Transcript Structural geology The movement of the Earth's plates

Structural geology
The movement of the Earth's
plates causes stress and strain
on the surface of the Earth.
P272-278
Rocks can deform
by folding or faulting
Folds
When there are compressional
forces folds can form
2 basic types:
anticlines-- layers go up like an anthill
synclines-- layers fold down
Folds that fold upward are anticlines
Folds that go down are synclines
If there is too much stress
faults can form.
 In
a fault the rock breaks
when stress exceeds strain
There are three types of faults.

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Normal
Reverse
Strike –Slip
Fault Terms

The wall that
overhangs the
other is called the
hanging wall

The wall whose
toe is under the
other is the
footwall
Normal fault
Formed from tensional forces

Hanging wall moves
down
Reverse fault


Formed from
compressional
forces
Hanging wall moves
up
Strike-slip fault


Formed from
shear forces.
Plates slide past each
other
Thrust fault

Thrust fault—low
angle reverse fault
Folding and Faulting
Uniformitarianism
The present is
the key to the
past
 James Hutton,

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
the Father of Geology
What we see now is what
has happened in the past
Idea popularized by Sir
Charles Lyell
The Principles of
Geology
Catastrophism

Earth has been
shaped by major
catastrophes in a
short amount of time
Art work inspired by the idea

The Future of
Catastrophism
Archbishop James Usher

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1664 in Ireland
Said Earth began
4004BC

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Based on Genesis
Added up
genealogies
October 23, 4004
BC
Attention! Achtung!
 For
your semester final, you may
use returned papers and notes,
but not your book
 You may only use them if they are
in a notebook, NOT loose from
your book!
Relative Dating

In 1669, Nicholas
Steno outlined basic
principles for
determining relative
ages in rocks
P185-190
`
Principle of Original Horizontality

Sed layers were
originally
deposited
horizontally
So, sed layers that
are not horizontal
have been deformed
Principle of Lateral Continuity

Sed layers extend laterally to the edge of
their basin or thin to nothing
3. Principle of Superposition

The oldest layers are on the bottom
Younger
Older
Principle of Inclusion
Included
stuff is
older than
the
intrusion
5. Principle of Cross-cutting
Relationships
Any feature that
cuts across a rock
or sediment must
be younger than the
rock or sediment it
cuts
Review the Principles


one piece of bread was
there for me to spread
the PB (or J) on (principle
of superposition);
the bread had to be
(relatively) flat for me to
spread the peanut butter
on it (principle of original
horizontality);


the peanut butter
probably covered the
entire piece of bread
(principle of LATERAL
continuity);
if I slice the sandwich, all
those layers (PB, J and
bread) had to be there for
me to cut through them
(principle of cross cutting
relationships;

if there is jelly in my
peanut butter, I put
the jelly on first - and
vice versa (principle
of inclusions).
Assignment
 Work
from the
bottom up
using the
principles you
just read about
`