Tenacity = resistance of
a mineral to breakage
Malleability = property
to break into fragments
Sectility = property to
be cut into thin shavings
Flexibility = ability to
be bent but does not regain its original shape after removing the stress
Elasticity = property to
be bent and regain its original shape after stress is removed
ROCKS
Petrology = study of
rocks
I.
IGNEOUS ROCKS = rocks formed by solidification
of magma or lava materials
Types of Igneous Rocks
1.
Volcanic (extrusive)
=originated
from lava
=fast rate
of cooling
=small
sized mineral grains
=fine rock
texture (Aphanitic)
Extrusive Igneous Rocks =
affected by viscosity (resistance to flow)
Factors Affecting
Viscosity
a.
Temperature of lava
=Lava
T>>Solidification T, less viscous
b.
Silica Content of lava
Maffic =
low silica (~50%), flows easily, dark colored
Felsic =
high silica (>65%), flows sluggishly, light colored
Texture of Extrusive
Igneous Rock
a.
Aphanitic
b.
Obsidian = volcanic glass
c.
Porphorytic = large crystals enclosed in a
matrix of much finer-grained minerals
d.
Vesicular = holes are trapped in rock when lava
solidifies while gas is bubbling through it
e. Pumise = Cooled viscous lava where the gas can’t escape easily, and lava is churned
into froth
2.
Plutonic (intrusive)
=from
lava
=slow
rate of cooling
=large
sized mineral grains
=coarse
rock texture (Phaneritic)
Intrusive Igneous Rock
a.
Shallow intrusive rocks
i.
Volcanic neck = formed from magma that
solidified within the throat of volcano
ii.
Dike = tabular, disconcordant (body not parallel
to any layering in the country rock)
iii.
Sill = tabular, concordant (body parallel to any
layering in the country rock)
iv.
Laccolith = concordant with thick central
portion and domes upward like a mushroom
b.
Deep intrusive rocks
i.
Pluton = crystallized at considerable depth,
irregular in shape
ii.
Stock = small disconcordant pluton wit an
outcrop area of less than 100 sq. km.
iii.
Batholith = large disconcordant pluton with an
outcrop area greater than 100 sq. km.
Weathering = mechanical
disintegration and chemical decomposition upon exposure to surface conditions
= very slow process
= disintegration of rock
formations
a. Physical
Weathering = fragmentation of rocks without change in its mineral composition
Factors
=> frost wedging, plants and animals, salt crystals, pressure release, wind,
wave action, abrasion, moving glaciers
b. Chemical
Weathering = Chemical decomposition of rocks
Factors
=> water (hydrolysis), oxygen, acids
Sediments = product of
weathering
= sometimes referred to as regolith
Agents of Sediment
Transportation
=gravity, run-off, rivers and streams, wind, waves,
glacial ice
Traction = process of
transporting coarse sediments along the bottom of stream by rolling/sliding
Saltation = movement of
sediment along of series of leaps
Rounding = grinding away
of sharp edges and corners of rock fragments during transportation
Sorting = process in
which sediment grains are selected and separated according to grain size, grain
shape or specific gravity
Deposition = when
material settles or comes to rest
= accumulation of chemical or organic sediments
II.
SEDIMENTARY ROCKS = formed by lithification of
sediments
Sediment Particles
>256 mm = Boulder
64-256 mm = Cobble
2-64 mm = Pebble
0.02-2 mm = Sand
0.002-0.02 mm = Silt
<0.002 mm = Clay
Boulder + cobble + pebble
= gravel
Silt + clay = mud
Lithification = group of
processes that convert loose sediments into sedimentary rocks
a.
Compaction = packing together of loose grains
tightly
b.
Cementation = precipitation of cement around
sediment grains binding them into a firm rock
c. Crystallization
= solidification of minerals form solution
Types of Sedimentary
Rocks
a.
Clastic = formed from lithification of sediments
that are fragments of pre-existing rocks
i.
Breccia = coarse-grained formed by cementation
or coarse, angular fragments of rubble
ii.
Conglomerate = coarse-grained formed by
cementation of rounded gravel
iii.
Sandstone = coarse-grained formed by cementation
of sand grains
iv.
Shale = fine-grained formed by cementation of
both silt and clay
v.
Mudstone = fine-grained formed by cementation of
clay
vi.
Siltstone = fine-grained from silt
b.
Organic = rocks that accumulate from the remains
of organisms
i.
Coquina = cementation of shells that accumulated
on the sea floor
ii.
Limestone = formed from coral reefs
c.
Chemical = from chemical precipitation
i.
Evaporites = from crystals that precipitate
during evaporation of sea or saline water
d.
Others
i.
Chert = hard, compact, fine grained formed
entirely from silica
ii.
Coal = from solidification of plant materials
Sedimentary Structures
a.
Cross bed = series of thin, inclined layers
within a larger bed of rock
b.
Graded bed = layer in which sizes vary gradually
from coarse grains at the bottom of the bed to progressively finer grains
toward the top
c.
Mud cracks = polygonal patterns of cracks formed
in very fine-grained sediment as it dries
d.
Ripple marks = small ridges on the surface of a
sediment layer by moving wind of water
e. Fossils
= traces of plants or animals preserved in rock
Bedding
= series of visible layers within the rock
3. METAMORPHIC
ROCKS
Metamorphism =
solid-state transformation of pre-existing rock into texturally or
mineralogically distinct new rock as a result of high temperature, high
pressure or both
a.
Contact (Thermal) Metamorphism = Temperature as
dominant factor
= non-foliated rocks
= heat comes from intruding magma
b.
Regional (Dynamothermal) Metamorphism = High
Temp and pressure
= deformed mountains
= large regions in continents
c. Progressive
Metamorphism = progressively greater T and P act on a rock with increasing
depth in the earth’s crust
Factors Affecting
Characteristics of Metamorphic Rocks
a.
Parent Rock = based on chemical composition
b.
Temperature = takes place above 200OC
c.
Pressure
1.
Confining pressure = pressure applied equally on
all surfaces of a body
2.
Directed pressure = pressure applied unequally
on the surface of the body
i.
Compressive Direct Pressure = squeezing pressure
on both sides
= flattens object perpendicular to applied
pressure
ii.
Shearing Directed Pressure = parts of a body
move or slide to one another
= flattens object parallel to the forces
exerted
d.
Foliation = parallel arrangement of the textural
or structural features of rocks
1.
Foliated
i.
Slate = fine-grained rock that splits easily
along flat parallel planes
ii.
Schist = fine-grained with visible platy or
needle-like structures
iii.
Gneiss = rock consisting of light and dark
mineral layers
2.
Non-Foliated
i.
Phyllite = rock in which newly formed micas are
larger than slate but can’t be seen by the naked eye
ii.
Migmatite = mixed igneous and metamorphic rocks
iii.
Marble = derived from limestone
e.
Fluids
f.
Time
