2.1.3 The Lithosphere (KQ1): Plate Tectonics

Plate Tectonics...memories should be popping into your head about the continents moving around, making what we have today from one "super-continent."  This movement really gives us the shape and distribution of our lands and oceans...and is the driving force behind a lot of our natural hazards that we will study soon.

...but, why does it move?  and what on Earth happens because of the movement?

Well...all of the crust (continental and oceanic combined) is broken into different tectonic plates that move in different ways.  Here's a graphic of the major tectonic plates and the direction they move.

Notice in the bottom key the terms subduction zones, divergent boundaries, and plate movement.  These will be important to understand in the next section, but you may be able to hypothesize what they mean just by looking at the names and direction of the arrows.

Look at the map again...where in America do you hear the most about earthquakes?  

Califorina!  

Look along California...right on a plate boundary...not a coincidence, the two (boundaries and earthquakes) go hand in hand.  

(Red = Highest Risk of Earthquakes)

Look back at the world map and the mess of plates boundaries around Japan...remember the big earthquake of 2011 that almost led to a nuclear disaster?  Generally doesn't happen in places away from plate boundaries.

Take a look here at that movement of the plates (evidenced by the movement of land) from 600 Million Years Ago to the super-continent, called "Pangea," to current day.  

We tend to think that the land masses just moved...but it was the entire plates, including both oceanic and continental crust, that changes the landscape.

Why do these plates move?  It is NOT the land moving on top of water...it is the crust (land and rock layer underneath the ocean) moving on top of the mantle.  There is uneven heat distribution in the mantle...basically cooler and warmer spots.  The warm rock moves toward the cooler spots (we'll demonstrate in class) due to convection.  That rolling movement of he mantle causes the crust to move in the same direction, causing tectonic plate movement.  Here is a great graphic of that movement.  We'll get into the terms shown in the picture in the next section.

As you can see, the convection cells, or pockets of heat transfer in the mantle, are moving the two plates in the oceanic crust away from each other, forming a mid-oceanic ridge.

The convection cells in the mantle are responsible for all tectonic plate movement and thus all the events that happen due to the movement.

2.1.2 The Lithosphere (KQ1): How Do We Know the Structure?

OK...so we just learned about the Earth's structure...but have you ever seen a 6400 km hole?  So how do we know what the Earth is made of...that there's different layers...and how they impact each other?

The following video explains it very well...puts it in pretty easy terms.  You do need to know the terms p-wave and s-wave.  They are used in earthquake measurements, and we will study them more...but go here for a quick definition of each and a cool animation to go along before viewing the video below.  It will make the video easier to understand.

2.1.1 The Lithosphere (KQ1): Structure of the Earth

Middle School!!!  Probably the last time you saw something like this:

While you did learn about this a while ago...we need to refresh our knowledge on it and probably dig a little deeper that you did then.  Why?  Because if you want to know how to  survive sustainably within Earth's environment, you have to know how the world works...and the central to understanding that is to know how the Earth is structured.

Let's go from the inside out...

INNER CORE

• Center (~6400 km in) to ~5200 km within the Earth
• Solid iron, it is solid, even though it is very hot, due to the fact that there is so much pressure on it!

OUTER CORE

• 2900 km - 5800 km within the Earth
• Semi-solid iron, nickel, other trace elements, not enough pressure to fully solidify

MANTLE/UPPER MANTLE

• 70 km - 2900 km within the Earth
• Solid rocks, but moving due to temperature differences
• The temperature differences give that movement through something called convection

CRUST - 2 TYPES

• OCEANIC CRUST
• Thinner layer of crust underneath oceans (only 5-10 km thick)
• Very dense - filled with dense rock, like basalt
• CONTINENTAL CRUST
• Thicker layer of crust making up land mass (up to 70 km thick)
• Less dense than oceanic - less dense rock, like granite

And, that's pretty much what you need to know to get started.  Next, we will be taking a look at how this structure creates the environment in which we live and makes the world a truly dynamic system...always changing, always moving, impacting our lives in every possible way!

1.5 MEDC vs. LEDC

MEDC and LEDC ... you are going to see these acronyms a lot in this course.  They are very important to understanding the impacts that different groups of people have on the environment.  So...what do they stand for???

MEDC:  More Economically Developed Country

LEDC:  Less Economically Developed Country

While each country's population is different, we can classify all of them in one of these 2 categories, depending on how far along they are in something called the demographic transition...but we'll discuss that a lot more in the population section of the biosphere unit.  What's important for you at this point is to know that the people in MEDCs are generally more affluent and have what economists deem a "better quality of life" than people in LEDCs.  

            (LEDC example:  Cambodia)                          (MEDC example:  USA)

Here is a general map that shows countries that belong to each group...you can definitely see a distinct line as to where the shift happens (except for Australia):

Here are some of the countries that belong to each...you should memorize a few from each to be able to reference in the future:

MEDCS: 
Australia, the UK, USA, Switzerland, Canada, France, New Zealand, Belgium, Germany, Ireland, Japan , Republic of Korea 


LEDCS: 
Bangladesh, Mali, Sudan, Peru, Fiji, Cambodia, Nigeria, Egypt, Zimbabwe

The two groups use resources differently for reasons we learn, and thus have different impacts on the environment.  You will see these acronyms discussed in every sphere, so it is important that you understand the basic difference before we even begin.

1.4 The Four Spheres

To get the best understanding of EM possible, we have broken up how the Earth works into 4 "spheres," which if you look at your Cambridge syllabus, is the basic setup for both the course and the exam.  The spheres are (in the order we will study them):

The LITHOSPHERE - The ground...sometimes referred to as "earth."  Technically, the upper mantle of rock and crust that forms the tectonic plates upon which the continents lie.  In this unit we will study the structure of the earth, natural hazards (tornadoes, hurricanes, etc), soil formation, erosion, human impacts on all of these, solutions to problems associated with them, and more.

The HYDROSPHERE - Water!  The bodies of water, present as ice, liquid water, or water vapour.  In this unit we will study how water is stored and transferred, human impacts on water, how to sustainably provide water to people all over the world, how to manage pollution of water, and more. 

The ATMOSPHERE - The air!  The gaseous shell outside the lithosphere and hydrosphere.  In this unit we will study the structure and characteristics of the atmosphere, patterns of air movement, climate and weather, human impacts,  management and effects of air pollution, and more.

The BIOSPHERE - The living organisms which occupy and use the other 3 spheres to sustain themselves.  In this unit we will study ecosystems, human impacts on ecosystems, preservation and conservation, worldwide efforts to support ecosystems, population impact on ecosystems, and more.

Together, these spheres are why our world works and why we can live in it.  Each has an impact on the others, and could not survive alone.

1.3 Sustainability

One key term that will pop up again and again in this course is sustainability.  You NEED to know this...it is fundamental to the goals of environmental management.  Sustainability is when you use a resource from the environment such that it is replenished (put back in) at the same rate the you use it.  

For example, if your allowance is $15 a week, and you only spend $10 a week, you are managing your money sustainably!  Congrats!

However, if you spent all $15 and decide you need gas for your car before your next allowance comes in, you'd have to dust off your bike (not such a bad thing, anyway), because there would be no money to pay for the gas.  You didn't "sustain" the amount of money you needed, therefore you were being "unsustainable."

In the environment, humans, especially since the industrial revolution, have been using many resources unsustainably.  For instance, the fossil fuels we use to power our cars and homes are non-renewable...this means that when we use them, it takes millions of years for them to replenish.  So, if we keep using them at the rate we are, sometime in the future (50 years...100 years...500 years???), we will not have any more.  Unlike the allowance, however, we won't be able to wait until there's more available.  We must use Environmental Management to find solutions before it's too late...and I trust that we will.


It's not all about the environment, however...sustainability takes into account economics and societal impacts as well.  We cannot merely just "switch" to not using resources...the societal and economic segments may crash.  They all need to work together in a cohesive way so that all three are strengthened by each other.

Watch this video...simple, quick explanation of sustainability:

One idea of how to make energy use sustainable:

1.2 Introduction to EM

OK...so, what is "Environmental Management (EM)," why do we care about it, and what will we be learning about in this course?  Good Questions!


We can find the best definition of EM for our use right in that big Cambridge syllabus..."Environmental Management is concerned with both local and global issues and with the various ways in which societies, governments and economic activity...use, misuse and attempt to manage both local and global environments."  Basically, this boils down to how different parts of our environment affect us, how we attempt to manage them for our betterment, and how to come up with solutions to fix those things we may have made worse or affect us negatively.  


There are many negative aspects to the environment...we've done a lot of things to hurt it...but, we have done good things as well, and the more aware we are of the environment, the more we will be able to protect it for our future and the future of those who will be here after we're gone.  In the future, it is the hope of environmentalists and environmental scientists alike that we will not be looking at the terrible things we've done, but the great things we did to restore and protect this wonderful planet.