2.1.5 The Lithosphere (KQ1): Evidence of Plate Tectonics
How do we know
that the plates have moved...where's the evidence? We know that
earthquakes and volcanoes happen, we know that there are mountain ranges
and deep and shallow parts of the ocean...but how do we know it's
caused by plate tectonic movement? This teacher does a really great job of explaining it in terms of paelo-magnetism (see below)...so instead of reinventing the wheel, let's watch him and learn.
KEY POINTS TO TAKE HOME:
The continents seem to "fit" together...this is known as geologic fit
We know from
looking at layers of rock that the magnetic poles on Earth switch every
so often (by every so often, I mean hundreds of millions of years)
The magnetic rocks on the crust change poles as you move away from known ridges
On both sides
of the ridge, the distance is the same to change the pole, showing that
the rock equidistant from the ridge on both sides was formed at the
same time
The is evidence that the plates are moving away from each other
This theory and the evidence is known as paleo-magnetism
One more piece of
evidence (my favorite) is from what a lot of boys want to be when they
grow up when they're in elementary school...dinosaur bone diggers
(paleontologists)! There have been bones of pre-historic creatures
(namely the mesosaurus)
and plants found on and near South America and South Africa, suggesting
strongly that at one point they were connected...there is no other
reasonable explanation for finding two of the exact same species that
far apart. This evidence is basically known as paleontology...or fossil evidence.
2.1.4 The Lithosphere (KQ1): Types of Plate Boundaries
When the tectonic plates move, they generally move one of three ways:
Away from each other (divergent/constructive)
Towards each other, with one going under the other (convergent/destructive)
Sliding alongside each other (conservative/transform)
These three
actions have different results on Earth and have shaped what Earth has
become today. Some of the following information can also be found in
your Pallister text on page 37. BTW...you will see some rock terms,
which you can click on to find a definition; however, we will study
these more in detail soon when we discuss the rock cycle. Divergent/Constructive Boundaries
What happens at these boundaries:
To "diverge" literally means to go away from one another, so "divergent" plates do exactly that
They
are also considered constructive, because this type of boundary brings
mantle to the surface, "constructing" more crust...when in the ocean,
this is known asseafloor spreading
New magma from the mantle rises to the surface to fill the gap between the moving plates
It is runny lava, which pours out almost continuously in a non-violent way, and cools to form basalt
This lava forms volcanoes with wide bases and gentle sides
What happens as a result of this action:
Rift valleysare formed along faults caused by the crust splitting as the two plates move apart. (Ex. East African Rift)
In the ocean, rift valleys result inoceanic ridges. (Ex.Mid-Atlantic Ridge)...really cool...underwater mountains!!!
Volcanoes and earthquakes can result from divergent plate boundaries
The following
graphic shows the formation of a continental rift valley, a continental
rift valley turning into a new body of water, and an oceanic rift valley
(ridge)
Clickherefor an animation of a divergent plate boundary
Convergent/Destructive Boundaries
What happens at these boundaries:
To "converge" literally means to go come together, so "convergent" plates do exactly that
They are also considered destructive, because this type of boundary brings crust back to the mantle, thus "destructing" it
Usually occurs at oceanic/continental plate boundaries
One plate, usually the oceanic plate (because it is more dense), sinks below the other
It is destroyed in the subduction zone
The subduction zone is the area where the oceanic plate slips under the continental plate
Sediments on the sea bed between the two plates are compressed and folded up to form the world's high mountain ranges (ex. Himalayas, Rockies)
The friction from plate movement in the subduction zone makes the rocks melt
This produces magma from which volcanoes are formed
What happens as a result of this action:
These volcanic eruptions can be violent as the lava is shattered into many pieces by explosions, and thrown out as rocks, ash, and other debris
Tall, steep-sided cones are built up (see picture of Osorno Volcano in Chile to the right)
Earthquakes are frequent; the ground shakes from the forced movement of rock against rock
The following graphic shows a typical convergent boundary forming volcanoes on the continent
Click here for an animation of a convergent plate boundary
Conservative/Transform Boundaries
What happens at these boundaries:
The
plates slide against each other, neither creating new crust nor
destroying it....movement that "conserves" the crust that is in place
They may be moving in the same direction, at different speeds, or in opposite directions
Stresses build up, which are then released by occasional, sudden plate movements
Friction caused by rock rubbing against rock forms earthquakes
Landslides, fires, and other destructive forces can be the result of earthquakes caused by conservative boundary shift
The following graphic shows an example of a conservative boundary
Hot Spots
The last phenomena you need to know about in this part are called hot spots. Hot
spots aren't really the result of plate movement...they can be at a
plate boundary, near one, or far from one. They are theorized to be the
result of extra-hot mantle pockets that push their way to the surface.
They can result in things such as volcanic islands and geysers. Two
great examples of these are the Hawaiian Islands and the Yellowstone Caldera and resulting Geysers,
both in the middle of plates. The spread of the land masses will
happen as the plate the hot spot is under moves, but the hot spot
remains stationary, like in the Hawaiian example shown here:
I have found an AICE Blog that has some great notes. I am posting the link here and will post assignments to accompany this. For now, assemble Cornell notes in your composition book. AICE Environmental Management
AICE EM: Add to Your Plate Tectonics Notes
Date: 9/18/2012
Description: The link at the bottom of the page is where the files with the additional notes for your tectonics plate activities can be found. Fill in your pages with any missing notes. The files say: PTnotespage1a-pdf-PTnotespage4.pdf
bring them to class tomorrow.
You should know the definitions of each word and set up groups of similar words. Vocabulary should be written in your composition book, numbered and each term should be highlighted or underlined. Determine the relationships within your groups, and among the groups you have developed. There will be a flashcard quiz on August 30, 2012.
AICE Environmental Management is one of the newest additions to the sciences in the AICE Curriculum at Mandarin High School(MHS). 'This syllabus covers environmental issues and their management, especially the human aspect. Through their studies, students will learn about environmental resources and their human exploitation, and about the goal of sustainable environmental management. Students also consider a range of case study material which can feature local, regional or global examples.'(cie.org)
Here is a video that highlights the topics covered in this course. Please note that the video uses the term "geosphere" whereas Cambridge uses the term "lithosphere". Assignment: Create Cornell Notes for the video.
Quest:There will be a crossword quiz on this on Tuesday, August 28, 2012.
1. Abiotic features
2. Accurate
3. Adaptation
4. Albedo
5. Biome
6. Biotic features
7. Climate
8. Community
9. Convection Current
10. Core
11. Crust
12. Deep Mining
13. Dependent Variable
14. Domestic Waste
15. Ecosystem
16. Fair
17. Fossil Fuels
18. Greenhouse Gases
19. Habitat
20. Igneous Rock
21. Independent Variable
22. Insolation
23. Insulation
24. Leaching
25. Mantle
26. Metamorphic Rock
27. Niche
28. Nuclear Fission
29. Nuclear Waste
30. Open Cast Mining: Method, used when minerals are closer to the surface. A conical open pit is dug on the top of a kimberlite pipe, the pit increases in size as the mining continues.
