Download Answer Key - With Teacher Comments given in class Plate

Answer Key - With Teacher Comments given in class
Plate Tectonics / Convection in the Mantle PPT Notes
Keyterms
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Density-mass/___volume__ The amount of ___matter_ in a given area or volume of that matter.
Fluid-matter that can __flow_. Can be solids, liquids, or __gases__
Convection - heat transfer____ within a fluid.
Convection current -a __current_ that develops from a fluid moving from an area of __high__
density to an area of ___low_ density.
How do convection currents form? When fluids heat unevenly and areas develop that are different in
density
What are examples of convection currents? Lava lamps; boiling H2O (water); (pasta in boiling H2O;
ocean currents; air currents in clouds; the mantle
Theory of Plate Tectonics
What is the theory of plate tectonics?
The _theory of plate tectonics_ explains the formation and movement of Earth’s plates.
The lithosphere is broken into sections called _tectonic plates_.
Plate Boundaries:
__Divergent_ Boundaries- The place where two plates (pieces of the lithosphere) move apart.
Most divergent boundaries occur along a __mid-ocean ridge__ where sea-floor spreading occurs.
A divergent boundary between 2 continental plates is a rift valley_.
What is a mid-ocean ridge? It is an __undersea__ mountain ___chain__ where new
ocean floor is produced at a divergent boundary.
What is a rift valley? It is a steep-sided _valley_ that becomes wider and deeper as the two continental
plates pull further and further apart (This line was added by Mrs. Best and is not in
the flipped video)
Convergent Boundaries:
The place where two plates come _together__ (often called a collision).
When two plates collide, the _density_ of the plate determines which one comes out on top.
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2 _continental__ plates collide= formation of __mountains (or mountain range)__
1 __oceanic__ + 1 continental collide= oceanic sinks beneath the continental plate
(__subduction_) and forms a __trench__ (a narrow, deep valley along the ocean floor).
_Subduction_- the process by which oceanic crust sinks beneath a less dense plate.
Subduction Diagram
(click on picture & expand to show details)
Transform Boundaries:
A place where two plates _(slip)/ scrape__ past each other, moving in opposite directions. We chose
“scrape” as a better word here since that word does a good job of conveying the friction or tension
that builds up as the 2 rough-textured slabs of rock try to move past each other in opposite
directions. Mrs. Best’s analogy—think of a rubber band that is pulled back, increasing the tension
on the band. The band snaps quickly when released and releases the tension. An earthquake
releases tension that builds up as the tectonic plates try to scrape past each other.
__Earthquakes, minor as well as major,__ often occur along transform boundaries, but _crust__ is
neither created nor destroyed.
Diagram of plate movement:
Divergent
Convergent
Transform
- Looking at the direction of the arrows for each diagram will enable the student to distinguish
between each type of plate boundary.
- The transform boundary diagram clearly shows the 2 blocks offset from each other and is probably
the easiest to recognize.
Landform feature here = fault line (ex. Is San Andreas fault in Ca).
Event here = earthquake
- To easily tell the convergent boundary diagram, look for the “telltale” subduction zone area where a
denser ocean crust is going under the other crust (less dense).
- Convergent boundary with subduction (either ocean-ocean or ocean-continent):
Landforms here = ocean trench, volcanic island arc (if ocean-ocean), coastal mountains (if
ocean-continental).
Events here = earthquakes (deepest of all boundary types), tsunamis, volcanic eruptions
- Not shown is a convergent boundary with both plates being continental;
Landform here = mountain ranges (ex.: Himalayans, Appalachians)
Event here = earthquakes that can be anywhere from minor to major
Evidence for Plate Tectonics
_Pangaea___- The name of the single land mass that broke apart 200 million years ago and gave shape to
today’s continents.
Students were asked to * the following information as important to be able to discuss on Friday’s test.
Mrs. Best reminded students that this information relates DIRECTLY to the “Continental Drift Activity”
(#16L) we did in class yesterday and provided the evidence that Alfred Wegener used to support his
theory of continental drift that he presented in 1915 (and, unfortunately, was rejected soundly by the
scientific community because he did not have any proof of what could cause the continents to move).
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Evidence for a Supercontinent
 Land features: mountain _ranges__ and _coal_ fields appear to line up according to
the shape of continents. Ex.: mountains in Scotland match up to part of upper
Appalachians in North America; coal fields in Great Britain match up to coal
fields in Appalachians
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_Fossils_: from ancient animals appear to link continents together as wellmesosaurus (the part colored brown yesterday), lystrosaurus (freshwater reptiles)
(the part colored blue yesterday), glossopteris (plant) the part colored green
yesterday).
Students should be able to discuss how fossils of different reptiles and
tropical fern plants appeared on continents that are now separated by an entire
ocean and how improbable it is that the same fossils should appear with such
separation across an ocean
Climate: _Temperature_ changes at specific locations show that continents may
have shifted toward or away from the equator over time.
Ex. In yesterday’s activity = fern grown in tropical climates found on
continents that today have very cold climates (Greenland, Antarctica)
Ex. Mentioned in flipped video = deep scratches in rock formations in parts
of Africa near the equator that match the type of scratches that a large glacier
leaves as it moves over the rock indicates that the climate of that part of Africa
was not always so warm, so Africa possibly was not always positioned where
it is today
Sea-Floor Spreading- the process by which molten _material—we have been using term
“magma” (which turns into lava as it hits the surface)_ adds new oceanic crust to the ocean
floor.
o The sea floor __spreads__ apart along both sides of a mid-ocean ridge (__divergent__
boundary), as new crust is added.
Sea-Floor Spreading Diagram
Students should click on picture and enlarge to draw the details.
How do we know the sea-floor actually spreads?
Evidence from _molten material- new material is erupting along __mid-ocean_ ridges.
Evidence from drilling samples- the age of rocks has been identified through drilling samples. Rocks
__farther__ from the ridge were the oldest, the youngest rocks were always in the ___center_ of the
ridges. As Ms. Schaefer pointed out in the flipped video, the research vessel Glomar Challenger
drilled samples across the Atlantic Ocean floor in 1968. The rock samples were dated. The pattern
of youngest to oldest from center of ridge outward was exactly the same on either side of the midocean ridge.