Download Sinking Slabs and Convection Connections

Sinking Slabs
and Convection
Connections
Explore: p. 672 - 678
• I can use simple models to simulate the forces acting on
tectonic plates.
• I can compare directions of plate motions with locations
of hot spots, spreading ridges, and trenches
• I can determine the velocity of the North American Plate
relative to the Yellowstone hot spot
• I can examine the depth-distance relationship for
earthquakes in a subduction zone.
Learning Targets
• What do you remember about the relationship between
density and temperature from IS1?
• What happens to the density of a substance as it is
heated?
• What happens to the density of a substance as it cools?
• How do differences in density cause substances to rise or
fall?
Entry Task
• Read Introduction on pg. 672
• #1. Video Demo
• #1a. – d. Answer in your science notebook.
Process & Procedure p.
672
• 2. Read the paragraph. Take notes on anything that is
new to you – especially vocabulary: mantle, plume,
upwelling, hot spots, mantle convection.
• 3. Which part of your sketch represents upwelling?
Downwelling?.
Process & Procedure p.
672
• Mantle – the layer of Earth that lies beneath Earth’s
crust.
• Plume – a rising column of heat. Plumes occur in the
mantle where hot material moves upward from the lower
mantle, in some cases, to erupt at Earth’s surface.
• Upwelling – refers to the upward motion of material in
plumes through the mantle.
Process & Procedure p.
672
• hot spots – outpouring of molten rock (lava) at volcanoes
caused by plumes of heat rising from Earth’s core through
the mantle.
• Mantle convection – the slow movement of the mantle
due to upwelling and sinking. The circular motion of the
mantle as it transports hot material and heat upward, and
then transports cooled material downward. The hot
material is lower in density, so it rises. The colder
material is higher in density and sinks.
Process & Procedure p.
672
• Video Convection & Plate Tectonics
• Video Hotspots
• Animation Slab Pull
Process & Procedure p.
672
• If plate motion is driven by mantle convection and upwelling,
then plates should be moving __________ from hot spots.
• B. If plate motions is only driven by plates being pulled, then
plates should be moving ________ subduction zones.
Process & Procedure #6
• Complete P&P #7 a-e with your partner. Use specific
examples in your explanations!
Process & Procedure #7
• 7b. About 53 hotspots are shown.
• 7c. In general, plates pass over hot spots. There is little,
if any, correlation between hot spots and plate direction.
For a relatively small number of hot spots on spreading
ridges, the plate moves away from the hot spots (e.g.,
Iceland, Galapagos, or Afar at the base of the Red Sea).
Many more are distributed beneath oceanic plates or
continents. Geologic evidence indicates that those hot
spots are generally relatively stationary for tens of
millions of years (although detailed recent work shows
that they can at times drift or migrate through the mantle).
P&P #7
• 7d. Plates move towards subduction zones. For example,
the Pacific Plate has a rapid velocity to the northwest
toward the Japan and Aleutian trenches. Also, the
Australian-Indian Plate is being subducted at the Java
Trench, which led to the Andaman-Sumatra earthquake
and tsunami in December 2004. Closer to home, the Juan
de Fuca Plate is being subducted beneath the Cascadian
volcanic arc.
P&P #7
• 7e. From a strict correlation point of view, plate motions
do not correlate well with the location of hot spots. Hot
spots indicate upwelling and convection in the mantle.
This suggests that convection by itself is not a sufficient
explanation for plate tectonic motions. Thus, the “pull”
of oceanic crust entering subduction zones correlates
much better with the direction of plate motions, and the
tectonic patterns and landforms on Earth’s surface.
P&P #7
• 1a. What part of the world
is shown?
• 1b. What tectonic plates are
included in the figure?
• 1c. What is the relationship
between earthquakes and
depth?
• 1d. What kind of tectonic
setting is shown by the
pattern of earthquakes?
R&C #1 p. 676
• 1e. Sketch in your
science notebook
where earthquakes
occur along this line.
What does the depth
of the earthquakes
indicate?
R&C #1 p. 676
•
•
•
•
Complete R&C #2 and 3.
Remember to use graph paper for your graph!
Read “Shakin’ Like Jell-O”
Earthquake proof building
R&C #2-3 p. 676