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
Mar 30, 2015
CHAPTER 19UNIT 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
19.5 OBJECTIVESDescribe the three major types of
rocks and how they formDiscuss physical and chemical
properties of each major type of rock
Describe the rock cycleExplain how to find relative rock
ages and absolute rock ages
SOME INTERESTING FACTSDiamond, 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
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)
MINERALS AREA natural, inorganic solid with a
definite chemical composition and a characteristic internal structure
Ex. Quartz, is silicon dioxide, SiO2
THE STRUCTURE OF QUARTZ
Think of Triangular Pyramids being put together a specific way, over and over and over
THE MINERAL QUARTZ
MOST ROCKS ARE A COMBINATION OF SEVERAL MINERALS
Granite is a rock composed of different minerals
Coal is decomposed plant matter
NINE MOST COMMON ROCK-FORMING MINERALS
Feldspar
Pyroxene
Mica
Clay
Calcite
Quartz
Olivine
Dolomite
Amphibole
THE APPEARANCE OF ROCKSAppearance and Characteristics
reflect mineral composition (what is it) and the way it was formed
There are three major types of rocks – Igneous
Sedimentary Metamorphic
IGNEOUS ROCKS FORM FROM LIQUID ROCK
Remember the difference between Magma and Lava
Magma is underground
Lava is on the surface
BOTH ARE FORMED FROM
VOLCANOES
Granite forms from magma
Granite cools underground,
Granite is courseYou can see
different grains
Obsidian forms from lava
Cools quickly on the surface
Obsidian is smooth like glass
Obsidian you can’t see grains
Granite is an Intrusive Igneous Rock
Obsidian is an Extrusive igneous rock
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…
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…
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
DINOSAUR NATIONAL MONUMENTQUARRY VISITOR’S CENTER
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
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
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
STALAGMITES AND STALACTITES
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
LIMESTONE (SEDIMENTARY) BECOMES MARBLE (METAMORPHIC)
Heat and pressure turn limestone into marble
Marble will often have bands of color and swirls
MARBLE, COLORADOUSED IN MONUMENTS IN WASHINGTON DC
MARBLE USED IN SCULPTURE
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
THE ROCK CYCLE
http://www.classzone.com/books/earth_science/terc/content/investigations/es0602/es0602page02.cfm
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
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