1. PHS Geography Physical Geography/Natural Disasters
Rocks
PHS Geography
Physical Geography/Natural Disasters

2. rock is made up of various combinations of minerals which in turn are made up of various combinations of elements
there are as many variations of rock as there are combinations of minerals, although some rocks are very simple in their chemical structure,
eg., diamonds are pure carbon (an element)

3. Elements form minerals
Minerals form rocks

4. ROCK CYCLE
The diagram in the next slide represents the ROCK CYCLE—a scheme that represents the processes of continuous changes that connect the three major groups of rocks: SEDIMENTARY IGNEOUS METAMORPHIC The category of rock type depends on how the rock was formed

5. http://pbs. panda-prod. cdn. s3. amazonaws

6. Here is another version of the Rock Cycle

7. http://www. volcanoworld. org/vwdocs/vwlessons/lessons/Rocks/Rocks8

8. IGNEOUS ROCKS
Form by solidification (crystallization) of melted minerals
means "of fire" or "fire made", from the cooling of the molten rock (lava on the surface; magma inside)
"intrusive" - made inside the earth's surface
"extrusive" - made outside the earth' surface
eg., the Shield

9. INTRUSIVE
Beneath the surface, MAGMA hardens to form INTRUSIVE rocks with easily visible (COARSE-GRAINED) crystal texture.
Formed in chambers called:
Batholiths
Laccoliths
Dykes
Sills
Volcanic necks
But all are underground!

11. EXTRUSIVE
At the surface, LAVA hardens to form EXTRUSIVE rocks with tiny (FINE-GRAINED) crystals or GLASSY (no crystal) TEXTURES
Found in lava fields from volcanic eruptions
And underwater volcanic vents

12. Granite Light-colored, coarse- grained, no pattern
Mostly quartz, feldspar, mica, and hornblende
Often used for buildings and monuments

13. Basalt Dark-colored, fine- grained, extrusive
Formed where lava erupted onto surface
Most widespread igneous rocks
Found locally in the Palisades along west shore of Hudson River, Connecticut River valley

14. Gabbro Dark-colored, coarse- grained intrusive
Similar composition to basalt—plagioclase feldspar with some pyroxene and olivine

15. Obsidian Natural volcanic glass Forms when lava cools very quickly
Usually dark, but small pieces may be clear
Fractures along curved (conchoidal) surface
Used as spear and arrow points, knives

16. Pumice and other igneous rocks
Light colored, frothy (many air spaces)
Same minerals as in granite, but finer in grain size
For more about igneous rocks:

17. Sedimentary Rocks
Sedimentary rocks may be made of rock fragments—sediments—or by chemical reactions. The classification of sediments is shown below.

18. Sedimentary rock
formed from the products of the decomposition of pre-existing rock or the remains of marine life
water does the work erosion and transportation mainly, but wind, ice and gravity are also important
sediments laid down in horizontal beds or layers, called "strata"

20. the pressure of overlying deposits causes sediments to solidify over time into rock- called ‘lithification’
layers may be uplifted and warped (folded) or broken (faulted) by tectonic forces
(eg., the West. Cordillera)

21. The rock that underlies much of extreme southern Ontario is limestone.
A local example is seen on the Grand River or the Niagara Escarpment.

22. Non-clastic rocks form by chemical precipitation (settling out from a solution.) Limestone is made from calcite, chert from quartz, and halite is rock salt.

23. Clastic rocks–made of cemented sediments—are classified by their grain sizes.

24. Biologic sedimentary rocks come from the remains of organic matter.
The most important of these is coal. Anthracite coal results from the greatest pressure and releases the most energy when burned. Other varieties are bituminous and lignite. “Petrified” (permineralized) wood is another organic rock.

25. More about sedimentary rocks
Shale is the most common sedimentary rock
Sedimentary rocks cover about three-quarters of the land surface
For more about sedimentary rocks:

26. Metamorphic Rocks Formed by heat and pressure changing existing rocks
REGIONAL METAMORPHIC affects a large area and results from plate tectonics
CONTACT METAMORPHISM affects rocks on a local scale, such as “baking” sedimentary rocks next to magma or lava

27. DIFFERENCES IN INTENSITY OF REGIOAL METAMORPHISM

28. CONVERGENT PLATE BOUNDARY

29. CONTACT METAMORPHISM
The extreme heat from the magma intrusion ‘bakes’ the rock that it comes in contact with and changes the elemental structure and texture of the rock.

30. CONTACT METAMORPHISM
CONTACT
METAMORPHISM
INGNEOUS INTRUSION
(DIKE)

31. “Foliated” rocks contain much mica and other rocks that produce layering or banding
Gneisses are common in the Canadian Shield

32. Non-foliated metamorphic rocks include marble, which comes from limestone, and quatzite, which comes from sandstone