1. BIOGEOCHEMICAL CYCLES
Everything goes around and around and around ……………………….

2. Law of Conservation Matter cannot be create or destroyed
It simply changes forms
Bottom line is there is a fixed amount of stuff
We’re not making any more atoms (elements)
They move around the systems
Where they are located in the system effects the system

3. An Amazing Thought
While the things made up of the atoms may be young, you for example, the atoms that you are made of have been around since the beginning of the universe.
Your atoms could have been part of an ancient tree, or a dinosaur!
Kind of weird isn’t it?

4. Plate Tectonics and the Rock Cycle
The rock cycle is the result of earth moving matter (rocks and minerals) via plate movement (plate tectonics)
The atoms that make up rocks and minerals start out in the mantle and eventually end up back in the mantle
Lets take a look.

5. Rocks Two or more elements combine to make minerals
Two or more minerals combine to make a rock
There are three types of rocks
Igneous rocks form from cooled magma
Sedimentary rocks are pieces of minerals or organic material cemented together
Metamorphic rocks are formed when either igneous or sedimentary rocks are subjected to enormous heat and pressure

6. Igneous rocks Magma is molten rock inside the earth
Think of it like a molten elemental soup
Does magma have a lot of energy or a little energy?
What does that tell you about the motion of the atoms in the magma?

7. Cooling
As energy leaves the magma, the atoms slow down enough to begin to bond
They arrange themselves into regular patterns
The rate of cooling determines the size of the crystal patterns in the rock
Would you expect magma inside the earth or out on the surface to cool faster?

8. Plutonic or Intrusive Rock
Magma inside the earth loses energy slower than magma on the surface
The elements have more time to form mineral crystals
Subsequently, the mineral crystals are bigger in intrusive igneous rock formed by cooling magma below the surface

9. Volcanic or Extrusive Rock
Magma that comes to the surface is called lava
It cools considerably faster
Subsequently, extrusive rock lacks the distinct mineral crystals / grains found in plutonic rock
It is still made of the same elements

10. Weathering
As soon as rock is exposed to earth’s surface, it is exposed to processes that break it back down into individual mineral crystals (we typically refer to them as sand)
This process is called weathering
There are two types of weathering, mechanical and chemical

11. Mechanical Weathering
Mechanical weathering or disintegration occurs when the rock is broken into progressively smaller pieces without changing it’s chemical composition
This is PHYSICAL change
I have the same basic mineral crystals I’m just breaking them into smaller pieces
Example:
Beating a rock into sand with a hammer

12. Causes of Mechanical Weathering
Wetting and drying
Freezing and thawing (Ice wedging)
Plant roots
Contact with other rocks
Rock slides or avalanches
Washing down rivers

13. Chemical Weathering
In chemical weathering the agent essentially changes the mineral crystal into something else
This is CHEMICAL change
The resulting substance no longer looks like or has the same properties it did before

14. Chemical Change Agents
Hydrolysis
Water combining with the minerals
Oxidation
Oxygen combining with the minerals
Carbonic Acid
Carbon dioxide combining with water then dissolving the minerals

15. Erosion
All these big and little pieces of weathered rock (sediments) can be moved by the wind and water
This is the process of erosion, the movement of sediments from one place to another

16. Deposition
Eventually the speed of the wind or water carrying sediments slows and it cannot support the weight of the sediments
The sediments fall and begin to stack up in layers
This is called deposition
As the wind or water slows, which size sediments will fall out first and which last?

17. Current
Fast
Slow
Rocks
Gravel
Sand
Silt
Clay

18. Sedimentary Rock
As the sediments and the remains of living organisms get buried deeper, they can become cemented together to form sedimentary rock
Clastic: Formed from cemented pieces of other rocks
Organic: Formed from the remains of plants and animals

19. Metamorphic Rocks
Rocks that are formed from other rocks when they are exposed to enormous heat and pressure
Igneous or sedimentary rock that has been exposed to enormous heat and pressure (for example at plate boundaries) literally gets squished becoming denser and changing appearance

20. The Rock Cycle
The movement of elements through this system is called The Rock Cycle

21. Elemental Soup
Magma cools allowing the elements to slow down and start to bond
1or more elements combine to make minerals, 2 or more minerals combine to make rock
The slower magma cools the bigger the crystals

22. Weathering
As soon as the rock is exposed at the surface, it comes under attack
Wind, water and chemicals are the enemy
These agents break the rock down physically or chemically

23. Erosion
The rock particles are carried off by the wind and water to be deposited

24. Sedimentary Rock The sediments pile up over time
As the sediments are buried they can become cemented together becoming sedimentary rock

25. Metamorphic Rocks
Igneous Rock
Anywhere Igneous or Sedimentary rocks are exposed to enormous heat or pressure they can be turned into metamorphic rocks
Sedimentary rock
Metamorphic Rock

26. And Back to Element Soup

28. Some Things to Remember
The process takes thousands or millions of years
There is no set pattern to the process. Metamorphic rocks can be uplifted and weathered etc.
The bottom line is the elements that start in the magma eventually end up back there.