Geology 1403 Lab 7
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Blinn College *
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Course
1403
Subject
Geology
Date
Dec 6, 2023
Type
Pages
12
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Name·
(..\.f.:>
Sr•r:
Geologic Structures
and
Maps
Geologic structures result from
the
deformation
of
rock due
to
compressional, tensional
or
shear
stress. This
is
most
visible in sedimentary rocks due
to
changes
in
the
original horizontal position
of
the
rock layers. Examples
of
structures are shown in
the
diagrams below.
3
3
3
younger
rock
3
3
3
2
2
2
older
rock
horizontal
layers
tilted
layers
fault
fold
The diagrams above are called
block diagrams.
The sides
of
the
block are called cross-sections.
The
upper
surface
of
the
block
is
a
geologic map.
A geologic
map
shows
the
distribution
of
rock
formations
at
the
Earth's surface.
Geologic map
symbols
(shown below) give information
about
structure
below
the
surface.
GEOLOGIC
MAP
SYMBOLS
~
35
strike and dip
D
u
fault
-
+-
syncline
geo
lo
gic
map
view
fL-
30
-
1-
anticline
3
2
-r-
-r-
plunging
syncline
plunging anticline
On
the
geologic map
view:
the
strike
and
dip
symbol
(r
,o
)
shows that
rock l
aye
rs are
dipping
(tilting) to the
eas
t
at a 30" angl
e.
(I
ma
gine
po
uring water on
a rock; the water will flow in the di
rec
ti
on
of
th
e dip).
Strike
is
th
e direction
of
a horizontal line
perpendicul
ar
to the dipping rock layer.
cross-secti
on
views
Lab 7 I Geol
ogi
c Struc
tu
r
es
and Maps
59
■
-
Nam
e·
~
k~c.l,
/
Sec
Name:
~
oi
Sec
Problem
1.
A. Number
the
rock layers on
the
geologic
map
surface
of
the
block diagram.
B. Place strike and
dip
symbols on layers 3 and 4.
(Use
layer 2
as
an
example)
.
Faults
A
fault
is
a fracture
in
rock along which movement
has
occurred.
Rocks
on either side
of
a fault are
called
fault
blocks.
There are three main types
of
faults:
normal, reverse
and
strike-slip
(shown in
the
diagrams below).
If
the
fault
plane
is
at
an angle (that
is
not
vertical
or
horizontal), the
upper
fault block
is
called
the
hanging wall
and
the
lower
fault
block
is
called the
footwall.
In a
normal fault,
the
hangi
ng
wall
has
moved
down
relative
to
the
footwall. In a
reverse fault,
the hanging wall
has
moved
up
relative
to
the
footwall. In a
strike-slip fault,
movement
is
horizontal. This type
of
fault
is
described
as
right-
lateral or left-lateral
based
on
the direction
the
opposite fault block appears
to
move
when
you
s
tand
facing
the
fault.
footwall
footwall
normal fault
reverse fault
left-lateral strike-slip fault
60
Geo
lo
gic
Struct
ur
es
and
Maps / Lab 7
•
j
■
Problems
2.
Complete
the
block
diagram
of
the
fault.
\Finish
numbering
the
layers
on
the right
side
of
the
fault.
Sec
~
Label
the
hanging
wall
and
footwall.
0.
·
Draw
half
arrows
on
the
cross-section
to
show
the
-\
movement
of
the
fault
blocks.
D.
What
type
of fault
is
this?
Normal
c§
3.
Complete
the
block
diagram
of
the
fault.
A.
Finish
numbering
the
layers
on
the left
side
of
the
fault.
B label
the
hanging
wall
and
footwall.
C.
Draw
half
arrows
on
the
cross-section
to
show
the
movement
of the
fault
blocks.
D.
What
type
of fault
is
this?
8
Reverse
4.
The
following
diagram
is
a
map
view
of a
fault
(you
are
looking
down
on
the
surface
at
a
road
broken
by
the
fault).
A.
Draw
half
arrows
on
each
side
of
the
fault
showing
the
direction
of
movement
for
that
block
.
8.
What
type
of
fault
is
this?
right-
lateral
strike
-
slip
MAP
VIEW
5.
Refer
to
block
model
#9.
Wh
at
type
of
fault
is
thi
s?
RQ_}&Cj;
W,\J
\\
L<1.J
-
Ge
ol
ogic St
ru
c
tu
res
and
Ma
ps
61
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Name:
___
_
6. Identify
the
type
of
fault
shown
in
each
block
diagram
below:
normal
fault,
reverse
fault, right-lateral
strike-slip
fault,
or
left lateral strike-slip fault
Label
the
hanging
wall
and
footwall
on
the
normal
and
reverse
faults.
D
62
Geologic
St
ructures and Maps
Lab
7
I
r
Name
~c)y
Sec:
_____
_
Folds
When
the crust
is
compressed
(as
in a convergent plate boundary) rock
layers
may
become folded.
An
anticline
is
an
arch-shaped
fold. A
syncline
is
a
U-shaped
fold.
The
axis
of
a fold may be tilted or
plunging
relative to the
Earth's
surface.
These
folds
are
shown
in
the block diagrams below.
anticline
syncline
plunging
anticline
plunging
syncline
In
cross-section
view,
anticlines
and
synclines
are
easy
to identify. But at the surface they appear very
similar.
There
are
two possible
ways
to tell them apart on geologic
maps
.
1.
The
relative
ages
of
the rock units
(2
is
the oldest rock on the geologic
maps
below).
Older
rocks
occur at the
center
of
an
anticline.
Younger
rocks
occur at the
center of a
syncline.
2.
The
direction rock
layers
are
dipping:
Rock
layers
dip away from
the
center of
an
anticline.
Rock
layers
dip toward
the
center of a
syncline
.
geo
l
ogic
map of
an an
ticli
ne
1
~
3
2
3
yo
ung
er
older
younger
geologic
map
of
a s
yn
c
lin
e
~
1
2
3
2
older
younger
o
ld
er
geo
log
ic
map
of a
plunging anticline
4
older
Domes
and
basins
are
folds that
have
a circular
shape
on a geologic map.
geologic map
of
a
plunging
sy
ncline
younger
geo
l
ogic
map
of a
basin
Lab
7
i
G
eo
l
og
ic Structur
es
a
nd
Ma
ps
63
L
~
y_
__
Sec.
L
(
,
.....
_
\
/?
~
l'..
A
,,
vi
Name
:
___
_ v
----=
./
__
¥-
_'-'_
'
1
_
'--V
_._J
~
t__
_
Sec:
____
_
Problems
7. Identify
the
type
of fold
shown
by
each
block
model.
Model
#
Type
off
old
Model 3
Model4
Model 5
Model 6
Model 7
Model 8
8.
A.
Number
the
rock
layers
on
the
geologic
map
surface
of
the
block
diagram
below.
8.
What
type of
fold
is
shown
in
the
block
diagram?
')'(V\e,,\~
C.
Place
strike
and
dip
symbols
on
the
upper
surface
of
rock
layer
2.
(Use
layer
3
as
an
example).
9.
A.
Number
the
rock
layers
on
the
geologic
map
surface
of the
block
diagram
below.
8.
What
type of fold
is
shown
in
the
block
diagram
?
~\.(_~1,,'(_
C.
Place
strike
and
dip
symbols
on
the
upper
surface
of
rock
layer
2.
(Use
layer
3
as
an
example).
64
Geologi
c S
tru
ctures
and
Maps
I
Lab
7
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r
Name:
~'(
Sec:
_____
_
10.
A.
The
diagram to the right
is
a geologic
map
.
older
rock
What
type
of
fold
is
shown
on
this geologic
map?
~
\-
f\\
)J\or;
f',V"\
\(,
\
~
B.
Draw
strike
and
dip
symbols
on
either
side
of
the center
of
the fold.
younger
rock
11
.
A.
What
type
of
fold
is
shown
on
this geologic
map?
~If\\
\ G
\'-V'Q.__,
B.
Which
rock
is
older?
€:J
r
B
1
.J
~
older
rock
C.
Which
cross-section
shows
what this fold
looks
like below the
surface?
CROSS-SECTION
VIEW
12.
A.
Based
on
this geologic
map.
do the
rock
layers
below the
surface
dip toward or
away
from the center
of
the
fold?
8
B.
What
type
of
fold
is
this?
away
from
Q\~fC)
~~
\;\~
C.
Which
rock
is
younger?
A®
13
. A.
Rock
unit 4
is
the young
est.
What
type of structure
is
this?
~~S
\
'1\
B.
Draw
the correct
cross
section view
on
the front
of
the block diagram.
\-
MAPVIEW
-I
I-
B
A
MAP
VIEW
MAPVIEW
Lab
7
I
G
eo
logic
Struc
tu
res
an
d
Map
s
65
:-.Jarne
~
c)
/
Sec
14
.
What
type
of structure
is
shown
on
this
geologic ma
p?
f\~
S¥O(,
\{\c
'
)
15
.
A.
Do
strike
and
dip
symbols
on
this
geologic
map
show
the
rock
layers
dipping
toward
or
away
from
the
center
of
this
structure?
toward
~
B.
What
type
of structure
is
this
~Yt
C.
Which
rock
is
younger?
(G::)
B
16
.
A.
Wh
at
type
of
structure
is
shown
on
this
geol
o
gic
map?
~
hrY,,
'-~
'
B.
Wh
i
ch
rock
is
older?
@
B
66
Geologic Struc
tur
es and Maps
L
1
younger
rock
MAPVIEW
MAP
VIEW
r
r
r
1
A
B
MAP
VIEW
•
J
~vs
\4..JVV_,iJy
GEOLOGIC
MAP
SYMBOLS
~
35
D
u
-+-
-1
-
-r-
- j-
strike and dip
fault
syncline
anticline
plunging
syncline
plunging anti
cline
17
. A. Identify the structure in the
geologic map below.
I
~
Y\(
1'-r'<.~
B. Draw strike and
dip
symboles
on
the rock
layers labeled A.
~ -
-1-
'-1
A
A
MAP
VIEW
19
.
A.
Draw
half
arrows on
the
cross-section
to
show
the
movement
of
the
fault blocks.
(hint: D means down, U means up)
B.
What
type
offault
is
this?
f\JC}f)
U
\
18.
A. Identi
fy
the structure in the
geologic map below.
110:\\G\\Y(\>
B.
Draw the correct geologic map symbol on
the center
of
this fol
d.
C.
Draw strike and
dip
symbols on the
younger rock layers.
1
~
r)
\--
...
ai
Qj
bO-"
...
OD-"
C
u
Qj
-"
C:
u
:::,
0
-0
u
:::,
0
0
...
-
0
0
...
>
0
...
>
MAP
VIEW
20.
A. Ident
ify
the structure below.
~~"'u)
Syr<i\<'{
__
B.
Draw
the
cross-section view on
th
e front.
21
. This geologic map shows
tilted
layers. What direction
are
the
layers dipping?
\
Rx-\
(
N
f
MAPVIEW
L
1l1
I
Geologic
Structures
and
Map
s
67
I
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Geologic
Maps
On
a
geologic map
each
rock
unit at the
Earth's
surface
is
represented by a
color,
letters and
sometimes
a pattern.
The
first letter(s), which
are
capitalized, indicate the geologic
age
of
the
rock
.
The
following lower
case
letter(s)
reference
the
name
of
the
rock
unit.
The
explanation or key
is
shown
as
a column
of
the
rock
units listed in order of
increasing
age.
The
youngest
rock
unit
is
at the
top
of
the column; the oldest
rock
unit
is
on
the bottom.
The
basic
rock
unit geologists
use
, called a
Formation
is
defined
as
a mappable unit
of
rock.
Formations
can
be
combined into a larger
rock
unit
called
a
Group
and
divided into smaller
rock
units
called
Members.
All
of
these
designations
can
be
used
on
a geologic map.
The
map
shown
below
uses
formations
only.
The
line separating rock units
is
called
a
contact
line.
:Dmr::··
::·:
omr
Bedrock
Geologic
Map of Montgomery,
Pennsylvania
Geologic S
tru
c
tur
es
and Maps
I
Lab 7
Z
MAHAHTANGO
Cl:
z
g
FORMATION
Dmh
s
t--MARCE--U-US--4
''"'"'"'"'"''"
'
''''''"'
'"''"'"'''''"''''''''"'"'
:::::
OlD
PORT
::::::
:::
FORMATION
::::
111
111~;
r ~
_
§~11111
-
•
•
•
_
_J
•
•
•
G½
~
1
Sec
_____
_
Questions
Refer
to
the
Bedrock
Geologic
Map of Montgomery.
Pennsylvania
22
. What
is
the name
of
the
oldest rock formation?
0\
c\
~ \
~
O\
23
. What
is
the name
of
the
youngest rock formation? \
1
(\./"\
V'Ni
:)
~
~~v:t"\
24.
During what geologic period
{age)
did these rock formations
form?~/
LA,.«:~
25
. What geologic structure
is
shown on this
map?
_"o=_
:
.....
~-'-'{'(,__;;__wx__.:;__
_________
_
26
. Below the surface,
do
the rock layers
dip
toward
or
away from the center
of
the
fold?
toward
e
27
. Draw a strike and
dip
symbol on the Mahantango Formation {Dmh)
28
. Draw the correct geologic map symbol on the center
of
this fold .
L.ib 7
Geologic
St
ruc
tur
es
and Maps
69
b
Name:
___
~\')
\0-)--
"'0
~
Se
~
W~~
_ \
v\
(;l(/4)
Use
the color
Geology
ofTexas
Map
provided
in
class
to
answer
the following
questions.
29.
At
which
of
the following
locations
would
you
find the
youngest
rock?
Amarillo
Midland
Houston
Dallas
30.
What
letters
are
used
to
represent
the
oldest
rock?
_____
_
31.
What
is
the geologic
age
of this
rock?
Precambrian
Paleozoic
Mesozoic
Cenozoic
32.
Which
of
the following
is
a
possible
absolute
age
for this
rock?
40m
.y
265
m.y
.
450
m.y.
1500
m.y
.
33.
Dinosaurs
lived
during the
Mesozoic
Era.
Which
location could
have
dinosaur
fossils
in
rocks
at
the
Earth's
surface?
Houston
Midland
Dallas
Corpus
Christi
34.
Observe
the
shape
of
the youngest units
on
the
map
(Qal)
.
What
is
currently depositing sediment
at
these
locations?
35.
Bryan
is
located
on
the
Yegua
Formation. During which geologic
epoch
did this
form?
Pliocene
Miocene
Oligocene
Eocene
36.
What
is
the
age
range
of
this geologic
period?
_______
_
37.
What
letters represent the
Yegua
Formation?
_______
_
38.
What
is
the
name
of
the Group to the
east
of the
Yegua
Formation?
_____
_
39.
Is
this Group older or younger than the
Yegua
Formation?
Older
Younger
40.
Do
rocks
become
older or younger
if
you
continue to the
east?
Older
Younger
41.
If
#1
is
the older
rock,
which diagram could
represent
the
subsurface
geology of this
eastern
portion
ofTexas?
A
B
WEST
EAST
WEST
EAST
70
Geologic Structures and Maps
I
Lab
7
•
•
•
J
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