环境地质学
Environmental Geology
主讲人,万新南 教授
Prof,Wan xinnan
地球内部过程
? Plate Tectonics
? Geologic Tectonics
? Earthquake
? Tsunamis海啸 and Coastal Flooding
地球内部过程
Geologic Tectonics
? Folds
? If subjected to stresses beyond超出 those that their strength can
resist,strata are permanently deformed by either buckling压弯曲 or
fracturing,The type of deformation depends on the mechanical
properties of the rocks and the nature of the stresses,In general,
stresses which are applied slowly,either deep within the Earth
where the confining pressure produced by overburden is high,or to
rocks that are not brittle,tend to produce folds by buckling or plastic
flow,The essential characteristic of a fold is a change of dip倾向,
This occurs at the hinge枢纽、绞链 of the fold,On either side of the
hinge is a limb翼,where the dip is comparatively steady,In real folds
the change of dip is seldom restricted to a line,but is concentrated
in a liner zone,The plane of symmetry that bisects平分 the angle
between the limbs is the axial surface (or axial plane),The
intersection of the axial surface with each bedding plane is an axis
of the fold.
地球内部过程
Geologic Tectonics
? Folds
? A fold where the limbs diverge偏斜、脱节
downwards (that is,where the dips of the limb
are away from the hinge) is an anticline背斜 ; a
fold where dips are towards the hinge is a
syncline向斜, If the axis is not horizontal,the fold
is said to plunge,with the amount of plunge倾伏、
插入 being the angle between the axis and the
horizontal line vertically above it.其倾斜量以轴线
及其上方的水平线夹角表示。
地球内部过程
Geologic Tectonics
? Folds
? Folds are described and classified by
certain features of their geometry which
are diagnostic of how they were formed,
The criteria and the terms used to define
folds are illustrated in Figure 4.12; they are
as follows:
地球内部过程
Geologic Tectonics
? Folds
地球内部过程
Geologic Tectonics
? Folds
地球内部过程
Geologic Tectonics
? Folds
地球内部过程
Geologic Tectonics
? Folds
(a) The dip of the axial plane,where it is
vertical the dip of each limb is the
same in magnitude,but opposite in
direction,and the width of outcrop
of any bed is the same on both sides
of the axis,In inclined folds,one
limb is steeper and its outcrop is
correspondingly narrower than that
of the other,Overfolding occurs
where one limb is overturned,such
that both limbs dip the same way,
The rotation of the axial plane,seen
from left to right in the diagram,is
probably produced by transport of
the fold with relative drag at its base.
(b) The size of the angle between the
limbs,this reflects the intensity of
compression of the fold.
地球内部过程
Geologic Tectonics
? Folds
Concentric folds同心褶皱 are
produced by simple bucking,
and the beds are curved
concentrically by the same
amount,The beds remain
constant in true thickness
and parallel to each other
after folding,Slip has taken
place along the bedding
planes,A concentric fold
becomes progressively less
open as the 'centre' of the
concentricit
地球内部过程
Geologic Tectonics
? Folds
In similar (shear) folds all layers are
deformed to a similar shape,and
the bed thicknesses are constant in
a direction parallel to the axial
plane,This produces an increase
of true thickness at the hinges and
a decrease on the limbs,Similar
folds are produced by differential
movements along minor shear
planes in a direction parallel to the
axial plane,Intense folding of
metamorphic变质 rocks at a time
when temperature and pressure
were high is usually of this type.
地球内部过程
Geologic Tectonics
? Folds
Flow folding is produced when
incompetent rocks flow in a complex
pattern of movement to accommodate
either the local stresses related to the
buckling of competent beds or lateral
changes in the loads of overburden
compressing them,The pattern of folds
which results is usually complicated,
and such that the shape of one folded
bed may bear little obvious relationship
to that of another,Folding is then
disharmonic,Folds involving a thick
layer of salt are of this type,The salt,
which is highly incompetent,rises
locally as salt pillows and salt plugs,
folding the beds above them to form
salt domes.
地球内部过程
Geologic Tectonics
Fractures in rocks
? Minor fractures in rocks,both
tensional and shear,are called
joints,Larger shear fractures,
where there are significant
displacements of rock bodies
across the plane,are called
faults,(The distinction between
a 'shear joint' and a 'small fault'
is arbitrary,depending on
circumstances and
significance,but the former
term usually suggests a
displacement of a few
centimetres.)
地球内部过程
Geologic Tectonics
? Faults
? As with all structural
surfaces,the orientation of a
fault is expressed by its
strike and dip,The
displacement across a fault
is called its slip,and the
terms used to describe the
components of slip (strike
slip,dip slip and throw) are
illustrated in Figure4.18.
地球内部过程
Geologic Tectonics
? Faults
Figure 4.18 Before fault
movement A and A' and B and
B' were adjacent to each other,
The total displacement A-A'
measured along the fault plane
is called the slip of the fault,It
may be resolved into strike slip
and dip slip,which are
respectively horizontal and
vertical components,in the
plane of the fault,Dip slip may
also be resolved into a
horizontal component and into a
vertical component (the throw of
the fault).
地球内部过程
Geologic Tectonics
? Faults
Only very small faults have a simple,clean-cut plane of movement,The
majority are zones of shearing,usually a few metres across,but major faults
may be more than 1 km wide,Within the fault zone there may be a number
of planes of movement displacing the strata by distributive slicing,or the rock
may be completely fragmented to form a fault breccia where competent
rocks are affected,or clay gouge where incompetent rocks have been
smeared out by shearing,(Gouge often acts as a seal to make the fault zone
locally impervious to groundwater circulation.) At the walls of the fault the
strata may show terminal drag in the direction of relative movement.
地球内部过程
Geologic Tectonics
? Faults
A fault described by its geometry in two different ways,(a) by the relationship
of its strike to the strike of the strata it affects,and (b) by the relative
magnitudes of its components of slip.
(a) If the strikes are nearly parallel,the fault is a strike fault; if they are nearly
at right angles,it is a dip fault; and if neither,it is oblique.
(b) Where slip is predominantly horizontal,producing a large strike slip
component and little throw or heave,the fault is described as strike slip,(The
terms wrench and tear are used to describe certain varieties of strike-slip
faults.) In faults of this type,the fault plane is near-vertical,and there is
usually a comparatively wide fault zone in relation to displacement..
地球内部过程
Geologic Tectonics
? Joints
The presence and orientation of joints have significant effects on the bulk
properties of rocks,and their description is an important stage in most site
investigations,Joints may be non-systematic,but often occur as a set of
parallel planes,If two or more sets are present,they form a system of joints,
Prominent joints which are continuous as a single plane surface for hundreds
of metres are called master joints.
地球内部过程
Geologic Tectonics
? Unconformity,overstep and
onlap (overlap)
The geological history of an area is preserved in the strata,If there is a
break in this record,because there has been no deposition of sediment and
probably erosion for much of the time,the gap is called an unconformity
between the lower and the upper series of strata,The surface corresponding
to this time gap is the plane of unconformity,If there have been no Earth
movements other than a vertical rise and fall relative to sea level,then the
dip is the same above and below the unconformity,If tilting,folding or faulting
of the lower formation (E-A in Fig.4.28) before the upper series (K-M) is
deposited on them has produced structural discordance,then the
geometrical relationship at the plane of unconformity is an angular
unconformity,The lowest bed (K) of the upper formation rests directly on
progressively older beds of the lower formation and is said to overstep from
E to B,The pattern of subcrops of E-A under bed K is identical to the
outcrops once produced by the lower structure before K was deposited,A
line of boreholes would show a systematic increase of the gap in the
geological record,in the up-dip directions of the lower formation.
地球内部过程
Geologic Tectonics
? Unconformity,
overstep and onlap
(overlap)
地球内部过程
Geologic Tectonics
? Unconformity,
overstep and onlap
(overlap)
If subsidence has increased the area of deposition of the
upper formation,then in the fringe of the area,where bed
K was not deposited,bed L rests directly on the older
formation E-A,and is said to onlap or overlap K
(Fig.4.28),Onlap is always accompanied by overstep,
The variable gap (with respect to the fullest sequence of
strata for the area) at the unconformity is a combination
of the absence of the top beds of the lower formation
because of overstep and the absence of the bottom beds
of the upper formation because of onlap.
地球内部过程
Geologic Tectonics
? Unconformity,
overstep and onlap
(overlap)
Figure 4.28 Overstep and onlap
(overlap),(a) The upper formation K-
L-M rests with angular unconformity
on a lower formation A-E,The
overstep of layer K which brings it
above successive beds of the lower
series is seen both in vertical section
and on the map,(b) This diagram
combines the overstep of the upper
formation with formation with onlap
(overlap) within the upper formation.
地球内部过程
Geologic Tectonics
Fractures in rocks
? More commonly,at depths where tension is
only relative and where rocks are brittle or
semi-ductile,failure takes place along shear
fractures,In these,movement has taken
place parallel to the plane of fracture,and
the strata on either side are displaced by
anything from a few millimetres to 100km,
The rubbing of one side of the fracture
against the other results in polishing,and
may produce grooves and ridges called
slickensides,strechted in the direction of
relative movement,Shears are formed
normal to the plane in which the directions of maximum pressure and minimum pressure
(that is,relative tension) lie,and at an angle
of approximately 30° to the former
(Fig.4.16),Two sets of shears,lying
symmetrically about the direction of
maximum pressure (at 60° one to the other),
should be produced,Both sets are
commonly present,but one set is usually
much better developed.
Environmental Geology
主讲人,万新南 教授
Prof,Wan xinnan
地球内部过程
? Plate Tectonics
? Geologic Tectonics
? Earthquake
? Tsunamis海啸 and Coastal Flooding
地球内部过程
Geologic Tectonics
? Folds
? If subjected to stresses beyond超出 those that their strength can
resist,strata are permanently deformed by either buckling压弯曲 or
fracturing,The type of deformation depends on the mechanical
properties of the rocks and the nature of the stresses,In general,
stresses which are applied slowly,either deep within the Earth
where the confining pressure produced by overburden is high,or to
rocks that are not brittle,tend to produce folds by buckling or plastic
flow,The essential characteristic of a fold is a change of dip倾向,
This occurs at the hinge枢纽、绞链 of the fold,On either side of the
hinge is a limb翼,where the dip is comparatively steady,In real folds
the change of dip is seldom restricted to a line,but is concentrated
in a liner zone,The plane of symmetry that bisects平分 the angle
between the limbs is the axial surface (or axial plane),The
intersection of the axial surface with each bedding plane is an axis
of the fold.
地球内部过程
Geologic Tectonics
? Folds
? A fold where the limbs diverge偏斜、脱节
downwards (that is,where the dips of the limb
are away from the hinge) is an anticline背斜 ; a
fold where dips are towards the hinge is a
syncline向斜, If the axis is not horizontal,the fold
is said to plunge,with the amount of plunge倾伏、
插入 being the angle between the axis and the
horizontal line vertically above it.其倾斜量以轴线
及其上方的水平线夹角表示。
地球内部过程
Geologic Tectonics
? Folds
? Folds are described and classified by
certain features of their geometry which
are diagnostic of how they were formed,
The criteria and the terms used to define
folds are illustrated in Figure 4.12; they are
as follows:
地球内部过程
Geologic Tectonics
? Folds
地球内部过程
Geologic Tectonics
? Folds
地球内部过程
Geologic Tectonics
? Folds
地球内部过程
Geologic Tectonics
? Folds
(a) The dip of the axial plane,where it is
vertical the dip of each limb is the
same in magnitude,but opposite in
direction,and the width of outcrop
of any bed is the same on both sides
of the axis,In inclined folds,one
limb is steeper and its outcrop is
correspondingly narrower than that
of the other,Overfolding occurs
where one limb is overturned,such
that both limbs dip the same way,
The rotation of the axial plane,seen
from left to right in the diagram,is
probably produced by transport of
the fold with relative drag at its base.
(b) The size of the angle between the
limbs,this reflects the intensity of
compression of the fold.
地球内部过程
Geologic Tectonics
? Folds
Concentric folds同心褶皱 are
produced by simple bucking,
and the beds are curved
concentrically by the same
amount,The beds remain
constant in true thickness
and parallel to each other
after folding,Slip has taken
place along the bedding
planes,A concentric fold
becomes progressively less
open as the 'centre' of the
concentricit
地球内部过程
Geologic Tectonics
? Folds
In similar (shear) folds all layers are
deformed to a similar shape,and
the bed thicknesses are constant in
a direction parallel to the axial
plane,This produces an increase
of true thickness at the hinges and
a decrease on the limbs,Similar
folds are produced by differential
movements along minor shear
planes in a direction parallel to the
axial plane,Intense folding of
metamorphic变质 rocks at a time
when temperature and pressure
were high is usually of this type.
地球内部过程
Geologic Tectonics
? Folds
Flow folding is produced when
incompetent rocks flow in a complex
pattern of movement to accommodate
either the local stresses related to the
buckling of competent beds or lateral
changes in the loads of overburden
compressing them,The pattern of folds
which results is usually complicated,
and such that the shape of one folded
bed may bear little obvious relationship
to that of another,Folding is then
disharmonic,Folds involving a thick
layer of salt are of this type,The salt,
which is highly incompetent,rises
locally as salt pillows and salt plugs,
folding the beds above them to form
salt domes.
地球内部过程
Geologic Tectonics
Fractures in rocks
? Minor fractures in rocks,both
tensional and shear,are called
joints,Larger shear fractures,
where there are significant
displacements of rock bodies
across the plane,are called
faults,(The distinction between
a 'shear joint' and a 'small fault'
is arbitrary,depending on
circumstances and
significance,but the former
term usually suggests a
displacement of a few
centimetres.)
地球内部过程
Geologic Tectonics
? Faults
? As with all structural
surfaces,the orientation of a
fault is expressed by its
strike and dip,The
displacement across a fault
is called its slip,and the
terms used to describe the
components of slip (strike
slip,dip slip and throw) are
illustrated in Figure4.18.
地球内部过程
Geologic Tectonics
? Faults
Figure 4.18 Before fault
movement A and A' and B and
B' were adjacent to each other,
The total displacement A-A'
measured along the fault plane
is called the slip of the fault,It
may be resolved into strike slip
and dip slip,which are
respectively horizontal and
vertical components,in the
plane of the fault,Dip slip may
also be resolved into a
horizontal component and into a
vertical component (the throw of
the fault).
地球内部过程
Geologic Tectonics
? Faults
Only very small faults have a simple,clean-cut plane of movement,The
majority are zones of shearing,usually a few metres across,but major faults
may be more than 1 km wide,Within the fault zone there may be a number
of planes of movement displacing the strata by distributive slicing,or the rock
may be completely fragmented to form a fault breccia where competent
rocks are affected,or clay gouge where incompetent rocks have been
smeared out by shearing,(Gouge often acts as a seal to make the fault zone
locally impervious to groundwater circulation.) At the walls of the fault the
strata may show terminal drag in the direction of relative movement.
地球内部过程
Geologic Tectonics
? Faults
A fault described by its geometry in two different ways,(a) by the relationship
of its strike to the strike of the strata it affects,and (b) by the relative
magnitudes of its components of slip.
(a) If the strikes are nearly parallel,the fault is a strike fault; if they are nearly
at right angles,it is a dip fault; and if neither,it is oblique.
(b) Where slip is predominantly horizontal,producing a large strike slip
component and little throw or heave,the fault is described as strike slip,(The
terms wrench and tear are used to describe certain varieties of strike-slip
faults.) In faults of this type,the fault plane is near-vertical,and there is
usually a comparatively wide fault zone in relation to displacement..
地球内部过程
Geologic Tectonics
? Joints
The presence and orientation of joints have significant effects on the bulk
properties of rocks,and their description is an important stage in most site
investigations,Joints may be non-systematic,but often occur as a set of
parallel planes,If two or more sets are present,they form a system of joints,
Prominent joints which are continuous as a single plane surface for hundreds
of metres are called master joints.
地球内部过程
Geologic Tectonics
? Unconformity,overstep and
onlap (overlap)
The geological history of an area is preserved in the strata,If there is a
break in this record,because there has been no deposition of sediment and
probably erosion for much of the time,the gap is called an unconformity
between the lower and the upper series of strata,The surface corresponding
to this time gap is the plane of unconformity,If there have been no Earth
movements other than a vertical rise and fall relative to sea level,then the
dip is the same above and below the unconformity,If tilting,folding or faulting
of the lower formation (E-A in Fig.4.28) before the upper series (K-M) is
deposited on them has produced structural discordance,then the
geometrical relationship at the plane of unconformity is an angular
unconformity,The lowest bed (K) of the upper formation rests directly on
progressively older beds of the lower formation and is said to overstep from
E to B,The pattern of subcrops of E-A under bed K is identical to the
outcrops once produced by the lower structure before K was deposited,A
line of boreholes would show a systematic increase of the gap in the
geological record,in the up-dip directions of the lower formation.
地球内部过程
Geologic Tectonics
? Unconformity,
overstep and onlap
(overlap)
地球内部过程
Geologic Tectonics
? Unconformity,
overstep and onlap
(overlap)
If subsidence has increased the area of deposition of the
upper formation,then in the fringe of the area,where bed
K was not deposited,bed L rests directly on the older
formation E-A,and is said to onlap or overlap K
(Fig.4.28),Onlap is always accompanied by overstep,
The variable gap (with respect to the fullest sequence of
strata for the area) at the unconformity is a combination
of the absence of the top beds of the lower formation
because of overstep and the absence of the bottom beds
of the upper formation because of onlap.
地球内部过程
Geologic Tectonics
? Unconformity,
overstep and onlap
(overlap)
Figure 4.28 Overstep and onlap
(overlap),(a) The upper formation K-
L-M rests with angular unconformity
on a lower formation A-E,The
overstep of layer K which brings it
above successive beds of the lower
series is seen both in vertical section
and on the map,(b) This diagram
combines the overstep of the upper
formation with formation with onlap
(overlap) within the upper formation.
地球内部过程
Geologic Tectonics
Fractures in rocks
? More commonly,at depths where tension is
only relative and where rocks are brittle or
semi-ductile,failure takes place along shear
fractures,In these,movement has taken
place parallel to the plane of fracture,and
the strata on either side are displaced by
anything from a few millimetres to 100km,
The rubbing of one side of the fracture
against the other results in polishing,and
may produce grooves and ridges called
slickensides,strechted in the direction of
relative movement,Shears are formed
normal to the plane in which the directions of maximum pressure and minimum pressure
(that is,relative tension) lie,and at an angle
of approximately 30° to the former
(Fig.4.16),Two sets of shears,lying
symmetrically about the direction of
maximum pressure (at 60° one to the other),
should be produced,Both sets are
commonly present,but one set is usually
much better developed.
