
• Organic Sedimentary Rock
– Forms from the remains of living things.
– Coal (plants), some Limestones (corals, clams,
oysters, plankton), Chalk
3 Main Classes of Sedimentary Rock
• Clastic Sedimentary Rock
– Made up of preexisting rock fragments that are
carried away from their source by water, wind, or
ice, and left as deposits.
– The individual fragments may become compacted
and cemented into solid rock.
– Grouped according to the size of the fragments:
• Rounded fragments = conglomerates
• Angular fragments = breccias
– Sandstones – sand sized particles (coarse-grained)
– Shale – clay sized particles, layered (fine-grained)
Clastic Sediments
• Sorting – currents of air
or water can separate
sediments according to
size.
• Well sorted – same size
• Poorly sorted – different
sizes
• Due to changes in the
speed of the moving
sediment as it get
deposited.
Stratification
• Layering of
sedimentary rock
• Stratification layers
are called beds.
• Cross beds –
slanted layers
• Graded beds –
largest sediments
on bottom
smallest on top.
• Ripple marks – evidence of shallow water or wind
(beach or river bed)
• Mud cracks – form when mud dries and shrinks
(flood plain, dry lake bed)
• Fossils – plants and animals get buried in
sediments before it becomes rock.
• Concretions/Geodes – form when minerals
precipitate out of fluids and build up around a
nucleus.
Metamorphic Rocks
• Metamorphism occurs when heat, pressure, or chemical
processes change one type of rock to another.
• Forms deep within Earth’s crust
• Changes the mineral composition of the rock
Two Main Types of Metamorphism
Contact Metamorphism
• When magma comes into
contact with existing rock,
heat from the magma can
change the structure and
mineral composition of the
surrounding rock.
Regional Metamorphism
• Occurs when large areas of
rock undergo
metamorphism.
• Brought on by tectonic
activity.
Classification of Metamorphic Rocks
Foliated Rock
• Minerals are arranged in
planes or bands.
• Extreme pressure may
cause the mineral crystals to
realign or regrow to form
parallel bands.
• May alternate between light
and dark bands.
• Slate, shist, gneiss
Non-Foliated Rock
• Do not have bands or
aligned minerals.
• Quartzite forms from
sandstone
• Marble forms from
limestone
Foliation