1. Chapter 19 Unit 5 Rocks and Minerals
The world formed from Stardust
We formed from the world
We all came from Rocks
So now Mrs Stanford is calling us
Nuclear waste and Rock-heads

2. 19.5 Objectives
Describe the three major types of rocks and how they form
Discuss physical and chemical properties of each major type of rock
Describe the rock cycle
Explain how to find relative rock ages and absolute rock ages

3. Some interesting Facts
Diamond, the hardest mineral on earth, is composed of Carbon. The same material needed for life as we know it.
Most of the earth’s crust is made of some form of quartz
Diamonds, Rubies, Quartz, Garnets, and most of the precious gems we are familiar with come in many colors

4. The colors of fireworks come from different minerals
Magnesium burns white and very hot (don’t believe me, burn an old VW Bug engine in a bonfire)
Copper burns green (copper is also toxic, many gem cutters don’t work with Malachite, which is a semi-precious gemstone containing copper)

6. Minerals are
A natural, inorganic solid with a definite chemical composition and a characteristic internal structure
Ex. Quartz, is silicon dioxide, SiO2

7. The structure of quartz
Think of Triangular Pyramids being put together a specific way, over and over and over

8. The mineral Quartz

9. Most Rocks are a combination of several minerals
Granite is a rock composed of different minerals
Coal is decomposed plant matter

10. Nine Most common Rock-Forming Minerals
Feldspar
Pyroxene
Mica
Olivine
Dolomite
Amphibole
Clay Calcite Quartz

11. The appearance of Rocks
Appearance and Characteristics reflect mineral composition (what is it) and the way it was formed
There are three major types of rocks – Igneous
Sedimentary
Metamorphic

12. Igneous Rocks form from liquid rock
Remember the difference between
Magma and Lava
Magma is underground
Lava is on the surface

13. Both are formed from volcanoes
Obsidian forms from lava
Cools quickly on the surface
Obsidian is smooth like glass
Obsidian you can’t see grains
Granite forms from magma
Granite cools underground,
Granite is course
You can see different grains

14. Granite is an Intrusive Igneous Rock

15. Obsidian is an Extrusive igneous rock

16. Sedimentary Rocks
Rocks are not permanent structures, they break down by a process called
Weathering
Weathering changes the physical form or chemical composition of rock minerals exposed at earth’s surface
Weathering can be from wind, rain, acids…

18. Sedimentary Rock Making new rock from old weathered rock
Rock formed from compressed or cemented deposits of Sediment
Sediment is weathered rock, carried away by wind or water and deposited in an new location
Sediments can be deposited by rivers, wind (sand dunes), glaciers, oceans…

19. Fossils
Sedimentary rock often includes the bodies or remains of animals and plants
Dinosaur National Monument, in North-West corner of Colorado is a large sedimentary rock formation that has been exposed by humans to uncover the remains of many dinosaurs

20. Dinosaur National Monument Quarry Visitor’s Center

22. Two ways to form Sedimentary Rock
Pressure – rocks and water above can squeeze sediments into sedimentary rock
“Glue” – rocks dissolve and enter pores and resolidify gluing the sediments together

23. Some types of Sedimentary Rocks
Conglomerate – made of pebbles and large visible rocks cemented together with a brown material of mostly quartz
Sandstone
Mudstone, if flaky called Shale
Limestone – made of fossils of organisms that lived in water

24. Limestone
Forms Caves
Limestone dissolves in water and leaves a cavity in the ground
Some minerals that are already in the water deposit in the cave leaving formations

25. Stalagmites and Stalactites

27. Some amazing formations found in caves

28. Metamorphic Rocks “to change form”
Rocks that started as Igneous or Sedimentary can be changed by “squeezing”, “heating” or sometimes a chemical process
Usually both heat and pressure are involved in metamorphosing a rock

29. Limestone (sedimentary) becomes Marble (metamorphic)
Heat and pressure turn limestone into marble
Marble will often have bands of color and swirls

30. Marble, Colorado Used in monuments in Washington DC

31. Marble Used in Sculpture

32. Slate
Shale (remember that’s flaky mudstone) turns into slate when heated and compressed
Shale and slate are often rock types where oil and natural gas can be found
Geologists searching for gas and crude oil look for evidence of these rocks

33. The Rock Cycle

34. http://www.classzone.com/books/earth_scienc e/terc/content/investigations/es0602/es0602p age02.cfm

35. How old are Rocks? Can be hard to tell We can find relative age using
“Law of Superposition”
Older rocks are on the bottom,
Examples Grand Canyon, Layers of rocks seen in Grand Junction Area…
Fossils in rocks lower in a rock face are older than fossils in rocks above them

36. To find the actual age we need something different -
To find the actual age we need something different Radioactive Dating
Radioactive elements will “decay” they break down to other elements or forms
Carbon, Argon, Rubidium, Strontium, Uranium and Lead are all used for Radioactive Dating
Determines absolute age of rock
Rocks in Minnesota are 3.2 billion years old
Rocks in Greenland are 4.2 billion years old