Download 1. Heat transfer - Bethpage Union Free School District

Sea floor
Spreading
Aim: Is the ocean
getting bigger?
1. SONAR (it’s an acronym)
a.
In the 1960s, SONAR was
used to map the ocean
floor.
b.
A ridge was found in the
Atlantic Ocean – longest
and tallest mountain chain
on Earth. (mid- Atlantic
Ridge)
c.
Trenches were found
along the coastlines –one
is 6x deeper than the
Grand Canyon (Mariano
Trench @ -11 km)
A ridge runs all through the oceans
Mid-ocean Ridge and Marianna Trench
Ridge
Trench
2. Core Drillings
a. Rock samples taken
from the crust indicate
that the continental
crust is older than the
ocean crust.
b. Also, ocean crust
sampled near the ridge
is younger than farther
from the ridge.
Relative Age
of
Ocean Floor

Red is younger

Yellow and
Green are older
a. A magnetometer detected
the magnetite (a mineral
made of iron) in the basalt
(an ignesus rock) in the
oceanic crust.
b. Earth’s magnetic field has
reversed its polarity many
times, called a magneticreversal when the north
pole swaps polarity with
south pole.
c. Pattern (isochron) on one
side of mid-atlantic ridge is
a mirror of other side.
3. Magnetic
Striping of Crust
4. Hydrothermal Vents
ROVs (remote operated
vehicles) saw steam and
lava coming out of the
ocean floor around the
ridge.
b. Vents are underwater
geisers
c. Interesting sea life found
around the heated water
of the vents
a.
http://www.divediscover.whoi
.edu/vents/index.html
 http://oceanexplorer.noaa.gov/gallery/maps/maps.h
tml
5. Theory of Sea-Floor Spreading
a.
b.
c.
The process by which molten material adds
new oceanic crust to the ocean floor.
The ocean floor is widening because new
ocean floor is being made at the ridges,
while old ocean floor is being destroyed
when it is pushed back down in a trench.
Finally a possible explanation for the
continents moving.
http://education.sdsc.edu/optiputer/flash/seafloorspread.htm
Textbook pages 65- 79
 Page
71 Questions # 1- 4
 Page 77 Questions #1 – 5
 Section Review pages 78-79
#1-14 AND #1-4
 Exclude
page 76 (Microplate Terraines)
Theory of Plate Tectonics
Continental Drift + Sea-floor
Spreading = Theory of Plate
Tectonics
Do Now: Lava Lamp
 Can
you explain how the lava lamp is working:
 What
is the heat doing?
 What is happening to the molecules of lava?
 What is happening to the lava’s density?
1. What are plates?
a.
The Earth’s
lithosphere is
cracked into about
20 pieces, like a
cracked egg shell.
b.
The less dense
plates float on the
more dense
magma of the
asthenosphere.
2. What is driving sea-floor spreading?
a.
CONVECTION: Heat
transfer by movement of a
fluid.
b.
Convection Currents in
the asthenosphere are the
forces that move the
plates of the lithosphere
c.
This movement is the
cause of continental drift
3. How does
convection work?
a.
During convection
magma heated from
the core rises, then
cools and sinks
again (like a lava
lamp)
b.
Heat is being
transferred from the
inner core to
asthenosphere
c. Sometimes lava comes out of the crack at the mid-ocean
ridge, pushing the plates apart.
d. This movement causes the plates above to move around.
e. Convection makes the plates move about 2 cm/year.
4. What happens when plates move
around?
a.
Geological features (landforms) are formed as some
plates push apart, push together, or slide past one
another.
b.
The features are called tectonic, formed from the
movement of lithospheric plates.
c.
Plate boundaries are formed where 2 pieces of plate
meet.
3 Types of plate boundaries

Divergent

Convergent

Transform
5. Divergent Boundaries
Boundary
between two plates that
are moving apart or rifting

Rifting
causes Sea-floor Spreading
Ex. 1 : Mid Ocean Ridge –
ocean crust diverging from ocean crust
Ex. 2: Iceland
tallest mountain on the mid-Atlantic ridge
Ex. 3 : African Rift Valley
2 continental plates are pulling apart
6. Convergent Boundaries
a. A place where two plates come together.
b. Collision between plates.
c. Three types of convergent boundaries:
 Continent-continent
collision
 Continent-oceanic crust collision
 Ocean-ocean collision
Convergent Type 1
a. Ocean plate collides with less dense
continental plate
b. Subduction Zone: where the more
dense plate slides under the less dense
plate
c. Volcanos and trenches occur at
subduction zones
Andes Mountains,
South America
Convergent Type 2
a.
Ocean plate collides with another
ocean plate
b. The more dense plate slides under the
less dense plate creating a subduction
zone called a deep ocean trench and
an island arc
Ex. 1: Mariana Trench
Bathyscape Triest 1960
Ex. 2 -Aleutian Islands, Alaska
Convergent Type 3
a. A continental plate colliding with another
continental plate
b. Have Collision Zones:
a place where folded and thrust faulted
mountains form.
Ex. - Himalaya Mountains
7. Transform Boundary
a. Boundary between two plates that
are sliding past each other in
opposite directions
b. Stress builds up and earthquakes
occur along faults (cracks)
The lithosphere
cracks from the
stress (pressure)
from the friction
of the plates
grinding against
one another.
Large faults
(cracks) are
created.
Ex. 1: San Andreas Fault
Plate Tectonic Map
Summary:

The movement of the tectonic plates of Earth’s
crust is caused by convection in the mantle.
 The
movement causes the plates to either:
 Converge
(collide)
 Diverge (move apart)
 Transform (slide past)