Structural geology The movement of the Earth's plates

download report

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.



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,



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


1664 in Ireland
Said Earth began
4004BC



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
`