Transcript 19.5 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
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
 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
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)
A
natural, inorganic solid with a
definite chemical composition and a
characteristic internal structure
 Ex. Quartz, is silicon dioxide, SiO2

Think of Triangular Pyramids being
put together a specific way, over
and over and over
 Granite
is a rock composed of
different minerals
 Coal
is decomposed plant matter
Feldspar
Olivine
Clay
Pyroxene
Dolomite
Calcite
Mica
Amphibole
Quartz
 Appearance
and Characteristics
reflect mineral composition (what is it)
and the way it was formed
are three major types of rocks –
Igneous
Sedimentary
Metamorphic
 There
 Remember
the difference between
Magma and Lava
Magma is underground
Lava is on the surface
 Granite
forms
from magma
 Granite cools
underground,
 Granite is course
 You 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
 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…
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…

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

Pressure – rocks and water above can
squeeze sediments into sedimentary rock
 “Glue” – rocks dissolve and enter pores and
resolidify gluing the sediments together

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

 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
Some
amazing
formations
found in
caves

 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

Heat and
pressure turn
limestone into
marble

Marble will often
have bands of
color and swirls


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


http://www.classzone.com/books/earth_scienc
e/terc/content/investigations/es0602/es0602p
age02.cfm
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

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
