Earth Science Notes
Earth Structure
Inner Core
•
• Diameter =
km
• 3200 - 3960
below surface
• Temp = 9032 – 10,832 ºF
•(
ºC)
• If the earth sliced open, the interior would
glow like a
Outer Core
• Plastic/
•
km thick
• 1,800 - 3,200 miles below surface
• Temp = 7200 - 9032 ºF
•(
ºC)
Mantle
•
km thick
•(
% of earth’s volume)
• Temp = 5400 ºF (
ºC)
• It is comprised of
distinct layers
Mesosphere
• This layer is considered a
substance
• A non-Newtonian substance sometimes behaves like a
and sometimes
like a
Asthenosphere
• Greek meaning “
• 124 miles (
• 45–155 miles (
”
km) thick
km) below surface
1
• Plastic/ Liquid
• Temp = 2640 oF (
oC)
Andrija Mohorovičić
First to use seismic waves to determine earth’s layers in
Mohorovičić Discontinuity (AKA
• It is the
)
between the crust (lithosphere) and the mantle
• It’s where seismic waves suddenly
Lower Lithosphere
• Litho refers to
• The rock layers in this region are very
• The broken nature of this layer allows
to reach the surface
Upper Lithosphere (AKA: Crust)
•
• Broken into
• High in
•
• Two types of crust:
with some flexibility
Oceanic Crust
• 4-7 miles thick
•(
km)
•
•
(alkaline) chemistry
• Age is relatively
Continental Crust
• Ave. thickness of 20 to 25 miles
•(
km)
•
•
• Much
(acidic) chemistry
than oceanic
2
Indirect Evidence of Plate Movement
(Past Evidence)
Principle of Original Horizontality
• Danish geologist Nicholas Steno (
)
• De solido intra solidum naturaliter contento dissertationis
prodromus, 1669
• This principle states that layers of rock are originally deposited
horizontally
• If those original layers are no longer horizontal , some kind of
caused them to change
Distorted Rock Layers
• Syncline
• Anticline
• Folding
• Tilting
Label:
Fossils… More Indirect Evidence
• Mesosaurus fossil
reptile
• The Mesosaur swam in the
between Africa and South America
waters
• It was not capable of swimming in open ocean
• How did it get to
?
Coral
• Requires
temps
And
to survive
• Fossil Corals in Wisconsin?
3
Ammonites & Belemnites
Mt. Everest
• The tallest mountains in the world have
• How did they get there??
• A logical answer is
of ancient marine creatures
Fort Peck Reservoir, Montana is far from the ocean…
Direct Evidence of Plate Movement
Displaced
Earthquakes
Volcanoes
4
Evidence shows the plates move… How do they move?
Convection is caused by differences in
• Heat rises because the molecules move
pushing other molecules out of the way making
it less dense
• When substances cool they tend to
due to the molecules being closer together
making it more dense
,
d
Demos
• Hot Air Balloon
• Convection Cell
Convection in the mantle causes plate movement
Forces Acting on Crust
Tension forces cause:
•
Tension force
Boundary
• Rifting
• Sea Floor
• Mid-Atlantic Ridge passes through Iceland
Hot magma rises
Compression forces cause:
•
Compression force
Boundary
• Mountain Building (
•
)
Zone
Magma cools and sinks
5
Shear force (Like a
)
Ok. Ok. The plates move… Where do we go from here?
Diastrophism
• Deformation of the earth’s crust due to
• Fractures can develop due to diastrophism
•
are created when plates collide or separate
Joints and Faults
Joints: Cracks in the rock layers in which the sides
relative of each other
•
Joints
• No displacement after cracking
The earth’s crust is broken into large sections called
Earth’s Plate Boundaries follow Fault Lines
Ancient plate boundaries are hard to spot.
An example is the
moved
…
Faults: Cracks in the crust in which the
sides have moved relative of each
other.
• Faulting describes the event that
caused the walls to move
Types of Faults
In order to identify different
of faults, we need identify the parts of a fault.
To do that we need to get some terms into your vocabulary…
Footwall
• This is underlying surface of an inclined fault plane
• It can act like a
Hanging Wall
• This is the overlying surface of an inclined fault plane
Hanging Wall
Footwall
6
Strike & Dip
• Strike: follows the cardinal directions
(North, South, East, West)
• It is where the plane intersects the surface
N
W
E
S
Dip: is the angle and direction at which a plane is
inclined from horizontal
• Faults are rarely perpendicular so the
dip angle will be between 0 & 90
• This graphic shows the dip as 18 degrees
Dip-Slip Faults
Normal Dip-Slip Fault AKA:
• Dip-Slip refers to the slippage of crust along the
DIP of the fracture
• It is a fault in which the fault movement
is
to the dip
• The HANGING Wall block
relative of the FOOTWALL
• It is caused mostly by
• It would be a type of
plate boundary
Reverse Dip-Slip Fault AKA
• A Reverse Dip-Slip fault is formed when the
HANGING Wall block moves UP relative
of the FOOTWALL
• The footwall acts like a wedge
• It is caused mostly by
forces
• This can be a convergent plate boundary
•
• Reverse Dip-Slip faults are referred to as
faults because one side
is thrust over the other
7
Strike-Slip Fault AKA:
• Caused by
forces
• There is little, if any,
displacement
Oblique-Slip Fault
• Has properties of
and
faulting
• Most often creates a
•
•
Plate Boundary
is being slowly torn apart by rifting and
Oblique faults
• Rifting can lead to sea floor spreading as can be
seen in the
Ridge
• This is technically an Oblique Fault
8