A2 Geography: Tropical Biome

A2 Geography: Tropical Biome

Soil MEDC and LEDC Case Studies

2.4.4 - The Lithosphere (KQ4): Soil MEDC and LEDC Case Studies

Soil MEDC and LEDC Case Studies

As with almost any environmental topic, the differences in how soil issues are handled in terms of preparation and response in MEDCs and LEDCs are quite different.  Here, you will read about one of each.  Pay close attention to the differences in how the respective governments handled them.  Yes, one is the US during the Depression...and yes, it was bad; but, the county did recover and prosper where as a LEDC may not.

MEDC:  The USA Dustbowl (Will open as a PDF)...Peer Reviewed article!!!

Quick questions...what did the USA learn from this experience?  How have things changed?

LEDC:  Himalayan Foothills (Also click on "Projects" tab for what is being done)

Due: Thursday, Nov. 19, 2015.  
Assignment: Type the following into a word document:
For each case, explain the situation, when it occurred, the location of the problem, who and how many people were affected.
For the Dust Bowl: What led up to this "perfect storm" of destruction? What did the USA learn from this experience? How have things changed?
For the Himalayan Foothills: What is the biggest threat? What is being done?

2.1.5 The Lithosphere (KQ1): Evidence of Plate Tectonics

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

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 as seafloor 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 valleys are formed along faults caused by the crust splitting as the two plates move apart.  (Ex. East African Rift)
• In the ocean, rift valleys result in oceanic 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)

Click here for 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

• What happens as a result of this action:
• Earthquakes...fault likes (Ex. San Andreas Fault)
• 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:

Sept. 26, 2012: Complete Lab Activity Questions

Answer the questions from Investigation 2 in your lab journal.

Compilation of Notes, Past and Present

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

Earthquake Gizmos

The instructions are on the linked file below.
AICE EM Earthquake Gizmos